drilling, tapping lock bolts.

[chuck-ia]

I allways seem to dread this part of gun building, making sure everything is marked where the hole is spose to be, and come out in the same location, etc., drilled through the stock and lock with a number 29 bit, drilled the stock and barrel with a clearance bit, all is fine, now just to tap, got about 3 threads tapped, I turn the tap a little and back off to clean the threads, turn the tap and back off, met a little resistance after about 3 threads and snap, broke the tap off in the hole, tap is flush so can not get a hold of it with anything, I laugh and say gosh darn it, (I'm lying) actually I was really *#)*^~. going at the broken off tap from the bolster side with a 1/16" punch was just making matters worse, ended up setting the lock bolster side down and pounding the broken tap out of the lock and retapping, threads seem just fine. How would you more experianced folks handle this? chuck-ia

[Steve Bookout]

Chuck, I have performed the same out of frustration/desperation and was able to succeed thusly:  1. The tap comes out and enough buggered up metal remains that I was able to re tap it without issue. 2. Re tapped for a #10 lock nail instead of the planned #8.  The hole can be welded up, but that metal is quite hard and commonly needs to be treated first unless you're using carbide.  Cheers, Bookie

[chuck-ia]

Thanks Bookie, I think it will be fine, threads seemed to clean up nicely, just glad the tap broke after about 3 threads. A couple of us would still like to come visit, we are only around 3 hours from you. chuck

[northmn]

I have used nails and other softer punches to break out and unscrew taps.  What is irritating is that I have seen new taps do this.  They are either too brittle or dull.  Usually you can salvage the hole and retap with a good one.  Worst case, you can drill out and tap in a bigger bolt, place it in and peen it, then retap.  Have done this on screwed up holes in location also.  Cannot repeat the words I use when these things happen and should seek repentence.

DP

[Birddog6]

I always tap with the tap vertical & the work piece down so the metal chips fall away from the piece I am taping.
Use taping oil...................................
Turn quarter turn & back it til you feel the lil bump it makes when it breaks off the chip, then go back up to the cut & quarter turn again, back it off to the lil bump & do it again.  You have to feel it.
Use a spiral point tap with a tapered shank & that will relieve about 75% of your broken tap issues.   I get mine from MSC & usually buy 3-4 at a time.
And lastly, when it gets dull, toss it away & forget it, as you are about to start problems you don't want.....

[don getz]

Can I assume that you are tapping the lock plate while it is still in the gun, using the clearance hole for a guide?  Luckily
I have not had a tap break in a long time.  We buy good taps, and I much prefer a two flute tap, they go thru so much
easier...I just turn them thru the drilled hole, no problem......Don

[David Veith]

To add to Don's and they do wear out. As a master of breaking them. You will learn how to remove them . The last one was a 5/16 in some D-2 Steel I watch a friend remove it in a mill with a JUNK carbide end mill. One more reason to own a mill. This tap I had tried breaking up, some acid that I had on hand. Don't think it was strong enough. One of your best friends is a VERY friendly machine shop/fab shop. Yes I do show up with a case of beer if I have a problem or not but I do show up every so often. Thank god for friends
David veith

[keweenaw]

If your buy carbon steel taps, instead of HSS ones, the broken piece will shatter into little bits if you hit it with a center punch.  On those lock bolts, I cut maybe three threads to get the appropriate alignment, then take the lock out and cut the rest of the threads.  It's too hard to properly lubricate the tap if you're working through the stock.

Tom

[Dphariss]

I would have likely punched it out as well. At least you had a through hole.
Get some high tech tapping fluid with Moly or other high tech lube. I have bottle of Castrol with Moly that has lasted though a lot of holes, thousands so cost per hole is almost nothing.
http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=1658595&PMT4NO=52503938
Break Free CLP, IIRC, works well.
Buy better taps, hi tech coatings help catalog will list the types and uses, from some place like MSC. Hardware store taps work but thats about all that can be said about them.
Anneal the parts may help. Castings may have hard spots heat to good red then cool slow.
If the tap acts like its not cutting right with good lube THROW IT AWAY.
On a thick part like a bolster you can go up one size in the tap drill if you do not mind a little slop. This will sometimes help if there is a weird hard spot in the part.
Remember drilling the hole can set up hard spots.
Holes in alloy steel need lube, a sharp bit and a feed rate to maintain an aggressive cut. Some steels will harden in front of the drill/cutter to the point of eating HSS drills and cutters. With proper feed rate the chip carries away the heat.

Dan

[Dphariss]

  We buy good taps, and I much prefer a two flute tap, they go thru so much
easier...I just turn them thru the drilled hole, no problem......Don

Right.
I tap 303-304 stainless 8x32 and you simply cannot do this reliably with taps from the local parts store. So I buy coated taps designed for stainless. I break one now and then but usually its my fault. Breaking good taps in steel, lock plates etc is very rare.
They work great for gun work too.
Good USA made 8x32 taps cost 6-10 bucks each but they WORK.

Dan

[chuck-ia]

Thanks for all the suggestions, The lock was in the gun and I was using the clearance hole for a guide, was using gun oil for a lube. The tap was a mac tools tap, and had been used before. I allways go probably less than a 1/4 turn and back up to clean chips, I think I probably put just a little too much pressure on the tap, not a big deal now, I will surely be more carefull in the future. This is the 7th lock I drilled and tap, sure did give me a sick feeling when I heard that snap. Anyway, the lock will not fall out of the gun now, now on to dovetailing 4 underlugs. thanks again, chuck

[Metalshaper]

OK, not exactly helpful to this situation?

but another "Old time" tip I found, was to mix a cutting oil into melted beeswax or parrafin !  this was blended really well and then poured off into a paper cup to cool and solidify. ( the graphic showed one of the old cone shaped water cooler cups )  when tapping a blind hole, you pealed the paper back from the wax 'cone 'and rubbed it over the hole. this fills it with the waxy oil combo!

then when you tap the hole, the hydraulic pressure, forcessss the wax and chips up & out through the flutes in the tap. thus keeping the tap lubed and the chips free from binding the tap.  Works pretty good in my attempts!!

I have since seen they make a modern Tappiing Wax, that is used in the same manner..

Respect Always
Metalshaper

[Steve Bookout]

Chuck, get thee to the shop.  The door's open unless I'm off panning for gold.  Cheers,  Bookie