Trepanning small diameters -- make custom tool or buy nnular cutter?

wa? What do tolerances have to do with the price of fish? It's a 1-3/8" hole, 5" deep in a 3" diameter bar. Not much more to it that I can see than that. The 1.375" implies a tolerance within a thou, but other than that it's pretty clear.
 
mattthemuppet2 said:
wa? What do tolerances have to do with the price of fish? It's a 1-3/8" hole, 5" deep in a 3" diameter bar. Not much more to it that I can see than that. The 1.375" implies a tolerance within a thou, but other than that it's pretty clear.
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Ordinarilly, I would agree but decimal representations of fractional inches are a special case. I wouldn't assume that the OP means 1/375+/- .001 instead of 1-3/8" +/- 1/64" or 1/32".
 
I'm just not sure where in any of the posts above do tolerances play a part in deciding to use either of the tools the OP asked about as neither are going to work on a 5" deep hole.
 
I used to have a Jet 9x20 lathe, I don’t think an annular cutter has a chance doing that. The slowest speed uses a torque limiting clutch that will slip when using too big a drill too quickly, so you will need to do small steps with the drills to get as big as you can until the clutch slips, then you will need to bore it. Make sure your tooling is sharp, that lathe needs all the help it can get, especially in a material like that.
 
Here's what I would do under these circumstances.

I would drill a 1/4 inch hole
the I'd use a chamfer to widen it to 3/8. by 1/8 deep. then I'd use what ever drills the machine would turn, up to 1/2 inch.
Then I would bore the rest using a sharp HSS boring bar.

I have done this before on an old 1/3 HP southbend 9a lathe. The SB lathe has more power than a small harbor freight lathe, and it still was all the lathe could do. Sometimes simplest is best.
 
Thanks for the feedback, guys. I think I'll pass on the annular cutter. I've got a big-ish solid carbide boring bar that just fits in an AXA holder. I like the idea of doing half from each end, too. The material build for this part is 72 $ at the local Metals Superstore in NC. That's without shipping. Amazingly, McMaster is similar even with shipping.
 
Dabbler said:
I would drill a 1/4 inch hole
the I'd use a chamfer to widen it to 3/8. by 1/8 deep. then I'd use what ever drills the machine would turn, up to 1/2 inch.
Click to expand...

I religiously use a hole 120-deg hole starting drill. Somehow never thought to chamfer for larger size drills. Thanks for the tip.
 
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