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View Full Version : 10" Atlas half nuts in brass?



fuzzy
01-22-2012, 06:39 PM
the half nuts on my 10" atlas are worn. I know that I can buy replacement ones. I would like to have brass instead of Zimak. I would like to make them myself if possible. I worry about using the lathe with the bad gears ( they still work ). I do have the milling attachment for the lathe to do the milling part of the process. I have done some machine work in the past and would enjoy the challenge. If someone does make them is it a good idea to use brass instead of the original Zimak.

Jeremy_BP
01-22-2012, 06:41 PM
Brass would probably be fine for half nuts. But then again, really anything is better than Zamak.

TOOLZNTHINGS
01-22-2012, 07:02 PM
Hello,

660 bearing bronze would be way better than brass, easy to machine.

Brian

SGW
01-23-2012, 09:05 AM
There are about a million alloys called "brass." Some of them may make good durable bearings, but a lot don't, and the common free machining 360 brass isn't one of them.

Do what Brian said - 660 bearing bronze. If you're going to all the work of making them, you may as well use a material intended for that kind of application.

fuzzy
01-23-2012, 01:20 PM
Does anyone have a pair (or single I think they are identical) worn out half nut for me to use as a pattern? Or possibly a drawing to work from. I am a poor draftsman and having the physical piece to look at and measure would be helpful. I appreciate the advice and will be checking with the advertisers in the magazine for the proper material as was suggested. Thanks!

gzig5
01-23-2012, 05:36 PM
Does anyone have a pair (or single I think they are identical) worn out half nut for me to use as a pattern? Or possibly a drawing to work from. I am a poor draftsman and having the physical piece to look at and measure would be helpful. I appreciate the advice and will be checking with the advertisers in the magazine for the proper material as was suggested. Thanks!

You've got two of them in your lathe don't you?

I looked at doing this on my 12" Craftsman and I decided if I was going to go through the trouble, I would want to tighten up the tolerances on the opening and closing mechanism, essentially making everything from scratch but I never got around to it. I can't find the link now, but a guy repaired the half nuts on his SB lathe by boring/milling out the bad threads, machined to size and split length-ways a commercial ACME tube nut, and then epoxying the halves into place with them closed down on the lead screw. It looked to be a successful repair and I would do the same even if I made new holders and closing actuator.

Edit..I can't find the link I wanted, but maybe something in this thread would help? http://bbs.homeshopmachinist.net/showthread.php?t=42036

gwilson
01-23-2012, 06:54 PM
When I had my 12" Craftsman/Atlas lathe,I wore out those Zamak half nuts in a few month's time. I meant to make some better ones,but I discovered the 10" Jet lathe and sold the Atlas.

What I intended to do was to use a face plate on the lathe,with a 90 angle plate bolted to it. I'd mount the bronze on the angle plate,after I'd finished with the other dimensions,and bore it out,then thread it with a single point Acme threading tool.

I was going to make a short length copy of my lathe's lead screw,and use it as a gauge to determine when the hole in the bronze was threaded enough.

Then,I'd have sawn the halves apart.

I wouldn't be real concerned about a little backlash in the nut. The slack is taken up when you engage the half nuts anyway. Backlash would not affect the accuracy of the threading,and the threading tool would start into the hole it was threading in exactly the same place as it did last time.

Mcgyver
01-23-2012, 07:08 PM
Hello,

660 bearing bronze would be way better than brass, easy to machine.

Brian

I'd think about the material a little bit.

The most worn out stump of a half nut will still move the carriage along with absolute perfect accuracy....provided the leadscrew is not worn. For accuracy, it DOES NOT matter how worn the nut is, so who cares if a soft material is used that wears a bit....and is soft enough not to wear the screw!

I've taken lots of feedscrew assemblies apart with bronze nuts and invariably the feedscrew is badly worn, usually I guess worse than the nut. Thats ok for say a crossfeed where its easy to make a replacement.....but I'd be very reluctant to put some tough material in there that'll wear away the leadscrew

here's one screw worn from a bronze nut and its replacement....I've seen worse

http://i20.photobucket.com/albums/b201/michael0100/DSC_9734-large.jpg



haha, i even had a pic of 'worse' loaded in the bucket



http://i20.photobucket.com/albums/b201/michael0100/crossfeedscrew.jpg

flathead4
01-23-2012, 07:15 PM
Member jayhawkman over at the PM site advertises rebuilt half nuts for South Bend and Atlas lathes. You might drop him a line and see what he has. Says he makes them out of brass.


http://www.practicalmachinist.com/vb/south-bend-lathes/worn-out-half-nuts-184625/

Tom

fuzzy
01-24-2012, 08:57 PM
I appreciate everyone's reply's. thank you. Looking at the pictures I wonder if I should use bronze. I am particular about keeping my lathe clean so don't know if I would have the kind of wear problems shown. I think that I will research the problem/solutions more.

Jim Hubbell
01-25-2012, 12:41 AM
I have made two sets of half- nuts for my ten inch Atlas. The first was, I believe a 660 brass. The second set was made of an aluminum-brass alloy. I don't remember the designation but it is listed in the Handbook. I simpley turned it from a round then milled away the excess and sawed it in two. A small amount of hand filling to fit the mounting slides and they will no doubt outlast me.
If you are interested I will try to post a picture. My dialup is VERY slow.

vpt
01-25-2012, 08:09 AM
Would say 6061 hold up better than the zemak? I know my nuts are worn but I haven't had a problem yet with my atlas. I always just figured if they went out I would make up a new set in 6061.

btw I have replaced the cross slide and compound screws and nuts in my atlas already. Basically because the acme rod is cheap from McMaster, I went with the precision screws. I figured if the half nuts went I would make up a new leadscrew at the same time as the nuts.