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Craftsman 101.07301 half nut cam

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92VwGTI

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#1
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.
 

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markba633csi

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#2
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
setscr1ax.jpeg
 
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92VwGTI

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#3
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

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#4
What material is the handle made of and how well does it tap?
 

markba633csi

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#5
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

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#6
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

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#7
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

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#9
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

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#10
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
 

David S

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#11
I am not familiar with your model number. I have the Atlas 618 and it came with spare parts as shown in the picture. The actuator is one piece with a square end that fits into the square on the handle.

long feed parts.JPG long feed lever.JPG

David
 

92VwGTI

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#12
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
At least one of the previous owners had no “feel” for mechanical repairs/adjustments. There were several parts overtorqued and/or broken and quite a few hack repairs. Regardless, it’s a good machine for me to learn on. In my experience, learning how something works and repairing it are the best ways to learn.

At this point I am leaning towards the set screw method of attachment. I really only need a way to hold the handle on so it doesn’t fall off during operation, the flats of the square shank will handle all of the rotational forces.
 

markba633csi

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#13
Fixing a messed up machine is sometimes the best way to learn- and for many of us it's a big part of the fun
 
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wa5cab

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#14
The 101.07301 (made by Atlas and sold by Sears) and the 618 (made and sold by Atlas) are mostly the same machines except that the former uses an earlier version Countershaft assembly and has sleeve spindle bearings and a ball-type thrust bearing. The carriages are the same.

If it were mine, I would convert the half nut lever assembly to the new style by drilling, countersinking and tapping the end of the scroll's square shaft and making a washer to go over the square hole through the lever.
 
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