Drilling tang bolt hole in tang on center

[jerrywh]

For the New guys
    First make a good center punch. Do not drill the hole full size on the first pass. For example if you want a 3/16" hole first drill the hole about 3/32". when you start it shorten up on the bit so it is only about 1/8" extending from the chuck. Drill it all the way through the metal. Then check the hole with a set of dividers to see if it is on center.
If it is on center use the full size bit to finish it. If it is off center you can correct it with small files by filing it so that the hole is on center, when it is finish it. Another way is to make a cut in the side of the hole towards the direction you want the hole to drift with a jewelers saw that will make the full size bit drift towards center. Most likely your trouble is caused by slop in the head stock of the drill press. Some times it will be necessary to drill in increments as I described. First 3/32" then a little bigger then full size so on and so forth until it is correct.
Any body who thinks something is easy usually doesn't know much about it.

[David Rase]

Good advice Jerry.  I do almost the exact same process.  I use my calipers to strike lines from each side to find center.  Then I center punch, drill undersize pilot hole, measure with calipers and correct center with a small rat tailed jewelers file and then drill the size hole I want.  I do this on the trigger plate as well, you just got to remember to only drill to tap drill size so you can thread the plate.  I then join the 2 holes using my drill fixture.
David 

[ron w]

same here, i'll scribe two lines from both sides, making tem just just a bit apart and put the c-punch between them. make light punch first, that can be easily drifted over if not perfect, check it's location, then,  if good, deepen the punch mark. the spread of my scribed lines is about the width of the tip of my punch,.....it helps to use those lines to center the punch between them.

[Heavies]

I am not a gun builder, but do have experience in drilling metal. 

To get a real accuate hole it helps to start the hole, in a good accurately placed center punch, with a center bit.   

Then like has been mentioned pilot hole with a smaller bit, then the actual size desired. 

Also, not mentioned, is not drilling metal at high speed revolutions.  The drill should only be turning fast enough that it produces long tails of shavings. This will not only produce better straighter results, it will cut faster, and your bits will last longer. Use cutting oil too.

Nothing will ruin a hole faster than a dull burnt out bit.

[Chowmi]

Jerry,
Thanks for that tip/technique. I had heard to drill a pilot hole, but never the part about chucking the bit way up in the drill.  I have had bits wander on me, most noticeably when I drilled a hole for the nipple drum in a percussion gun. That was painful and humiliating! 
I will be drilling and tapping for a vent liner soon, and will try your technique.

As you said, so much of this looks easy and it is not. After watching multiple videos and reading most of the building books, I found that the stuff that seemed so easy never really is. In,


Thanks again,
Norm.

[Long Ears]

Thanks Jerry, I've fought that exact issue for years. I think most of my problem is I don't drill completly through the tang and then only use two sizes of bits. A few years back I even purchase a new bigger fancier drill press thinking it was a runout issue. It wasn't. I use my mill now with a home made clamping system. It's amazing how much work goes into one hole to make it right. Bob

[ron w]

using the center bits is a good idea. but I still requires that either the set up for drilling the pilot be accurately centered (same as with any drill operation), or the center punch mark be right on the money. the only real benefit from a center drill is that because of their short length and rigid design, they usually won't wander like a regular twist drill bit might. given the  preliminary set up requirements for a good hole are met, this absence of wander is a specifically important aspect.

[P.W.Berkuta]

How true Ron -- set-up and as Heavie and others have pointed out using a center bit helps a LOT in starting the hole in the correct position. Jerry is a wise man and his method is fool-proof and as Mike Brooks once said "you got to hold your tongue just right"!

[T*O*F]

I dunno!!  Sounds to me like someone screwed up drilling a hole and decided to post how he fixed it.   

[Boatman53]

I use a 'Vix Bit' when needing to center a hole in hardware. It has a spring loaded collar the centers the bit in the hole. They make different sizes for different drill/screw sizes. Here is one site but they are widely available if you know what to look and ask for.

http://www.houzz.com/photos/39433279/Vix-Bit-9-Vix-Bit-Pre-Drill-Bit-for-9-64-Hinges-8-9-and-10-Screws-contemporary-power-tools
Jim

[Phip]

Really helpful, Jerry. I'm working on my first two builds simultaneously, and this tang bolt drilling is coming up fast as something I can't put off any longer. This post gets printed out and put into my bench notebook.

[Boatman53]

You're welcome Phil. I usually use the smaller size to drill a pilot hole then come back and drill the proper size hole especially for larger screws.
Jim

[SingleMalt]

Of course, you do have to hit the target with the punch.

[ron w]

vix-bits,...I have several.....are great for centering a smaller hole inside an already existing hole, such as drilling screw holes for cabinet hinges or butt hinges for hanging doors, but they don't do any more better than a regular bit for centering a hole on surface, such as we are talking about in this thread. I have used them all m working life as carpenter doing mostly finish work.

[jerrywh]

I dunno!!  Sounds to me like someone screwed up drilling a hole and decided to post how he fixed it.   

   That's right. It was in 1963. I learned this stuff from reading old black smithing books from the 1800's.