Drill & tap questions

geologist

geologist

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I have never drilled and tapped anything in my life that wasn't wearing a skirt ;)

I am going to install new beads onto the rib of my controversial Dominion Arms SxS. I am going to do it myself since I don't care if I fcuk it up.

TBS I need advice on what equipment I will need to install a higher accessory bead ie. drill the hole and tap it.

I would also appreciate any tips on setting up to do it, ie. jigs etc.

What type of taps would be appropriate? I assume that a hand powered tapered tap is the way to go? Will I have to order these small taps from Brownells?

I assume that I will need a drill press, will a cheapy from Cambodian Tire do? What type of drill bits do I need?

Thanks to all from a non-machinist who only got a 75% in high school metal shop. :D
 
Pick out the bead you want. If its a 6-48 thread, then you will need the appropriate hand tap and #32 drill. You probably will have to go to a proper machine shop supply house for the correct drill, or you can often order a set for home gunsmithing that includes the proper tap and drill. I'd centre punch the mark and drill with a drill press. I'd also use the drill press chuck as a manual way (power off) to start the tap perpendicular. Some light oil and a back and forth motion to cleanly cut threads and keep the chips clear as you make progress. If you can't drill through deep enough, well beyond where you will need to thread, you may need a bottoming tap to cut full threads all the way through.
 
Couple more things. Don't break the tap off in the hole, thats a major pain in the ass to undo. So if it gets to hard of going, back off. Apply some pressure initially when starting the tap so that it bites in and starts cutting threads, not chewing up the first depth, and keep the tap straight, that's where using a drill press chuck to hold the tap initially helps.
 
Follow Grizzly's pointers and you'll do just fine, especially the advice to use the drill press to guide the tap with NO power. For a short small hole like you are doing I would probabley do the whole thread with the tap in the drill chuck. Also make sure you have good cutting fluid, I prefer Relton Rapid Tap.

Good Luck
 
Bacon fat works, so does lard.

No kidding! Animal fats make a decent cutting oil. They go rancid fast, sitting around, but for something like a tapped hole, or such, good stuff.

Hole diameter (the rough guide) is major diameter, minus the pitch of the thread, in whatever units you are using.

eg: 1/2 -20 thread. Major dia is .5 inch, pitch is .050", or 1/20 inch

Subtract .050 from .5, equals .45" drill. The nearest size is a 29/64, at .4531, which is also the drill specified on the chart for a 1/2-20 thread.
Works in metric, too!

Anyways, lots of charts available online and in books, that you can use. Drill carefully, take your time, dont force the tap. Use a tap handle rather than a wrench! Way too easy to put the side pressure on a tap with a wrench, and snap it.

Do your planning carefully, and it'll be so easy you'll wonder why you hadn't done more of this stuff sooner!

Cheers
Trev
 
geologist said:
I have never drilled and tapped anything in my life that wasn't wearing a skirt ;)...
Click to expand...

Well, I hope you were using something bigger than a #8 "bit" :p

Busy Bee Tools (and possibly other places) has a handy spindle tap you can use in a drill press:

busybeetools.ca/cgi-bin/picture10?NTITEM=B1992

You might also consider a centre drill, which is stiff enough not to flex when you're starting the hole:

busybeetools.ca/cgi-bin/picture10?NTITEM=125281

:) Stuart
 
I always use a centre drill as well. They are cheap and make the hole in the right place. Way better than centre punching!

Scott
 
Carol Smith's book recommends a specific tapping lubricant called alumilube for tapping aluminum (now I'm not thinking anyone's going to go out and buy a tub of it just for a hole or two), barring which he recommends using kerosine or diesel fuel as an alternative. Just thought I'd mention this, as the latter two sound like readily available alternatives.
 
Grizzlypeg said:
Some light oil and a back and forth motion to cleanly cut threads and keep the chips clear as you make progress.
Click to expand...

When he says back and forth, that means maybe a 1/4 turn of cutting, then turn back to pull the chips out. Turn back at least 1/2 a turn. Once I get the tap going, I will spin it all the way out to clean out chips. Go slow, it is very easy to break off a small tap like a 6-48 and a major b!tch to clean out the busted tip, because the tap is harder than your drill bits.

Mark
 
Grizzlypeg,

For aluminum, WD-40 is great too. One of the few things it really good for, besides as a fire starter, IMO. Won't help on steel, though.

mmattockx,

If he goes a 1/4 turn in, then half turn out, he'll not make great progress, after that first quarter turn, will he? :D

The whole forward then back thing is subject to some debate. A full turn forward and a quarter back is a decent pace, if you can keep the side loading off the tap. I've tapped enough holes with a tap in a cordless drill, to say from experience, that if you can keep the tap cutting smoothly, that matters more than whether you are breaking the chip loose ever turn or half turn.

For a through hole, use a "taper" tap, and run it right in. It gets really picky when you need to tap a blind hole in thin stock without punching through. Then you really need the full set of taper plug, and bottoming taps.
And steady hands.

Cheers
Trev
 
trevj said:
Grizzlypeg,

For aluminum, WD-40 is great too. One of the few things it really good for, besides as a fire starter, IMO. Won't help on steel, though.

The whole forward then back thing is subject to some debate. A full turn forward and a quarter back is a decent pace, if you can keep the side loading off the tap.
Click to expand...

WD is mostly kerosene, which makes sense for aluminum.

I have had small taps load up the flutes with chips in less than 1 turn and jam tight. For bigger taps, say over 1/4" or so, 1 turn is a reasonable amount to go. YMMV.

Mark
 
How'd we get onto aluminium? Wouldn't the web between the two barrels be steel so the barrels can be silver soldered to it?

Geologist, everyone here has great advice. But this is a job where you COULD do it with a hand drill but it's best if you can use a drill press exactly as Grisslypeg suggested. The only reason it could possibly be done with a hand drill is because it's a Dominion so likely the barrels are a bit crosseyed anyway. Or if you've shot it and found that it's worthy of an accurate bead then I'd suggest a proper setting up and drill press to do it right as well.

The only other issue is that if this has the regular webbing between the barrels that sort of forms a "ditch" rather than a raised rail then the bead will be sitting down in the valley between the Grand Tetons. Hard to maintain much peripheral vision when you're eyeball is focused down a trench. In that case a blued riser ramp or post for the front bead and a nice little ghost ring for the back would be a nice combo.
 
I worked at a place that had an automated tapping machine made in West Germany. It had a clutch drive so it could slip if there was too much tension and it had a setting to reverse the tap back out once it hit a set tension having bottomed out. The machine cut the threads all in one motion, no backing off to remove chips. First piece of work I ran the machine on, I broke the tap off inside the work. That one became a display model, as it was too much work to remove the tap, and the medal too valuable to discard. After that, with less tension setting, it worked like a charm and successfully tapped all the holes. Now, with a cnc controlled machine, the holes would also be tapped in one shot. Still, having broken a few taps, I'd never be too aggressive with a tap that was no longer turning smoothly. Aluminum, that was my dumb misdirection. I made some wrong assumptions about what the rail was made of. How come there's no smiley to show a red face of embarrassment?
 
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