Atlas 618

I got my lead screw and half nut set. Both are incorrect for my 618. The lead screw apparently came from a Craftsman with the crank handle on one end. I don’t know what the half nuts fit. They fell completely through M6-13A guide.
 
The 618 and the 101.07301 have different part numbers for the lead screw for some strange reason. I do not know what the difference is, if anything. But the half nuts are the same. And neither screw has a hand wheel on it. So the parts that you bought must be off of one of the AA (Double-A) lathes that Sears sold briefly during WW-II and again from 1948 until 1959 or 1960. So the parts that you bought could be for a Craftsman but not one built by Atlas. Unfortunately, most people don't know this. Whether you can get your money back may depend upon how the seller described it. If he said that it fits any of these numbers, you should be able to: 101.07301, 101.21400, 101.21200 or 618. If he only said that it fits one or more of the following numbers, it depends on how understanding he is: 109.0702, 109.20630, 109.21270. Note that the first of these was sold under the Dunlap badge but the other two had Craftsman badges.
 
wa5cab, I contacted both guys about the parts. The lead screw came off a 109 style lathe. The guy I got the half nuts from said there were two types of half nuts for the 618 type lathes. He did give measurements on his ad when I bought them. I didn’t know there was more than one type. Both said to send them back and they would refund my money. I would much rather have the correct parts. Anybody in need of either before I send them back? The half nuts cost $40 and the lead screw was $20.
 
OK. I missed that the half nuts came from a different seller than the lead screw.

Yes, on there having been two versions of the 618 half nuts. I never knew exactly what changed because we don't have the drawings, just that something had changed. If you look at the 1945 and earlier parts manuals that we have, you will see that they say part number M6-12 for the Half Nuts, M6-13 for the guide and M6-12X for the complete assembly. The 1950 and later says M6-12A, M6-13A and the complete assembly is M6-12AX. The difference appears to be the width of the half nuts and the width of the slot in the guide. So those changed sometime between 1945 and 1950. If I remember, next time that I talk to Tom at Clausing, I'll ask him whether the drawing gives the serial number at which the change happened.
 
wa5cab said:
OK. I missed that the half nuts came from a different seller than the lead screw.

Yes, on there having been two versions of the 618 half nuts. I never knew exactly what changed because we don't have the drawings, just that something had changed. If you look at the 1945 and earlier parts manuals that we have, you will see that they say part number M6-12 for the Half Nuts, M6-13 for the guide and M6-12X for the complete assembly. The 1950 and later says M6-12A, M6-13A and the complete assembly is M6-12AX. The difference appears to be the width of the half nuts and the width of the slot in the guide. So those changed sometime between 1945 and 1950. If I remember, next time that I talk to Tom at Clausing, I'll ask him whether the drawing gives the serial number at which the change happened.
Click to expand...
Hi:

My Atlas 618 needed new half nuts. When I ordered them, I didn't know about the changes to the part. The following shows the old half-nuts in the (old) bracket and the new ones which would obviously not fit. After I got the matching bracket, the parts installed without any issues.

Atlas618_halfNuts_old_new.jpg

I believe the half-nuts were enlarged to stop them from wearing out as fast. More threads engaged on the lead screw would spread the wear, IMHO.

Craig
 
Go with the wider half nuts in the pic. They are in MUCH better condition than the narrower half nuts. The "V" shaped threads on the narrower half nuts used to be squarish, but have worn considerably. This will result in a lot of slop / backlash between the half nuts and the lead screw - and a tendency to disengage, which of course is the very problem you've been having with your lathe.

Given the rust pitting on portions of your lead screw, i'd still replace it, but i'm betting that everything would work just fine with the new half nuts and the old lead screw. The lead screw threads look a bit rust pitted, but not significantly worn. They are supposed to be squarish.
 
First, I think that if you use a wire brush, the lead screw will clean up nicely. I could be wrong but the rust visible in the photo near the right lead screw bearing looks like it would clean up nicely.

Second, the highest 618 serial number that we have in the database is 027421 from which I guessed that a total of about 28,000 were made from mid 1937 up through mid 1972. We have no production figures to go by and it would be reasonable to assume that more were made in the 1940's than in the 1960's but I would guess that your machine was made in the 1960's. We do know that the 1945 parts manual showed the narrow half nut and guide (M6-12 and M6-13) and the 1950 one shows the wide one (M6-12A and M6-13A). So I would guess that your 618 didn't originally ship with the narrow half nuts. You might, if you can, ask the previous owner when he bought the lathe and whether or not he remembers changing the half nuts.

However, it would appear that that problem has been fixed!
 
I have a very uneducated question. Is there a top and bottom half or are they, my belief, exactly the same?
 
There should have been an instruction sheet packed with the two split nuts, There was with the larger set that I bought for my 3996. I just had a look at it and there is no mention of caring which one went on top. If you didn't get an instruction sheet, the one for the 10/12 says to use a flat file and file a bevel on the four corners where the two come together, and then carefully debur the filed areas.. The two parts may or may not be the same, but it doesn't matter which one goes on top.
 
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