single flute, 3 flute or 6 flute countersinks.

[737mechanic]

What are the advantages and disadvantages of the 3 types of countersinks. I see single flute, 3 flute and 6 flute chatterless countersinks. I need to order a couple but I am not sure which to go with. Also which is most common 60 or 90 degree.

[millman5]

It depends on what I am using them for. If it's a countersink for a flat head bolt I think most if not all common flat head bolts are 82 degree & I like a single flute for that.

The term chatterless on a multiple flute doesn't seem to mean much. If anything I think they are worse to chatter.

I use countersinks for lots of deburring & chamfering & quite often run them in cordless drills for that, either a 3 or more flute 60 deg. there.

I might also note 99% of my work is in mild or easily machinable alloy steel

[doorknob]

The metric flat-head screws that I have used require a 90-degree countersink.

I am going to try using a combined countersink/drill (that looks like a center drill) in aluminum, but I might also try an aircraft-style 90-degree single-flute countersink of the type that mounts into a "microstop" device.