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Countersinking in Stainless?

I frequently need to countersink screw holes in stainless, usually 303. I know I'm supposed to use a slow speed, coolant/lube and a fairly agressive feed to avoid work hardening the metal. If I use the quill feed on my Clausing mill, I frequently get chatter, even with "chatterless" countersinks. I think the problem is that it's bouncing up and down vertically, rather thna an issue with teh stiuffness of the small mill. The other problem with using the quill is accurately setting the depth stop, which is time consuming if you only need to do a few holes.

One alternative is to use the knee with the quill locked. I don't seem to get nearly as much chatter, but it's harder to maintain a good feed rate while eyeballing the knee dial to know when to stop. The good news is that it's pretty easy to get an accurate, repeatable depth without any particualr set-up, but only if I go slow on the feed.

The other option is to use a depth stop countersinking tool. I've seen these, but never used them. They have a sleeve that acts as a depth stop, but I'd be concerned it might score the surface of the work if the stop-sleeve spins as it's making contact or when you reach the depth you want. Presumably once the tool is set up, there's no problem with setting the depth, but you'd have to use the quill feed, which gets you back to the chatter problem.

I've tried several different styles of countersinks. I've tried the ones with a hole bored through them, the multi-flute "chatterless" ones (Severance brand, I believe), single flute "Ford" countersinks, etc. One thing I haven't tried is carbide.

Any tricks or suggestions would be greatly appreciated. Favortite countersinks, lubes, techniques, etc.?

Thanks!

Doug Whiter

Reply to
Doug White
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| The other option is to use a depth stop countersinking tool. I've seen | these, but never used them. They have a sleeve that acts as a depth | stop, but I'd be concerned it might score the surface of the work if the | stop-sleeve spins as it's making contact or when you reach the depth you | want. Presumably once the tool is set up, there's no problem with | setting the depth, but you'd have to use the quill feed, which gets you | back to the chatter problem.

I used these for years. Magnavon, maker of MicroStops, is an example of what you're talking about, and very popular in the aviation industry. There's a bearing inside that allows you to push the tool against the work and bring the countersink down, without the tool moving against the work. That the bit has a pilot is also a very important part of getting a clean hole and avoiding chatter. On some surfaces where we might get tiny scratches caused by the foot, we simply apply masking tape to the foot or work surface, and adjust the tool accordingly. In most areas you would see a piece of skin or thick aluminum mounted to the wall, full of holes and countersinks, where the tools are adjusted and set up for depth prior to being put on the airplane. There are stops that have one side of the foot cut out to clear items, narrow bodies, long bodies, very short bodies, and a dozen other body styles to accommodate every need. Get 'em on ebay or most aviation suppliers

Reply to
carl mciver

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One of my clients btw.

I buy these surplus from Reliable Tool for $5 each, and the cutters are $4 a pound. Lots of various types of these cutters in a pound.

As for them spinning..I simply hand hold them with my left hand as I pull down the quill with my right.

Chatter usually, in this case, means you are turning too fast, based on my experience.

Gunner

"I think this is because of your belief in biological Marxism. As a genetic communist you feel that noticing behavioural patterns relating to race would cause a conflict with your belief in biological Marxism." Big Pete, famous Usenet Racist

Reply to
Gunner

I've been checking out the Ebay stuff & the like. Most of it is for aircraft work, and they mostly seem to be 100 degree cutters. 82 degree cutters are available, but I haven't found any bargains on them yet. There are a couple of "Reliable Tool" companies out there. I haven't found one on-line that lists these.

That sounds easy enough.

I'll keep that in mind.

Thanks!

Doug White

Reply to
Doug White

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