Hope someone can settle an argument: The part is a 1" long x 3/8" OD x
3/16" ID brass bushing that needs a 6-32 set screw. Tap drill goes all the way through both walls for convenience. Hand tap with straight flute tapered tap and 'T' handle. Quick prototype level part, only making 2 of them, precision not required.
Questions: tap dry or use what lubricant? Backup the usual 1/3 turn to break the chip necessary on this part?
There must have been a hundred students at school that have taped
3/4 brass "hammer heads" with 3/8-16 threads over the last many years without a drop of fluid and without a single "backup" of the tap. :-) Also a large number that have done a blind hole in 1/2-20 about
3/4" deep. If a material dosent make stringy cuttings, no need to back up a tap. Even if it does that is what a spiral point tap is for. :-) ...lew...
RoyJ wrote in news: snipped-for-privacy@corp.supernews.com:
Do yourself a favor and go buy 2-flute gun taps in all the smaller sizes you use, and 3-flute gun taps for the larger sizes. They throw the chips in front of the tap, which means you'll never have to back up in any material unless it's a blind hole, and then only to empty the chips when you're done. Tap brass dry, aluminum with kerosene or d-limonene (orange oil), and steel with Rapid Tap. Once you try gun taps, you'll wonder how they still sell the standard 4-flute taps.
Just 10 minutes ago I tapped 16 10-32 through holes in 3/4"
6061 using a 2 flute tap and a cordless drill. Lube was a couple of drops of Alumi-cut. No backing up, just stick it in the #21 hole and tap 3/4" through.
I do it every chance I get. My big problem is that the chuck can't grab the hardened tap well enough. Any thoughts or ideas? I'm not quite ready to grind 3 flats on the tap.
Maybe a "tap socket"?? Chuck up a 1/4 hex by 1/4 square adapter, snap on the tap socket, insert tap. Find out just how good all those slip clutch settings really are on your cordless drill.
formatting link
I've actually used these before to hold 3/8-16 taps and drive them with a 3/8 air butterfly. Worked well in 1/4 steel flatbar.
The 8-32 should be no problem. 6-32, however, is the thread from hell. Someone made a poor choice many years ago when they decided to stretch the 32 TPI standard all the way down from 10-32 to 6-32. By the time you get to a #6 screw, the threads remove such a large percentage of the overall diameter that the resulting thread (and tap) is quite weak for either side loads or over-torquing. With the tap in a hand drill (battery powered or with a power cord) it becomes hard to hold the drill motor in line with the hole for the whole time of tapping
-- especially when you are trying to switch the drill from forward to reverse.
What would be a much better way to go would be with a tapping head in a drill press -- but this can run into money if you aren't lucky about picking up an appropriately sized used one on eBay or at a swap meet.
The gun taps -- pretty likely. The tapping head (if you don't already have one) --probably not. :-)
Just got back to checking this thread. Yes, I use gun taps in variable speed drills all the time. Don's right though. 6-32 is right on the ragged edge of sensible. It all depends on the alloy you're tapping, how far you're going, and which lube you use. 1/4" 6061 or thiner, through hole, proper lube, and a sharp tap, and you can pull the trigger all day long. Give it a try. At least the 6-32's are inexpensive. As with any tapping job, keeping the tool aligned to the hole is really important. It's just that much harder to do with the weight of a cordless drill.
- Bruce
"DoN. Nichols" wrote in news: snipped-for-privacy@Katana.d-and-d.com:
My experience has been that for 6-32 into aluminum, especially if handheld, thread-forming taps are the way to go. Lube the tap with sticky wax. I use Lenox saw wax. The thread-forming taps are stronger than cutting taps, and tend to follow the hole automatically rather than trying to go off at an angle.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.