Thread: What type of drill bit?

I'm making a set of one piece scales and have some 1/8" barrels and torx head screws for the pivot - I'm aware that drilling out the pivot to accommodate the barrel is beyond an ordinary HSS drill bit so can anyone advise the type that I should be looking for? Also any advice on just how much bigger than the barrel would be appreciated.

i would prefer a generic spec rather than specific makes or retailers as I'm in the UK - as you can probably work out.

thanks in advance.

Cobalt steel is the best kind of drill bits. What kind of material are you drilling through Rob?

I use carbide when I need to go thru hardened steel. Clamped down and with plenty of coolant besides.

Keep in mind that drilling hardened steel is one thing, drilling through an existing hole is quite another. The difference is that with a preexisting holes, the drill bit slams itself pretty violently into the burrs and ridges of the sides of the holes. this effect is the worst when the old hole is only slightly smaller than the new hole. It is of course possible to drill through the hole, but odds are that you'll destroy the drill bit(s) in the process. Drill bits are steel, so harder -> more brittle.

Ding, ding, your drilling the blade pivot hole. I figured it out.

Bruno has a very good point especially on those very old Sheffield blades that have the square-ish holes. Those are hell on tooling. Might you know anyone with a machine shop they could use a carbide endmill to mill a clean round hole?

Originally Posted by HARRYWALLY

Cobalt steel is the best kind of drill bits. What kind of material are you drilling through Rob?

It's an existing blade - Taylor's Eye Witness 3000 - so Sheffield steel, and as Bruno said, I'm enlarging the existing pivot.

Thanks for the advice everyone.

HF has many cheap sets of "diamond" jewelers' files. An hour spent could do what you wish. Alternatively, the same source has a set of "diamond" Dremel bits which take a really light touch but will do the job.
Used both methods at different time to close a too large hole in a blade.
~Richard
PS. Not all tangs are fully hardened but some are.

I have drilled hardened knife tangs with the masonry drill bits before, but have also melted some of those same bits, too Not sure if they have a size small enough to end with a 1/8" hole or not? I have some of the bits in 5/32", not sure of the final hole size yet. Carbide may work, or a narrow diamond bit in a Dremel? A #30 wire bit will allow clearance for a true 1/8" diameter pin w/o binding. A 1/8" pin will usually not fit into a hole drilled by a 1/8" pin.

Or you could just anneal the pivot area. A carbide drill is very fragile so make sure there is no lateral pressure or it will snap if subjected to torque. Carbide prefers high speed and plenty of cutting lube.