NEW Leadscrew for Atlas/Craftsman 6" lathe from Clausing

[SG51Buss]

I've been meaning to replace the 65 year old leadscrew on my Atlas/Craftsman 6x18 101.07301 6" lathe for over 25 years.
The Acme threads look like V-threads in the middle of the screw.
I had investigated 3 options:

1- Cut/machine/join a piece of precision Acme threaded rod to the original.
-- Couldn't find precision 1/2" - 16 TPI Acme rod, without expensive special order.

2- Acquire an eBay item.
-- After looking at various eBay $25-$100 offerings, I just knew there would be wear and other secret problems.

3- Buy a new one from Clausing or Sears.
-- Sears wanted $180, Clausing $148

The new LeadScrew from Clausing arrived in 3 days in a stout cardboard tube.
It had been pickled and wrapped very thoroughly.:ups:



The original part number, L9-35, has been superceded by part number 3950-16, which includes the fitted thrust collar.
The parts support representative at Clausing said they had been out-of-stock, and have replenished the supply from a new run in September 2014.

Clausing Service Center
2019 North Pitcher St.
Kalamazoo, Michigan 49007-1822
(800) 323-0972

 

[SG51Buss]

Be advised that this new leadscrew is not a drop-in replacement.
Need to do some meticulous work. :fingerwag:

Cleaned off the new leadscrew and checked for straightness.
Found a very slight bend, only about 0.005" runout. Got it to less than 0.002".

 

[SG51Buss]

The thrust collar, as fitted, is about 0.285" thick.
The stud spacers that fit between changegears and the banjo are 1/4" thick.
To provide proper gear alignment, and clearance to any large gears that may run behind a spaced-out leadscrew gear, the thrust collar needs to be faced down to 0.247".

The threaded/keyed end of the leadscrew holds the leadscrew gear and its spacer.
Since the gears and spacers are 3/8" wide, their total width is 3/4".
To ensure that the leadscrew's gear clamping screw presses against the gear/spacer, and not prematurely bottom on the leadscrew shaft, the protruding end of the leadscrew needs to be a little shorter.
In this case, 0.735" will work.

Here are the dimensions of the original ~1950 leadscrew end.

 

[SG51Buss]

Measure the new leadscrew's thrust collar and protrusion.
With the above dimensions in mind, perform the appropriate facing cuts.

 

[SG51Buss]

The tops of the threads of the new leadscrew were slightly distorted from thread forming.
Instead of squared/flat tops, they had a slight "U" shape.
This made the leadscrew's outside diameter about 0.503"-0.504", too big to fit through the original support bearing.
The leadscrew had to be turned and carefully fine-filed and stoned to a diameter of about 0.4995"-0.5000".

This pic shows a close-up of the reworked new leadscrew, the thread tops resurfaced and flat.
The original 65 year old leadscrew shows V-shape thinning of its threads.




Want minimal wear on bearings and half-nuts.
So, finely sanded any rough spots and burrs, then polished the threads and shaft bearing surfaces.
Thoroughly clean, wipe everything down with a "red shop rag".
If any red fibers can be found on a surface, it needs to be polished some more.

This new leadscrew works great...:morningcoffee:

 

[Crafted]

My QC42 is worn sharper than that. Great post. Learned something. I'll be replacing mine as part of my refurb. I remember 18 years ago when I obtained it. I bought some parts that were missing, replaced a broken handle, purchased the milling attachment. However, I remember choking at the screw price. Wish I had gotten it then.

 

[great white]

Great post. Subscribed for future ref!

:thumbzup:

 

[SG51Buss]

Thanx, guys. Just another "measure twice, cut once" type of thread.

It would be great if someone could comment/confirm that thrust collar dimension.
The 0.285" thickness may actually be correct for a different 6" lathe, I just don't know...

 

[T Bredehoft]

My pre-1963 (no Zip Code) Atlas Clausing 6" x 18" very nearly unused lathe had a .237-8 spacer.

As to mis-alignment of the lead screw, I disassembled the compound and lead screw to clean dried grease from them, upon re-assembly I first put in the lead screw and secured it, then slid the compound onto the ways.I had to lift the end of the lead screw about quarter inch. This put a bind on the screw where it went through the frame. I removed the compound and put the support for the right end of the lead screw on the screw. I had to raise it about 1/4 in to get the screws in.

Tom

 

[wa5cab]

Steve,

The part number 3950-16 indicates that it was made for the 6" MK2. I wasn't aware that there was any difference but that's handy to know. Unfortunately, we don't have the drawing of the original part.