A Different Way to Repair a Worn Lead Screw
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- Опубліковано 26 вер 2024
- While we were refreshing our old Bridgeport mill, we discovered a lead screw that was pretty beat up and in need of replacement. But this is a machine shop - so instead of buying a new one, we discovered it would be faster, cheaper, and more fun to make it ourselves.
Check out our video series on the Bridgeport mill starting here:
• Bridgeport Mill Refres...
Instagram: @vanovercustoms
Kyle, I like what you are showing. My understanding of using telescoping gages shown to me by an old timer (my grandfather) is to insert the gage at a slight angle, tighten the anvil just enough to hold it , and slowly rock the gage til you feel it clear the diameter. This is much more accurate.
You are right since the video I have updated my technique
Michael,you are absolutely right. That is the most reliable method of getting an accurate interpretation from a telescopic bore gauge. This method was taught to me by the guys in the toolroom during my apprenticeship years.(that is a very long time ago😂)
Taper pins are another great way in this situation.
Totally legit repair. There were some cool things to lean here despite the fact you could have turned it down from a larger screw. Anything you do on that gorgeous Colchester is worth my time.
Thank you sir
Nice work! As you said, there are many ways to make that repair.
But, I'm wondering about wearing gloves around revolving spindles?
Do it at your own risk
I almost lost my hands on a lathe and emery paper with gloves on.
Totally legit fix.
There are always more ways than one to skin the cat.
It’s as accurate and strong as new or a turned down acme screw as others preferred.
Suspect there were features on the screw you didn’t want to have to perfectly recreate - so this gave you the accuracy you wanted without having to do so.
Only suggestion: no reason at all not to have heated the female before press fit.
Simple torch woulda sufficed.
That would have bought some insurance against galling when pressing.
Your method worked fine in the end - but just a little torch work might have bought you some safety margin.
Thanks for posting.
Agreed on torch thanks for comment
Made in a day, labour, $100 hr +, =$800, + part cost, that $300 is looking pretty sweet now.😉
However, GREAT REPAIR and an EXCELLENT teaching video on a repair, well done and thank you.
Very true! But done on a day off for fun. Priceless
well done, I learned a ton, even better when you broke the tap and worked it out, these little things get edited out I bet of so many videos, thanks again.@@VanoverMachineAndRepair
@@stevefrench2276 absolutely
so it took you a hole day what do you charge for a days work ? in my place of work a day is 800+
Around that depends on work. Also this video was a year old it’s a little different these days
As your ends are already press fit, I would stick to a quarter inch hole for my spring pin.
Good videography and no music (noise). I like it!
Subscribed.
Thank you
29:25
Gloves with the lathe on, near a thread with a HUGE open burr on the end, just insane.
AND wrapping the emery cloth all the way around the work, hoo baby.
You live pretty dangerously!
Indeed I do
This would be a good application to use a tapered pin rather than split pin. Having a few common size tapered reamers is a good investment.
Yea I agree. At the time I was going to do it but since I have no tapered pins or reamers I didn’t want to start collecting those items for this project. One day
Once you've reached the maximum travel of the carriage, you can measure the remaining length using a caliper.
Great tip
you would be surprised by how many medium size machine shops rely on a tape measure for measuring long parts like that to hold a .030 tolerance.
Yeah I believe it
why didn't you use coolant while drilling the shaft or while boring it out on the lathe? I wonder if you could have changed all the threads on the orginal part to match the worn out section and then created a new brass/bronze nut to match? thinking outside the box...
No coolant is for video. It’s easier to see on video without all the smoke
1. This video is dope. Thank you for the long format.
2. Lots of comments around here with, “you should’a / could’a”, really ignore (or, under value) the relevance of heat treatments.
3. This video is pro, and you’re cool. New subscriber.
Thanks man
Watched. I've had issues with blind press fits due to air compression pockets. A machinist taught me how to add a relief channel to a turned part. He taught me to mount the pin section iin the lathe and then use an external thread point to make a shallow spiral groove in the pin surface, actually just a smidge more than a scratch pass to provide an air channel. The pitch doesn't really matter but you should pick very coarse one so that the spiral leaves a lot of undisturbed surface. This allows the air to escape but doesn't weaken the shaft or require a relief hole somewhere else. Works great. I also tried same technique to create oil distribution channels on a shaft that ran in a plain bronze bearing to which I added an oiling fitting. Not quite as nice as grooves in the bearing but it worked. .
Ok good to know I have don’t lots of presses like this with no issue but I see the logic, thanks.
@@VanoverMachineAndRepair He also told me I could also mill barely-there flat along the length of the pin that's going to be press fitted into a blind hole.
@@kentswan3230 You can also get the same anti compression effect by simply filing a small flat onto the press fit male part. Decompression groove is also essential when assembling light press fits with Loctite retaining compound adhesive.
@@howardosborne8647 True enough and simpler than milling or grinding a flat depending on the press fit pin hardness. thanks for the tip re Loctite as I haven't tried that but will. What Locktite formula do you normally use when for this?
I think you did great man .. I watched Abom79 repair a lead screw and he went about it different but yours is just as nice and just as strong .. Just subbed up to your channel ..👍👍
Thanks man I appreciate it
Hi, I have to do a similar repair and was considering options - as a total amateur I was thinking of buying a thread rod as you have done. But rather sleeving it I was going to buy a threaded length the same as the original but machine down the rod to form the ends. Appreciate your input?
It depends on the end features, hardened shaft requirements etc. The repair in the video is probably less work overall all considered.
I have a little experience under my belt I think I would do it this way as well. Some of those diameters on the end have lowish tolerances. Not terribly difficult but if you goof you might be in trouble. I did this on my cross slide feed screw except I threaded both sides and used a grub screw covered in locktite to join them. Worked great
All the methods who are possible are the right one if you get the result right. I did think of doing the ends in a lathe but then I notice the fine and maybe harden face at the ends and realize this method shown here is a smart one. Easy and quick fix..... and Elcheapo.
Indeed
While I haven’t checked out McMstr-Carr for thread lengths of rod, I wonder about the tolerance of the lead of the thread is for the cheaper threaded rods used? Lead and feed screws are usually around .005 over 12”. One reason ball screws came into use. I would think if the screws are run on cnc, lead could be held closer, albeit at higher cost. In this situation, as someone mentioned, digital readout would cover any length problems but still allow for a cheaper repair. Outside of that, nicely done.
Thank you
Beautiful machine man
Thank you
I did much the same thing as an apprentice 40 years ago for our Cincinnati mill. Here in new Zealand it wasnt so easy to get an acme threaded rod or my boss was to tight to buy it so I had to cut the new lead screw thread myself in the old Colchester master (If I remember correctly) I chose this way to repair as one end had a spline and I had no means to replicate it. Nice job
Thank you!
Nice work, but I don't get two things. One, why not get a slightly longer threaded rod and machine those two ends fully? It looked like just a bearing journal and a thread. Maybe a keyway. Overall seems like similar amount of work and you would've had the bridgeport usable while working on the new shaft. Second, is leadscrew wear really that important in a manual mill to fix it? I have a horizontal milling machine that has about 20 thou of backlash in the middle of X travel with the nut set to be tight on the ends. As long as I know it's there it's not causing me any issues. (I have to lock other axes and snug table lock bolts if I want to climb mill anyway). So I fail to see why go to the effort of fixing it, especially that you're planning to replace it with a ball screw. The only reason I can think of, is if you plan to do a cnc conversion with the leadscrew, use it for a while and then fit balls crews. Backlash is definitely not ideal for cnc, but in a manual mill it is entirely manageable.
Have you ever done contour milling on a manual milling machine?
Try it with a 20 thousand slack on your lead screw and you will get the proper answer! In my world, the tighter the better!
Yeah your right to a point. It was so bad that under a heavy cut the cutter would occasionally catch and the table would jump. That’s due to excessive backlash. Also i use the full range of motion on my mill and I would rather it be consistent from end to end and not tight on ends. Lastly the shaft was to long to fit between my tail stick and headstock and would not clear my spindle bore. Plus looking to try a repair like this for fun.
Nice repair. I would have used taper pins, but nice job. I roll pins on tow handles and they break a lot … but are easy to access.
So far so good
Looks like you did a very good job it looks like it turned out very good so keep up the good work and I will keep watching god bless
Thank you
I enjoyed the repair too. I am a word nerd as well as a machine repair technician. I insisted that my repair staff use correct terminology. So I cringed every time you called the screw a shaft and when you called the split nut a bushing.
Your bearing splitter arbor press setup was a clever idea. I think that I would have flipped the splitter so that press load would be against a square shoulder.
Good points
I hope you’re doing well! I have a couple of ideas for an auto disengaging lead screw nut that I’d like to share with you.
Segmented Nut Design: This would involve the nut being split into 2 or 4 pieces, held together by a spring. When the screw hits a stop, a spreader cone would disengage the nut.
Cone-Shaped Ramp Nut: In this idea, a cone-shaped ramp nut could be positioned at the end of the shaft or along it with a jam nut. A spring-loaded half nut would then roll up onto the ramp to disengage.
I think both concepts could offer some interesting functionality. Let me know your thoughts, and if you’d like to chat further!
Best,
Dean
Yeah cool ideas but probably not needed on a Bridgeport. Most machines use simple back lash eliminators in the form of two nuts. Most backlash is no issue if you know how to use the machine properly
@@VanoverMachineAndRepair There are thousands of macines that use lead screws. I wasnt referring to any machine in particular. Just a way to make a mechanical stop for any machine you would not want to use a limit switch on or want to start a cycle and walk away .
@@jameselliott9397 yeah true good ideas
@@VanoverMachineAndRepair Thanks. Please let me know if you design one. I have thought about it a little more. I think the ramp nut may need some vanishing threads. I an going to make one set soon from brass.
@@jameselliott9397 will do
Repairing on a budget is normal for small shops. Personally speaking, as a life long mechanical engineer, your repair is fine as there is no real load on the shaft, unless you use excessive load when cutting. Well done.
I appreciate your engineering perspective. Thank you
Thanks for recording the repair that you made. Do you remember what material the threaded stock was made from? Mc Master offers several.
Thanks Again
The cheapest one probably
@@VanoverMachineAndRepair Man after my own
heart
Nice fix but I have no idea where I would get acme screw rod in New Zealand
Sorry I don’t know about New Zealand
I'm faced with the same type of repair. Does it matter if the shaft stub receives the acme shaft or the acme shaft receives the stub?
I don’t think so i like doing sub on acme so I am not putting till pin through threads
Nice Work, i wish I had seen it before ordering only the Nut for my Deckel milling mashine.
I wonder, what for a backlash you are getting. Is it maybe as accurate as from the factory or does it cone down on what accuracy the threads have?
I have a dro so accuracy is measured by that but works great backlash is almost nothing
Great Job.👍👍👍
Thanks
i was wondering, how come you do a lot of dry work when i see other shops doing lub for drilling and such? i was curious the reasons and the whys.
Camera work mostly. Coolant is messy
I have very cheap Taiwan copy of Bridgeport.
It costed me whole $500.- CAD.
If I will need this kind of repair, my 2.5 tons 1960 TOS - Zbrojovka will do it with no problem !
Good
With a weight scale, and magnifying glass, and temperature control it is possible to make measurements to within 10 thousands of an inch, with a flat style tape measure, even up to 20 feet in length.
I bet
I have the same lathe but the older version but it has the same spindle. Are you sure it's the spindle and nit the cross slide being loose in the working area? My lathe was beat and spanked but when I checked the spindle I could maybe get 2 tenths of deflection using a bar up and down. My cross slide on the other hand had like 7 thou in one spot and when I tried to adjust the gibs it'd jam up at the travel limits. Not to mention the saddle it's self having a lot of wear as well
Sorry, meant to mention that I was having a hard time parting as well then realized that the cross slide was actually tipping as I was trying to part. Basically the parting tool was tipping the toolpost and cross slide causing it to dive and break tools
Yeah good insights but yeah my spindle had 5 thou deflection I did half a video on it but never posted it.
Nice job young man
Thank you
oh yea I'm doing my 1954 round ram as we speak the shaft my buddy gave me is right length but the shoulders on the end need turned I also have to have to cut an extra woodruff ....on that machine with no lead screw
Dang lol
Very interesting. Thank you. Wearing gloves on a lathe is surely a no-no. Scratch pass = spring pass? If consistency of thread wear is the important thing, surely the cheapest and quickest repair is to recut the thread and then use the split nut to take up the slack?
I came to find that thin rubber gloves are just fine... If they catch, they rip instantly, and if not, they save me from washing hands every 20 minutes... Washing gloves is much easier and faster, hell, sometimes i will just blast them off with brake cleaner to get the oil and small chips off...
I couldn’t fit the screw on the lathe to recut it. Due to length and diameter
cool dude!! cant you machine your own acme thread lead screw? just asking...
Yes check my newer videos
I did the same for my lathe with a threaded rod inside and glue it in with loctite. Works also fine.
Yeah it works
Damn man that's a lot of work to save $250
Indeed it is
How do you know that the replacement screw is not twist, bend or bow?? Is it made for precision task??
It’s standard threaded rod. Not ground. Ground is better but 5x the cost and the tolerance of this formed rod is pretty good considering the price. Also repair is in use everyday works great.
@@VanoverMachineAndRepair tanks for your answer
It might be useful to put the url or link in the comments where you bought that lead crew for $44. That makes it possible for others to also carry out such a repair for that price.
he told you
mcmaster carr
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Great job. Are you a job job that do repairs only?
We do repairs and new parts just no cnc
@@VanoverMachineAndRepair I love manual machines that are in good condition but I have no idea about CNC and I don't want to know too.
Nice repair, , but the rollpinn will never shear of probebly much stronger than the key at the drive side
Yeah maybe. Over a year of daily use no issues so far
The final clip ,The shaft looked shorter than the cutoff shaft what was its final lenth as you didnt measure it on camera, the rod on table looked a inch longer
Hmm might be a video thing. They were same length within 10 thou probably.
I need to do same thing on my wrong fu RF-30, I believe my threads are 23.5-10P where do I get?
Metric threads are harder to get sorry not sure
doing this as a 1st year apprentice in 1951
Very nice
Of course. All threaded rods are created equal.
Yep lol
Hey there. How is this holding up? Do you have any complaints so far? I am thinking about doing your method for my own machine
Holding up great
@@VanoverMachineAndRepair awesome, thank you for the reply and content
@@LonnieHeadley absolutely
This is a totally legit repair if you have a DRO.
Even the mcmaster precision screws only give +/-.009" per foot so obviously you need a DRO, which he has.
Acme threaded Lead Accuracies can be:
± 0.004 in/ft - Standard Rolled
± 0.001 in/ft - Precision Rolled
± 0.0005 in/ft - Precision Ground
Many machines have pieced leadscrews, most notably if they have a retrofit servo feed, and even then it's usually only a slip fit with a taper shear pin.
There's not that much torque involved due to the mechanical advantage of the lead.
And runout would have to be huge for it to matter since the bearing supports never get that close to the nuts.
Lastly, length is non critical without a servo feed because one bearing floats. With a servo feed the adapter gets pinned at assembly so the length is comepnsated that way. And if the screw is fixed length, already pinned, it gets shimmed with round shims.
Most of these comments are from people that probably haven't torn down a single machine.
Perfecty fine.
Thank you!
I've seen two other guys on UA-cam use this fix on their lathe. It's a smart fix.
Thanks!
Would love to know what the part number is from Master-Car?
I don’t remember the part number, but it should be extremely simple to find on McMaster Carr by searching acme thread
LOL wtf did I just watch. For all that work, you could have just bought your acme all thread long enough to machine the features you need on either end.
True if I could fit it in the lathe which i could not. Lathe was not long enough, spindle bore to small to fit through
@@VanoverMachineAndRepair Was that some other lathe you were using at 28:00 ? It seems to fit through the bore?
Enjoyed watching the repair. Good method. Cheers Tony
@@VanoverMachineAndRepair …… how did you turn it down for the press fit then?
Changed my mind - nothing to add.
👍
I can't imagine why you would want to rebuild a leadscrew when you have a digital readout.....you could "almost" have a piece of all thread as the DRO is the accuracy decider.
Climb cuts don't work very well if there is too much backlash.
@@kennethstaszak9990 I broke a lot of end mills when I had backlash in the ACME thread: I haven't broken one yet (over 2 years) now that I have ball screws i.e.3 thou backlash max.
@@johnantliff I would like to convert but as a home shop I haven't been able to convince myself to spend the $2K.
@@kennethstaszak9990 I took a chance and bought ball screws from AliExpress and turned/ground the ends as required. They turned out to be better than expected (about 2-3 thou backlash max - the X axis was a double nut and Y axis a single nut as space was tight). I had to modify the Y axis fitting i.e. hog out some of the casting to get it to fit but overall the total spend was no more than about $500 NZ. I then fitted 3 stepper motors for another $200 (second hand old plotter motors) and I use Mach3 and driver boards and power supplies, again from AliExpress (about $50 each). I have found the CNC control to be very useful for cutting out irregular shapes using Aspire to generate the toolpaths. I made most of the running gear for my Galloways Engine (see ua-cam.com/video/qkiMJKSYOMg/v-deo.html) using the CNC mill - saved a lot of hand work!
@@johnantliff Checked out your video. NICE!
Why not just turn a whole new shift? I don't understand why you went this route.
That is also an option. I’m showing an alternative way to do it. That’s more cost-effective and time effective.
Also, at the time I’m making this shaft, I didn’t have enough length on my lathe to turn the Acme section one shot.
why didn't you just make a new lead screw and brass nut? i would have when that way you have the machine to do this type of work too
Machine length and travel prohibited lead screw machining
Oh, man! Use oil for drilling!!
Sometimes I do
1) I'm pretty sure the acme thread you can get from places like McMaster does NOT meet the accuracy specs of the original, especially in terms of total accuracy over its entire length.* 2) Who cares about the overall length of the thing? You could probably be 1/8th of an inch over at the part that mates with a hand wheel and it would be fine. What you care about is the distances between, and diameters of any bearing surfaces and their relationship to the threaded portion. For much of the rest of it, yes, even a tape measure is good enough. *Of course if you are using a DRO rather than the dials, like we did in the bad old days, you may get away with this.
Your probably right on acme however it’s accurate enough and works great
at just abouts 47:38....you grind into the acme thread !!!!
Perhaps
Why didn't just cut the old nut in half to remove the play .
Because the screw was worn too
And how much your day of work would cost if you would bill it to a customer? ;)
Way more. Though not every day is billable in a shop. A year ago when I did this I had lots of free time.
Machinist's rule no.1 : Never wear jewellry ! Even the long beard is a safety hasard !
Yep yep
Just use Locktite and edit the video to take 5 minutes.
Lol
Interstingly Woods Creek Workshop made a similar repair on his tool and cutter grinder leadscrew a few days ago. ua-cam.com/video/WUvY-I64N7I/v-deo.html
Yeah I saw that
😛😛😛❤❤👍👍👍👍👍
👍
Good idea. But wearing gloves while operating a machine tool is a very dangerous practice.
It can bee
I wonder how many downvotes this had. This was a terrible presentation, the guy didn't mention what types of issues screws have as they wear, how to notice these issues, how he knew something was wrong with the screw that needed repair, what he thought was wrong (until like half way through), or explain why what he's about to do will fixe it..... then proceeds to 1) fail to measure the screw after recommending we do this, then 2) just jumps into cutting it in half without even explaining why he's doing it... I don't understand the comments, I'm sure this person knows how to machine, but they completely fail at making an explainer video, or and even fail at basic communication skills. I know this guy is trying but this video is useless, perhaps worse?
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I started watching this but then almost dropped my teeth. I can not imaging taking any advice from a person who calls a feed screw a "SHAFT". It is NOT a shaft. It is a precision feed screw. The difference is in the basic use of the two things. A shaft is used to transmit power via rotation. A lead screw is used to create precise linear movements via the use of a nut. Totally different things.
You can not properly measure it with a tape measure or with any method that involves the use of visual alignment between the edge of a scale and features on the lead screw. Perhaps you got lucky with the fit.
And commercial, threaded rod is NOT accurate enough to replace a feed screw. It just isn't. That mill should have a BIG sign PERMANENTLY attached that declares it too inaccurate for any kind of precision work. $44 vs $300 plus! Do you think the OEM of the machine perhaps knows something about accuracy? And yea, I did pick up that it has a DRO and you intend to replace this with a ball screw at some future time. Excuses, excuses!
At least you pinned it. I was half expecting you to WELD it together.
Settle down there. I’ve done tons of jobs with that screw being replaced since this video happened about a year and a half ago. I’ve got paid on those jobs. Yes I understand in a perfect world I would go out and buy a precision ground “shaft” 😝. I’m sure in that same perfect world you would be making $400,000 a year and have much better things to do than comment on this video and unhelpful way. But that’s not reality.
You're seriously weakening the shaft repairing it in this fashion. It is indeed a poor man's repair in more than one way.
Well, I am a poor man so it’s a good fit
@@VanoverMachineAndRepair Fair enough.
Why have you made a simple job so complicated ?
Showing other ways of doing things
Hay clean your parts up before machining .Don't be a metal butcher !
Dirty is good
No one else spotted the wearing of gloves on the lathe?
That’s a big health & safety no no.
For your own good, don’t wear gloves around rotating machinery.
Same goes for grinders & the mill.
Look it up & look after yourself.
Your correct
Make it out of steel instead of lead and it should last longer ;)
True
What do you mean by loose spindle?
What point in video you referring to
@@VanoverMachineAndRepair Before you part the ends of the lead screw you say the lathe has a loose spindle. What do you mean by that?
@@ophirb25 yes the spindle was loose on the inside. I fixed this and I have a video on it that I will eventually release. Short story one of the jamb nuts loosened and caused spindle bearings to loose preload.
Excellent repair man..nice job.
Thanks 👍