6 AT collet set up

[cross thread]

It is tiny , stock collets 9/32 max - 1/32 smallest . I have a MT set up that is 1/2 max - 1/8 smallest . So why would I want the 6 AT ? Aside from the fact that you can pass a rod through the spindle , the main thing this was original Atlas tooling and that was the draw for me . Be it pretty much useless but it's mine and I love it . I have a few questions that I know you guy's can help with . My machine is an Atlas / Craftsman 101.07301 six inch swing , that's the one with back gear and spindle bushings not Timken bearings .
As you can see in the picture the set up came with a spacer that is about 1 inch long , when using that one the tube is not long enough to thread into the collet . I made a 1/4 inch thick spacer to make it fit . My spindle is 8 3/8 long so obviously this fit a shorter spindle . My seller included a picture of the name plate and it was 101.21400 .
Would someone with a 101.07301 Timken or a 101.21400 and a 101.21200 (MK 2) tell me the length of their spindle , please .
I would like to make some pot chucks also called emergency chucks for this set up , the collet thread is not something normal that I could run a die on so I will have to single point it . The thread size is .415 - 27 , has anyone ever heard of that ?
Thanks , Mark .
collets by mark westi, on Flickr

 

[wa5cab]

Mark,

First, you should always include the "101." on the front of any Sears model number that was made by Atlas. At this late date, there is almost no chance of someone else making and Sears selling anything that they used to get from Atlas, Atlas-Clausing or Clausing-Atlas but play it safe. And also, the first Atlas model # of the MK-2 6" was 3950. That was the one with the ball bearings. The later one where they went back to the original Timken bearings was 10100. Sears did not sell that one.

Second, where did you get 6AT as the part number for the 6" collets? We have a copy of the Atlas drawing and it says M6-751. I will confirm that it got uploaded after I finish and save this.

Third, where did you get the thread specs? The drawing says that they are 0.420"-28 RHUSF.

 

[cross thread]

OK Robert , from now on I promise "101" xxxxx . What I'm curious about is the spindle length but it doesn't really matter so please anybody no need to waste time on that .
The part number M6-751 is the # Atlas assigned to the whole set up , draw in tube , collets , collet nose , thread protector . As an aside my set up came with a 1"-10 thread protector .
These collets are 6AT some of them are even "factory" marked 6AT , mine were made by Royal . I have seen them also made by Sutton .
Here is the Atlas paper work on the 6AT . Note M6-750 . However on the lathesUK's Atlas attachments and accessories for the 6 inch (6 inch) is Atlases wording not mine . http://www.lathes.co.uk/atlas-6-inch-lathe-accessories/ .
For the specs on the collet , my bad they are in fact 28 TPI . The OD that I measured it turns out only one is .415 the rest are .420 .
As for the .420-28 RHUSF thread I'm sure the information is in the Machinery's Hand book somewhere , but it doesn't really matter I'll be single pointing .
Mark .

 

[wa5cab]

OK. The .PDF problem was either fixed or fixed itself so the drawing of M6-751 collet is now in Downloads.

It is difficult to judge intent 78 years on but I think that originally the collets were all M6-751 and the 6AT came later and possibly not originally from Atlas. There are or at least were originally drawings of both draw tube assemblies and/or all of the individual parts, the closer-adapter, and both thread protectors.

RHUSF means Right Hand Unified Special Fine. Which wasn't dreamed up by Atlas. It came from ANSI and the British equivalent, whose name escapes me at the moment. M6-750 is the Atlas part number or order number for the whole setup, not M6-751.

Fourth, I am afraid that you will have to re-do the spacer on the draw tube. Because the tube is a loose fit inside the spindle. it will tend to drop down slightly, causing the collet to not quite to lie on the spindle axis. You will need to taper the nose like the original one is so that the hand wheel end will center up in the spindle through-hole and pull the collet in straight.

 

[kopcicle]

The 10100 uses the 701-088 spindle and tapered roller bearings
The Craftsman 101,21200 uses the 701-083 spindle and uses the 6305 bearings
The Tapered bearing can be used in the 101.21200 using 30305 Timkin https://cad.timken.com/item/tapered...ings-ts-tapered-single-metric/x30305m-y30305m
If you really want 17mm width instead of 18.250mm width use 237 cone -233 cup and pay $2k for the pair
Even if you use the 30305's on the 701-083 spindle how are you going to preload them ?

My best suggestion is to find the total AXIAL clearance/tolerance for the 6305, carefully measure from shoulder to shoulder on the spindle and make a spacer that fits over the shaft and between the inner races , and positively locate the races in the bearing and be done with it. It's how we do motorcycle axles and have done for eons.

@wa5cab , Robert you can keep or put the above anywhere you want/need

As for the drawbar , don't over think it. I have metric and imperial made from old lamp hardware. The handle/wheel was whatever I had in scrap or spares. the spacer to locate the bar and wheel is however essential. We hav enough going on with these little lathes without having some out of round off balance chunk of thing going round on the back of the headstock.

Yeah too many words but ..

 

[cross thread]

Hi kopcicle , thanks for all that info . My machine , a 101 07301 is a bushing spindle model and back geared . Plus the stuff I'm going on about has nothing to do with bearing preload , there is no bearing preload on my machine only a threaded collar at the end of the spindle to takes up end play . A bit of trivia , I believe my machine to be a very early version (37'-8' ?) as it has a double start 3/8-20 lead screw . That lead screw was on the very first 101 07300 , non back gear .
OK , I should have stated . In my haste to fit the M6750 (-1) ? assembly to my lathe I did not make the spacer correctly , nor the right material . As I didn't have the right material , that material is on order from McCarr , I will use 12L14 . I made the spacer to establish the new thickness , it is about .200 and yes I realize that I have to include the locater angle .
Thanks , Mark .

 

[kopcicle]

Additional note:
The 10100 Atlas did indeed have tapered roller bearings.
The 101.21200 uses 6205 deep groove ball bearings
the 10100 uses the 701-088 spindle
The 101.21200 uses the 701-083 spindle
30305 Timken would accomplish the the swap but..
They are 18.250 mm wide
If you want 17mm wide use the 237 cone -233 cup and shell out $2k for the pair.
The issue with the swap isn't the width however
How do you preload the bearings?

Practical consideration is tale the axial clearance of the 6305 you entend to use

 

[wa5cab]

kopcicle.

I am going to leave them at least for the time being but in the future, please do not upload files to the various Fora that are already uploaded to Downloads. It just duplicates and wastes server storage space.

Also, he has, as he wrote, a 101.07301 which has sintered bronze bushings instead of ball or tapered roller bearings. The only way that he could use the tapered roller bearing spindle would be to change the entire headstock. Which besides being a PITA would also change the spindle nose threads to 1"-10 which he does not want to do.

 

[kopcicle]

kopcicle.

I am going to leave them at least for the time being but in the future, please do not upload files to the various Fora that are already uploaded to Downloads. It just duplicates and wastes server storage space.

Also, he has, as he wrote, a 101.07301 which has sintered bronze bushings instead of ball or tapered roller bearings. The only way that he could use the tapered roller bearing spindle would be to change the entire headstock. Which besides being a PITA would also change the spindle nose threads to 1"-10 which he does not want to do.

For the time being I'll go back to the 101.212 restoration

 

[wa5cab]

kopcicle,

OK. Another problem would be t,hat the holes for the bushings in the 101.07301 headstock are through holes AFAIk. No locating shoulder. The spindle axial load in the 101.07301. like in the babbit bearing 10" and 12", is taken by a thrust bearing.