dang hard steel

[bama]

Need some help guys.

 I am building a little southen rifle and it is iron mounted. I got the trigger guard from TOW and filed it up a bit and it filed just fine. I went to drill to pin it to the stock and got about half way threw the lug and hit a hard spot. I have wore out 4 brand new 1/16" drills trying to get this hole with no luck. I thought that I would anneal it to soften it, took it to a bright orange heat and let air cool and it is still to hard to drill.

So some of you guys with a good metal background tell how to soften this thing so I can get this hole drilled.

[coutios]

  Might try reheating and burying in ashes to insure a slow cool down. Also that hole may have polished and the drill can't bite to get started. Sense the hole is started might try clamping in a vise, slow drill speed down, use a good cutting oil
and cross your fingers... Than there is always carbide...

Good Luck
Dave

[Jim Kibler]

Here are a couple of thoughts Bama.  You could try to drill it as is with a carbide drill.  Another option is to anneal it.  You likely need to cool it slower than just an air cool with such thin sections.  A good way of acomplishing this without a heat treat oven is to  just start a charcoal fire with normal briquets and place the guard in the fire.  Let it burn and cool down slowly with the fire.  You should have better luck drilling it after this.  

[Jim Kibler]

A bit more infomation about the likely cause of your problems...   The guards cool pretty fast in investment casting and the structure is likely pretty hard as cast.  During drilling the drill likely dulled and then when you continued to try to drill heat was built up and a thin martensitic "white layer" was formed.  This structure is very hard and difficult to cut.  Annealing should help.  You may also be able to drill from the backside and meet up with your previous hole.  Good luck.

[bama]

Thanks  guys.

Jim I tried drilling from the opposite side and I can hardly mark it with the drill. I don't know why only half the lug would be hard but that is what I have. I will try the charcoal and see if that helps.

[billd]

I've seen peices of the ceramic the molds are made from break loose and go into the molten metal.   Not on gun parts, but on valve castings we machine at work.  Ruins the casting and the carbide tool too.

If that's not the case with your trigger guard, I would think you work hardened it.  I would try to drill thru with a larger drill then weld up the hole and redrill with the correct size drill.

If you have a rigid enough set up, a carbide drill should work.  But if you break that you're in a worse position than you started with.
Bill

[D. Taylor Sapergia]

Bama, i had the same problem with a tumbler blank that would not drill for the hammer screw.  I heated it red and dropped it into sand.  No go.  I heated it red in the sand, and let it cool...again, no go.  I went out to the Rod and Gun Club and picked up a big cookie tin full of ashes from our fire place, heated it red, dripped it into the ashes...again, no go.  Now I've spent many many hours, ruined several number dirlls, or at least dulled them well, all to no avail.
I called Tom Curran, and then Cody Tetachuck, and they both gave me the same advice.  So, I built a little birch wood fire behind the shed, and when I had a nice bed of coals, I took my portable oxy/act. set out to the fire, heated the tumbler red hot, and dropped it into the coals.  After about three hours the fire was out, and I could pick up the tumbler.
It drilled like a piece of brass.  Le voila!

[bob in the woods]

This may sound strange, but what about drilling when hot? I have filed parts when hot.

[Robby]

You could always cut it off, solder, or weld on a new tab.
Robby

[bama]

Robby that is a good idea, I don't know why I didn't think of it. I guess because the lug is there and fit into the stock. I have some scrap that I could use and it would be quicker than builing the fire.

Thanks again guys

[Dphariss]

Need some help guys.

 I am building a little southen rifle and it is iron mounted. I got the trigger guard from TOW and filed it up a bit and it filed just fine. I went to drill to pin it to the stock and got about half way threw the lug and hit a hard spot. I have wore out 4 brand new 1/16" drills trying to get this hole with no luck. I thought that I would anneal it to soften it, took it to a bright orange heat and let air cool and it is still to hard to drill.

So some of you guys with a good metal background tell how to soften this thing so I can get this hole drilled.

Probably chrome from a 1958 caddy bumper
You will have anneal it and this might even not work. Try heating the part slowly until the color goes past blue to grey then allow to cool and try drilling it. This can sometimes work when full anneal might not.

It is important to keep a positive feed when drilling these things and use a good dose of cutting oil.
It could be cast of an alloy that will harden in front of the cutter or have an inclusion that does the same. Making sure its cutting well can keep it from doing this IF thats what happened.
As someone else pointed out you might need carbide.

Dan

[ramserl]

had the same thing happen with a but plate.  Had to use carbide drill and then I ruined my countersink

[Birddog6]

I have had that happen a couple of times on cast iron trim. Both times drilled them with a solid carbide drill bit.   On a bit that small, you must insure it doesn't move when it goes thru & run at high speed or it will snap the carbide bit off.   

Keith Lisle

[bama]

Thanks again for all the comments. The rear lug was the same as the front lug.  I did cut both of the lugs off and made new lugs that I pinned into the finials then silver soldered. The new lugs drilled with no problem.

I don't think I have ever run into this problem before on a cast trigger guard but I won't waste time in the future on trying to drill them if they don't drill easy. It is just to easy to install a lug than to fight drilling a small hole in hard steel.