Thread: Countersinking holes in steel bars

Hey Jill,

The best way is with a counter sinking bit, not the elcheapo bunnies one but the one with a hole drilled through it at an angle. (Not sure what they are called, but they are the ducks nuts) depending on your hole size the one we use at work starts at about 4mm, they might go smaller, try the metal work guys, they should have an idea of the name.

HazzaB

The round hole ones are definitely the best but the last time I priced them they cost an arm and a leg. McJing sell a 3 flute HSS countersink in different sizes. For something like your application I would just use a large drill bit.

If you feel like it practice with some scrap to get an optimum drill speed to minimize chatter. I generally drill a small hole (3mm) first, then drill the countersink ann then drill the full size hole.

Once I had to drill a lot of them I managed to find a broken bit that was the right diameter and cut it down so there was only 1" of flutes left and sharpen it to the desired angle.

Yep a bigger drill bit, do you have a drill press?

You could make a d-bit..

Mcjing sell a range of the ones with a hole drilled at an angle, for not a large amount of $ compared to engineering supplies.

thanks for the helpfuil replies. Are these the recommended McJing ones shown here suitable for steel bars?

What would be the most common size for use on holdes for with 6 gauge and 8 gauge woodscrews?

The bits are chamfering cutters, on their site, they are listed as HSS but check with them that they are suitable for steel. I use them mainly on wood and non ferrous metals.

Hi BobL is spot on. Drill 3mm hole then countersink then hole size required. When countersinking keep the drill speed slow. Drill press the best you can set your depth. tallow or bees wax is good as a cutting agent. G. Smith