How can one cut out a plug on a lathe? Just a parting tool?

Used the hole saw a few times like that, not a problem, slow, plenty of lube and frequent retraction to clear the teeth.
This hole was cut with a hole saw.
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Potd - Project Of The Day- What Did You Do In Your Shop Today?

For the sake of closing this argument and getting back to discussing machining etc. can a ask an administrator to remove the offending two photos from my post #3240. I can seem to figure out how to edit it myself in this new software.
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see post number 9831
 
savarin said:
Used the hole saw a few times like that, not a problem, slow, plenty of lube and frequent retraction to clear the teeth.
This hole was cut with a hole saw.
www.hobby-machinist.com

Potd - Project Of The Day- What Did You Do In Your Shop Today?

For the sake of closing this argument and getting back to discussing machining etc. can a ask an administrator to remove the offending two photos from my post #3240. I can seem to figure out how to edit it myself in this new software.
www.hobby-machinist.com www.hobby-machinist.com
see post number 9831
Click to expand...
I'll see what I have for hole saws. To be honest, hole saws are a little scary. I've had them grab, especially drilling it by hand. An ex-boss was drilling a 4 inch hole through a wall (at his home) with a 1/2" drill. The hole saw grabbed, the extension handle spun around and knocked him out cold. His wife found him on the ground unconscious. Fortunately, he recovered. In a lathe, I'm not as worried about that, but I do have a healthy respect for the power of a grabbed tool.
 
If you make sure the saw is tight on the arbor and drill, use lots of cutting oil and spin the work at a relatively slow speed and don't feed too fast you should have no problem. The worst that could happen is the motor stalls.

Roy
 
The rigidity of the lathe makes disaster far less likely. I don't much like anything over 1/2 in a hand tool! Annular cutters are frequently used in magnetic base drills with great success and despite the strength of the magnet result in far less rigid setups than a lathe bed and tailstock.
 
Found a hole saw, but it was too big for what I wanted. Need to root about the garage to see if there are any others.
I recently ground a 0.150 wide parting tool, for my spindle light. Maybe I can use it, or modify it. I'll draw some lines in cad to see how small/big a circle I can cut out without rubbing. I mean, what the heck, use what you have?

So drawing this out, it looks like it might work as is. It looks like one can cut a plug as small as 2" in diameter, with the tool profile that has been previously ground. No drawings yet, I seemed to have screwed up the units. Be back in a few...
 

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Might be able to use a 1/8" round toolbit, or an old drill or end mill. Grind it down halfway, and that is your cutting face. Make the grind length your entire DOC (1/2", or 1/4" if you can go from both ends). Shape the cutting face so it gets gradually wider until the body of the tool can pass. The diameter of the cutter with curve more sharply than the diameter of the hole you're cutting, so clearance is taken care of once the cut has started. As Bill Hudson pointed out above, you can use a standard lathe tool to start the groove, then perform the bulk of the work with a tool that starts off inside the groove (meaning it can be less pointy).
 
Tool is almost long enough, but not quite, so I'll have to flip the piece. It's about 0.450 long. I'm going to grind the tool to be a little more than 0.500", so it can be done in one pass. Belt sander makes this easier than one might expect. Worst thing that can happen is I spend 5 minutes to make a new tool. As long as the relief is greater than 11 degrees with a tool width of 0.150", the minimum plug size I can cut is 2" in diameter. That's good enough for what I want, without difficult grinding. The actual relief I ground is about 14 degrees, so I'm going to give this a try. The bit on the right, is what will use, after a little more grinding.
IMG_20200413_132211_topview.jpg

It has 14 degree relief on the front and both sides. Flat top.
 
I do this all the time on my 9" Southbend lathe. If you grind your own HHS bits, it's pretty easy. Relief is key (the bits in the previous post look good). A 1/2" deep/thick plate might require you to make a couple of grooves (keep the cut a little wider than the tool, cutting one side then the other).

A 7 x 16 lathe might be a little small for this depending on the diameter of the plug/hole. So, as they say you work with what you got, and maybe one of the other methods makes more sense to you. For me the rigidity of the lathe and the fact that I've ground a lot of bits, makes the lathe my obvious choice.
 
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