Yes, mechanical accuracy, flatness etc and temperature dependence is a rabbit hole one may never emerge from. Very good background and history lesson, thank you!
If you ever decide to give up your day job, you'd make a tremendous instructor. You take the time to research your subject matter before spouting off what you've found out. You also have a passion for the subject material. Let's face it, you've been part of several machine scraping classes and I'm sure that in those 5 days for each class, not everything is, or even can be, covered. I never tire of hearing you talk about these things. Keep it up! Hope your recovery continues to go well.
That's kind of what he did. He tried from teaching a&m and runs an educational website and UA-cam channel. He occasionally works at the Georgia museum of agriculture doing machine work and such. I would guess he considers this kind of thing his day job though.
If you dont need extreme accuracy, a piece of 3cm granite from your local granite countertop shop is great, pick the closest tightest grain structure you can find in the scrap 'black absolute' is one of the best but other colors work great. Ive use it for lapping and scraping parts in with no issues, ex exhaust manifolds, headder flanges, filter housing mating surfaces, carb bases, water outlets and such.
A friend of mine went to a company that made tombstones. He got one where they misspelled the name of the deceased, it was really cheap. He then lapped it in.
@@transmaster perfect scrap material for this purpose a mistake in a headstone cannot be fixed it must be replaced, theyd sell it to you for a song lol!
I'd be careful with glass plates, they are more flexible than you might think. Also the flatness isn't that great, I built a simple device for measuring flatness and tested a pane of glass, the indicator jumped all over the place even if it seemed to be flat. Anyway, I built a simple surface plate out of a broken granite tile (actually two, both halves were usable). The surface was somewhat ground already, but just to be sure I got some abrasive powder (silicon carbide) and lapped both plates onto eachother. The result turned out pretty good. It's not perfect, but I'd definitely trust it way more than a piece of glass.
Keith a very useful ready reckoner for Fahrenheit to Centigrade is that 61ºF = 16ºC and 82ºF = 28ºC and then just interpolate between the two sets of equivalents.
@@davidmam I think the conversion factor is actually 5/9 not 5/8. But therein lies the difficulty because it’s hard to remember! Otherwise I’d agree with you that the math isn’t too scary.
quick and dirty for C to F double the c and add 30 ,not completely accurate but near enough plus its a easy in the head one works the other way also - 30 / 2
The cast iron ones are also great because you can use them as a nice fixture plate for welding. Now how many people just cringed at the above sentence? :)
German brand Holex makes cast iron surface plates still, we have a large 1meter x 2 meter one brand new at work, thats the largest they make. its like 3x6 foot. the scraping job on it is just beautiful
Great information Keith, learned something new about the difference between those materials. Concerning the moving cart, use large wheeled castors that won't get hung up on small bits left on the floor. That thing has "top heavy" written all over it. Pretty sure you already thought of that but a reminder doesn't hurt.
Semi-related. We needed a 3x4 inspection surface for 120 pound ceramic objects to be sure the bottoms of the objects were flat within +/-0.06. Unglazed fired ceramic is extremely abrasive. I have purchased many surface plates both granite and, years ago, cast iron. Anything we used for a table would be highly abraded. So standard surface pates are not suitable. Granite surface plates would last only a few days. I searched for an old worn-out / damaged cast iron plate or machine base that could be repeatedly ground back to flat as it was worn from use. No such animal in the budget cost range. I resigned to building a cheap temporary table from steel. A local shop said they had a piece of WWII Sherman tank armor in their parking lot for years. They wanted it gone and at scrap steel prices. Could I use it for the inspection table if I altered some of the dimensions? Sure. I had the armor Blanchard ground both sides so it could be flipped over when one side wore out. Wow! After thousands of heavy parts dragged around on the table, the surface was still flat within +/- 0.0001 after 3 years. Did not have to flip it over and use the other ground surface. Absolutely amazing. I have seen cast iron and steel worn -0.01 after a few hundred heavy ceramic parts. Too bad the project is complete. Would like to keep that inspection table for the next future job.
Yeah no doubt. Armor plating is just that, armor. Hardened tool steel essentially. Ceramic will cut or abrade most anything. Even considering the plate was designed to stop ordnance, it's still impressive it stood up to 3 years of what amounts to the worst possible conditions outside of what it was made for. Pretty awesome.
Nice find. I was recently in a shop of an older gentleman who builds and repairs some high-end race cars, and he had a cast-iron surface plate for inspecting for damage and alignment. He said it was 10 feet by 20 feet. The side rails under the perimeter of the top looked to be about three feet tall. I can only imagine how heavy this thing had to be.
I watch Indians and Pakistanis do some ummm “interesting” repairs with welders and lathes….i would LOVE to see Keith comment objectively on those videos!!!
@@RASAllusion, Some of those videos are fun to watch, it’s almost unbelievable some of the stuff that they rebuild. They’re not afraid to work, that’s for sure.
and I see there that wonderful book... such a fantastic read about "how to start a machinery manufacturing company" without meaning to be so. It's worth noting also that another factor wher cast iron outperforms steel is vibration damping, which is another good reason to use it for building machine tools
We have a cast iron one at the shop I work at. Its 4’x6’. Hasnt been lapped in years and hasnt been used as as surface plate for a long time. Mostly used as a workbench now. We have a few smaller granite surface plates for inspection use.
I picked up a 16" x 16" cast iron plate with a wooden cover from an auction. I wasn't planning on buying it, but no one was interested and got it for next to nothing. As i'm a novice engineer, I have yet to used it in anger, however there's been several times when it's been useful for lapping on emery (had been using glass). I doubt it's accurate, but well within the tolerances I will be doing. I'm really hoping Adam finds something similar and Keith would be willing to do a swap, to keep a tool that gramps might have used in the family.
A great video Keith! So much information about the merits of cast iron versus granite surface plates. I've only room for a 12" x 12" granite in my tiny, tiny shop 7' X 5' yes that small in which I have a 12"x 19" lathe with a milling machine attachment. All the rest of my machinery is outside under cover lol. When I used to be a teacher we had a brand new 24"x 24" cast iron surface plate on a cast stand about 38" high and apart from myself on personal projects I only ever saw it used a couple of times by students. (My head of department taught the senior year examination students ) now it has probably been scrapped along with a 9" Viceroy Shaper, and a Tom Senior Horizontal mill that I was the only one to use. ( until I left of course) there were also 4 , 12"x and at least 24"lathes. One with a vertical milling attachment. Again I was the only one to use it in the 10 years I was there. All probably scrapped or just sold off. What a bloody waste!
Keith, If an object is high in the middle and low at the ends, it's referred to as hog. If its low in the middle and high at ends, it is referred to as sag. Bob
Thanks for the information. I have a small benchtop cast iron surface plate in my shop. I love it and use it all the time. Mine came from England, and is in great condition. I always kind of wondered how granite and cast stacked up against each other. Glad to see your recovery is going good. God bless you and your family!!!!
if I was doing a scrape job that had to really be close (say a P&W jig bore), I would always try to use a cast iron plate. I have always felt that cast iron rubs better than granite. Probably just me, but granite tends to smear the blue rather than simply hit the high spots. Still you can do quite well with granite if you know what you're after. Most people use way too much blue on the granite surface. Still for something really big there's usually no other way. I most always rubbed my strait edges off a granite plate that was cut to a certain contour (extremely important) but would be out of spec when measured. Most folks start off on a bad footing when they start a scrape job (or lap a granite plate). Really big ones are never moved, so you have no real choice in the matter. Anything smaller than a 6' x 9' was brought to my shop, and I'd let it set for two or three days. Cast iron is easier and you can start on it in 24 hours. A machine must be leveled and then tweaked in till the bottom axis is as strait as you can get it. I might add here that I usually did this with a Federal Electronic level, or at least a laser (the electronic level is much easier). Sometimes it takes the better part of a week to get this done as the machine will change everyday. I once had a Devlieg jig mill that took a solid three weeks on the x-axis alone. Still the numbers were a bitch before you started (.000020" in 12 feet). After you level the base everyday, you can start on the next slide and rough it in. Once it quits moving you can go to work. In the shop, I always had three or four strait edges to scrape, and several cast iron parallels. Angle plates can be nasty to do if done right. You need three angle plates to master off of, and this alone is rare. Yet they numbers are easy. Small ones (6"x 6") I had, but a big one I didn't. My master angle plates (a wooden box of five) were kept locked up and never used. My final check for squareness was with a 12" callibrated cylinder square.
granite plates can be very accurate, but the same accuracey can be had with a cast iron plate. Cast iron will wear much better than granite. Granite is also affected by temps and humidity. A lab grade plate with be flat with in a tenth of an arc second (.000025" in a foot of travel), but that figure is miss leading! You shoot the plate with an auto-collomater, and lastly a plain-o-cator. There are Federal specs for both systems and you use both on each plate. To really get a good plate (cast iron) you need three plates to rub the one you are scraping. That's where the term come refering to the three are masters. You never use a master for any other thing. The underside of both plates will show you three points it will set on. That is critical. You can't really rotate a granite plate to use when scraping another surface (say a table top). You mentioned having the surface plate ground. DON'T! Grinding creates an undue stress in the surface, plus imbed the grit from the wheel in the surface. I learned this the hard way. Always plain the surface. A milling operation will be just as bad as grinding. You said something about a 4 foot by 8 foot granite plate. Go with a 6 foot by 9 foot one. An 8 foot table will give you headaches trying to use something eight foot long on it. Noticed you have a grey granite plate. Those can be a bitch to lap! They seem much harder than the typical black plate. Pink is slightly softer, but also prone to hard veins running thru the granite. Those veins will show up as wide white lines. i used synthetic diamond dust most of the time, but real diamond is several times more expensive. Real diamond dust cuts a little faster, but you also must be careful. Just avoid putting something heavy on top the plate for lengthy periods of time (Cadillac Gauge comes to mind), as they'll warp it. Keep the plates covered with a wood top or even cardboard. I used Masonite with felt pad glued under it to allow a little air flow across the surface. Somebody else asked about a glass plate. I've seen one, and there's no way to lap it without making a mess. Just toss it. Plus glass is too fine causing a surface gauge to stick at the worst times.
I saw a 4x8 iron plate posted locally for scrap cost. I believe it was several tons and stood at bench height without legs. If I had room for it, I would own it for the simple fact they look cool. Until i have more room, my little bench top iron plate will do.
Great video Keith my dad was a Fitter at the same iron works as I served my time as a sparks . away I digress the fitting shop had the old fashioned oak block floor end grain up set on pitch ( nice for the legs and does not ding your tools ) the surface plate was some 20 foot by 12 foot and was constructed on a raised concrete slab, said to be six foot deep, the interesting thing was the cast iron top was made up of separate CI cubes about 1 * 1 * 1 foot , it was used to sett up for machining large casting for the items they assembled , the overhead crane had two blocks one 5 ton and the other 20 ton ( that's 2240 pounds ton ) , I never knew how good it was
Hmm, I still have the sink plug that came out of our granite counter top and I’ve been thinking about what to do with it. Now I at least have an idea. Great video.
absolutely!! use it for typical shop needs those are really good surface plates for us hobby shop machinists/mechanics. Ive used one for years and it works great!
I would like a surface plate, just a small one and I wondered about old cast iron ones, probably more than good enough for my work. What I was wondering though was about rust. If you cover the table and perhaps dont use it for months do they rust, how would you stop it and would it ruin the table?
Minor factoid. Mirrors. OPTICALLY Flat. I have 3, taken from Commercial Photocopiers. About 5\8" thickness Glass. Precision ground to be capable of magnification ... My Mom said they are nice.
Nice find! I was a scraper hand at a machine tool rebuilding shop in Cleveland Ohio in the 70's. My shop had a beautiful 4'x8' scraped cast iron plate, the master of the shop full of many smaller surface plates, straightedges, and squares. It was treated as such, not used for storage, and always clean. I have also used granite, but find a scraped surface a little better for spotting, the transfer of the blue marking medium for the piece being scraped, that's just my opinion.
My father was a Electrcal Engineer Inspector and his standard instruments were kept in the "Standards Room" never to leave at a constant temperature of 68F or 20C. Before he retired he took me on a visit to see all the amazing testing equipment they had. The most interesting for me was a 7KW lamp to imitate the sun and a Catapult Room with a sled on rails for acceleration measurements.
You forgot to mention the biggest advantage of granite plates: they have much better wear resistance! Cast iron is very soft and if you are going to put dozens of heavy parts on such a plate every day and slide them around to take your measurements then you will very soon find out that you now have a measureable valley in the middle of the plate while under the same load a granite plate would still largely maintain its flatness. Cast iron plates make for good master surfaces but if you want to use them for routine work then you will end up having to regularly check and scrape them. It was what they did 100 years ago but in the modern era of disposable tools and instruments it is just way too much maintenance for any industrial use. That is the main reason why noone uses big cast iron plates anymore and only the smallest ones are still somewhat popular because of the great advantage of being portable and comparatively lightweight.
When I was a 17 year old apprentice, I wiped down a cast iron surface plate with alcohol, I got yelled and immediately proceeded to wipe it down with WD40
No sir, you can cause a localized swelling on granite plate. Doall makes a small black granite gage block stone - used to remove positives. Iv'e use to stone down around such divots on black granite. They are known for being softer than the pink granite, for instance. Thanks for your informative comparison of reference surfaces.
I picked up a tablesaw wing from work, almost 2 feet by almost 3 feet. Cast Iron, and I don't know what it came off of. If I can get it to within 0.001, I'll be happy. I will not need much more tolerance than that. I work at a woodworking store that sells machines, and hardwood lumber. I repair (customer's stuff) and refurbish (consignment stuff.) I ALWAYS hit the top of a tablesaw, with a fine stone I have, just for that purpose. I see the same exact thing you have shown, where a burr was kicked up. I do NOT like sanding down the whole table, especially if there is a shiny patina there. That stone doesn't harm the patina. steve
This was really interesting. I had the chance to install some signs at an aircraft parts manufacturer a few months ago, and they used a granite plate as a reference but had an old Air Force 6ftx12ft cast iron surface plate for absolute accuracy. It was scraped to an overall flatness of 1050 (grade AA). For reference the highest grade I've ever heard of is a 1100 overall flatness, I don't know if it's even possible to make one better. They said that using the cast iron plate is required by the FAA for absolute accuracy in turbine parts, since they are machined down to a +/- .0005 threshold. I honestly thought cast iron was inferior until they explained that in a climate controlled room, it needed less maintenance and was easier to clean. The only downside is that it should never be moved once installed and flattened. even a grain of sand under the leg can throw it off over time. mainly because it deform the feet and cause raised edges that will make it unscrapable until the feet are remachined flat.
Friend's dad owns a "Machinery Rebuilding" place...OK, so they USED to rebuild A LOT. They now do more reselling and sourcing than anything. He has two MASSIVE surface plates, one is Cast Iron and it HAS to be at least 12 x 10. He said he got it out of the tank plant in the 80's when they no longer needed it. He also scored a MASSIVE (again, at least 12 x 10) Granite plate. I mean, i've NEVER seen something that big. He has had people look at the Cast Iron plate, but not the granite...at over 20 Tons the Granite plate is SUPER impractical for almost anybody anymore. He jokes that he's going to turn it into the family grave marker. I couldn't even imagine having that kind of hardware, even when I did small end machine building. I do want the PM lathe he has there, but his son constantly says "No, that's mine". His dad continues to say "I'm going to sell it to him if you don't get it the h3ll out of here". BTW: He's closing the shop this year or next. :( Maybe I'll go over and see what kind of goodies I can get. :)
I have a smaller 24x24”. I noticed in the Browne Sharpe Catalog that they have handles on them. One on each end. They way so much why would they have handles?
I am wondering why one cannot manufacture surface reference plates by use of a high-powered sideways scanning laser. It would vaporize material that is too high, and achieve an almost atomic flatness, over a large area. Of course, mass bends light, but on this scale, it would be unmeasurable. Or should I just patent the idea now?
I’m surprised to see you with two precision plates. One being granite and the other being cast iron, since I’ve never seen you make anything that required that kind of precision. All I ever hear you say is …”it’s not a critical dimension”. Or “this doesn’t have to be exact because it’s not critical.”
I bet you could double what you paid if you was to sell the plate to Adam just because of its Origin I was in engineering for 30 years and still perfected the cast iron over granite plates but I guess I am old school
At the 10 minutes of the video I noticed that it is mentioned. " the surface plae will crown or convex " . In my opinion he should have said that it will " crown or concave ", To crown or covex is the same direction. Crown or concave are opposite to each other.. Even though this is a fine video.
I don't buy the reason for changing to granite from cast iron. The USA wasn't so short of iron it needed to save a few tonnes for the war effort. Bear in mind the US built so many aircraft carriers it didn't have the manpower to operate them. No, the reason granite was used is that it's simply far better than cast iron and during WW2 huge technical advances were being made in high precision engineering such that better surface plates were needed.
Having a small home shop I cheat and use my cast iron table saw surface. I found this flatter than the granite "scrap". I have also used a wing of my 8" jointer for longer items. For the very few times, I have needed an accurate surface this has saved the day.
Size for size the granite will weigh less than a cast iron plate. It's not often noted, but granite and aluminium are nearly identical in density. Of course, granite is far more rigid than aluminium.
I've cleaned the granite plates with various cleaners from the manufacturers (some with lanolin! ), but how do you clean a cast iron plate? Also, do cast iron plates have problems with magnetism? I've seen some pretty large degaussers but nothing big enough for your surface plate. Looking forward to you returning to that stoker engine project!
You can be certain I would never take a cast iron surface plate for granite...lol! Shameless pun out of the way I might add that granite plates come in different grades, and some shops even require them to be calibrated periodically.
I love the machining videos you produce, but I'm never disappointed with a talky one. Your enthusiasm is infectious, your teaching style engaging and your subject matter always of interest. Nice purchase.
Working at Kearney and Trecker I can attest to the fact steel weldments were a different animal. Cast iron was more stable, as machines would heat up tolerances would change with the steel til it leveled out.
Temperature is a constant that effects a lot of measurements,the set of gage blocks are most accurate at 68*f according to the information on the sheet on the box
Enjoyed the video nice to know why there not a lot of cast iron surface plate Around last place I worked at they put it in a storage build , had stuff piled on it
I prefer granite to cast iron for several reasons but mainly bc one they don't rust and two if something is accidentally dropped onto it a cast iron which could leave a raised edge/high spot whereas the granite might chip but there won't be a raised edge. Edit* Of course you talked about my main issues LOL
How interesting that cast iron maintains flatness better than granite over temperature changes! I always thought of granite as being immune to thermal variations, the fact that it isn’t is really interesting to me. (Not that I’ll ever do anything that even a grade B plate wouldn’t be massive overkill for, but I’m a measurement geek, so so this sort of thing is fascinating to me 😁) Thanks for a great video as always!
Quite so. Even moving a granite to a different location on your shop floor, or jacks under the plate require calibration to assure plate is still to desired flatness after relaxing into new location. We're talking millionths here. Wouldn't matter for what I was doing in my shop; mattered to the aerospace shops I've worked in.
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Yes, mechanical accuracy, flatness etc and temperature dependence is a rabbit hole one may never emerge from. Very good background and history lesson, thank you!
If you ever decide to give up your day job, you'd make a tremendous instructor. You take the time to research your subject matter before spouting off what you've found out. You also have a passion for the subject material. Let's face it, you've been part of several machine scraping classes and I'm sure that in those 5 days for each class, not everything is, or even can be, covered. I never tire of hearing you talk about these things. Keep it up! Hope your recovery continues to go well.
That's kind of what he did. He tried from teaching a&m and runs an educational website and UA-cam channel. He occasionally works at the Georgia museum of agriculture doing machine work and such. I would guess he considers this kind of thing his day job though.
If you dont need extreme accuracy, a piece of 3cm granite from your local granite countertop shop is great, pick the closest tightest grain structure you can find in the scrap 'black absolute' is one of the best but other colors work great. Ive use it for lapping and scraping parts in with no issues, ex exhaust manifolds, headder flanges, filter housing mating surfaces, carb bases, water outlets and such.
For lapping components like carb mounting faces, oil pump faces, small heads, etc I just use a plate of glass.
A friend of mine went to a company that made tombstones. He got one where they misspelled the name of the deceased, it was really cheap. He then lapped it in.
Tempered glass works in a pinch too.
@@transmaster perfect scrap material for this purpose a mistake in a headstone cannot be fixed it must be replaced, theyd sell it to you for a song lol!
I'd be careful with glass plates, they are more flexible than you might think. Also the flatness isn't that great, I built a simple device for measuring flatness and tested a pane of glass, the indicator jumped all over the place even if it seemed to be flat.
Anyway, I built a simple surface plate out of a broken granite tile (actually two, both halves were usable). The surface was somewhat ground already, but just to be sure I got some abrasive powder (silicon carbide) and lapped both plates onto eachother. The result turned out pretty good. It's not perfect, but I'd definitely trust it way more than a piece of glass.
Keith a very useful ready reckoner for Fahrenheit to Centigrade is that 61ºF = 16ºC and 82ºF = 28ºC and then just interpolate between the two sets of equivalents.
C = (F-32)*5/8
F=8/5*C +32
Straightforward conversion every schoolboy knows
@David Martin actually it's 9/5 and 5/9, but you're right otherwise.
@@davidmam I think the conversion factor is actually 5/9 not 5/8. But therein lies the difficulty because it’s hard to remember! Otherwise I’d agree with you that the math isn’t too scary.
quick and dirty for C to F double the c and add 30 ,not completely accurate but near enough plus its a easy in the head one works the other way also - 30 / 2
Negative 40 is negative 40, in both.
steve
The cast iron ones are also great because you can use them as a nice fixture plate for welding.
Now how many people just cringed at the above sentence? :)
One option I didn’t hear; portable propane shop griddle. You’d have the most precise pancakes around.
Nice score! I use my cast plate for most of my work and only use my granite for the fine stuff.
Nice to see you coming along, Keith. The lesson on surface plates - Most informative and interesting.
German brand Holex makes cast iron surface plates still, we have a large 1meter x 2 meter one brand new at work, thats the largest they make. its like 3x6 foot. the scraping job on it is just beautiful
Great information Keith, learned something new about the difference between those materials. Concerning the moving cart, use large wheeled castors that won't get hung up on small bits left on the floor. That thing has "top heavy" written all over it. Pretty sure you already thought of that but a reminder doesn't hurt.
Semi-related. We needed a 3x4 inspection surface for 120 pound ceramic objects to be sure the bottoms of the objects were flat within +/-0.06. Unglazed fired ceramic is extremely abrasive. I have purchased many surface plates both granite and, years ago, cast iron. Anything we used for a table would be highly abraded. So standard surface pates are not suitable. Granite surface plates would last only a few days. I searched for an old worn-out / damaged cast iron plate or machine base that could be repeatedly ground back to flat as it was worn from use. No such animal in the budget cost range. I resigned to building a cheap temporary table from steel. A local shop said they had a piece of WWII Sherman tank armor in their parking lot for years. They wanted it gone and at scrap steel prices. Could I use it for the inspection table if I altered some of the dimensions? Sure. I had the armor Blanchard ground both sides so it could be flipped over when one side wore out.
Wow! After thousands of heavy parts dragged around on the table, the surface was still flat within +/- 0.0001 after 3 years. Did not have to flip it over and use the other ground surface. Absolutely amazing. I have seen cast iron and steel worn -0.01 after a few hundred heavy ceramic parts.
Too bad the project is complete. Would like to keep that inspection table for the next future job.
Yeah no doubt. Armor plating is just that, armor. Hardened tool steel essentially. Ceramic will cut or abrade most anything. Even considering the plate was designed to stop ordnance, it's still impressive it stood up to 3 years of what amounts to the worst possible conditions outside of what it was made for. Pretty awesome.
Nice find. I was recently in a shop of an older gentleman who builds and repairs some high-end race cars, and he had a cast-iron surface plate for inspecting for damage and alignment. He said it was 10 feet by 20 feet. The side rails under the perimeter of the top looked to be about three feet tall. I can only imagine how heavy this thing had to be.
Heavy enough to influence the orbit of the earth based on where it is sitting, I reckon. That's just plain huge.
Until I started watching your videos I had never heard of surface plates.
Good to see you still crankin out the videos!!!! Go man, go.
I watch Indians and Pakistanis do some ummm “interesting” repairs with welders and lathes….i would LOVE to see Keith comment objectively on those videos!!!
@@RASAllusion, Some of those videos are fun to watch, it’s almost unbelievable some of the stuff that they rebuild. They’re not afraid to work, that’s for sure.
Well Thank You Keith for the demonstration of the different surface plate. Good topic and good video
Keith, very much enjoyed this ‘lecture’. Thank you …
and I see there that wonderful book... such a fantastic read about "how to start a machinery manufacturing company" without meaning to be so. It's worth noting also that another factor wher cast iron outperforms steel is vibration damping, which is another good reason to use it for building machine tools
Always wondered about temperature change and stability.
That book is listed, used, for $500 to $1000! Craziness. Moore Tool sells it for $150. No idea why the used market is so inflated.
We have a cast iron one at the shop I work at. Its 4’x6’. Hasnt been lapped in years and hasnt been used as as surface plate for a long time. Mostly used as a workbench now. We have a few smaller granite surface plates for inspection use.
Thanks for sharing some very good information. I usually learn something with each episode you publish.
I picked up a 16" x 16" cast iron plate with a wooden cover from an auction. I wasn't planning on buying it, but no one was interested and got it for next to nothing. As i'm a novice engineer, I have yet to used it in anger, however there's been several times when it's been useful for lapping on emery (had been using glass). I doubt it's accurate, but well within the tolerances I will be doing.
I'm really hoping Adam finds something similar and Keith would be willing to do a swap, to keep a tool that gramps might have used in the family.
Thanks - I learned something today!
Book arrived safely in johannesburg on 27/1/2023. Most expensive book i have ever purchased!
Great content. Thanks for posting, I learned quite a bit
60°F equals 15.8°C. In Germany, a temperature of 20°C (68.0°F) is considered the reference temperature (Maßbezugstemperatur).
KEITH GREAT FIND, GLAD YOU ARE DOING FINE, TELL ALL HELLO...SEE YOU WHEN...
sell it to Adam he has been spending money like a drunken sailor anyway
A great video Keith! So much information about the merits of cast iron versus granite surface plates. I've only room for a 12" x 12" granite in my tiny, tiny shop 7' X 5' yes that small in which I have a 12"x 19" lathe with a milling machine attachment. All the rest of my machinery is outside under cover lol. When I used to be a teacher we had a brand new 24"x 24" cast iron surface plate on a cast stand about 38" high and apart from myself on personal projects I only ever saw it used a couple of times by students. (My head of department taught the senior year examination students ) now it has probably been scrapped along with a 9" Viceroy Shaper, and a Tom Senior Horizontal mill that I was the only one to use. ( until I left of course) there were also 4 , 12"x and at least 24"lathes. One with a vertical milling attachment. Again I was the only one to use it in the 10 years I was there. All probably scrapped or just sold off. What a bloody waste!
Keith,
If an object is high in the middle and low at the ends, it's referred to as hog. If its low in the middle and high at ends, it is referred to as sag.
Bob
Thanks for the information. I have a small benchtop cast iron surface plate in my shop. I love it and use it all the time. Mine came from England, and is in great condition. I always kind of wondered how granite and cast stacked up against each other. Glad to see your recovery is going good. God bless you and your family!!!!
if I was doing a scrape job that had to really be close (say a P&W jig bore), I would always try to use a cast iron plate. I have always felt that cast iron rubs better than granite. Probably just me, but granite tends to smear the blue rather than simply hit the high spots. Still you can do quite well with granite if you know what you're after. Most people use way too much blue on the granite surface. Still for something really big there's usually no other way. I most always rubbed my strait edges off a granite plate that was cut to a certain contour (extremely important) but would be out of spec when measured.
Most folks start off on a bad footing when they start a scrape job (or lap a granite plate). Really big ones are never moved, so you have no real choice in the matter. Anything smaller than a 6' x 9' was brought to my shop, and I'd let it set for two or three days. Cast iron is easier and you can start on it in 24 hours. A machine must be leveled and then tweaked in till the bottom axis is as strait as you can get it. I might add here that I usually did this with a Federal Electronic level, or at least a laser (the electronic level is much easier). Sometimes it takes the better part of a week to get this done as the machine will change everyday. I once had a Devlieg jig mill that took a solid three weeks on the x-axis alone. Still the numbers were a bitch before you started (.000020" in 12 feet). After you level the base everyday, you can start on the next slide and rough it in. Once it quits moving you can go to work.
In the shop, I always had three or four strait edges to scrape, and several cast iron parallels. Angle plates can be nasty to do if done right. You need three angle plates to master off of, and this alone is rare. Yet they numbers are easy. Small ones (6"x 6") I had, but a big one I didn't. My master angle plates (a wooden box of five) were kept locked up and never used. My final check for squareness was with a 12" callibrated cylinder square.
That plate would make a beautiful coffee table for coffee table books……..like Foundations of Mechanical Accuracy.
Nice! Though the misses might not agree
@@zHxIxPxPxIxEz I’ll let her put some flowers on it as well.
granite plates can be very accurate, but the same accuracey can be had with a cast iron plate. Cast iron will wear much better than granite. Granite is also affected by temps and humidity. A lab grade plate with be flat with in a tenth of an arc second (.000025" in a foot of travel), but that figure is miss leading! You shoot the plate with an auto-collomater, and lastly a plain-o-cator. There are Federal specs for both systems and you use both on each plate. To really get a good plate (cast iron) you need three plates to rub the one you are scraping. That's where the term come refering to the three are masters. You never use a master for any other thing. The underside of both plates will show you three points it will set on. That is critical. You can't really rotate a granite plate to use when scraping another surface (say a table top).
You mentioned having the surface plate ground. DON'T! Grinding creates an undue stress in the surface, plus imbed the grit from the wheel in the surface. I learned this the hard way. Always plain the surface. A milling operation will be just as bad as grinding. You said something about a 4 foot by 8 foot granite plate. Go with a 6 foot by 9 foot one. An 8 foot table will give you headaches trying to use something eight foot long on it. Noticed you have a grey granite plate. Those can be a bitch to lap! They seem much harder than the typical black plate. Pink is slightly softer, but also prone to hard veins running thru the granite. Those veins will show up as wide white lines. i used synthetic diamond dust most of the time, but real diamond is several times more expensive. Real diamond dust cuts a little faster, but you also must be careful. Just avoid putting something heavy on top the plate for lengthy periods of time (Cadillac Gauge comes to mind), as they'll warp it. Keep the plates covered with a wood top or even cardboard. I used Masonite with felt pad glued under it to allow a little air flow across the surface.
Somebody else asked about a glass plate. I've seen one, and there's no way to lap it without making a mess. Just toss it. Plus glass is too fine causing a surface gauge to stick at the worst times.
I saw a 4x8 iron plate posted locally for scrap cost. I believe it was several tons and stood at bench height without legs.
If I had room for it, I would own it for the simple fact they look cool. Until i have more room, my little bench top iron plate will do.
Glad you're feeling better, sir.
Thank you Keith. This was great information and well presented. It also has an "Aboms, eat your heart out" bonus on this beautiful plate!!
Great video Keith
my dad was a Fitter at the same iron works as I served my time as a sparks . away I digress the fitting shop had the old fashioned oak block floor end grain up set on pitch ( nice for the legs and does not ding your tools ) the surface plate was some 20 foot by 12 foot and was constructed on a raised concrete slab, said to be six foot deep, the interesting thing was the cast iron top was made up of separate CI cubes about 1 * 1 * 1 foot , it was used to sett up for machining large casting for the items they assembled , the overhead crane had two blocks one 5 ton and the other 20 ton ( that's 2240 pounds ton ) , I never knew how good it was
I was thinking Adams Grandfather could have used it also. And another advantage is Granit doesn't rust.
Hmm, I still have the sink plug that came out of our granite counter top and I’ve been thinking about what to do with it. Now I at least have an idea. Great video.
absolutely!! use it for typical shop needs those are really good surface plates for us hobby shop machinists/mechanics. Ive used one for years and it works great!
I would like a surface plate, just a small one and I wondered about old cast iron ones, probably more than good enough for my work. What I was wondering though was about rust. If you cover the table and perhaps dont use it for months do they rust, how would you stop it and would it ruin the table?
Great video! If one wants a welding table, two words... ACORN PLATE!!
You never really gave me the WHY but THANKS for the vid
Minor factoid.
Mirrors. OPTICALLY Flat.
I have 3, taken from Commercial Photocopiers.
About 5\8" thickness Glass.
Precision ground to be capable of magnification ...
My Mom said they are nice.
An advantage of cast iron is ...
It's magnetic
Some times pretty handy for measurement
The last about 15 videos are a disgrace to the channel. You're posting fillers.
Nice find! I was a scraper hand at a machine tool rebuilding shop in Cleveland Ohio in the 70's. My shop had a beautiful 4'x8' scraped cast iron plate, the master of the shop full of many smaller surface plates, straightedges, and squares. It was treated as such, not used for storage, and always clean. I have also used granite, but find a scraped surface a little better for spotting, the transfer of the blue marking medium for the piece being scraped, that's just my opinion.
Very interesting. I wouldn’t have guessed that iron was better.
My father was a Electrcal Engineer Inspector and his standard instruments were kept in the "Standards Room" never to leave at a constant temperature of 68F or 20C. Before he retired he took me on a visit to see all the amazing testing equipment they had. The most interesting for me was a 7KW lamp to imitate the sun and a Catapult Room with a sled on rails for acceleration measurements.
You forgot to mention the biggest advantage of granite plates: they have much better wear resistance! Cast iron is very soft and if you are going to put dozens of heavy parts on such a plate every day and slide them around to take your measurements then you will very soon find out that you now have a measureable valley in the middle of the plate while under the same load a granite plate would still largely maintain its flatness. Cast iron plates make for good master surfaces but if you want to use them for routine work then you will end up having to regularly check and scrape them. It was what they did 100 years ago but in the modern era of disposable tools and instruments it is just way too much maintenance for any industrial use. That is the main reason why noone uses big cast iron plates anymore and only the smallest ones are still somewhat popular because of the great advantage of being portable and comparatively lightweight.
Surprised it's not on 3 points. Bench plate maybe?
I am needing help or someone to help me upgrade a porter 300c 20 inch jointer...any recomendations?
Could you share your preferred method for preventing rust on on things like the cast iron surface plate?
When I was a 17 year old apprentice, I wiped down a cast iron surface plate with alcohol, I got yelled and immediately proceeded to wipe it
down with WD40
No sir, you can cause a localized swelling on granite plate. Doall makes a small black granite gage block stone - used to remove positives. Iv'e use to stone down around such divots on black granite. They are known for being softer than the pink granite, for instance.
Thanks for your informative comparison of reference surfaces.
I picked up a tablesaw wing from work, almost
2 feet by almost 3 feet. Cast Iron, and I don't
know what it came off of. If I can get it to
within 0.001, I'll be happy. I will not need much
more tolerance than that.
I work at a woodworking store that sells
machines, and hardwood lumber. I repair
(customer's stuff) and refurbish (consignment
stuff.) I ALWAYS hit the top of a tablesaw, with
a fine stone I have, just for that purpose. I see
the same exact thing you have shown, where a
burr was kicked up. I do NOT like sanding down
the whole table, especially if there is a shiny
patina there. That stone doesn't harm the patina.
steve
This was really interesting. I had the chance to install some signs at an aircraft parts manufacturer a few months ago, and they used a granite plate as a reference but had an old Air Force 6ftx12ft cast iron surface plate for absolute accuracy. It was scraped to an overall flatness of 1050 (grade AA). For reference the highest grade I've ever heard of is a 1100 overall flatness, I don't know if it's even possible to make one better. They said that using the cast iron plate is required by the FAA for absolute accuracy in turbine parts, since they are machined down to a +/- .0005 threshold. I honestly thought cast iron was inferior until they explained that in a climate controlled room, it needed less maintenance and was easier to clean. The only downside is that it should never be moved once installed and flattened. even a grain of sand under the leg can throw it off over time. mainly because it deform the feet and cause raised edges that will make it unscrapable until the feet are remachined flat.
Friend's dad owns a "Machinery Rebuilding" place...OK, so they USED to rebuild A LOT. They now do more reselling and sourcing than anything. He has two MASSIVE surface plates, one is Cast Iron and it HAS to be at least 12 x 10. He said he got it out of the tank plant in the 80's when they no longer needed it. He also scored a MASSIVE (again, at least 12 x 10) Granite plate. I mean, i've NEVER seen something that big. He has had people look at the Cast Iron plate, but not the granite...at over 20 Tons the Granite plate is SUPER impractical for almost anybody anymore. He jokes that he's going to turn it into the family grave marker. I couldn't even imagine having that kind of hardware, even when I did small end machine building.
I do want the PM lathe he has there, but his son constantly says "No, that's mine". His dad continues to say "I'm going to sell it to him if you don't get it the h3ll out of here". BTW: He's closing the shop this year or next. :( Maybe I'll go over and see what kind of goodies I can get. :)
Wish the book could be obtained for a sane price (it's >$500 on Amazon right now)
I have a smaller 24x24”. I noticed in the Browne Sharpe Catalog that they have handles on them. One on each end. They way so much why would they have handles?
It would be interesting to see you check that old girl with your granite surface plate! Cheers! 🍻👍😊
I am wondering why one cannot manufacture surface reference plates by use of a high-powered sideways scanning laser.
It would vaporize material that is too high, and achieve an almost atomic flatness, over a large area.
Of course, mass bends light, but on this scale, it would be unmeasurable.
Or should I just patent the idea now?
Keith, your voice sounds a bit different, a little - um - more treble and less bass. Are you doing okay? Hope to see you at the Bar-Z. Jon
I’m surprised to see you with two precision plates. One being granite and the other being cast iron, since I’ve never seen you make anything that required that kind of precision. All I ever hear you say is …”it’s not a critical dimension”. Or “this doesn’t have to be exact because it’s not critical.”
I think most people today take surface plates for granite.
Thanks Keith you are looking good . Hi from the land down under
Don’t take cast iron for granite
Why do you call the granite one a surface plate? Surely that is a surface table? I have a cast iron surface table. A plate is hand held I thought?
I bet you could double what you paid if you was to sell the plate to Adam just because of its Origin
I was in engineering for 30 years and still perfected the cast iron over granite plates but I guess I am old school
At the 10 minutes of the video I noticed that it is mentioned. " the surface plae will crown or convex " . In my opinion he should have said that it will " crown or concave ",
To crown or covex is the same direction. Crown or concave are opposite to each other..
Even though this is a fine video.
I don't buy the reason for changing to granite from cast iron. The USA wasn't so short of iron it needed to save a few tonnes for the war effort. Bear in mind the US built so many aircraft carriers it didn't have the manpower to operate them. No, the reason granite was used is that it's simply far better than cast iron and during WW2 huge technical advances were being made in high precision engineering such that better surface plates were needed.
Having a small home shop I cheat and use my cast iron table saw surface. I found this flatter than the granite "scrap". I have also used a wing of my 8" jointer for longer items. For the very few times, I have needed an accurate surface this has saved the day.
Size for size the granite will weigh less than a cast iron plate. It's not often noted, but granite and aluminium are nearly identical in density. Of course, granite is far more rigid than aluminium.
Hiya Keith
Sadly, this book appears to be extinct.
If you wring those two plates together you'll never get them apart. ;)
I've cleaned the granite plates with various cleaners from the manufacturers (some with lanolin! ), but how do you clean a cast iron plate? Also, do cast iron plates have problems with magnetism? I've seen some pretty large degaussers but nothing big enough for your surface plate. Looking forward to you returning to that stoker engine project!
If you are going to put it on casters then make sure it’s chained down when Adam visits 😂
The book is available on order from Moore Tools for $150 USD.
You can be certain I would never take a cast iron surface plate for granite...lol!
Shameless pun out of the way I might add that granite plates come in different grades, and some shops even require them to be calibrated periodically.
I scrolled all the way down here looking for this pun. You made my day. TYVM
@@surlyogre1476 sorry I had too 😆 I even told my wife.
You should restore it and give it to Adam booth, it would mean the world to him.
So the big take away is that if I can get my hands on a good ol' cast iron surface plate, I should take it for granite?
I love the machining videos you produce, but I'm never disappointed with a talky one. Your enthusiasm is infectious, your teaching style engaging and your subject matter always of interest. Nice purchase.
Very well stated !!
Why not put a sheet of plywood over the granite plate to protect it from getting damaged ?
Welding table! I suppose he dumps in his den as well...
Working at Kearney and Trecker I can attest to the fact steel weldments were a different animal. Cast iron was more stable, as machines would heat up tolerances would change with the steel til it leveled out.
Thats a griddle. Cook me some eggs and bacon
Welding table!!!??????? OMG NOOOOOOO!!!!!
Magnetic fixture and guages on cast iron.
Keith saw something big and iron and had to have it.
Temperature is a constant that effects a lot of measurements,the set of gage blocks are most accurate at 68*f according to the information on the sheet on the box
One advantage of the cast iron plate is that you can clamp instruments with magnetic bases to it.
Enjoyed the video nice to know why there not a lot of cast iron surface plate
Around last place I worked at they put it in a storage build , had stuff piled on it
And it is still battleship grey :)
I prefer granite to cast iron for several reasons but mainly bc one they don't rust and two if something is accidentally dropped onto it a cast iron which could leave a raised edge/high spot whereas the granite might chip but there won't be a raised edge.
Edit* Of course you talked about my main issues LOL
rust is indeed a problem for most of us home shops!! so yea granite for me too!
15.556c
Good to see you Keith.
It looks like you're starting to round the corner with your health.
Gettin' old ain't for sissies......
Regards,
Duck
Is that the Diresta band saw I see back there?
I'm totally on-board with dropping granite surface plates on my enemies.
-40 C equals -40 F Canada eh!
How interesting that cast iron maintains flatness better than granite over temperature changes!
I always thought of granite as being immune to thermal variations, the fact that it isn’t is really interesting to me. (Not that I’ll ever do anything that even a grade B plate wouldn’t be massive overkill for, but I’m a measurement geek, so so this sort of thing is fascinating to me 😁)
Thanks for a great video as always!
Quite so. Even moving a granite to a different location on your shop floor, or jacks under the plate require calibration to assure plate is still to desired flatness after relaxing into new location. We're talking millionths here. Wouldn't matter for what I was doing in my shop; mattered to the aerospace shops I've worked in.