Drilling holes for pins

[Langadune]

I've read that you should drill holes for handle pins larger than the diameter of the actual pins... some have even said as much as 1/8" larger. Is this because the holes will "shrink" after heat treat or is there some thing more to it?

 

[Bo T]

I've read that you should drill holes for handle pins larger than the diameter of the actual pins... some have even said as much as 1/8" larger. Is this because the holes will "shrink" after heat treat or is there some thing more to it?

In the tang of the knife the holes can be drilled larger. Typically epoxy is used to glue the handle in place which fills the holes in the tang. The holes in the handle material should be drilled with a fit as close as you can to the diameter of the pins.

 

[Darrin Sanders]

I drill my holes about .015" undersize before heat treating and then drill them to size with a carbide bit after heat treat. That way I get a nice, clean, decarb free hole of the correct size.

 

[Stacy E. Apelt - Bladesmith]

In my experience, if the tang holes in the blade are the exact size for the pins....the handle scales will be a bear to get installed ( especially with three or more pins). There is also a problem with peening bolsters and end plates on if the holes are an exact fit (it can cause gaps).

By drilling the tang holes at 150% of the pin size it allows a tiny amount of wiggle room when installing the pins in the handle. Wood will "move" in sanding, drilling, and by temperature and daily humidity. What was a perfect fit when drilled on Monday may not let the last pin go through on Saturday. It is a BIG problem when you have the handle epoxied up, and are slipping the pins in...and one won't go through the tang!!!

The holes through the wood need to be just slightly larger than the rivet/pin size. You want the rivet/pin to slide in easily, with just the smallest bit of friction, but not really requiring any force. You will have to experiment with the exact size drill needed in some scrap wood - OF THE SAME WOOD TYPE - and determine what size drill bit works. In numbered/lettered bits, one number up usually is about right. In fractional size bits, 1/64 larger works, but may be a tiny bit sloppy. The resin will fill the gap, and should make that invisible.

Notes -
1) Corby bolts, and similar mounting hardware need an exact size counterbore. It is best to get the drill bit and the bolts from the same supplier if possible.
2) Sharp drill bits are very necessary in drilling wood. Fast speed and even feed rate will prevent tear-out. Wood bits have different point angles than metal bits, BTW.
3) Place a sacrificial block under the scales when drilling to prevent break-out chipping.
4) Different woods drill differently ( Doh!). Some woods leave the hole exactly as drilled, and some close up after the drill is removed. On these woods, running the bit through several times helps somewhat, but selecting the right drill size to get the required fit is a better option.

 

[12345678910]

I've read that you should drill holes for handle pins larger than the diameter of the actual pins... some have even said as much as 1/8" larger. Is this because the holes will "shrink" after heat treat or is there some thing more to it?

A 0.125" pin will not slip fit into a 0.125" hole, as Stacy said, you need some clearance.


You need as little clearance on the handle as possible so it looks good, you need more in the tang holes to easily fit and not have problems with hole shrinkage.
A #30 number drill is .128 5" for your handle material.




If you are having trouble getting a close size


Some pin sizes run into huge leaps when you jump to the next # or Letter drill
(likely not a problem for 1/8"


In even fractionial hole sizes such as you can also find reamers that are dowel pin sizes + .001


or you can get decimal size reamers at just about every size.

That would give you more options for nice fit when you run into trouble.

 

[Bomp]

To get my tang holes a little larger I use a chainsaw file in the same size as the drill bit. I also countersink the holes just a little. It seems to give it just enough play to get the scales sitting nice and flat and gives a little pocket around the pins for the epoxy to sit. Like stated above it seems like this doesn't happen with the smaller size pins. They usually have a little more play. Don't know why that is

 

[Jastab]

I made the mistake of drilling them .005" bigger than my pins.... never again. Ill go .060"over from now on. What a pain in the butt!

 

[tss1004]

Disclaimer: I'm no expert.

Great advice above. The only thing that I'll add is that for micarta (only), and especially handle scales on full-tang designs, I drill slightly undersized on the handle material only (I use oversized bits in all my tangs). This helps keep it all tight and uniform in addition to clamps and epoxy. I've not had a scale or handle come loose yet, even during destruction tests. Just my .02.

 

[Langadune]

Thanks for the great replies guys... I had originally thought while test fitting my scales and pins "Hey this is a perfect fit... why would anyone oversize the hole?" Then my better judgement kicked in and I remembered people around here usually have good reasons for doing things the way they do.