Drill bits for plastics

[knoba]

Hi Knoba,

Thanks for the compliment. I have similar trait to Ken's toolmaker mentor concerning "finishing the areas that no one else will ever see".

For years I have been temped to reduce the lip relief for some larger nominal sized import drills I use for drilling brass with the tailstock in the lathe. A few times I had 3/4" drills pull the tailstock chuck out while drilling out brass or bronze round stock prior to boring. No serious accidents but something to avoid. I found rolling a small section of printer paper in between the chuck and tailstock Morse tapers seem to make it hold better but doesn't fix the root cause.

Thanks, Paul

I had similar issues with an old Hardinge lathe, it was remedied by skimming out the tail-stock quill socket with a morse taper reamer and then making sure the tail-stock ejector mechanism was working as it should. If I knew I was going to be hogging out a lot of meat and/or the material was soft I would give the morse taper insert a sharp, but gentle, tap on the end with a soft face mallet. I've not had any 'moments' with it since...

That's a pretty cool & interesting technique you mentioned, I'm not sure I've heard it before and I won't forget it. Thanks for passing it on!

[Paul Jones]

Knoba,

Last month I bought a fine cut No. 3 Morse Taper to do exactly what you described for the skimming out the tailstock. I have been waiting for an opportunity to change out my 4-jaw chuck so I can insert a MT5 dead center into the headstock for accurately centering the reamer. I normally use a 3-jaw chuck but lately a lot of my projects require offset turning with the 4-jaw.

Thanks for confirming the technique.

Paul

[knoba]

Sounds like you're well ahead of the curve. If you get the chance to document the process, Paul, I think it's definitely worthwhile publishing for others to see!