A Different Way to Repair a Worn Lead Screw 

Nice fix. I think I would have ordered an appropriately longer acme screw and turned new ends on it.

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.

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.

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.

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.

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!

Once you've reached the maximum travel of the carriage, you can measure the remaining length using a caliper.

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.

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?

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.

Nice work! As you said, there are many ways to make that repair. But, I'm wondering about wearing gloves around revolving spindles?

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.

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

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. .

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.

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 ..👍👍

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.

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

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.

Excellent repair man..nice job.

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.

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

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.

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 !

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.

I did the same for my lathe with a threaded rod inside and glue it in with loctite. Works also fine.

Great Job.👍👍👍

so it took you a hole day what do you charge for a days work ? in my place of work a day is 800+

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?

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...

Beautiful machine man

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.

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?

Nice fix but I have no idea where I would get acme screw rod in 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?

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

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

Nice job young man

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

I need to do same thing on my wrong fu RF-30, I believe my threads are 23.5-10P where do I get?

Damn man that's a lot of work to save $250

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.

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.

How do you know that the replacement screw is not twist, bend or bow?? Is it made for precision task??

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

Nice repair, , but the rollpinn will never shear of probebly much stronger than the key at the drive side

doing this as a 1st year apprentice in 1951

Would love to know what the part number is from Master-Car?

Great job. Are you a job job that do repairs only?

Of course. All threaded rods are created equal.

Make it out of steel instead of lead and it should last longer ;)

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.

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

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.

What do you mean by loose spindle?

Oh, man! Use oil for drilling!!

at just abouts 47:38....you grind into the acme thread !!!!

Why didn't just cut the old nut in half to remove the play .

And how much your day of work would cost if you would bill it to a customer? ;)

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.

Machinist's rule no.1 : Never wear jewellry ! Even the long beard is a safety hasard !

Interstingly Woods Creek Workshop made a similar repair on his tool and cutter grinder leadscrew a few days ago. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-WUvY-I64N7I.html

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.

I've seen two other guys on RU-vid use this fix on their lathe. It's a smart fix.

😛😛😛❤❤👍👍👍👍👍

Just use Locktite and edit the video to take 5 minutes.

Good idea. But wearing gloves while operating a machine tool is a very dangerous practice.

You're seriously weakening the shaft repairing it in this fashion. It is indeed a poor man's repair in more than one way.

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?

Why have you made a simple job so complicated ?

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.

Hay clean your parts up before machining .Don't be a metal butcher !