Countersinks- Single flute/Zero Flute....?

[EmilioG]

Great information Mikey. I don't have any MA Ford cutters but may get a set if they come up for a good price.
I have several in 82 and 90° of various sizes for metric and imperial fasteners and to chamfer holes when needed.
A good amount of cutting oil is also key, I think. I was running my CS's much too fast.

 

[Rustrp]

You just run a grinding stone (Dremel sells these) inside the hole, keeping the stone flat against the inside wall of the hole.

Thanks, I will give this a try. I haven't had a problem with them cutting and I like the results produced, it's how long they stay sharp on steel or stainless that's the issue.

 

[Rustrp]

I was running my CS's much too fast.

Which will result in you thinking it's junk. :|

 

[mikey]

Great information Mikey. I don't have any MA Ford cutters but may get a set if they come up for a good price.
I have several in 82 and 90° of various sizes for metric and imperial fasteners and to chamfer holes when needed.
A good amount of cutting oil is also key, I think. I was running my CS's much too fast.

Actually, if you look at the recommended cutting speeds for zero flute cutters, Weldon suggests speeds that are too high, especially for their smaller countersinks. For Aluminum, they recommend 1000 - 2000 rpm and for mild steel and cast iron, 200 - 1000 rpm. I find this too high for what amounts to a single flute cutting edge. At these speeds you get tiny chips, not a curled chip. I guess that's okay but I much prefer a lower speed and a positive feed to produce a continuous chip. The cutting edge lasts longer and I don't overheat my tool this way.

 

[mikey]

Thanks, I will give this a try. I haven't had a problem with them cutting and I like the results produced, it's how long they stay sharp on steel or stainless that's the issue.

Try to keep the grinding stone flat against the inside walls and go all the way around the cutting lip. This has worked well for me for a very long time. For steels, especially stainless steels, I think we agree that slow speeds work best and hopefully this will keep work hardening to a minimum. Let us know how things work out!

EDIT: I should be clearer about the grinding thing. You are using a cylindrical stone inside the tool and coming in from the back side, the opening opposite from the cutting edge. You keep the stone flat against the wall of the tool and grind the entire inside wall of the hole. This simply guides the stone so you don't roll the edge at the cutting interface. Use a light touch. It takes me less than 30 seconds to sharpen a zero flute cutter this way and it cuts like new. Hope this is clear.

 

[EmilioG]

Would using the tapered round dremel stone work?

 

[chips&more]

I also have the Cogsdill Micro-Limit precision depth control countersinking tool (pic). It’s not for everything you want to countersink. But when used, it does a real slick job of it. Easy to control depth, easy to have the countersink lined up & square, repeating the same countersink is a snap, chatter is hard to do and you can use a hand held drill motor to do it, And I’m sure there is more than one brand out there, Dave.

 

[mikey]

Would using the tapered round dremel stone work?

Dunno', never used a tapered one. I use the pinkish colored one, about 1/4" OD with straight sides.

 

[Toysinthehood]

I prefer multiple flutes. Single flute: That's all we had in school, and usually they had problems of their own already. Chatter: Try slow rpm and increasing feed or somehow cutting a multi staged countersink. You're basically ramming it in instead of sneaking up so the metal *probably* is more or less being formed depending on when it decided to break a chip. If you were boring a(n) internal taper would you start at the maximum depth of cut or work your way into the material.

Sent from my RCT6513W87 using Tapatalk

 

[Bob Korves]

I also have the Cogsdill Micro-Limit precision depth control countersinking tool (pic). It’s not for everything you want to countersink. But when used, it does a real slick job of it. Easy to control depth, easy to have the countersink lined up & square, repeating the same countersink is a snap, chatter is hard to do and you can use a hand held drill motor to do it, And I’m sure there is more than one brand out there, Dave.
View attachment 232565

Dave, in the aircraft industry where those are mostly used, they are called micrometer countersinks, and indeed you can make high precision countersinks with them, accurate and repeatable to .001" in depth. The aircraft mechanics mostly use them for countersinking Alclad aluminum sheet for exposed flush countersunk rivet heads. I have just one of them, and it is a treasured tool. The aircraft guys also use angle air drills with a very short 1/4-20 socket and short threaded drills, countersinks, counterbores, etc. (like those at the left side of your photo) for working in the tight quarters of aircraft wings and other god awful places with poor access. I am looking for one of those air drills for a reasonable price and with a reasonably slow speed. I have lots of the 1/4" tools, and they are sold cheap on ePay, high quality, too.