I find these videos relaxing. Not only do I like your oration (a five dollar word for story telling), but that you show the things that doesn't always finish the way expected. I enjoy watching various car and truck repair/ rebuild shows but am always amazed how easy parts seem to come off and on for them, how clean the broken parts are and the fact they also never seem to get dirty.
Watch Gerolf on The Post Apocalyptic Inventor doing his "Scrap Yard" repair marathons. NONE of his stuff is clean to start! The guy does superb restorations! Gives good tips too on how to get things apart that are rusted solid!
Holy smack, you’re making me feel like Neanderthal when casually throwing around lines like “dead nuts at 50 millionths”! I am proud, as a home shop guy, in the half-a-thou range for parts. But with the knowledge gained here I think my shit is going to evolve in a big hurry. Thank you for helping us extinguish ignorance and fire up the flatness! Killer explanations, camera work, and accessibility! Thank you! CY Castor
He's got to be talking 50 millionths of a metric metre. I don't think even the apex of NIST goes to 50 millionths of an inch. Nanometers yes. A thousandth of an inch is 25.4 mm share by 1000 which is 25.4 micro or millionths of a meter. Unless I've made a big error in learning he's lapped that to two thou and you've got machine tools scraped in with the marking blue ink method the 4 times more accuracy than lapping. You must be chuffed achieving half a thou in your home shop. I hope to do the same one day.
I was just thinking through "what if a pair had mutually dished/domed surfaces - so they seemed flat but just mated" But then I realized in the set of three - you'd always end up with two dish, or two dome that would always work their way flat. NEAT
Hi Tom, just wanted to say Hi from Darley Dale, England, home of the late Sir Joseph Whitworth, credited with true plane and surface plate early development and decimalisation of the inch. Yep he created the thou! Great to see you producing this stuff. Love all your videos and am an avid watcher. Keep up the great work.
you need a bigger flat to check those. Guess how you can get 3 good flats ;) It is neat to see this process done with metal, I have always been on the glass pushing side. Made few couple 14in flats for optical testing of telescopes. That kind of segmented surface is also used in optical work. The idea is to cut grooves on the back of one of your 3 glass blanks, adding a fourth broken surface to the rotation. It comes into play during fine grinding and polishing (6um and finer) and is used as a bruiser to break down the fresh abrasive charge at the beginning of each wet. It is extra work adding that fourth surface, but it really helps prevent scratches from contaminated abrasive.
Great vids. I have currently rather little use (and not at all the right workshop) for precision work, but I enjoy them anyway and there's always something to take away, like the neat trick to use a taper thread to securely hold the sensor. Thanks for sharing!
Tom the hole in the middle is exactly what is done to make optical mirrors for telescopes. The process of progressive grits between two pieces of glass blanks will wallow out the center until a parabola is formed, and thus a mirror when finally polished. To prevent the hole, a lap of a larger diameter would be required on the top side. Not any authority for sure, but info as per reading on the subject.
I started grinding a mirror for a 6" reflector telescope back in high-school. The first stage was to get the mirror blanks flat, then concave with a hemispherical profile, a parabolic profile came next then final polishing. There were lots of grinding patterns depending on what part of the shaping was underway. After way too long, I had the mirror ground out, but not polished. That was as far as I got; had a good 'wet image' from the mirror, even a decent knife-edge test. Good form, but rough surface. Never got around to making the pitch-lap for polishing. Life intruded.
Now by the reflection of that spherometers base its doesn't seem very flat sir XD thank you for your content! I am thoroughly amazed at how simple it is with time to make a flat plane I can use for my knife moding.
Mr Wizzard this wave length , lapping , micron stuff is going to have you bonkers by Bash time. Bruce bring hm a straight jacket and keep a close eye on him. Great job thou Wizzard
Tom if you finish up doing a video on the optical flats etc could you discuss whether LEDs work as monochromatic light sources? I just use the overhead workshop lights and the fringes come up ok, but wondered whether making up a coloured LED source may be better.
Hard to obtain a bright enough single junction element with a decent life span. Multiple LEDs are difficult as each may present a slightly different wavelength. If they are produced with colored gels or dyes it would be worse as the gels will vary with lot and time/usage. Cherry picking would get you there but easier just to use a sodium lamp or etc. I usually just located the one florescent light in the shop that worked best.
If multiple LEDs are slightly different wavelengths how would that differ from a white florescent light that is every visible wavelength? Building a small lightbox with a ring array or similar of single colour LEDs would be much cheaper and easier than a sodium lamp that's for sure
Is that a serious question? Why bother? Because a monochromatic light box will cost hundreds of dollars, if you can find one used. Which you most likely won't here in Australia. A handful of LEDs and a power source will cost a few bucks, tops. LEDs are, by design, monochromatic. However I have never tried it to see if what works in theory works as well in practice, hence why I asked Tom if he was doing a video on it whether he could consider a cheaper/more readily available monochromatic light source.
LEDs aren't very monochromatic. They have a wide bell shaped frequency curve. Laser diodes are sharper but I think not as sharp as spike filtered out of a fluorescent
Pete F short answer is yes you can by using monochromatic light filter films, green yellow or red would work best. And passing the LED light through that. Any single wave length of light will produce a fringe pattern, just the measurement distance between fringes will change with the wavelength change. You can also build your own optical light box as well, despite the cost of them on the retail market, there's very little to them. Just a sodium bulb, some MDF and a beam splitter plate. Will still cost some $$ because splitter plates aren't cheap. You can get away without a splitter plate, but reading fringe lines just through the optical flat without a splitter is an art form much like reading your future from tea leaves. You would also need to get yourself a high precision optical flat. The jinkier your light source setup, the better your flat needs to be to compensate for it. A 1"dia single surface optical flat will set you back around $150.
Watched a Foyle's War tonight. Foyle runs thru a long tortured explanation of something and says "... and boom, Bob's your Dad's brother!" Strikes me funny for some reason.
Great video Tom!! Very detailed and well put together. One thing I think you should talk a bit more is using the flatness of the surface. Like the wavelength of the light source the spectral width and flatness of the optical flat. When using an interferometry measurement the flatness of the piece that you can measured is only as good as the reference piece. So if the reference is lambda/10 at 633nm then anything flatter then that can not be measured. Since lambda/20 optical flat is commercially available and not very expensive. Perhaps you can do a comparison. Also can you tell us the definition of the flatness? For example if you have a lambda/4 flat is it over the whole surface has lambda/4 or lambda/4 over 1 inch?
I had the opportunity a few years ago to work with a master optician whose specialty was making large optical flats for laser fusion research. His technique for checking fringes against a reference flat was to draw a few lines with a wax pencil on the surface to be measured. This would hold the reference flat just far enough to avoid contact with any residual grit while still giving nice fringes. Something you might want to try next time...
REALLY surprised to see that the meter on the spherometer isn't a mirror scale for such a precision instrument! I found I could greatly improve my analog readings on my old AVO 8 multimeter using its mirror scale and even my 40 year old home brew linear bench supply has a meter about the same size as yours but with a mirror scale and it didn't cost much more.
Hi Tom, Would it be a little quicker to start with plates that were first surfaced ground, just to get abetter surface to start with...??? Second question would you know of a good inexpensive source for an LVDT sensor? So far it's an enjoyable series... ;) Cheers, Pierre
Hi Pierre, I found two or three sensors on eBay, but I couldn't find a datasheet for them (LG1000 and M758490-05 are two part numbers to get you started). I imagine that the 5 wires will be 1,2 (primary), 3,4,5 (the two secondaries with one of them being a centre tap that joins the two secondaries). Not sure what the difference in voltage per mm of movement will be - what you don't pay for in the price, you'll probably pay for in time to reverse engineer! If you make one work, I'll be sure to watch! Good luck :)
Thanks Adam, I'll be looking into it, not certain to get any device done yet, it will depend on the complexity of the driving unit, haven't done serious electronics since 1991 when I got into manual works... Pierre
I would have done the same, ground them first to take most of the unevenness out. Or you could have given them a rub on the surface table with some wet and dry to flatten them out first.
Tom, How about more discussion on the different types of abrasives used and when? What about removing embedded (charged) abrasives from the plates for changing grits or type of abrasive for another operation. Once a plate has been used with diamond how do you then switch it to AO or garnet??? Still so many unanswered questions....
Hey Tom, Any chance you'll make it to NYC CNC's open house? I hear Adam will be there demonstrating four jaw indicating... Perhaps round two is in order? ;)
Hi Tom, congratulation for your very clear explanation of the entire lapping process. I am following your channel from Italy and I find it really interesting. I also have a question for you: let's say that I want to make a very flat surface with the 3 planes method and I don't want to make the grooving first because i need a continuous surface. Is there a method to create such a flat with lapping method? best regards Daniele
hi. awesome series. i am a boatbuilder and alu welder but really intrestested is precision metalworks. is there another video coming where you talk about aluminium and brass plates that you showed in the first video? thanks hendrik
I'm taking a crack at this with some cast iron 5lb weights. I've made good progress but I wonder how you kept the burrs down on the edges of the grooves and also managed to keep your plates so clean? Mine shreds a paper towel almost instantly. Did you do any deburring beyond the filing you did in episode 1? I also wondered how do you know when you have to much abrasive and also how often are you adding abrasive at each stage? The cleaning stage is very important and I didn't clean my plates enough on the lower grits. The abrasive hides defects and I didn't really see the issues until it was very very clean. Next round i'm going to dedicate a brush per grit and really soak them down to get everything off and blow them off after.
Nice series of videos Tom, would it be a time saver to surface grind the laps prior to lapping? I use that brass bushing collet trick to hold a thermocouple in place.
Very interesting stuff! With that tight fit on the pipe adapter was the saw cut really necessary? I am certain the bore would have collapsed enough to lock the part even without the cut based on the tight fit to the sensor.
I don't know if the holding is where the saw cut would come in handy. I think it would be more helpful on being able to get the sensor back out when needed. Just my thinking.
I was figuring the part would be clamped by non permanent deformation. I did not intend for the forces applied to actually yield the part. I am confident it would work without the cut and the clamping would be better as the stress would be a pure hoop and not a broken hoop with a large stress concentration. Schunk toolholders clamp end mills by the same process only the deflection is provided by a hydraulic force rather than mechanical, once the force is released the part slides right back out.
Absolutely fascinating. It would appear that the plate measured is at least as flat as the surface plate. In relative terms how flat is the surface plate when compared to say super-laboratory grade surface plate or something as ordinary as plate glass? I guess i am asking how flat is flat?
Chris Draper he mentions his plate was AA grade, which is lab grade flatness, in the first video. copy/paste from starrett below. The flatness tolerances for three standard grades are defined in the federal specification as determined by the following formula: Laboratory Grade AA = (40 + diagonal squared/25) x .000001" (unilateral) Inspection Grade A = Laboratory Grade AA x 2 Tool Room Grade B = Laboratory Grade AA x 4.
Quick question, Tom, Because of the back and forth action you are using for the lapping, do you think it would also be a good idea to add a series of 90 degree turns to the bottom lap? I know the rotational lapping helps correct any potential grooving/swayback issues due to the back and forth action, I just thought a turning of the bottom lap as well may be an idea.
All the square cuts were convex? Maybe from internal stresses? As they'd've been concave had cutting forces pulled 'em up, no? Diamond paste+stropping gets my knives their very sharpest. I use Shapton Kuromaku thru 5,000 grit (they get very pricey). Strop with diamond paste (4µm→1µm) some ppl use 0.5µm! For knives it takes less skill to use a "Fixed Angle Sharpener."
Tom, wondering if you can apply the techniques you are demonstrating to scrap pieces of granite (3 of course) to end up with some relatively flat surfaces for home use? Mostly for lapping parts to flat w sand paper. Would abrasives be the same or does stone require something different? Thanks for the great series!
d t You'd need to cut the grooves in your granite to allow the slurry to exit which would be a pain in the ass if trying to make a surface plate. Granite is lapped with cast iron laps normally not to different to the ones being made here just bigger, which in turn have been lapped flat using the 3 plate method.
chris0tube My mistake, I got the impression he wanted to use the granite as a surface plate, in which case you wouldn't want a pile of grooves cut in it. I'm not sure a granite lap would be ideal as generally the lap needs to be softer than the material being lapped. Also you can pick up small A grade granite surface plates for less than the cost of a cheap grinder and a diamond wheel.
chris0tube I'm sorry I'm missing your point, I thought you were saying it was easier and/or cheaper to buy a grinder, cutting disks, lapping paste and spend a day grooving and lapping 3 granite blocks than to buy a surface plate.
call me curious for a moment... explain to me why it should be 'beneficial' that the lap should be softer than the material you want to use the lap on??? I am struggling to get my head around this... If I go to all the effort of making a set of lapping plates that are essentially a near on perfect flat plane, that I then want to use as the basis for lapping some other part so that other part becomes a perfectly flat plane, in reference to the lap, then surely I would want to be using A) a lapping compound that will not abrade my lap but is hard enough to abrade the surface of the actual item I am attempting to lap using the lapping plate? otherwise, if my lapping plate was softer than what I want to lap, my lapping plate would wear before the item I am trying to lap....
Lloyd Milton Regardless of lapping or polishing nearly all texts on the subject suggest that the lap be softer. As rightly explained, to be charged. If the part is softer the part becomes charged and will cut the lap, so the lap being softer actually preserves the surface of the lap.
I understand the principle of the 3 plates is to distribute error. If so, what is the purpose of the A on B then B on A cycle? It seems logical to cycle thru all three plates first then flip moving units or do not flip at all. This issue is raised in the context of lapping a lighter plate onto a heavier plate where flipping is not practical. Thanks. Great videos!
The disk on top will naturally want to go concave while the bottom plate goes convex. So one round of A on B followed by B on A will in theory negate any curvature introduction.
Clear. How does the calibration guys use just a smaller plate on a much larger heavy surface plate still get a flat outcome. Is it just working to correct the mapped errors? Thanks.
Tom, such great videos. I have two questions (1) what is the easy way of cleaning the abrasive before using optical flat. I found these diamond partical destroy my optical flat easily. (2) why you need three adjuster screw instead of two ball + one adjuster ?
So what's the story with 'A on B' and then 'B on A'? I'd have thought that those two would have the same effect. Why does it make a difference which one is on top?
Tom, I’m thinking about making a set of lapping plates. I’ve followed these 3 videos and the work does not seem overly difficult for even a modest shop. However, what I was interested in doing first was a surface gauge/squareness comparator. I’ve seen other people building one based on one you built, but for the life of me I can’t find a video on your gauge. Could you point me in the right direction? So far, I’ve been taking ideas from Stefan gotteswinter and another one I’ve seen but who made is alluding me currently, I’d like to take ideas from yours as well.
I'm LAZY . . . * or smart ? . . . I would START the lapping process with around 10 micron , then 5 . . . & finish with 1 to submicron size ; all diamond dust - thinned ( or carried ) by fractionated coconut oil ! ( mineral oil works great too ! ) With diamond grit , quite often, LESS is more effective ! Time of work would be cut by nearly a magnitude . . . though the possibility exists that some of the coarser grit may embed , however . . . the finer grit should mitigate the coarse . End result is the big deal . . . as long as you enjoy the ride ;) Good stuff Tom ! ! !
Tom, in an earlier video you discussed the issue of the lapping being uneven between the outer edge of the plate and the center section because of the lapping motion causing more polishing action in the center of the plate, which is always in contact. Thus, limiting the back and forth stroke of the polishing action. What do you think of the idea of making the plates over-sized and just cutting away the uneven edges of the plate once the rest of the plate is flat and polishing is complete?
It shouldn't work very well, because of the internal stresses of the metal, any cutting of it will effectively stress and strain relief the plate, causing a new resting state to be achieved, which is unlikely to be as flat as your previous lapping action.
Really enjoyed the series, thanks man. Probably could’ve been one thirty minute video, but I’m not complaining! I don’t know if I missed it, but did you mention Whitworth?
Does that sphereometer sensor work off of capacitance? I don’t think you mentioned exactly how that instrument compares the three points with the sensor in the middle. I’d love to try to make something like that for myself. Super interesting instrument and another great video in this awesome lapping series. 👍
Why do the rings on the one plate matter if all else is flat? Wouldn't they just act as another relief for film? Thanks for sharing another interesting and informative post Tom!
Hi, I thought the idea with the sphereometer was to null it out on a flat then make a measurement on the surface under test or are you saying the cast iron is flatter than the surface table ?..great fascinating stuff
I would think that rotating the disks gives a different abrasion on the outer edge than in the center of the disks because of weight distribution and definitely because of the greater motion at the edge than in the center.
This is why you use three plates. The third averages the wear. Take your two plates. One is convex-raised center. One is concave-raised edge. Well call them A and B. Now posit a 3rd plate that's equally convex to A. Call it C. A on B = full surface contact. Nothing changes. A on C = both are convex so the raised centers get the wear, the edge doesn't make contact. Both become flatter. B on C = nearly full surface contact, but C is slightly flatter so it makes less contact in the center and slightly wears the edge of B making it flatter. B on A - nearly full surface contact, but both are slightly flatter than the first pass. C on A- both are convex so the raised centers get the wear, the edge doesn't make contact. Both become flatter. C on B- nearly full surface contact, but C is slightly flatter so it makes less contact in the center and slightly wears the edge of B making it flatter.
OK! Thanks for the process description! (Lying awake last night in bed I came to approximately the same conclusion and am thankful for the fullness of your response!)
I just started my Own machine shop and foot promoted to head "tool maker", they mean machinist. Are there any tips or websites I can go to get blueprints for making different set up pieces and tooling to save money for both and impress my bosses? You and Rob have amazing channels. I watch your guy's videos almost every day
What a great idea for that test instrument you made I have hundreds literally hundreds of those kinematic Adjusters for optical assemblies that I used to service for the biomedical field I got stuck with a bunch of the inventory so there you go. I don't have the handles for him but you can adjust them with an allen wrench or make handles is easy enough
Pictures that evaporating liquid on that plate by the pattern it's giving because as it hits that edge as the air goes over the sharp edges it's going to cause vortices that change the whole story if you could separate each block from the effects of the other blocks next to it that would be a different story
I'm curious to know how flat a 25inch square sheet of glass is, i've used glass/sand paper for many years to lap Cylinder Heads on Motorcycles. I now wonder if i've been adding a Concave or Convex surface.
The glass distorts while it's cooling but high quality float glass should be quite flat, more than adequate for flattening a cylinder head. Tom is talking about 50 millionths of an inch (0.000050 in or 0.00127 mm) in the video and he isn't finished polishing. I doubt that even a Formula 1 race team would go to that extreme. Head gaskets and sealants are also used to accommodate differential expansion of the engine components.
I love de class you've gave. I searched for long time how the first precision instrument was made, and you showed. Can I do the same to make straight edgees e surfece plates? By the way I have to apologies about my english, I'm from Brasil and I'm learning.
Fresnel effect, if the angle of incidence is wide enough, even a brick is reflective. I was wondering if you could hack a wireless drawing tablet (like a Wacom) to make a wireless spherometer. OTOH, that would be an expensive little project, and who knows how precise those sensors are (I guess they're made for pressure, not for travel)
“About a quarter of fifty millionths right there” is the most American measurement I’ve ever heard in my life 😂
I am confused. Fifty millionths or a fiftymillionths?
As a Euro-Metric boy I have literally no idea.
@@Outland9000 Pay attention,class is in session. Professor Tom will be"Interrogating the plate".
All welcome. SILENCE!!!
1/4 of 50 millionths is approximately 32 nanometers. Credit is to the calculator app on the Samsung.
@@allennelson1987 1 millionth of an inch = 25.4nm / 12.5 of those makes close to 320nm. You must have dropped a decimal. Easily done lol 😉
The amount of toys you have seems unlimited. The fact that you know how to use them all is also impressive
They are tools, not toys, at least that is what I tell my wife.
@@Volcker1929 ALL tools are big boys toys and just like young boys we HATE when other people touch our toys! 🤔🙄🤣🤣🤣
Enjoyed Tom! I like that cool little tool for checking flatness. The bushing trick is one to remember!
I find these videos relaxing. Not only do I like your oration (a five dollar word for story telling), but that you show the things that doesn't always finish the way expected. I enjoy watching various car and truck repair/ rebuild shows but am always amazed how easy parts seem to come off and on for them, how clean the broken parts are and the fact they also never seem to get dirty.
Watch Gerolf on The Post Apocalyptic Inventor doing his "Scrap Yard" repair marathons. NONE of his stuff is clean to start! The guy does superb restorations! Gives good tips too on how to get things apart that are rusted solid!
Fascinating. Its amazing what can be done with patience and elbow grease.
thanks for being a great teacher Tom!
Thank you,Tom.
I appreciate you and your work.
Looking real good Tom! Cant wait for part lapping using the plates.
ATB, Robin
Holy smack, you’re making me feel like Neanderthal when casually throwing around lines like “dead nuts at 50 millionths”! I am proud, as a home shop guy, in the half-a-thou range for parts. But with the knowledge gained here I think my shit is going to evolve in a big hurry. Thank you for helping us extinguish ignorance and fire up the flatness!
Killer explanations, camera work, and accessibility!
Thank you!
CY Castor
He's got to be talking 50 millionths of a metric metre. I don't think even the apex of NIST goes to 50 millionths of an inch. Nanometers yes. A thousandth of an inch is 25.4 mm share by 1000 which is 25.4 micro or millionths of a meter. Unless I've made a big error in learning he's lapped that to two thou and you've got machine tools scraped in with the marking blue ink method the 4 times more accuracy than lapping.
You must be chuffed achieving half a thou in your home shop. I hope to do the same one day.
I was just thinking through "what if a pair had mutually dished/domed surfaces - so they seemed flat but just mated"
But then I realized in the set of three - you'd always end up with two dish, or two dome that would always work their way flat.
NEAT
Gold Star👏😂
The 3 plates method is one of the finest logical gems of engineering. Its deduction is well worth a read.
This method is the basis of ALL precision manufacturing. Every measurement is ultimately derived from these flat surfaces.
This has been a very good learning experience for me, thanks Tom!
Great video series! The best videos I have seen on lapping plates. Thank you for sharing your knowledge.
Hi Tom, just wanted to say Hi from Darley Dale, England, home of the late Sir Joseph Whitworth, credited with true plane and surface plate early development and decimalisation of the inch. Yep he created the thou! Great to see you producing this stuff. Love all your videos and am an avid watcher. Keep up the great work.
Thank you for sharing, please never stop!
What a timely segment. Great give away on the pipe plug collet.
That spherometer collet is pure genius. I just took my hat off and it will remain off.
That was just flat out a good video, thanks.
Get out!
I love your videos, Tom. Thanks ever so much!!!
the Fresnel lines measurement is sweet, what a great way to measure curvature
Great video Tom, intriguing and interesting!
fantastic,cant wait for the next video tom. appreciate all your hard work.
good stuff my brain retains this kinda stuff for years for some reason and I seek it out and always want more
Fantastic video segments. Really enjoyed all the parts.
Great series Tom. Now you have a set of plates flatter than last weeks diet Coke.
😂😂😂😂😂
Thanks for making this series of videos very informative
you need a bigger flat to check those. Guess how you can get 3 good flats ;)
It is neat to see this process done with metal, I have always been on the glass pushing side. Made few couple 14in flats for optical testing of telescopes. That kind of segmented surface is also used in optical work. The idea is to cut grooves on the back of one of your 3 glass blanks, adding a fourth broken surface to the rotation. It comes into play during fine grinding and polishing (6um and finer) and is used as a bruiser to break down the fresh abrasive charge at the beginning of each wet. It is extra work adding that fourth surface, but it really helps prevent scratches from contaminated abrasive.
That is really cool Tom. I like your brass pipe fitting collet
This would make an excellent subject for a paper for a high school physics student.
Wait that means we are related Tom,
Bob is my uncle as well..
Great vids. I have currently rather little use (and not at all the right workshop) for precision work, but I enjoy them anyway and there's always something to take away, like the neat trick to use a taper thread to securely hold the sensor. Thanks for sharing!
Very cool!
Thanks for sharing Tom
TOM YOU DO EXCELLENT WORK
Tom
the hole in the middle is exactly what is done to make optical mirrors for telescopes. The process of progressive grits between two pieces of glass blanks will wallow out the center until a parabola is formed, and thus a mirror when finally polished. To prevent the hole, a lap of a larger diameter would be required on the top side. Not any authority for sure, but info as per reading on the subject.
I started grinding a mirror for a 6" reflector telescope back in high-school.
The first stage was to get the mirror blanks flat, then concave with a hemispherical profile, a parabolic profile came next then final polishing.
There were lots of grinding patterns depending on what part of the shaping was underway.
After way too long, I had the mirror ground out, but not polished.
That was as far as I got; had a good 'wet image' from the mirror, even a decent knife-edge test.
Good form, but rough surface.
Never got around to making the pitch-lap for polishing. Life intruded.
Now by the reflection of that spherometers base its doesn't seem very flat sir XD thank you for your content! I am thoroughly amazed at how simple it is with time to make a flat plane I can use for my knife moding.
Mr Wizzard this wave length , lapping , micron stuff is going to have you bonkers by Bash time. Bruce bring hm a straight jacket and keep a close eye on him. Great job thou Wizzard
Theres nothing like admiring the mirror surface of something you just lapped
Those Snap On tappet wrenches are great wrenches for stuff like your device. And they still work on those old tappets
Tom if you finish up doing a video on the optical flats etc could you discuss whether LEDs work as monochromatic light sources? I just use the overhead workshop lights and the fringes come up ok, but wondered whether making up a coloured LED source may be better.
Hard to obtain a bright enough single junction element with a decent life span. Multiple LEDs are difficult as each may present a slightly different wavelength. If they are produced with colored gels or dyes it would be worse as the gels will vary with lot and time/usage. Cherry picking would get you there but easier just to use a sodium lamp or etc. I usually just located the one florescent light in the shop that worked best.
If multiple LEDs are slightly different wavelengths how would that differ from a white florescent light that is every visible wavelength? Building a small lightbox with a ring array or similar of single colour LEDs would be much cheaper and easier than a sodium lamp that's for sure
Is that a serious question? Why bother? Because a monochromatic light box will cost hundreds of dollars, if you can find one used. Which you most likely won't here in Australia. A handful of LEDs and a power source will cost a few bucks, tops. LEDs are, by design, monochromatic. However I have never tried it to see if what works in theory works as well in practice, hence why I asked Tom if he was doing a video on it whether he could consider a cheaper/more readily available monochromatic light source.
LEDs aren't very monochromatic. They have a wide bell shaped frequency curve. Laser diodes are sharper but I think not as sharp as spike filtered out of a fluorescent
Pete F short answer is yes you can by using monochromatic light filter films, green yellow or red would work best. And passing the LED light through that. Any single wave length of light will produce a fringe pattern, just the measurement distance between fringes will change with the wavelength change.
You can also build your own optical light box as well, despite the cost of them on the retail market, there's very little to them. Just a sodium bulb, some MDF and a beam splitter plate. Will still cost some $$ because splitter plates aren't cheap. You can get away without a splitter plate, but reading fringe lines just through the optical flat without a splitter is an art form much like reading your future from tea leaves.
You would also need to get yourself a high precision optical flat. The jinkier your light source setup, the better your flat needs to be to compensate for it. A 1"dia single surface optical flat will set you back around $150.
Is there a part four coming?
Great as Always Tom
Watched a Foyle's War tonight. Foyle runs thru a long tortured explanation of something and says "... and boom, Bob's your Dad's brother!" Strikes me funny for some reason.
Great video Tom!! Very detailed and well put together. One thing I think you should talk a bit more is using the flatness of the surface. Like the wavelength of the light source the spectral width and flatness of the optical flat. When using an interferometry measurement the flatness of the piece that you can measured is only as good as the reference piece. So if the reference is lambda/10 at 633nm then anything flatter then that can not be measured. Since lambda/20 optical flat is commercially available and not very expensive. Perhaps you can do a comparison. Also can you tell us the definition of the flatness? For example if you have a lambda/4 flat is it over the whole surface has lambda/4 or lambda/4 over 1 inch?
Ive always wanted to grind my own optics for a giant telescope.
You can do it. If someone else can,you can.
Ask Tom to point you to that particular rabbit hole.
Wikipedia. Please try grinding a spherical primary mirror with a meniscus corrector.
I had the opportunity a few years ago to work with a master optician whose specialty was making large optical flats for laser fusion research. His technique for checking fringes against a reference flat was to draw a few lines with a wax pencil on the surface to be measured. This would hold the reference flat just far enough to avoid contact with any residual grit while still giving nice fringes. Something you might want to try next time...
Good stuff, Had to come back and hit the Thumbs Up button... :)
I wonder if you could make plates from granite counter top with diamond lap?
I bet you could. Might need thicker plates and a specific granite. That would be interesting.
i learned something here ,thank you very much
REALLY surprised to see that the meter on the spherometer isn't a mirror scale for such a precision instrument!
I found I could greatly improve my analog readings on my old AVO 8 multimeter using its mirror scale and even my 40 year old home brew linear bench supply has a meter about the same size as yours but with a mirror scale and it didn't cost much more.
@oxtoolco how would you make the two sides of the plate flat & parallel as well?
At 19:47 My Dad used to call it a 'gnats nadger' when in polite company.
Hi Tom,
Would it be a little quicker to start with plates that were first surfaced ground, just to get abetter surface to start with...???
Second question would you know of a good inexpensive source for an LVDT sensor?
So far it's an enjoyable series... ;)
Cheers,
Pierre
Hi Pierre,
I found two or three sensors on eBay, but I couldn't find a datasheet for them (LG1000 and M758490-05 are two part numbers to get you started). I imagine that the 5 wires will be 1,2 (primary), 3,4,5 (the two secondaries with one of them being a centre tap that joins the two secondaries).
Not sure what the difference in voltage per mm of movement will be - what you don't pay for in the price, you'll probably pay for in time to reverse engineer! If you make one work, I'll be sure to watch! Good luck :)
Thanks Adam, I'll be looking into it, not certain to get any device done yet, it will depend on the complexity of the driving unit, haven't done serious electronics since 1991 when I got into manual works...
Pierre
I would have done the same, ground them first to take most of the unevenness out.
Or you could have given them a rub on the surface table with some wet and dry to flatten them out first.
"My exercise is to create the classic three flat planes of a very high quality with really simple tools."
From his Instagram.
An interval timer app for the phone would work nicely for this.
Tom,
How about more discussion on the different types of abrasives used and when? What about removing embedded (charged) abrasives from the plates for changing grits or type of abrasive for another operation. Once a plate has been used with diamond how do you then switch it to AO or garnet??? Still so many unanswered questions....
Hey Tom,
Any chance you'll make it to NYC CNC's open house? I hear Adam will be there demonstrating four jaw indicating... Perhaps round two is in order? ;)
Can you explain what that electronic sensor is/does, and how it works? Some kind of load cell or strain gauge? What is it?
He said it's an "LVDT". www.te.com/usa-en/industries/sensor-solutions/insights/lvdt-tutorial.html
Thank you Jeff. Good man.
I'm curious why you did not surface grind at least the contact face to first eliminate the slight dishing from the lathe? Cheers!
Hi Tom, congratulation for your very clear explanation of the entire lapping process. I am following your channel from Italy and I find it really interesting. I also have a question for you: let's say that I want to make a very flat surface with the 3 planes method and I don't want to make the grooving first because i need a continuous surface. Is there a method to create such a flat with lapping method?
best regards
Daniele
I don't really know this stuff, but I _think_ from what he said in part one that the method would be the same, you'd just have to go slower.
The grooves carry the slurry off to make the tool; then you use the tool to make the uniform flat you desire.
15:50 every time you show something super cool i want to go buy it, so now i want to buy a optical flat and a helium light source >>"THANKS"
Thanks for sharing the knowledge/fun.
hi. awesome series. i am a boatbuilder and alu welder but really intrestested is precision metalworks. is there another video coming where you talk about aluminium and brass plates that you showed in the first video? thanks
hendrik
Wouldn't having a rotating linear motor make this a lot easier?
I'm taking a crack at this with some cast iron 5lb weights. I've made good progress but I wonder how you kept the burrs down on the edges of the grooves and also managed to keep your plates so clean? Mine shreds a paper towel almost instantly. Did you do any deburring beyond the filing you did in episode 1?
I also wondered how do you know when you have to much abrasive and also how often are you adding abrasive at each stage? The cleaning stage is very important and I didn't clean my plates enough on the lower grits. The abrasive hides defects and I didn't really see the issues until it was very very clean. Next round i'm going to dedicate a brush per grit and really soak them down to get everything off and blow them off after.
Nice series of videos Tom,
would it be a time saver to surface grind the laps prior to lapping?
I use that brass bushing collet trick to hold a thermocouple in place.
Very interesting stuff! With that tight fit on the pipe adapter was the saw cut really necessary? I am certain the bore would have collapsed enough to lock the part even without the cut based on the tight fit to the sensor.
I don't know if the holding is where the saw cut would come in handy. I think it would be more helpful on being able to get the sensor back out when needed. Just my thinking.
I was figuring the part would be clamped by non permanent deformation. I did not intend for the forces applied to actually yield the part. I am confident it would work without the cut and the clamping would be better as the stress would be a pure hoop and not a broken hoop with a large stress concentration. Schunk toolholders clamp end mills by the same process only the deflection is provided by a hydraulic force rather than mechanical, once the force is released the part slides right back out.
So how does a brass spring work if it can't return to its natural state?
Absolutely fascinating. It would appear that the plate measured is at least as flat as the surface plate. In relative terms how flat is the surface plate when compared to say super-laboratory grade surface plate or something as ordinary as plate glass? I guess i am asking how flat is flat?
Chris Draper he mentions his plate was AA grade, which is lab grade flatness, in the first video. copy/paste from starrett below.
The flatness tolerances for three standard grades are defined in the federal specification as determined by the following formula:
Laboratory Grade AA = (40 + diagonal squared/25) x .000001" (unilateral)
Inspection Grade A = Laboratory Grade AA x 2
Tool Room Grade B = Laboratory Grade AA x 4.
Oh OK - I missed that reference . Thanks.
Nice mod with the brass fitting.
Quick question, Tom, Because of the back and forth action you are using for the lapping, do you think it would also be a good idea to add a series of 90 degree turns to the bottom lap? I know the rotational lapping helps correct any potential grooving/swayback issues due to the back and forth action, I just thought a turning of the bottom lap as well may be an idea.
That is effectively being done as the sequence includes both 'A on B' and 'B on A'...
im high as fuck and have been watching this stuff for the last 2 hours
been there...done that...
it would be interesting to check your finest guage blocks with that machine
offset dual rotation grinding using the plates. like lens grinding. concavity is easy to control
All the square cuts were convex? Maybe from internal stresses?
As they'd've been concave had cutting forces pulled 'em up, no?
Diamond paste+stropping gets my knives their very sharpest.
I use Shapton Kuromaku thru 5,000 grit (they get very pricey).
Strop with diamond paste (4µm→1µm) some ppl use 0.5µm!
For knives it takes less skill to use a "Fixed Angle Sharpener."
Tom, wondering if you can apply the techniques you are demonstrating to scrap pieces of granite (3 of course) to end up with some relatively flat surfaces for home use? Mostly for lapping parts to flat w sand paper. Would abrasives be the same or does stone require something different?
Thanks for the great series!
d t You'd need to cut the grooves in your granite to allow the slurry to exit which would be a pain in the ass if trying to make a surface plate. Granite is lapped with cast iron laps normally not to different to the ones being made here just bigger, which in turn have been lapped flat using the 3 plate method.
chris0tube My mistake, I got the impression he wanted to use the granite as a surface plate, in which case you wouldn't want a pile of grooves cut in it. I'm not sure a granite lap would be ideal as generally the lap needs to be softer than the material being lapped. Also you can pick up small A grade granite surface plates for less than the cost of a cheap grinder and a diamond wheel.
chris0tube I'm sorry I'm missing your point, I thought you were saying it was easier and/or cheaper to buy a grinder, cutting disks, lapping paste and spend a day grooving and lapping 3 granite blocks than to buy a surface plate.
call me curious for a moment... explain to me why it should be 'beneficial' that the lap should be softer than the material you want to use the lap on???
I am struggling to get my head around this...
If I go to all the effort of making a set of lapping plates that are essentially a near on perfect flat plane, that I then want to use as the basis for lapping some other part so that other part becomes a perfectly flat plane, in reference to the lap, then surely I would want to be using A) a lapping compound that will not abrade my lap but is hard enough to abrade the surface of the actual item I am attempting to lap using the lapping plate? otherwise, if my lapping plate was softer than what I want to lap, my lapping plate would wear before the item I am trying to lap....
Lloyd Milton Regardless of lapping or polishing nearly all texts on the subject suggest that the lap be softer. As rightly explained, to be charged. If the part is softer the part becomes charged and will cut the lap, so the lap being softer actually preserves the surface of the lap.
I understand the principle of the 3 plates is to distribute error. If so, what is the purpose of the A on B then B on A cycle? It seems logical to cycle thru all three plates first then flip moving units or do not flip at all. This issue is raised in the context of lapping a lighter plate onto a heavier plate where flipping is not practical. Thanks. Great videos!
The disk on top will naturally want to go concave while the bottom plate goes convex. So one round of A on B followed by B on A will in theory negate any curvature introduction.
Clear. How does the calibration guys use just a smaller plate on a much larger heavy surface plate still get a flat outcome. Is it just working to correct the mapped errors? Thanks.
Tom, such great videos. I have two questions (1) what is the easy way of cleaning the abrasive before using optical flat. I found these diamond partical destroy my optical flat easily. (2) why you need three adjuster screw instead of two ball + one adjuster ?
once your done would you ever harden the surface to prevent wear when using them to lap something
Ahhh , good point
So what's the story with 'A on B' and then 'B on A'? I'd have thought that those two would have the same effect. Why does it make a difference which one is on top?
Gravity makes the top go concave so they get switched to keep evenness.
Tom, I’m thinking about making a set of lapping plates. I’ve followed these 3 videos and the work does not seem overly difficult for even a modest shop.
However, what I was interested in doing first was a surface gauge/squareness comparator. I’ve seen other people building one based on one you built, but for the life of me I can’t find a video on your gauge. Could you point me in the right direction? So far, I’ve been taking ideas from Stefan gotteswinter and another one I’ve seen but who made is alluding me currently, I’d like to take ideas from yours as well.
Nice. Way nice.
Excellent!
I'm LAZY . . . * or smart ? . . . I would START the lapping process with around 10 micron , then 5 . . . & finish with 1 to submicron size ; all diamond dust - thinned ( or carried ) by fractionated coconut oil ! ( mineral oil works great too ! ) With diamond grit , quite often, LESS is more effective ! Time of work would be cut by nearly a magnitude . . . though the possibility exists that some of the coarser grit may embed , however . . . the finer grit should mitigate the coarse .
End result is the big deal . . . as long as you enjoy the ride ;) Good stuff Tom ! ! !
Tom, in an earlier video you discussed the issue of the lapping being uneven between the outer edge of the plate and the center section because of the lapping motion causing more polishing action in the center of the plate, which is always in contact. Thus, limiting the back and forth stroke of the polishing action. What do you think of the idea of making the plates over-sized and just cutting away the uneven edges of the plate once the rest of the plate is flat and polishing is complete?
Great stuff, thanks for posting.
It shouldn't work very well, because of the internal stresses of the metal, any cutting of it will effectively stress and strain relief the plate, causing a new resting state to be achieved, which is unlikely to be as flat as your previous lapping action.
they require constant "tuning" wish I had time to explain how early telescope makers like 1450's era mde lenses
Really enjoyed the series, thanks man. Probably could’ve been one thirty minute video, but I’m not complaining!
I don’t know if I missed it, but did you mention Whitworth?
Does that sphereometer sensor work off of capacitance? I don’t think you mentioned exactly how that instrument compares the three points with the sensor in the middle. I’d love to try to make something like that for myself. Super interesting instrument and another great video in this awesome lapping series. 👍
You had some copper topped plates in a previous video. I'm wondering what they're used for?
Loving this series Tom! Thanks for sharing :)
Why do the rings on the one plate matter if all else is flat? Wouldn't they just act as another relief for film? Thanks for sharing another interesting and informative post Tom!
Hi, I thought the idea with the sphereometer was to null it out on a flat then make a measurement on the surface under test or are you saying the cast iron is flatter than the surface table ?..great fascinating stuff
I've watched the first three parts, I still don't know what use you have for flat lapping plates :-(
Would it be possible to use the 3 flat serrated plates to float a granite slab that’s larger than the plates? Say a 2ft x 3ft granite slab.
Can I ask Tom" what cut the round cast iron into 1' blocks. Will large cast round pieces surface grind ok.
Metal suppliers use large horizontal metal band saws generally.
I would think that rotating the disks gives a different abrasion on the outer edge than in the center of the disks because of weight distribution and definitely because of the greater motion at the edge than in the center.
Why would this process not make the cast iron two spherical surfaces, one convex the other concave?
This is why you use three plates. The third averages the wear.
Take your two plates. One is convex-raised center. One is concave-raised edge. Well call them A and B.
Now posit a 3rd plate that's equally convex to A. Call it C.
A on B = full surface contact. Nothing changes.
A on C = both are convex so the raised centers get the wear, the edge doesn't make contact. Both become flatter.
B on C = nearly full surface contact, but C is slightly flatter so it makes less contact in the center and slightly wears the edge of B making it flatter.
B on A - nearly full surface contact, but both are slightly flatter than the first pass.
C on A- both are convex so the raised centers get the wear, the edge doesn't make contact. Both become flatter.
C on B- nearly full surface contact, but C is slightly flatter so it makes less contact in the center and slightly wears the edge of B making it flatter.
OK!
Thanks for the process description! (Lying awake last night in bed I came to approximately the same conclusion and am thankful for the fullness of your response!)
I just started my Own machine shop and foot promoted to head "tool maker", they mean machinist. Are there any tips or websites I can go to get blueprints for making different set up pieces and tooling to save money for both and impress my bosses? You and Rob have amazing channels. I watch your guy's videos almost every day
You are very distracting😉
What a great idea for that test instrument you made I have hundreds literally hundreds of those kinematic Adjusters for optical assemblies that I used to service for the biomedical field I got stuck with a bunch of the inventory so there you go. I don't have the handles for him but you can adjust them with an allen wrench or make handles is easy enough
a Zygo will be much easier to use as its already “polished” than a lvdt?
Pictures that evaporating liquid on that plate by the pattern it's giving because as it hits that edge as the air goes over the sharp edges it's going to cause vortices that change the whole story if you could separate each block from the effects of the other blocks next to it that would be a different story
All very interesting, but I’m having trouble understanding the point and application. So ya have a couple flat disks, so?
Scott Carlon These can be used to lap other objects flat.
Optics, for one. Flatness is a reference tool like measurement for precision.
I'm curious to know how flat a 25inch square sheet of glass is, i've used glass/sand paper for many years to lap Cylinder Heads on Motorcycles. I now wonder if i've been adding a Concave or Convex surface.
The glass distorts while it's cooling but high quality float glass should be quite flat, more than adequate for flattening a cylinder head. Tom is talking about 50 millionths of an inch (0.000050 in or 0.00127 mm) in the video and he isn't finished polishing. I doubt that even a Formula 1 race team would go to that extreme. Head gaskets and sealants are also used to accommodate differential expansion of the engine components.
Dinxsy so long as it is done in a figure 8 pattern.
Very good thanks
I have one question can i chargr silicone carbide that are for automotive valve lapping.
I love de class you've gave. I searched for long time how the first precision instrument was made, and you showed. Can I do the same to make straight edgees e surfece plates? By the way I have to apologies about my english, I'm from Brasil and I'm learning.
Fresnel effect, if the angle of incidence is wide enough, even a brick is reflective.
I was wondering if you could hack a wireless drawing tablet (like a Wacom) to make a wireless spherometer. OTOH, that would be an expensive little project, and who knows how precise those sensors are (I guess they're made for pressure, not for travel)
That glass piece you have were did you get that