counter sinking screws

rayclar · Jan 17, 2012

Hi all, noob here as far as allunium goes. I have to countersink some flat head screws in 1/4 inch allunium and would like to know the easiest way of doing it. I have limited metal working tools but lots of wood working tools. Any help would be appreciated. thanks ray

Haywire · Jan 17, 2012

If you don't want to spring for a countersink bit you can use a drill bit the same diameter as the head of the screw. The taper won't be exactly right, but it'll get the job done as long as your material isn't too thin. Test on scrap first of course.

Ian

SandburRanch · Jan 17, 2012

A 7 flute rose counter sink would be my choice but they are more difficult to find than lesser 3 fluted. As mentioned, a twist drill can be used and to give a better fit it can be ground to the correct angle. In either case, if possible, use a drill press with a depth stop and the work clamped to the drill press table.

All good wood workers have a counter sink don't they?

rayclar · Jan 17, 2012

yes i have wood counter sinks 5 flute, just did'nt realize i could use them on aluminum. What speed should i set the drill press at ? thanks all

SandburRanch · Jan 17, 2012

rayclar said:
yes i have wood counter sinks 5 flute, just did'nt realize i could use them on aluminum. What speed should i set the drill press at ? thanks all

Somewhere less than a speed for hickory like maybe try around 500 to see how that works. By the seat of the pants guessing here.

Baby Grand · Jan 17, 2012

Shouldn't be a problem using the wood CS. Aluminum transfers heat so fast you'd really have to lean on that drill at high speed to over heat it. Like Sandbur says, using a drill press rather than a hand drill will give you much better results - less chance of "pentalobbulating" with the 5 flute CS.

RoyJackson · Jan 17, 2012

I suggest a countersink. They aren't that expensive. A countersink stop would be nice, but only if you have a lot of usage for one.

Most flush screws use an 82 degree countersink...but not all. Some are 90 degrees (these are included angles, BTW). A typical drill bit has a 119 degree included angle.

I wouldn't countersink aluminum sheet less the .06" thick and definitely never countersink if .04" or less. That thin sheet should be dimpled.

Shield Arc · Jan 17, 2012

rayclar said:
yes i have wood counter sinks 5 flute, just did'nt realize i could use them on aluminum. What speed should i set the drill press at ? thanks all

If you happen to have a little kerosene, dip the countersink in it before cutting the aluminum.

SandburRanch · Jan 17, 2012

Baby Grand said:
"pentalobbulating" .

I tied a wheel weight to a clothes pin, clipped the pin to my tongue, let the weight dangle and still can't pronounce that word.:laughing:

SandburRanch · Jan 17, 2012

Shield Arc said:
If you happen to have a little kerosene, dip the countersink in it before cutting the aluminum.

I had forgotten about that. Thanks

rayclar · Jan 20, 2012

I don't have kerosene, would diesel oil work the same sheild arc?

GregbkH · Jan 20, 2012

If it's a one time job just go buy an 82 degree bit from the hardware store. If you think you are going to be doing more of this type work, consider getting a decent set. Cost more. I have a set of 82" Uni-bits that work awesome but they were pretty spendy.

Shield Arc · Jan 20, 2012

Oh I don't know, never tried it. Might work, give it a try, can't see where it would hurt anything.

Mark @ Everlast · Jan 20, 2012

Whatever method, watch your eyes! Aluminum won't come out with a magnet at the eye doctor's. I guess if I fear anything when working, its getting a piece of aluminum in my eye.

Bigkrank · Jan 20, 2012

On of the few things besides cleaning decal glue that WD40 is actually good for is lube for machining aluminum.

Shield Arc · Jan 20, 2012

Mark @ Everlast said:
Whatever method, watch your eyes! Aluminum won't come out with a magnet at the eye doctor's. I guess if I fear anything when working, its getting a piece of aluminum in my eye.

Good point Mark. Have you ever used a match form the cardboard foldable book of matches to remove small pieces of steel from your eye?

dstig1 · Jan 20, 2012

You'll shoot your eye out! :laughing:

RobertBrown · Jan 20, 2012

Bigkrank said:
On of the few things besides cleaning decal glue that WD40 is actually good for is lube for machining aluminum.

beeswax works good too

sparc · Jan 21, 2012

My choice would be a weldon countersink from Weldon Tool.
There are others who seel this style countersink. Try Enco or
McMaster-Carr to name just two of them.

They will give you the cleanest countersink and work on wood equally well.
You should be able to find a set of 4 for less than $40

www.weldontool.com

http://www.weldontool.com/catalogs/weldon/Weldon1998-R.pdf

varmint · Jan 21, 2012

The Weldon countersink set is a great thing to have, but since we don't know just what angle the original poster needs, maybe he should match a countersink to the fastener before sinking a lot of money into something. I have always found that the single flute, high speed steel countersink, like Morse, work well in metal. Aluminum, as someone mentioned, draws heat away nicely, so other than chattering, it's easy to machine. Just take a fastener to your tool store, Harbour Freight or Sears or whereever, and match the angle to the countersink. Done.