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View Full Version : Lead screw wear, when is it time to replace.



Ken_Shea
12-25-2009, 09:46 PM
The deeper I get into cleaning up this Clausing 5914 the more is seen that causes concern. I don't mind spending some bucks but do not want to unnecessarily. My guess is, presuming it is factory available, that it will be costly, alternatives to factory are probably available though. It is not standard TPI being 7/8-8 if recalled correctly.

Does wear cause any significant issues?
What I call substantial wear is seen in the drive slot and the thread both.

What about the thread dial gear wear, the worm gear that drives the carriage or the split nuts, should these be replaced at the same time if/when a lead screw is replaced?

If pictures would help let me know.

Thanks
Ken

In the left mostly unused area
http://i187.photobucket.com/albums/x175/Ken_Shea/LeadScrewLeft.jpg

You can see the slot wear
http://i187.photobucket.com/albums/x175/Ken_Shea/LSR.jpg

Does not show up well but this is in a high wear area showing sharper thread crowns.


Thread dial gear, the gear tooh crown is almost to a knife edge.
http://i187.photobucket.com/albums/x175/Ken_Shea/ThreadDialgear.jpg

spope14
12-25-2009, 10:15 PM
Both look fair to me. Any wear in the leadscrew keyway will be picked up through backlash. The thread dial gear looks like it needs a good kerosene bath and toothbrush clean-up.

Both are hardened quite well.

My eyes would be on the drive key for the leadscrew, this is a soft steel part that could have wear or swedging, and the half nut, which is bronze of brass. These are the primary wear parts or chip embedding parts on all lathes I have seen

Ken_Shea
12-25-2009, 10:22 PM
Probably didn't need told of the parts needing cleaning :)

I haven't got to the split nuts as yet, but will soon, I am curious as to what condition they are.

I have seen lead screws much worse but none of them have I ever used, so I am unsure what difference it really makes.

Walter
12-25-2009, 10:35 PM
Ken I run a 5914 at work, I've also done alot of work on this machine. The 1/2 nuts are not badly priced but still not cheap new. IIRC about $120 from the factory. The nuts are a bit different, at least on mine they were Cast, not Bronze.

I'd not worry much about that leadscrew, it looks mostly alright, but check the support on the tailstock end and make sure it's in good shape. I ended up having to drop a bronze bushing in mine as it was flopping about.

Ken_Shea
12-25-2009, 10:57 PM
Well, that's two for two being serviceable, that's good.\
The looks of it bugs me but I can live with it as long as it doesn't impact the quality of the turning or threading.

Walter, I had checked the end support, very little play but it will still be getting new bushings, front end had essentially no play.

spope14, are those drive keys a separate item?

clutch
12-25-2009, 11:08 PM
I have to wonder if that threading dial gear was kept in contact when not threading.

One of the weakness of this unitized system is that the drive key working in the slot can cause wear and distortion to the acme threads that can cut your half nuts.

I'm not being critical. I have a 6903 out in my shop.

I'd just run it and deal with what ever issues that come along. The feed slot groove isn't going to hurt your turning.

The acme section looks pretty good from your pictures.

I'm not sure what rides in the slot, checking that as already mentioned might be a really good idea. My machine is pretty low wear so I haven't been into that part of the machine.

Clutch

Ken_Shea
12-25-2009, 11:15 PM
Clutch,
I can tell you that the threading gear was locked into the engaged position, unlike the proper practice of rotating it out of contact with the lead screw when not in use.
EDIT:
I guess in all fairness, could be the last thing done with this lathe was threading so not sure if it remained engaged or not.

If it wasn't so late I would tear into the carriage assembly a bit more yet tonight to take a look at that drive key and split nuts.

Black_Moons
12-26-2009, 01:07 AM
I kinda would suspect the threading dial gear could of been made like that. The thing has absolutely *0* force on that gear so id really doubt it would wear that badly. also as its just an indicator, untill it starts wearing to the point of skiping teeth positions its still fine.

As far as the acme leadscrew, Wear can cause threading problems, in that as you move from a worn to an unworn area, you cause a small error in the pitch. try threading a really long fine thread and see if a 'coupleing' nut (those 2"~ long ones) will still fit without binding anywhere. if it will you surely have little to worry about in thread accuracy as long as your only making mechical threads and not leadscrews for other machines.

Ideal with a machine like that, the leadscrew teeth itself are not used except when (rarely) threading, so its likey while that slot has a lot of wear, the teeth themselfs are still unworn. This is why its important to buy a lathe that does not use the lead screw for feeding, but at the very least has a keyed lead screw (like yours) and a rack gear for feeding, and idealy a completely seperate keyed shaft for feeding.

darryl
12-26-2009, 02:20 AM
What is the function of the slot on the leadscrew? You have a pair of half nuts in the carriage which close over the leadscrew to begin pulling the carriage along. The threading dial gives you an indication of when you can slam the half nuts closed to keep things in sync with the thread you're cutting, otherwise it does nothing except help jam swarf into the leadscrew threads. I can think of nothing that requires being keyed to the leadscrew, except the drive gear which would only need an inch or so of slot if a key was used. The slot that runs the length of the leadscrew is just a place for swarf to go when the half nuts and the dial gear are engaged.

Black_Moons
12-26-2009, 02:32 AM
that slot on the leadscrew likey drives a worm gear inside the carriage and that drives another gear, and THAT drives the standard feed (via rack gear along the bed) or the cross feed (Via driving the cross slide lead screw)

Some lathes have an entirely seperate rod for this perpose.

This prevents every day turning from wearing out your acme threads, as well as allows you a handwheel on the carriage to move the carriage around.

Fasttrack
12-26-2009, 03:10 AM
erm ... Just beacuse it doesn't have a feed rod doesn't mean there isn't a handwheel on the apron to move the carriage around - that is supplied via a rack and pinion set up.

I would make a new gear for the thread dial. That is worn out and yes, they wear out. You'll find that you'll be making a really critical thread and the dial will skip a couple of teeth at the worst possible moment. Don't ask me how I know this ;)

Usually, they are made out of bronze and keeping them engaged all the time results in wear, even though they don't have any significant load on them. I think they getted loaded with chips and dirt. Anyhow, I made a new gear for a WWII era Cincinatti Traytop lathe. I only had a piece of solid copper and some SS to work with, so I made a hob from SS and the gear from solid copper. Not the best material choice, but ... it's what I had and it was a "charity" project for a student lathe. ;)

It's a fun and easy project. Grinding the tool to cut the acme thread might take 20-30 minutes to get it done properly if it's your first time. Otherwise, it's not tough. I say put the lathe back together and once it's working, your first project should be a new gear.

http://bbs.homeshopmachinist.net/showthread.php?t=31417&highlight=thread+dial

(also see the link DP posted)

darryl
12-26-2009, 04:03 AM
Ok, I see there is a function for the slot- it drives a gear that slides along the shaft with the carriage. My bad for not seeing that earlier.:o

Black_Moons
12-26-2009, 08:32 AM
Id highly recommend cleaning that leadscrew at least :)
if done in place iv figure out a few good cheats...

Like take a wire brush and naptha, dip in naptha, brush leadscrew, repeat (grit hopefuly sticks to brush and transfers to small can of naptha)

Once that stops taking a whole lot of dirt out, buy some COTTON string (not nylon or any of that other trash) but just some old crappy soft cotton string that fits the thread groove, soak it in way oil (or whatever you want all over your lead screw) and start the lathe with the string at 1/2 to 1 turn around the leadscrew

NEVER wrap the string around your hand or anything, just grasp it beween fingers, or wrap it around a small tool like an allen key and hold that.

then just pull on the 'loose' end so you are constantly feeding fresh string across the leadscrew, it will suck most of the remaining grit into the oily string. You may have to wipe it down a few times with a cloth as the grit will also tend to move out of the groves and smear over the top of the thread.

half hour to an hour and you can clean a 30" long leadscrew to spotless if that carriage is not in the way and the lathes feed is assisting you.

The half nut should be removed and just repeatly wire brushed and rinsed in naptha. I just submersed my half nuts and other feed nuts in naptha and shook them violently underwater beween brushings. (Wear nitril groves)

Ken_Shea
12-26-2009, 09:32 AM
"Id highly recommend cleaning that leadscrew at least :)"

What is with this advice about cleaning :D
My post starts with "The deeper I get into cleaning up this Clausing 5914" :), I mean really, who would take a lathe apart to clean and inspect, just to put components back filthy.
EDIT:
But... I do like the string method you mention.

Making that gear would be very good experience and I have another lathe that can be used, I have put into Clausing an email asking availability and pricing on that gear and other items. we will see how that goes before taking the time to make a hob to cut it, especially since I would have to purchase a length of 7/8-8 acme rod, or make that too is also possible but still more time.

Doozer
12-26-2009, 09:50 AM
Check the feather that rides in the leadscrew keyway as well.
It is likely worn.

--Doozer

Carld
12-26-2009, 09:53 AM
Ken, you can roll the lead screw over 180 deg and cut a new slot in it and if the threads are in real good shape that is what I would do. If you don't have a mill a machine shop could do it for you and is probably less than a new lead screw. I would definitely replace the key that runs in the lead screw slot and you may have to bush or replace the gear the lead screw runs in.

I would look hard at the half nuts and consider replacing them if they have a lot of wear. The thing is when they are engaged and the slop is taken out the screw is running against the worn area so look real good at that, will it cause a thread pitch to vary?

For the threading dial, check with Boston gear and others to see if they have a gear like yours. If so it may be cheaper than from the factory or new old stock.

If your doing all this repair work do it once and do it right. A half ass job gives half ass results.

winchman
12-26-2009, 09:55 AM
Perhaps you could set the lead screw up on a mill, and make the slot the same width for the entire length. Then make a new stepped key so one side fits the slot and the other side fits the gear that runs the carriage feed.

Roger

Ken_Shea
12-26-2009, 10:14 AM
Doozer,
I believe that is the Drive key that spope14 had mentioned and will certainly be checked.

Roger, had that thought as well depending on the drive key, which I did not see in the exploded view drawings but did inquire at Clausing.

Carl,
Now I hadn't thought of rotating 180 and re-slotting. The threads are worn more then what they appear in the pics.
The lead screw was one of the items, also the split nuts in the inquiry sent to Clausing last night.
It will not be put back together half assed, on the contrary, my inclination is to go too far, trying to have a good balance on this, like living with the nasty looks and just concern myself with the mechanics.
I will also check out Boston gear, hadn't given them a thought either.

Carld
12-26-2009, 10:18 AM
I guess that's one of my problems when I repair something of mine, spending to much on the repairs for what return I will get. It's been drumed into me when I was young and learning and it's hard to keep from replacing every worn part I see. :D ;)

It's hard for me to keep from striping down every machine tool I buy and completely rebuilding it. In the last 10 or so years I have been able to control myself and only do it with reason or just cause now.

Duffy
12-26-2009, 11:10 AM
Ken:- Keystone Threaded Products is right in your state. They will almost certainly have a length of replacement rod. WHEN you get to replacing the drive spline in the worm gear, be sure to tell, (show,) us how you do it. I have a Logan 820 that could use a new one, and short of paying large for a replacement worm, I am at a loss. Duffy

lazlo
12-26-2009, 11:12 AM
That's a lot of wear, IMHO. I would re-cut the existing key slot.

Clausing does list a replacement leadscrew in their 2005 price list -- $484.

Ken_Shea
12-26-2009, 11:19 AM
Ken:- Keystone Threaded Products is right in your state. They will almost certainly have a length of replacement rod. WHEN you get to replacing the drive spline in the worm gear, be sure to tell, (show,) us how you do it. I have a Logan 820 that could use a new one, and short of paying large for a replacement worm, I am at a loss. Duffy

Duffy, I had seen that site from another link, perhaps one of your post. Thanks

Ken_Shea
12-26-2009, 11:31 AM
That's a lot of wear, IMHO. I would re-cut the existing key slot.

Clausing does list a replacement leadscrew in their 2005 price list -- $484.

I did not want to hear that :( but did expect it really.
Well, that won't happen, I do not like the wear on the existing lead screw threads, it should not be a bad job to machine that slot and prepare the ends to match the original on a alternative replacement shaft.

After removing the carriage assy, found further and substantial wear on the rack pinion, the rack looks pretty good, pictures after I clean it first :D

The split nuts look real good, but I am not sure how they are supposed to look when new and with the lead screw wear it's difficult to get a feel for fit.

It is going to get a new lead screw and associated parts as needed to correct the wear.

Walter
12-26-2009, 02:03 PM
I guess that's one of my problems when I repair something of mine, spending to much on the repairs for what return I will get. It's been drumed into me when I was young and learning and it's hard to keep from replacing every worn part I see. :D ;)

It's hard for me to keep from striping down every machine tool I buy and completely rebuilding it. In the last 10 or so years I have been able to control myself and only do it with reason or just cause now.

Carld,

I have the same problem and the same inclinations. That old 5914 really is a nice little lathe and worth the attentions paid to it. I've done some horrendous work on ours (8" high strength cast iron replacement parts for an old 56 ton Minster blanking press). and regularly use it to it's fullest, it's been a surprisingly good little lathe. biggest thing I've found is to make sure the carriage, cross, and compound aren't loose, you'll see some ugly results if they are. also Beware that leadscrew, mine has reached out and grabbed my coat and shirt a few times and tried to reel me in. luckily enough theres a shear pin on the right side near the QC that will break when you brace against the lathe bed and shove away hard enough ;)

Fasttrack
12-26-2009, 02:06 PM
FWIW, the whole process of grinding a single point threading tool for acme threads, making the hob, and hobbing the gear only took 4 or so hours, and that was my first time doing it. Someone with more experience could probably do it much quicker.

Still may be cheaper to purchase a new one, but I thought it was a fun project ;)

John Stevenson
12-26-2009, 02:41 PM
Just clean it and put it back together.
The leadscrew is two fold, the threaded portion together with the half nuts seems fine if what you say about the nuts is true and we have no reason to disbeliee you.

Those two components take care of the threading.

The keyway which is worn only controls the power feed so providing the pickup key in the drive wheel is in the best condition just accept it as it is.

If not you are faced with either a new leadscrew or machine the keyway and make a matching component for the drive wheel.

Play in the power feed train isn't a problem as it's always in the same direction and even from new this isn't a design feature that is paid much attention.

.

Ken_Shea
12-27-2009, 11:37 PM
Not all bad news upon inspection,
Appears that at some point prior to extensive use the Split nuts had been replaced, look like I would expect new ones to look. You can see the essentially no wear pattern on the back side of picture #2

Now the drive key in the worm gear is an entirely different story, not sure what a new one looks like but it is doubtful that a 3/16 slot is for a key that is machined down to about 1/16.
http://i187.photobucket.com/albums/x175/Ken_Shea/SplitNuts.jpg

http://i187.photobucket.com/albums/x175/Ken_Shea/SplitNutBack.jpg

http://i187.photobucket.com/albums/x175/Ken_Shea/DriveKey.jpg


I am hoping the rack is still decent, it looks OK from what can be seen, until it is removed and cleaned it is hard to say.

Carld
12-28-2009, 12:15 AM
The half nuts look good. Just cut a new keyway in the lead screw and repair the key in the gear. Most those type keys have a pin or two on the back to hold them in the gear. You can make a new key and put a pin in it.

Your on your way to having a nice lathe.

darryl
12-28-2009, 04:22 AM
Um- I don't think I'm being too picky about this, but I don't like the looks of the half nuts. Looks like one flank on the threads is worn a fair amount. I'm thinking if you go with a new leadscrew you should replace those also. To me they don't look good.

The key is absolutely toast. Maybe the gear will survive though. I think you should check to see how much play there is between the worm gear and the lead screw. If it's sloppy, you're probably asking for an accelerated wear situation again. With that much wear in the slot, it's been making grinding powder for some time already- either clean it all up and put it back together, or change all those parts at the same time. That's my gut feeling on it.

lazlo
12-28-2009, 06:04 AM
Um- I don't think I'm being too picky about this, but I don't like the looks of the half nuts. Looks like one flank on the threads is worn a fair amount.

Agreed. Those are very worn Ken -- they look like V-thread forms.
As you know, I have the half-nuts out of mine at the moment. I'll take a picture in the morning...


I'm thinking if you go with a new leadscrew you should replace those also. To me they don't look good.

The "I Ain't Making Parts for NASA" crowd is going to rolls their eyes, but it's going to be tough to find a replacement leadscrew that's accurate enough. Keystone only sells rolled acme thread intended for jackscrews -- it's spec'ed as +/- 0.009" per foot pitch error. Even the precision thread milled acme from MSC or McMaster is 3 tho per foot error. The 5914 shipped with a toolroom-grade leadscrew with 2 1/2 tenths per foot pitch error.

That's going to affect every thread you cut...

EVguru
12-28-2009, 06:12 AM
I wonder if the solution might not be to fit a ball screw as a relatively cheap solution to the longditudinal feed. You wouldn't need half nuts becuase you can backfeed a ballscrew. Cross feed could be taken care of with a motor.

I'd have to wonder though, how bad is the rest of the machine?

Ken_Shea
12-28-2009, 09:41 AM
When I fit the half nut to a unused portion of the lead screw there was just a nice positive fit, no rocking or lateral movement, I will be glad to compare a known good set Lazlo.

With regards to the condition of the rest of the lathe, the bed ways looks good with a few surface pits at the top, nothing rides there I don't believe. The main head bearings seem, as best one can tell by hand rotating are very smooth, the external gear change gears all look very good and rotate smoothly, all the bearings in the variable speed system need replaced ($110), the lower belt. ($50 not eom), but there is a lot piling up here that is not to my liking. I paid $700 for it, if it could be put together properly for say another grand or so, (not sure it can) that would put the total to $1700, still not a bad price for a lathe this size and knowing what you have. Junking or parting it out is out of the question. If more has to be put into it then market value, I won't like that but still again, I would know what i have.
Into it deep enough, mechanically speaking, that not too many big surprises should show their ugly head, except for the cost of parts.

EVguru,
Fitting it with a ball screw is not where I want to go, though it could be a solution but complicated IMO. The most difficult part now is the cost, the mechanical aspect is time consuming but not that difficult.

Carld
12-28-2009, 09:47 AM
Looking at one half of an Acme thread nut it is hard to see if the threads are good. that is because of all the angles and flats in there.

If as Ken says, the nut is a good fit on the screw then the nut is ok. If it is worn it will have end play in it and since he said there is no end play it's good to go.

Ken, I googled your lathe and I like that lathe. I used one at a place I worked. I rebuilt the vari drive system on it. I sure like that feature although it is somewhat troubling. I believe you would be spending wisely by repairing as needed and keeping that lathe.

Ken_Shea
12-28-2009, 10:08 AM
Prompted by the last few post, just went back for a second look and fit check, it was checked at the very start of the thread and no play was found, but moving it away from the start a few threads, and still on a section that does not get used there is end play after all :(, although nothing like in the worn area of the lead screw where it actually wobbles :(

Dang it!

Carld
12-28-2009, 10:17 AM
Ken, read my post above your last post please.

Ken, if the nut has wear it would have slop in the area of the new unworn thread too. The fact that it is tight in an unworn area and loose in a worn area is ok.

Here is the thing, the worn lead screw will give a bad pitch on a thread your cutting in that area of the lead screw. You can test the accuracy with a dial indicator and measure the travel of the carriage for each revolution of the chuck. I think you'll find that unless the lead screw is extremely worn it will still produce a usable thread.

Have you looked at the lead screw to see if you could flip it 180 deg and make it work with a little remachining?

Carld
12-28-2009, 10:21 AM
I went back and looked at a site with photos of your lathe type and I believe you can flip the lead screw and have good threads by the head stock. It is seldom, if ever, that you would cut threads by the tailstock end of the lathe.

Look at yours and consider that change.

JCHannum
12-28-2009, 10:32 AM
The key looks like it is silver soldered in place, it should be replaced before reassembly.

The half nuts and the gear for the thread counter are worn and will need replacement before too long. Judging by the photos, they should be well within the abilities of a HSM to duplicate.

The leadscrew itself and the keyway in the leadscrew do not appear to be excessive. I would not be too concerned about replacement of either for normal homeshop use. If they are properly cared for, they should be good for years of service.

The wear in the keyway of the leadscrew will not have any effect on the accuracy of the machine. As long as it does not cause any mechanical binding, it should be of no concern. Similarly, the leadscrew, while worn in spots will cut an accurate thread over an inch or so. Unless long, dead accurate threads are contemplated, little will be gained by replacing.

McNeillMachine
12-28-2009, 10:43 AM
I haven't read the whole thread here, but If you do need a new lead screw, I would check with Joe at Plaza Machinery in VT. He seems to carry a lot of parts for this lathe.

Ken_Shea
12-28-2009, 10:44 AM
Carl,
I have looked at the lead screw numerous times during this thread trying to find some way or talk myself into reusing. It can be rotated 180 and that can be done here on the mill with a little fixturing but the thing just sours me to putting it back on, in spite of the likely over $500 cost.

Flipping is complicated by the one end being female and the other male, still, that is feasible. You are right, don't believe I have ever threaded over 6" so the tail stock end threading limitation is pretty much moot.

Ken_Shea
12-28-2009, 10:47 AM
Thanks McNeill, I will keep that reference.

Ken_Shea
12-28-2009, 10:59 AM
Jim H.
Under consideration, it eats at me though.

Thanks

Carld
12-28-2009, 11:05 AM
Almost all my machining experience has been repairing parts or making new parts. I have recut the keyway in lead screws and replaced the key in the driven gear with great results. I even had to bush a gear and make a rectangular key once and made half nuts on a large antique lathe. Flipping the lead screw end for end on your lathe would be a piece of cake.

I don't have the knowledge and background that OldTiffle and Evan have but when it comes to repairing and making a duplicate part I excel. I have finished jobs that others had thrown their hands up and gave up on. It seems like everywhere I went I always got the reconstructive work on the shop machines. While I don't like to do the maintenance work I did enjoy the machine work to make and repair.

Your making a mountain out of a mole hill about these repairs, just work it out in your mind and do it.

Ken_Shea
12-28-2009, 11:15 AM
Your making a mountain out of a mole hill about these repairs, just work it out in your mind and do it.

Ha-Ha, yeah, I some times excel at that, thanks for the kick.

Would save a lot of money, which is really adding up now.

darryl
12-28-2009, 03:40 PM
One thing that has occurred to me a couple times during this discussion is the making of threads and the accumulating error of a less than stellar lead screw. How often would you be making threads of much length- and what would you be using them for? Unless you're making lead screws, it probably won't much matter if you can't make a thread that's accurate to one thou in a foot. And as far as being a feed screw, a low grade threaded rod would be accurate enough for that. As it is, with the wear on the rod you already won't have the level of accuracy that a new fairly decent acme rod would give.

It's very likely you could be satisfied with a decent rolled thread acme rod, and so the challenge would come down to milling the slot and preparing the ends. (and deburring the threads where the slot is cut) The half nuts could be remade by cutting an acme nut in half and fitting the pieces in place of the worn parts. It would be a project of course, but to save several hundreds it could be worth it.

Ken_Shea
12-28-2009, 04:40 PM
Your right Darryl, I had posted that I have never turned a thread over 6", should i need one, I have another lathe here at the shop that this can be done on, including metric threads which the 5914 will not do, at least inexpensively.
Flipping end for end would give a very good section of essentially unused leadscrew, for little more then some labor to adapt each end, don't think the slotting would even need done since the bad section would now be much further toward the tail stock.
Still it looks like the parts could all be replaced including bearings and belts for about $1000 and simply put it back together.

I did get the additional part quotes back from Clausing.

Q-395S Split nut Pair - $151.76
DL-628 Thread Dial GEAR - $66.76
696-098 LEADSCREW for 36" - $440.00
5900-44 Drive Key - $7.04
Q-384 Rack Drive Gear - $91.28

lazlo
12-28-2009, 04:43 PM
Flipping end for end would give a very good section of essentially unused leadscrew, for little more then some labor to adapt each end, don't think the slotting would even need done since the bad section would now be much further toward the tail stock.

That would be a PITA -- the drive end of the leadscrew is counter-bored to mate with the drive shaft on the QCGB for the shear pin.

Ken_Shea
12-28-2009, 05:44 PM
That would be a PITA -- the drive end of the leadscrew is counter-bored to mate with the drive shaft on the QCGB for the shear pin.

Agreed, this whole thing is becoming a PITA :D
Looks to be enough room to drill another, if necessary, certainly doable. One thing for sure, it's not going back on the same as it came off, that may mean flipping and it may just mean biting the bullet and replaceing the leadscrew along with the other components, the total difference is about $500 dollars, there is a large coffee can full of change here that probably has more then that in it :D

darryl
12-28-2009, 06:27 PM
Those prices are scary- $90 for one small gear, $60 for the other-

At my local supplier, I was told 'that acme rod is going to be expensive'- up to 10 times the price of ordinary threaded rod. So they were prepping me for the high price- just under $40 for three feet. That was only half inch though.

Ken_Shea
12-28-2009, 06:38 PM
Those prices are scary- $90 for one small gear, $60 for the other-

At my local supplier, I was told 'that acme rod is going to be expensive'- up to 10 times the price of ordinary threaded rod. So they were prepping me for the high price- just under $40 for three feet. That was only half inch though.

Yes high, but I feel it is fairly priced considering they don't sell thousands of them, now the lead screw is another story.
From what Lazlo posted, there is a big big difference in general Acme rod and the Clausing lathe leadscrews with regards to pitch error per foot. See post# 30, if this screw is that quality I can see where the additional cost comes from.
I am going to ask them what the error is should I order it.

KDuffy
12-28-2009, 09:47 PM
Check out the error on Keystone's stock, you said you have another lathe. I used to have info for a supplier of threaded rod, may have even been Keystone, but the error was very small, on the order of .0005 per foot, that was rolled, hardened and ground threaded rod. Prices were pretty reasonable as I recall, been more than 10 years when I was considering a similar project. Just saying look around open mindedly. The half nuts would be a fun project too!

Don Young
12-28-2009, 10:12 PM
Pictures can be misleading but it certainly looks to me like the half-nuts are badly worn and the leadscrew threads are in reasonably good condition. Unless you are making something like a micrometer or a leadscrew for a jig borer I think that leadscrew will be perfectly satisfactory. Most good micrometer screws have errors in the order of 0.0001" per inch or 0.0012" per foot. You will notice that any one micrometer generally does not go from 0.0000" to 12.0000" (a foot long screw).

There certainly is nothing wrong with wanting everything to be as good and accurate as possible but whether you will notice the difference is also a legitimate point. I believe that threads on commercial fasteners can have pitch errors of a few percent, much worse than your leadscrew is likely to produce. Since the wear is gradual and not abrupt, I would challenge you to cut a thread with it and detect a pitch error without laboratory inspection equipment! If your threading work is going to be subjected to lab inspection, that changes the picture.

I don't know what kind of work they were doing but I was given some old leadscrews that were in use until they actually stripped. I don't think that is a good idea!

nheng
12-28-2009, 10:23 PM
You might want to check with Joe at Plaza Machinery in VT for various parts. I saw a number of Rockwells and pieces there but it was several years ago. Den

Ken_Shea
12-28-2009, 10:25 PM
You might want to check with Joe at Plaza Machinery in VT for various parts. I saw a number of Rockwells and pieces there but it was several years ago. Den

Already have Den, that was a suggestion earlier in the thread, waiting for a reply presently.