Countersink

Agreed. Use oil or something similar as a lubricant in aluminum ALWAYS. Aluminum becomes gummy on just about any tool at just about any speed sooner or later.

Run the RPMs as slow as possible... "Play with" your downward pressure to minimize chatter as needed. Pilot hole is absolutely necessary.

Ask in rec.crafts.metalworking for a more professional-soundign answer. :)

Regards, Joe Agro, Jr. (800) 871-5022

"Joe AutoDrill" wrote in news:ZKnzg.1110$eG.309@trndny08:

I have used my Stanley 1/2" countersink in wood and brass with no issues. Even starting to countersink a hole in soft pine using the Bosch CS resulted in horrible amounts of chatter.

What RPM are you running when this happens? Is the tool new or at least sharp?

I don't have the RPMs for countersinks memorized, but I'd guess that if I had to simply walk up to a drill press (you are using a drill press and not a hand drill, right?) and make a counersunk hole, I'd run it at 1/2 the speed of drilling to start.

Rough, ver conservative drilling RPMs can be found on my site at:

"Joe AutoDrill" wrote in news:f0ozg.7909$Ju.7125@trndny09:

I chucked the Bosch bit in my drill press at the lowest speed and it chattered very badly. I decided to try a variable speed hand drill and no matter what speed i tried, it chattered. Wood, Brass, it doesn't matter. I think I will have to order a set to get a good countersink that I can use in my drillpress. I wish I could find a Stanley 3/4" countersink. BTW, I clamped the pieces to the drill press using c clamps.

You are on the right track. Sounds like the Bosch bit may either be dull, a specialty bit for something else, or simply doesn't like you.

Much success.

Also, final thought on RPM... Some folks countresink up to 3X the diameter of the inside hole... In that case, you may want to drop the RPMs even further... i.e. a 1/4" hole with a 1/2" ctrsink will have the ctrsink run at 40-50% of the hole drilling rpm. But... a 1/4" hole with a 3/4" ctrsink will run at 33% or less the speed of the drilling rpm, etc.

When in wood, it usually doesn't matter as much unless you want a clean hole and/or no burnt wood. I haven't met a wood worker yet who uses coolant other than air...

Regards, Joe Agro, Jr. (800) 871-5022

I've had good luck with this style countersink in wood, aluminum, and plastic:

-- Timothy Juvenal

I gather the holes are already drilled ??. If not, drill the countersink first with a drill bit the right size for the screw heads, than drill the hole through the centre for the screw shank. The smaller bit will self centre in the larger, countersink holes.

Regards John

ORDER A GOOD SINBLE FLUTE FROM

"Hambone Slim" wrote in news:3hpzg.123$ snipped-for-privacy@news1.epix.net:

Too small. I need a 3/4" countersink.

Upscale has the pricier ones, and I have the cheaper model:

Tanus

Tanus wrote in news:44ce9109 snipped-for-privacy@x-privat.org:

not big enough.

R. Pierce Butler skrev:

Name wrote in news: snipped-for-privacy@giganews.com:

that could work. I will have to get one the next time I order from Lee Valley.

Countersinks are for sissies. Real men use a plug cutter and recess the screws, welding the plug in place.

"Edwin Pawlowski" wrote in news:VKOzg.11217$Ju.7756@trndny09:

Hard to do that with 3/8" thick aluminum plus make the screw removable.

Get a bigger one.

That's what an ex girlfriend once said.

Tanus