Machining A Taper

[Paul_RR]

Hello and Happy New Year! Newbie here. I'm trying to make a tapered insert with a through-hole that is used to secure a circular seal. The taper is 20 degrees; the small end is 0.5" diameter and the larger end is 0.64" diameter. Depth is just under 0.2”.


I've made a couple - one out of Delrin and one from aluminum. The way I did that was to turn the taper (small end away from the chuck), drill the through-hole, and then cut-off the part at the larger face. Here's where I run into my problem. I need to drill a countersink for a screw head on the larger face, and I can't come up with the proper method to do that. As the part is rather small, I have a hard time securing it on my drill press. I've resorted to holding it by hand (not the safest alternative, I know) while drilling the countersink. More easily done on Delrin than aluminum, but not precise by any means.


Is there a way to "reverse" taper (smaller end on the chuck side)? That would seem to require an awful lot of extra material removal for tool clearance, but maybe I'm missing something. Maybe there's a better way to secure the part on drill press? I've attached a drawing of the part as well as a couple of photos showing the completed part. Any suggestions would be appreciated!

 

[rlgustin]

I have done jobs like this before. I first left enough stock protruding out of chuck, if you're using a collet that's even better, to make four pieces, don't forget to add width of parting tool and material to face off each piece. Next face, center drill and drill to depth needed. Counter sink piece and part to length. For following parts face, counter sink and part. After you completed this make a stub arbor, you can turn an 82 degree angle on end and a stub same diameter as your hole size, make sure stub does not protrude out of part. Finally tap piece with a tap 2 diameters smaller than stub. Mount piece on arbor an turn taper.

Sent from my LG-D850 using Tapatalk

 

[Jimsehr]

Make the part with the drilled hole and taper for the screw first. Leave the OD straight. Then cut off to length.
Now take a piece of 5/8 dia stock and turn a dia to the size you drilled part. Turn it just a little shorter then part length.
drill and tap that turned dia to a socket head cap screw size where the screw can pinch the part to the 5/8 piece of stock
then turn the 20 degree OD.
jimsehr

 

[Wreck™Wreck]

Yes, one may do anything if cost is not a factor.
In this case turn the front work from stock then turn the back taper and part off.

Use the compound for the taper, if the part requires backwork this will present a problem.

Good Luck

 

[Paul_RR]

Excellent suggestions! Sorry for not responding back sooner - had houseguests yesterday and today, so early morning is the time I have available to respond. Never thought of machining and threading a small arbor to mount the piece before turning the taper. Thanks for helping out a new guy!

 

[sanddan]

I would

1. face end
2. drill hole
3. machine countersink
4. machine relief using cutoff tool to .500 dia. 2 thicknesses of parting tool.
5. machine taper
6. part off

 

[Eddyde]

+1 on machining the whole part before parting off, The arbor will work but is more work.