[rcazwillis]

Simple question for those in the know. I know none of the verbiage, so bear with me. I want to flush mount some bolts. I want to use the tapered head bolts. What type of drill bit do I use? Is this an 82 or 60 degree angle or what? Will the center drill bit used on my lathe have the correct taper? I am working with aluminum.

[HuFlungDung]

Wow, "bolts", "tapered", "drill bit", "82 degree angle", "flush mount", "center drill", "lathe", "aluminum" (and all spelled correctly). Who do you think you're kidding, you've got some experience alright

An 82 degree countersink is what you would be looking for. The so called 'zero flute' style is highly recommended. That is the kind with the hole drilled through the body of the tool to form the cutting edge.

[rcazwillis]

Spell check saves the day!

Since you responded, more questions.

Is the combination drill & counter sink better than a the countersink only tool?

Do I need a countersink in multiple sizes? Will one large one cover multiple size bolts? I am visualizing not drilling the taper as deep for smaller diamter bolts.

[ViperTX]

Countersinks that are made for a particular size are the easiest to use and get consistent results across a bunch of holes ...unless you have a CNC setup or a DRO.

It is easier to have a drill and countersink to insure that the hole and the countersink is concentric and it's a one step operation.....the problem is that drill bits dull or break ....also a combo drill and countersink is made for a particular size of bolt or screw......

[HuFlungDung]

Yes you might want to get a set of 3 or so, starting from smallest on up. This is because the tip of the larger countersinks is often lacking capability to cut at a tiny diameter.

[pauluk]

if your using metric screws the countersink angle is 90 degs

[rcazwillis]

Good tip on metric. I build motorcycle parts part time and have a design in mind that will require these type of bolts. Thanks.