Brass ACME nut repair

I have been reading your threads and it is clear you have never rebuilt a lathe. You will find that this is the tip of a big iceberg. You can do 2 things, rebuild it right, use it like it is, or sell it and buy one that isn't clapped out.

So let's examine the first option. You don't have the tools to make your own parts, so you either have to buy the parts or pay some one else to make them. The advantage is you will know how to do this right the next time. You will spend a lot more money and time than you think and finally understand why it was sold for what you paid in the first place.

The second option will teach you how to use a lathe. It will also teach you the tricks necessary to do accurate work with junk. (very valuable) Most importantly, sooner or later you will get a chance to use a good machine and then you will understand the difference first hand. After that, you will know why your machine was sold for the price you paid.

The third choice is one you should make, but won't, until you experience either option 1 or option 2.

Lastly, how do I know this? Because the brass nut is not brass. It is bronze. Probably Phosphor or Silicon Aluminum and much harder than brass. Please do not take offense to this reply. I am not trying to insult you. This is solid advice because many of us have been there and done this before, including me. I think this task is not only beyond your skill set, but you probably do not have access to a complete machine shop that this task will require. Furthermore, I really do not want to see you to waste the money option 1 will cost, because it isn't economically prudent. You are far better off spending the correct money for a good machine. Let me put option

1 in perspective. The last lathe I rebuilt was a 13 x 40, late model South Bend and it wasn't clapped out. It took me 18 months and $3,000 and I had all the tools I needed before hand. That cost did not include the purchase price. I did it because I liked the machine, not because it was the smart thing to do. Another thought you need to make is that the cost of the working machine typically represents about 50% of the total investment. The rest is the investment in tools and accessories. Often this last 50% can be even more. So I suggest you think about compatibility of tool cross use and the cost and general availability of the tool family, as this can vary widely as well. Steve

yep

Steve, what did you have to fix with your lathe?

As far as the machine shop goes, I have a mill, which is not much but it lets me do quite a few things that I need.

Anyway, I think that you are right. And I had some experiences with DIY projects that ended up costing many times more than would be new brandname items, if I take the cost of my time into consideration.

Anyhow, for now, my plan is to keep the lathe for a couple of months, learn how to use it a little bit, fix easy things (such as that on/off switch that I talked about, nut etc) and then I will sell it, properly described of course.

i

I read posts like this frequently but in reality any machine tool built before the advent of ball screws had backlash in all its adjustments. Apprentices were taught to cope with this problem by making all adjustments in the same direction - opposite to the force being applied by the cutting tool. In your lathe's case, assuming normal turning operations, you back the tool off and then readjust it toward the work until you reach the dial setting you had used for the previous cut and then as much more as you want for the next cut.

If you want less slop then just make a new nut.... after all, you've got the lathe to bore and thread the new nut.

Bruce-in-Bangkok (correct Address is bpaige125atgmaildotcom)

====== also see

It might be better to epoxy the nut in place as it will be easier to get back out if necessary..... also easier to shim into exact position. Setscrews might be good also.

Unka' George [George McDuffee]

------------------------------------------- He that will not apply new remedies, must expect new evils: for Time is the greatest innovator: and if Time, of course, alter things to the worse, and wisdom and counsel shall not alter them to the better, what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman. Essays, "Of Innovations" (1597-1625).

======== You can also get a piece of 3-4 X 5 LH "allthread" from the URL I posted for the nuts see

entire rebuild kit [some assembly required]

Unka' George [George McDuffee]

------------------------------------------- He that will not apply new remedies, must expect new evils: for Time is the greatest innovator: and if Time, of course, alter things to the worse, and wisdom and counsel shall not alter them to the better, what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman. Essays, "Of Innovations" (1597-1625).

I took the screw out. It has some wear, but nothing major. On a cross slide screw, if I use a new nut, I will have modest backlash, which is totally OK.

You can adjust the cross slide in the opposite direction if you pull it by hand to "aid" it's motion.

i

Is this what you are refering to?....Paul

Looks like a great find, but this is for a different Clausing.

i

Steve, can you share, what did you have to do to fix up your lathe?

I do not want to eliminate all backlash, just some. The screw has wear, but not much.

I will post some numbers on the backlash prior and after the replacement.

i

What about facing?

John Martin

I'm not positive, but suspect that the nuts and leadscrews sold by McMaster-Carr might be somewhat low precision. That might not be important for the compound or cross slide where travel is usually short, but you should be aware of it so you can make an informed decision.

Mike

I think that all cross slides should have backlash, I just want to have it smaller. I think that I can do it without breaking anything and can always reuse the old nut.

Hmm ... maybe.

I don't know what the design of this nut is, but the nut for my Clausing 5418 is a 'T' shape in bronze with the vertical bar of the 'T' upside down -- running through the top of the cross-slide. In its center it has a spring-loaded ball and a bore down to the leadscrew so you can oil it regularly.

Note; that half of the slop is likely to be wear in the leadscrew itself. To check this out -- crank to the very outer position which still has the leadscrew fully inside the nut and check how much backlash you have there. What you find there will be what comes from the nut, and what is in the middle will be from the wear on the leadscrew, since the leadscrew tends to wear mostly in the middle. If you discover that the leadscrew is a large component of the slop, you should plan to either purchase and replace the leadscrew too, or to make a replacement leadscrew (left-hand ACME threading).

As for the epoxy you want to put in -- look up "Moglice" which is an epoxy designed for just this kind of work -- rebuilding nuts and the sliding surfaces on the carriage.

Oh yes -- if you try the epoxy/Moglice approach and the leadscrew is worn, if you have the leadscrew in the most worn section while you pour the epoxy, you probably can never get the leadscrew out of the nut. :-)

Check the design. I think that this is probably the best route. And make a new leadscrew while you are about it.

:-)

There must not be many of these made here. I think that the machine you got was made in England, not in the USA.

Good Luck, DoN.

And -- one thing which you can do is to mount a dial indicator with a two or three inch travel so it measures the motion of the cross slide. This will be more accurate than a worn leadscrew in a worn nut. (If it were just the nut worn, you would have the same backlash all the way through the range, and your dials would be accurate enough. However, if the leadscrew is worn, that will be more so in the middle of the range, and will introduce extra errors -- unless you are measuring cross-slide travel with something which does not depend on the leadscrew.

My 5418 had the leadscrew and nut so badly worn that it was producing 0.070" of backlash in the middle of travel -- and this on a

1/2" diameter leadscrew which produced a full 0.100" travel per rotation when in good shape.

However -- the leadscrew and nut were a lot less expensive for mine -- at least back when I got it. :-)

And at least you have a larger bore than I did. Beware that you will probably need to make a left-hand thread ACME, not just a normal ACME if your cross-slide is like mine. Check it out before you order anything.

Good Luck, DoN.

Check the width of the crest of the thread on the screw. Compare the crest in the middle and at the extreme ends to get an idea of how worn it is. (The accurate way to do this is with an optical comparator and with dial indicators on the slides.)

As an example, the cross-slide leadscrew in my Clausing 5418 looked like this at the ends (as it should) (Of course -- view with a fixed pitch font like Courier -- I expect Iggy to do this normally, but others may not): _ _ _ _ _/ \_/ \_/ \_/ \_

But the middle looked like this:

_/\__/\__/\__/\ _

The nut was worn too -- but not nearly as much as the leadscrew.

Good Luck, DoN.

I have this too, but not much. I received the nut today and it does fit the leadscrew. I machined it today to be of yoke shape instead of square. I need to solder a little extra brass padding to complete the shape, and drill/tap that for the screw. I hope to have a replacement in a few days. I will not in any way disturb the original nut, so this is all quite safe.

It also is for a different part of the lathe. This is a leadscrew and nut for the compound, not the cross-slide.

Enjoy, DoN.