Dumb idea of the day

M

mickri

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I have a craftsman 12x36 lathe. Spindle bore is 25/32. I have often wondered if I could bore it to a larger size. And if so, how much could you go. There is a guy who goes by Varmint Al who bored out his HF mini lathe from .808 to 13/16. http://www.varmintal.com/alath.htm This is what got me wondering about boring the spindle on my lathe.

The tailstock end of the spindle on my lathe has 1.25x 20 threads. The minor diameter is 1.1905. Subtracting 25/32 leaves a wall thickness of .205. Going to a 13/16 bore would leave a wall thickness of .189. A 7/8 bore would leave a wall thickness of .158. That is probably the biggest that I could go. What would be the minimum wall thickness that you could have without sacrificing the strength of the spindle.

I know. Just buy a bigger lathe. That isn't going to happen.
 
Sounds like a fool's errand. That's a lot of work for .050" maximum, and thats discounting any loss in rigidity by shrinking the bore size. And if the spindle is hardened, The juice just ain't worth the squeeze.
 
Sure you could take a little off the ID, but there isn't a lot of meat there- isn't a lot to gain
-M
 
Can your project be reworked so it's a turn between center job? Between centers makes it a "no-go" for parting, but might be a thought.

Bruce

p.s. Are you sure you couldn't shoehorn one of these in (the lathe, not the model)? No price given, Craig's List in the LA area. A "paltry" 4 1/8" spindle bore.

1663175753247.png
 
BGHansen said:
Can your project be reworked so it's a turn between center job? Between centers makes it a "no-go" for parting, but might be a thought.

Bruce

p.s. Are you sure you couldn't shoehorn one of these in (the lathe, not the model)? No price given, Craig's List in the LA area. A "paltry" 4 1/8" spindle bore.

View attachment 420342
Click to expand...
Do you think that gal is the operator?
She should tie up her hair before use.
 
The tailstock threads are only .500" long. The OD is 1.250" with a wall thickness of .2344 for 1.25" Then the OD increases to 1.5" and stays at this OD except for a small 2" OD section before the spindle threads.

Spindle.jpg
Like the title says "Dumb idea of the day." What use? Who knows. Maybe a barrel that won't fit between 36" centers and is slightly too big to fit in the 25/32 spindle bore.

I don't think that it would be a big job. Just run the reamer through the spindle. Wouldn't even need to remove the spindle from the lathe.
 
Before I modify any machine, I ask myself these questions. Is this a onetime only thing? Then I would come up some other way. If you do modify, can you reverse it to the original? Will the modification affect the strength and rigidity of the machine? In your case, what are you trying to do? An alternative would be better.
 
At this point I am not trying to do anything. Don't need a bigger spindle bore for any current projects. It is just a thought that I wanted to explore.
 
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