Craftsman 101.07301 half nut cam

[92VwGTI]

Hello all,

I recently bought a new cam for the half nut on my 07301 and although it’s the part number for my lathe, it is different from what I removed. Is this the correct part for my model? The new one is the longer one and it is not threaded and I have no way to affix the lever. I can drill/tap if needed but I’m just trying to source the error here.

 

[markba633csi]

I believe your original one was modified by the PO. Normally they are pressed on and the end of the shaft dimpled in to secure it to the handle.
But having the screw fastener is a handy idea especially if you might have to disassemble the parts again. I would probably choose a #8 or #10 screw
thread rather than 1/4-20 if you were to duplicate the PO's mod
Alternately, you could drill and tap the handle itself to accept one or two setscrews at 90 degrees to the shaft instead-
Mark

 

[92VwGTI]

I believe your original one was modified by the PO. Normally they are pressed on and the end of the shaft dimpled in to secure it to the handle.
But having the screw fastener is a handy idea especially if you might have to disassemble the parts again. I would probably choose a #8 or #10 screw
thread rather than 1/4-20 if you were to duplicate the PO's mod
Alternately, you could drill and tap the handle itself to accept one or two setscrews at 90 degrees to the shaft instead-
Mark
View attachment 269292

I definitely like the idea of the screw rather than press fit. I think I’m going to go with the set screw idea as the previous owners design didn’t work very well. Thanks for the help!

 

[92VwGTI]

What material is the handle made of and how well does it tap?

 

[markba633csi]

The handle is zamak alloy, easy to machine
two setscrews would probably be optimum, at right angles to each other to bear on two adjoining flats on the shaft. Maybe 8-32?

 

[wa5cab]

Sorry, but that isn't what happened. Early production lathes have the square outer end of the scroll (half-nut actuator) extending all of the way through the lever, with the outer end peened to secure the handle in place. I haven't been able to pin down when the change was made but later production has the square outer end somewhat shorter and drilled and tapped. The square hole no longer goes all of the way through the lever and the outer side of the lever is drilled through and countersunk for an oval head countersunk (rack and panel) screw. You either need to find a later handle or you need to mill the outface face of the handle flat and use a thick flat washer with the hole in it countersunk. If I were doing it, I would also add a square spacer to fill the hole, with the hole through its center partially countersunk.

 

[92VwGTI]

Sorry, but that isn't what happened. Early production lathes have the square outer end of the scroll (half-nut actuator) extending all of the way through the lever, with the outer end peened to secure the handle in place. I haven't been able to pin down when the change was made but later production has the square outer end somewhat shorter and drilled and tapped. The square hole no longer goes all of the way through the lever and the outer side of the lever is drilled through and countersunk for an oval head countersunk (rack and panel) screw. You either need to find a later handle or you need to mill the outface face of the handle flat and use a thick flat washer with the hole in it countersunk. If I were doing it, I would also add a square spacer to fill the hole, with the hole through its center partially countersunk.

The photo quality appears to greatly diminish uploading to the forum but my handle has a square hole all of the way thru. The square end of the old half nut cam was either broken or cut from the cam itself and is inside of the lever.

 

[92VwGTI]

Here’s a few more pictures. The one on the right in both pictures is the old one. You can see that the square portion is broken off.

 

[92VwGTI]

The whole function of the previous setup relied on the clamping of the lever to the small nub that stuck up from the cam. The only way it worked was to have that screw holding the lever on cinched down so tight the lever required quite a bit of force to actuate. Another problem with this design is that every 2-3 times you release the half nut, the screw will loosen enough that it no longer functions and has to be retorqued. Had the square shank been connected to the cam and the screw used only for holding the lever on this design may have been practical, but not in it’s separated state. I have a very hard time believing that this was a factory design, especially considering how well thought out the rest of the machine is for a hobby tool. I suppose anything was possible in the 30’s tho.

 

[markba633csi]

Looks like what you had was a total kludge from the previous owner/butcher
The new part should work much better no matter which way you attach the handle
I was never fond of the dimple style technique, using 90 degree setscrew(s) makes more sense to me