Thread: Daddy Drill Bits

Manic,

if the HSS is not touching it be careful about using some of the more exotic drill bits unless you have a very steady hand. They may be hard but not very flexible and may just shatter.

Definitely eye protection required.

Other option if you can get at it is to weld a short length of angle iron to the head. Often the heat loosens it a bit then the angle iron can provide the torque to loosen.

Not sure as to where in Melbourne you are. For solid carbide drills you should try a firm called Hales. They are a engineering supplier for toolmakers, or AAA in Bayswater also servicing tool makers . There are others around as well. If the part is small and removable from the car and you really absolutely have to have that bolt out you can get is spark eroded out. Most tool rooms will be able to help you out and only one bolt will not cost overly much, a second mortgage can be paid of in no time Recommend heli coiling the thread after as you would have stuffed the thread by the time you drill it out.
Cheers Hall

Using a cutting oil (eg, Trefolex) helps prolong the drill bits as it helps cool the metal and bit. Don't drill too fast either as this is what sometimes burns the bits up.

When I need to drill a bolt out of a casting of some sort, I sharpen the drill bit backwards and drill anticlockwise; i.e. so that the drill bit cuts when run anticlockwise. Usually you then get to a stage where the drill bit bites and unscrews the broken bolt.
Another technique is to get an arc welder, soak a welding rod in water, hold the welding rod against the bolt, being careful to touch only the bolt, and have someone else switch the welder on (wear your welding mask). By holding the stick against the part before switching on, you don't actually strike an arc, but the rod will get red hot in just a few seconds. Switch off and repeat with another rod or two. This applies a lot of heat to the bolt, which once it cools will often be loose enough to remove easily.

to get out your stubborn bolt, first drill a small hole in the centre of it,
1/8th inch or so, then you can pop a bigger drill into the broken off bolt.

most of the problems with drilling out big bolts is that the centre of the larger drill cannot start cutting, so it heats up and you destroy thr drill bit.
by drilling a small hole first, the large bit can start on its cutting edge easily.

thanks for the tips. I will try again with stronger bits, a slower cutting speed, cutting oil and a pilot hole.

I tried various options to remove the bolt before deciding on drilling it out and helecoiling it. I didnt think I would get stuck on drilling the bolt too!

Ideally I would like a carbide or cobalt left handed 6mm drill bit and a cobalt/carbide 8mm bit. I could then drill the 6mm clean through the bolt for a chance to catch and then if needs be finish it off by drilling the whole bolt through with the 8mm.

I just scoured the net and did not find one online retailer (in australia) that I could buy from. Ebay has a bunch of Overseas, but I would like to get something this week. I went to Bunnings and they dont have what I'm looking for. Search for AAA in bayswater pulled up all kinds of businesses, Hales looks like industry suppliers, not a walk in shop... Is there a good online shop for cobalt/carbide drill bits or anywhere that has this kind of stuff on the shelves in eastern suburbs, highett area?

I use the sutton cobalt drills, have never had an issue, Look after them (by comparison to the others at least) they come & stay sharp. And reasonable priced

some thing is not correct

drilling out a bolt is no big deal, the problem is if you have buggerd up one drill bit my cooking the thing you could have hard faced where you want to drill.

always start with a small drill say 3mm etc.

heating up and cooling a couple of times with an arc welder is a good method