Countersinking large holes

[JayRS4]

There what I was thinking of, as said, i thought they were only to debur, they look a bit fragile for full on countersinking unless it was in al like you mentioned

 

[the artfull-codger]

Hi Pete, you're right about those csk bits, they are really good as you say,& allso a commercial item, I made a couple quite a lot of years ago out of silver steel & hardened & tempered them, I used them mainly on alloys with ''trend'' cutting paste (the finest cutting paste for non-ferrous metals) it's even better than ''rocol'' for alloys,the broken drill home made ones are hss as opposed to carbon steel A=cheaper B=hss tougher for steel.

 

[chap]

If you've got more time than money, you could make one by turning a conical blank, milling just over a 1/4 of it away; drill and tap; make up a cutter from gauge plate that screws to it; harden the cutter. Done

Probably take 2 hours, depending how you're set-up, so £40 for a HSS one isn't too bad.
Like i say, only really works out if you're time rather than money rich!

 

[Pete.]

Is Gauge plate the same as flat ground stock? I have a fair bit of that.

 

[chap]

Yeah, the same.
For cutters i use something like 4x20mm, heat to orange and soak for 30sec, then quench. I generally don't bother tempering.

Being able to make cutters is rather handy, can really get you out of the crud!