# M6-25M Extension bracket and enough confusion to last the day...



## kopcicle (Dec 26, 2020)

First, let's identify the victim. 


This is an early MK II with the cast iron headstock. Current upgrades are the headstock bearings, Metal gibs for the cross and compound, Phase II QCTH, and a thorough cleaning that uncovered a few common ills that were fixed.  



My current boggle is .5mm pitch threads. 

So I have acquired a drawing describing the extension bracket and 3D printing is in progress on two fronts. The first is an 80% in-fill for immediate experiment/use and the second is for 15% in-fill for lost PLA casting. Seems that any less than 15% in-fill risks dimensional stability. @wa5cab   I hesitate to post my drawing or code to avoid any confusion after reading some previous posts.

Now the issue is how and where/when to use it. "Do the file "Atlas M6-735 Instructions For EXT BRKT For MM Threads.pdf" strike a familiar note"? 

So today with some time on my hands I'll attempt to CAD/Code the part for my router and see if I can mill it out when I get back to the shop.

As for the bracket , M6-25M the drawing I have is dated 2-23-38 and probably has nothing to do with the later 041-464 change gear bracket from the Mk II . In any case the bracket will get drawn , coded , built , and added to the library for what ever reason. Most likely for my brother's 618 and any others that can benefit.

For .5mm pitch the 54 on the screw is easy enough. B for back position. Position "C" again is easy enough 44B and 46F. Now without the bracket here to play with it gets a bit curious. "A" is the position furthest from the screw and 36B , 20F. Position "B"is the source of confusion. As I understand it position "B" is between the screw and position "A".   The 20B and 40F designation are no problem but I for the moment I fail to see how it all fits together. I suppose It will have to wait for me to be sitting in front of the machine.

In advance, Thank You all for your efforts here. If there is any way anyone can help clarify this it would be appreciated.

~kop


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## Jim F (Dec 26, 2020)

From MOLO


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## kopcicle (Dec 26, 2020)

Yes Jim I have that. I still can't seem to reconcile the gear chain with the bracket, with the positions, with the ratios, on the lathe :-/ 

For .5mm pitch, right to left I read it as , 
32 from spindle stud gear, to 38/20 in position "A" , to 40/20 in position "B" , to 46/44 in position "C", to the 54 on the screw in the back position.   Additionally position "B"  shows as 20 ("B" for back), 40I ("F" for front and "I" for idler). 
Does all this fit on the bracket and mesh ? I really wish I was sitting in front of it right now :-( 

~kop


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## Jim F (Dec 26, 2020)

Should work, not that many big gears.
Be thankful you do not need a 127/100 gear.......


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## benmychree (Dec 26, 2020)

127/100 gives the exact inch/mm conversion, all other gear combinations are only approximate.


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## kopcicle (Dec 26, 2020)

@benmychree , John, 127/100 does give the exact inch/mm conversion however over a 20mm length the difference is minimal. 

@Jim F , Jim, I do not need a 127/100 gear! see above. I just can't seem to visualize the combination of gears without having the thing in my face  

~kop


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## Jim F (Dec 27, 2020)

Did you get it figured out ?


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## kopcicle (Dec 27, 2020)

...as with most of my "round to-its"    I'm working on it


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## Jim F (Dec 27, 2020)

I think I have it figured out.


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## stevejigsaw (Dec 31, 2020)

@kopcicle just out interest what headstock bearings did you use for your 10100?


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## kopcicle (Dec 31, 2020)

Atlas 6" 10100 lathe would like to order new Timken tapered roller bearing
					

I've never bough bearings before, and I do not know that much about them anyways. Does anyone know the part numbers to order for an atlas 10100 lathe, think blue paint :) I did search the forum yesterday and found people looking for them but I never saw a specific part number or a link to a...




					www.hobby-machinist.com
				












						Bearings Bushings Atlas Lathes & Mills.pdf
					

List of spindle bearings and bushings for Atlas and Atlas/Craftsman lathes and mills




					www.hobby-machinist.com
				




The 2 cups are Timken 07196, the front cone is Timken 07100, the rear cone is Timken 07079.

Okay, with all that I had my bearing guy "whip something up" If I can't find the receipt I may still have the boxes with the old bearings in them. I wonder why I do that knowing I'll never re-use those bearings but...


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## topcat41468 (Dec 31, 2020)

Just send in a print for the bracket out of SLS glass impregnated nylon.   It'll take a few weeks to get here with the holidays, but once I get it I'll let you know how it works in "not metal".


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## stevejigsaw (Jan 1, 2021)

topcat41468 said:


> Just send in a print for the bracket out of SLS glass impregnated nylon.   It'll take a few weeks to get here with the holidays, but once I get it I'll let you know how it works in "not metal".


And are you going to use it on a 618 or MK2(10100)?


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## topcat41468 (Jan 1, 2021)

A 618, actually a craftsman 101.07301.


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## stevejigsaw (Jan 1, 2021)

I saw this pop up on ebay today.

NEW ATLAS CRAFTSMAN 6 INCH LATHE M6-735 METRIC THREADING KIT+INSTRUCTIONS USA


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## kopcicle (Jan 1, 2021)

Appears I'm not the only one chasing this grail ....


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## kopcicle (Jan 1, 2021)

so, let's review




This is the first mention I find of the extension gear bracket.


On the left is a 618metric  threading chart. On the right is a Mk II metric threading chart
On the left for the M6-25 bracket. On the right for the 041-464

The original info doesn't apply to me
The MK II manual makes no mention of the accessory bracket but does add "position B" between the screw and "position A". I wonder if I have enough room for position "D" in the MK II.

The plot thickens. All I wanted was M6 x .5 mm threads ...


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## stevejigsaw (Jan 5, 2021)

I also have an Atlas Mk2 the same as yours but I haven't done a lot of thread cutting only manually using the tail stock so sorry I can't help more. In saying that I would be happy to hear how you go on your quest for M6 x .5 mm threads


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## kopcicle (Jan 5, 2021)

stevejigsaw said:


> I would be happy to hear how you go on your quest


No problem. I've never been able to keep such things to myself 

While I'm here. Things that make you go , hummmmm.


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## kopcicle (Jan 9, 2021)

So , I needed the bracket as I ran out of room on the AB slot.
"When calculating the ratios, ignore any idler gears; the 20 and 24 in your tumbler and the 40 in position-B.

Reduction = (32/32) * (32/36) * (20/46) * (44/54) = 0.3149

16 TPI / 0.3149 = 50.81 TPI"

*Courtesy of Brett Riggs gofastforless.com / mrriggs@gofastforless.com
Brett is another of my recurring victims when it comes to odd machine issues.

The original bushing was an issue on the bracket slot. It had too much chamfer and seized on tightening. I used the sharp shoulder from the one I made and moved the original to the bracket attachment/position "B".
The "A" and "B" bushings are upside down , shoulder to the outside.


I didn't have time for a scratch pass as she said "time to go"!

I'll follow up tonight .



~Dennis

P.S.

A friend upgraded to a 10" heavy a year or so ago and had a pair of NOS half nuts for his 6" left over . With no warning they showed up in the mail Friday with a Merry Xmas note attached! "Here's a pair of half nuts. That is two whole nuts. Now ya got a pair!" 

Sometimes it's a good thing when your friends are close relations of Richard Cranium, ~D...


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## kopcicle (Jan 10, 2021)

Spindle is 32T
Tumbler is 20-24-32T
end or position "A" is 36 Back 20 front
Position "B" is also the attachment point for the M6-25M extension bracket.
"B" is 20T back (spacer) 40T front (idler)
position "C" is 44T back 46T front
Gear on screw is 54T in the back position.
Lead is of course 16/in

Of curious note this setup will move away from the chuck in normal "forward" rotation when the half nuts are engaged. (the extra gear in the chain)
*_edit: I suppose this is what the reverse tumbler is for,right? (du'oh)_

I'm stealing time where I can. I did get a scratch pass in last night but was not able to measure it. I'll be doing that shortly .


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## kopcicle (Jan 10, 2021)

and it works!


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