Machining a New Lead Screw for a Covel Surface Grinder - Left Hand Acme Threads

Machining a New Lead Screw for a Covel Surface Grinder - Left Hand Acme Threads
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[@bellofbelmont]

I lost dad in 1995. He would have LOVED youtube and your channel in particular. Great vids to watch and learn. Jim Bell (Australia)

[@capitanschetttino8745]

I love when you make brand new and fully functional parts for old machines. Its like a little time travel for me. Beautifull.

[@Ambidexter143]

It's enjoyable to watch an expert show how a difficult job is actually easy to do when you know what you're doing.

[@fredbloggs4829]

I have seen at least 3/4 of all your videos, and I really enjoy the instructional ones. The videos where you take the time to explain the details. Even after seeing so many videos from the past, it's really enjoyable and like a re-fresher course. I hope your friend likes his new lead screw.

[@ThomasBurns]

Another great video. It's so educational to watch you work!

[@mongomay1]

Thanks Keith and Ron.

[@wirenut003]

Nice accurate workmanship .The guy should be happy with new part.

[@rickpalechuk4411]

That nut is probably packed full of grinding dust to take out that shaft like it did. Thanks for sharing Keith, Cheers

[@dtoad48]

or the nut was replaced a few times and shaft never.

[@rickpalechuk4411]

@@dtoad48 That's possible also. Sure was lots of crud on the shaft when he screwed the nut on at the end.

[@ronwilken5219]

I'm rather surprised that Keith didn't take that nut to the parts washer first to get all the crud out of it before threading it onto the new shaft. No wonder it didn't feel very sloppy. It sure deposited a bunch of crud onto the new screw. Yes the new screw is to proper dimensions but it's not matching the nut. Should it have been made to match a cleaned, used nut or make a new nut to match the new screw? As Kieth said, an expensive piece of bronze so maybe the screw should have matched the worn nut.

[@elrond12eleven]

@@ronwilken5219 Brass nuts never wear much on steel shafts because steel chips and other abrasive gunk stuck in more soft brass and scratch hard steel. The same is in clockwork - steel shafts of cogwheels wear more than holes in brass plate.

[@rickpalechuk4411]

@@ronwilken5219 And being for cross feed adjustment maybe they felt it is not as critical as Z increment. It has started an interesting discussion 🙂

[@JTL1313]

You can purchase a new nut (without the flange) for a reasonable price from McMaster Carr and then make a flange to fit the nut. You can also purchase 3/4 -10 Acme bar from various venders and machine it down for the 1/2” threads and flats. Not having Kieth’s skills; that is what I did for my surface grinder lead screw an nut replacement.

[@t.d.mich.7064]

Back in the late sixties, I lived just a few miles from the Covel (pronounced Cov'-el) facility. My sister-in-law took care of their payroll dept. I believe they were purchased by Atlas Press Co around 1968, and went out of business in the mid 70's. I would drive past and see the Scraper Hands outside the building taking a smoke break. Scraper in one hand, butt in the other, with spotting blue on their hands and apron. I thought to myself, I'm glad I'm a Toolmaker!

[@LNM0000]

Seen Steve Summers just pull the toolpost back towards him when he's returning the tool. And another name drop.... as Rob Renzetti says, everything flexes, its just a question of how much 😎. Cracking videos mate 🙂

[@davidhudson5452]

Well done Keith

[@richardjohnson1764]

Makes want to get a dro for both my lathes. Nice work.

[@murphymmc]

Very nice Kieth. As a friend of mine once said, "You don't beat a guy at what he does for a living". It's a pleasure to watch and learn. Thanks.

[@paulcopeland9035]

Keith doesn't do this "for a living"! He is a superb hobiest with a world class shop. His "day job" is with Bayer crop science. The guy is busy to say the least.

[@billmorris2613]

Good morning to all from SE Louisiana 7 Jan 22.

[@bustednuckles2]

There is no substitute for experience and that blazes brightly here.

[@Wilett614]

I NEVER pile tools up on my Lathe Headstocks ! A SAFETY Hazzard you don"t Need or Want : ) I have a "Cincinnati Tray Top" Lathe But NEVER set tools up on the Headstock Tray for that reason . And never had an Issue : )) Nice video Presentation , Most guys cant even turn RIGHT Hand Acme threads let alone Left handed ones ! I own A Vintage Covel Surface grinder like the one you made that lead screw for . I have Made numerous New Parts for it as well .... Thanks

[@latisimusd]

As a retired fella that is building a home hobby machine shop. Watching you produce that part was so enjoyable and relaxing. Gives me some confidence in my projects. Great info on the tool pressure on the last two passes for your final measurement :-)

[@EvanLightner304]

When I do acme threads I set the compound parallel with the ways, that way I can trim the side of the thread to get a little play in the thread. First time seeing someone do the 14° method. Nice work

[@erich9244]

Thanks for bringing us along for the ride I feel like it is shop class and I am in 10th grade again, bless you for your explanations and sharing your wisdom :) Keep on keeping on!

[@tinkmarshino]

Always a nice way to spend a winter afternoon.. Thanks Keith for sharing your passion.. Not only did I enjoy them all but I learn an awful lot watching you.. I have always been a hands on learner and this is great! Carry on!

[@rexmyers991]

“I like it!” Me, too! Very nice job, Keith. As always I learned something. Thanks

[@Scorpio722]

Great to see a classic Covel still in use. Used to work with one of the Clausing-Covel field tech/mechanics years ago. Great videos Mr. Rucker!

[@almostanengineer]

I love the viewer projects, you never know what your gonna get, and it’s always interesting.

[@TrPrecisionMachining]

good job keith

[@MrUSNMasterChief]

Thank you Keith, Great Job as always.

[@aner_bda]

Watching threads be cut on a lathe is just so memorising and soothing somehow. Thanks as always for sharing these projects.

[@steveb9270]

Hi there greetings from down under. Love old school machining the young push button kids today could learn a lot from us old farts . LOL 😆 I work for a valve manufacturer here in oz and cut acme threads nearly every day , you don't have to turn the top slide just keep it on 0 plunge into the depth then you might have to go sideways a bit on the final cut ,. Keep those videos coming cheers 🍻

[@davidhaywood9071]

Your ability makes difficult jobs look easy.

[@yt66228]

Very well done. Need to make one for my grinder. Thanks.

[@ronmurphy9819]

Beautiful and inspiring. Thank you

[@forresta65]

a thing of beauty.

[@jimc4731]

You could make that nut adjustable to tighten it up a little. Split the flange end in on center for about 1 1/2" and drill and tap two 1/4"-20 parallel cross holes on each side of center, the screws to tighten onto the shaft to take out play. Not much work for a great improvement! Keep up the good work! JIM 🙂

[@forbesmathews89]

That will tighten things up , But will not help the back lash.......

[@mdouglaswray]

The best thing about old machinery is that you can FIX IT.

[@echoewest2685]

Fun to watch, thanks for sharing!

[@MikeBaxterABC]

Just got to say the intro music is so calming, and let me know I'm going to be entertained and probably learn a thing or two as well!:)

[@varmint243davev7]

Very nicely done !

[@fredclark4033]

Everything is so much better when you know what you are doing. Thanks Keith

[@elrond12eleven]

Brass nuts never wear much on steel shafts because steel chips and other abrasive gunk stuck in more soft brass and scratch hard steel. That's why lead screws are made of steel and nuts are made of brass - it's cheaper to make a new screw rather than new nut. The same is used for glass polishing in making lenses or concave mirrors for telescopes: abrasive sticks to soft base (rosin, sealing wax etc.) and cuts pretty hard glass.

[@billspear7702]

A bronze disk will cut a diamond the same way, diamond dust is introduced at the start of the cut, and largely self replentishes as the cut procedes.

[@jstephenallington8431]

Great video as always Kieth. It's interesting that the screw was so worn but not the nut. As you know, the nut is made of a somewhat soft material (brass or bronze) and the screw is made of a harder material so of the two the nut will wear out first being easier and cheaper to replace than the screw. Maybe the nut had been replaced once before. Anyway, I'm looking forward to the next video episode.

[@CothranMike]

J, I too noticed that and agree the nut should have worn out first so that's probably the second nut as you state. Bronze nut did however wiggle up and down even if it didn't wiggle back and forth in the thrust direction. I also saw dirty gritty oil inside the nut which means it needs to be cleaned out or it will lap the new shaft as it did the old shaft. -- MikeC

[@larrywalker7759]

Wear is not always inflicted onto the softer material because there is another factor to consider than just the 2 dissimilar metals in this assembly. It is true that brass or bronze is softer than steel, but in this application (part of a surface GRINDER) you must factor in the inevitable presence of abrasive particles that are shed from the grinding stone both in normal operation use and during dressing of the stone. Of the 3 different materials in the equation here, the abrasive stone particles are by far the hardest. Over time some of this "grit" will find its way into the interface of the steel threads of the rod and the brass threads of the nut where the particles will embed into the brass. At that point, the abrasive particles begin to remove traces of steel from the rod while effectively "protecting" the nut against wear. I have seen this to be the case where a soft material is in contact with a hard material, the soft material usually outlives the hard material.

[@don4364]

Always enjoy watching a true master at work. Thank you for the intuitive video.

[@roylucas4414]

What a great video! I enjoyed each step in the process. Thank you.

[@jaydoherty8402]

Keith someone pointed out that your threading tool was rubbing the live center while you were dialing in the last couple passes on the 1/2-13 end of the shaft (around 13:50 in the video). Might want to check on your live center. Although you don't usually grip parts that high up on the live center anyways so probably no big deal.

[@CothranMike]

Jay, I haven't read any further than your comment and mine is hours after yours so this may already been covered but the type of live center that he's got is a double angle; the center of the 60° is only on the very point the rest of it is just clearance for that very problem which is your point I think, the tool holder for the insert is going to butt against that turning surface. I was also looking for that as the diameter got smaller and smaller. I did see where the chip riding along with the insert body scrapes some oil off the surface and made a shiny spot, and then a larger spot. I also saw where the spacing changed a bit in the z axis toward the chuck so all was well. I have had to remove for clearance that portion closest to the engagement area on several tools, but that was just the demands of the work. We all deal with life's gotcha's as we understand them at the time. Even it it was pressing at that point and rubbing - creating heat, that surface is intended to be clearance for any tooling used on the supported shaft end. No problems unless he had bent the axial thrust bearing or applied pressure to dislodge the tailstock. He was well short of that. -- MikeC

[@dfishpool7052]

Thank you Keith for an excellent presentation on cutting the LH thread.

[@cschwad559]

I love single point threading, will do it at every opportunity.

[@wrstew1272]

I have seen some of his work, and wish that I could justify the addition to my tool stable. Jewelry for woodworking. Great job, it’s pleasant to see a practitioner of the metal arts at work.

[@richw0123]

lovely job, I regularly make tiny pivot pins for surgical instruments out of Titanium, around 1mm diameter for work, I still love watching turning and chips being made, even by other people, it's the best bit of my job.

[@bwyseymail]

Small stuff . . . I assume you have been watching Joe Pie's model machine tool videos.

[@richw0123]

@@bwyseymail yes, those videos too!

[@wilkuyf1559]

love your videos keep em coming , regards from Holland !!!!!

[@markbernier8434]

I had expected the shaft to be heat treated. Please explain why not. Also, I would have liked to see the inside of that nut, maybe run a tap through it if the owner had not.

[@ellieprice363]

Great job. I made a lead screw almost identical to this one for my Kent 6 x 18 manual grinder. Mine was 3/4-10 L.H. acme also worn badly in the center. The first shaft I made was a little loose so I made the second slightly larger to compensate for nut wear. I recall feeding straight in instead of at the 14.5 angle. If kept oiled soft shafts like this will last a long time.

[@scottnj2503]

Tool pressure gem. Sage advise🤓 I'd not have thought that.

[@brandenpatterson2776]

Great project Keith !

[@AmateurRedneckWorkshop]

You made that look easy. I don't remember ever cutting an Acme thread.

[@MachiningandMicrowaves]

I've tried using a travelling steady/follow-rest when cutting long threads, to help counteract deflection from tool pressure in the middle of the cut. Seems to work OK on Acme threads, where the thread tips are wide and flat, but close to completion of the thread forms for ISO metric threads, where the support was really needed, it wasn't as effective because of the sharp tips to the thread forms. Also there are clearance issues, as the rubbing surfaces of the rest need to be ahead of the cut, so chips don't get caught under the pads, and that might mean the rest interferes with the rotating centre or a shoulder. My current project needs a 7/16" 12 tpi Acme leadscrew in stainless steel. That's going to be fun.

[@billmorris2613]

With the two pieces laying next to each other the wear in the original one was easy to see. I could actually see that there original was slightly concaved.

[@bulletproofpepper2]

Thanks for the info!

[@MatthewScott]

Great work as always

[@catfishgray3696]

PET THE CATS AND DOGS, TELL EVERYBODY HAPPY NEW YEAR, GREAT VIDEO...

[@cameronmccreary4758]

Very nice work, congratulations!

[@justinduffey9237]

Thanks Keith

[@alanroy5629]

Amazing precision

[@johnlee8231]

nice job

[@ruperthartop7202]

Great, thanks Keith

[@quinntalley1681]

Good, clear, and concise explanations, as always. Thanks.

[@garthbutton699]

Thanks for allowing us to look over your shoulder🤗😎🤗😎

[@llapmsp]

Another awesome job. Thanks for sharing.

[@passenger6735]

Very nice work Keith. He'll be well pleased with that. It would have been a nice bonus to have done the nut as well.

[@RB-yq7qv]

Nice Job

[@robertseltmann]

Nice job

[@ericgelman2792]

I’m lucky enough to have a Ron Brese plane-he makes beautiful tools

[@seephor]

Keith. I'm not sure how eager you are to try something new but I think it would be cool to try and spray weld the entire acme thread full then recut the threads. I'm not saying this would be better in any way but it would be interesting to see how the threads cut as well as the longevity of the repair. Just a thought.

[@timziegler9358]

Fine job! It is a pleasure watching you work. Best wishes.

[@kenbolton6850]

Well done

[@billmorris2613]

As usual I really enjoyed the ride.

[@briand01]

looks beautiful

[@edwardconway5955]

Great Video!

[@teamidris]

I cut my nut, rotated it a bit and soldered it back together. And that was okay, but I still wonder about getting it in the pipe crimp to reduce it. Maybe even run a tool down it. that looks like it would take a ball screw, and oh my goodness are they good 😊

[@elsdp-4560]

Thank you for sharing. Enjoyed.👍

[@organbuilder272]

Interesting, Keith. Master machist at work. Yes, surprising that the nit was not a little loose. but a beautiful fit. Thanks for the tutorial as well, Keith.

[@bcbloc02]

Nicely done!

[@d.gregorybrown7779]

very nice

[@ninjagobble]

Awesome work!

[@philstevens8950]

Keith,I just came across your videos and heard you mention a museum and was wondering what the name and location is . Thanks Phil Stevens

[@kentuckytrapper780]

Excellent job Keith, great video, keep'um coming..

[@RichardHeadGaming]

Screwing around on the lathe I see, nice work.

[@55ATA3]

I would change the nut, you don't want any damage that the nut has to be transferred to the new shaft. But I like to be take extra care on the equipment that I need to be right the first time. At least I would check the nuts threads with a thread gauge to see if there is any damage to it.. Great video, thanks for showing us how much care is needed to make a good lead screw.

[@geckoproductions4128]

nice video thanks

[@samrodian919]

I think that nut must have been replaced at least once, if not twice given the amount of wear on the leadscrew. Usually the bronze or brass nut is deigned to be replaced as it wears. I've just this weekend replaced my main brass nut for my longitudinal feedscrew as it was totally worn out. There is spa good bit of wear in the feedscrew, but I've cut and shut and reversed the worn part to the tailstock end and made joining pieces to go into the ends of the feed shaft and the non threaded ends at each end which now have two 90 opposing stainless roll pins to attach the joining pieces so now the unworn part of the feedscrew is at the headstock, working end of the lathe and the new brass nut I've made is nice and reasonably tight with no appreciable backlash. My problem was that the Chinese lathe I have has a feedscrew of 0.100" pitch, but it has a metric outside diameter of 19.98 mm or a nominal 20 mm metric trapezoidal thread. And without an optical comparator I've no idea if it's an Acme 29 degree or a metric trapezoidal 30 degree thread. As I can't find anywhere any specifications of a metric 20 mm X 2.54 mm pitch I've gone with a theory of 0.020" clearance and gone with an extra 0.20"over the minor diameter of the feedscrew to give me the clearance it needs. It seems to work ok. Only time will tell lol

[@johnquinn3899]

Interesting piece of work Sir !!

[@glennmoreland6457]

Good video 🇬🇧🙂

[@brianhostak3961]

Nice!!

[@tonyc.4528]

I'd try making one myself if my lathe was running, but it seems you need a working lathe to make the parts for non-running lathe!

[@tomgale8154]

they work hard buy them a beer from time to time

[@jwaterous224]

I think surface grinders have a bit of movement on that nut since the grinding head is resting on ways and some movement occurs during operation of automatic down - feed. Anyway Keith got some math into this episode of left hand ACME thread turning. Nice turn out.

[@millomweb]

Keith, I bet it's nice to be threading a decent length of bar for a change !

[@markwatters6875]

Thank you for another great video.

[@mjk8710]

Good work Keith l/h acme thread cool to see sir 💯👍🏻🇬🇧

[@Holman673]

Neatly worked, I had enough made a new brass nut, then it would probably keep a little longer, but it is perhaps an additional cost

[@outbackladas]

Well done, nice job 👍

[@teamidris]

Seven mins in, oh hell yes on flex :o) My boring bar is a game of a tiny last cut run in both directions. Then it does a nice job.