drilling through set screws

I have a similar job, but my screws are brass. I chuck up a .020 drill in a Dremel Tool. And drill thru a 4-40 set screw with no problem. Can you get your customer to switch to brass screws? Or maybe SS. I don't think they are hard.

Ted, I think I would be on the funny-farm already if I had to drill through 50 of them. I have to do this occasionally, but haven't had much success. DoN Nichols suggested using a transformer with low voltage, high current (soldering transformer I think) to kind of heat the setscrew to cherry red with a carbon probe, then drill. The heating softens them up. I haven't been able to try this as of yet, but it sounds like a good idea. Sorry I can't offer any more than this. Ken.

I have had to do a similar thing in order to make orfices for pneumatic cylinders. The set screws we had were case hardened, but did not seem to be hard throughout. I was drilling a #60 hole through them though. I used a HSS running as fast as the hand drill could go with a slow feed. After I did 3 of them and broke the bit on the 4th. I got a solid carbide drill and ran it at 4000RPM with .001 feed. Thats the fastest RPM and the slowest feed I could get. I was able to drill the other 10 just fine. Use lots of coolant to flush the chips away with a peck if needed.
You might want to try a different manufacturers set screw. They might not be hardened all the way through.
Welp, adios de John
At work, I have been given the glorious task of drilling a 1/16 hole through the centre of 1/4-20 set screws. I realize these are case hardened, as are SHCSs which I have drilled through in the past without any problems; however, these set screws are bringing me to my wit's end. They seem to be hard throughout. I have tried normal HSS drills, and cobalt drills, neither of which barely penetrated the surface. I have now resorted to solid carbide drills which work wonderfully, but are too brittle--I've already snapped two. It's a simple job, but tedious and frustrating. If anyone could offer some insight on how I can drill through 50 set screws without going through as many carbide drills, it would be appreciated.
Thanks,
Ted

Why don't you just buy vented set screws? A quick web search yielded

This is a job for a "hole popper". They're usually found in the general vicinity of wire EDM machines. It'd take longer to insert and remove the screw from its jig than it would to put the hole in it.

Heat them to soften then drill then harden them again.
Sam

Are they supposed to be case or hardened throughout?
Sounds like somebody ordered the wrong thing.
Bing

Sorry, I guess I kinda mis-read your post. I thought these setscrews were already in position locking a pulley/shaft in place or something. That's the problem I've run into - getting old setscrews out of the pulley/shaft for disassembly. I guess in your case you wouldn't want to soften them - but as another poster mentioned, there are vented setscrews which would save you a lot of time/trouble. Ken.

Ted, try speed and feed of a cobalt drill with a carbide one. dd.

Greetings Ted, Recently I had a job requiring 1/8" holes through Thompson 60 case hardened shafting. The holes went through the sides so it was 60 Rc, then softer, then 60Rc again. Carbide was my choice but the drills wanted to break on exit. The trick was to use a diamond hone on the corners of the drill so that the corners were rounded. Almost like a ball nosed endmill. The sharp corners were grabbing on exit but the rounded corners didn't. I don't mean dulling the drill point, just changing the shape. Hope this helps. If it does, please let me know. Cheers, Eric

Ted:
You could use a 1/16" center cutting four flute carbide end mill to start your hole and get below the threads, then do a tool change to your carbide drill to drill it the rest of the way. You could even try to drill it all the way through with a 1/4" flute length 1/16" carbide end mill, but that might be iffy. I'm assuming you're doing this on a CNC, if not, you could make a cheapie drill jig by getting a little piece of O-1 tool steel - drill and tap for your set screw - then cross drill your 1/16" hole (be sure to make your exit hole larger to allow for drill wander) - heat it cherry red and throw it in some oil - clean it up and off you go to your Bridgeport or drill press.

Ken DoN Nichols suggested using a transformer with low voltage, high current (soldering transformer I think) to kind of heat the setscrew to cherry red with a carbon probe, then drill. The heating softens them up.
I do like this idea. Will try it next time.
Bob AZ

That's a cool sight. As long as the set screws can be stainless steel, and they can make schedule, it would be the right way to go. I think someone would be hard pressed to make their own cheaper than they could buy them.

I just went to the site myself. It's obvious that I didn't know Ted was drilling his set screws the long way. Therefor my comments can be put in the "round file".

These probably aren't vented screws. They would not use heat-treated steel screws for that.
Typical vacuum system harware would be gold plated stainless with a slot along the side to vent.
Jim
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