Countersunk Holes Come Out "Fluted"

[WA3LKN]

Occasionally I need to countersink a hole in metal or plastic, and I use the bit shown in the photo.

The edges of the hole aren't smooth but are 'fluted'.

What am I doing wrong? Too fast drill speed? Too slow drill speed? Too much pressure on the drill press?

Countersink.jpg

[KF5FEI]

If you are doing plastic or aluminum, try a zero-flute countersink bit.

[KG0MN]

I always use medium speed on my drill or drill press and maintain a steady downward pressure as well. From what you describe it sounds as if your bit may need a good sharpening if you are pushing down to hard or if the bit is dull you will cause it to chatter and cause the fluted opening you describe. Take your fingernail and pull it toward the straight cutting edge on the bit, if you can feel a slight rolling over of the cutting edge that could be your problem. I bought some flat diamond embedded files to sharpen the router bits I own and they were worth every penny it cost me.

[KW4MW]

Occasionally I need to countersink a hole in metal or plastic, and I use the bit shown in the photo.

The edges of the hole aren't smooth but are 'fluted'.

What am I doing wrong? Too fast drill speed? Too slow drill speed? Too much pressure on the drill press?

Countersink.jpg

If the Holes are "fluted"
(1) either the bit, the workpiece or both may not be stablized; securely clamp the work to the drill press and tighten the chuck on the countersink - if the countersink shaft has 'flats, make sure they are aligned properly in the chuck jaws
(2) make sure that the countersink turns true by watching the point - it should not move side to side, otherwise you have a bent shaft or a chuck that is closing improperly - check the chuck for debris
(3) make sure that your drill press table is square to the feed and firmly locked in place
(4) if you're already doing all that then you need to reference a machinist handbook for the correct rpm and quill feed for the material you are using.
(5) plastics and soft metals are the worst materials to counter sink -

Good luck ..mike

Try

http://www.endmill.com/pages/trainin...ink%20Data.pdf
or
http://severancecanada.com/index.cfm...rogramming.cfm

[KC9UDX]

Don't ever use multi-fluted c'sink tools unless you have a super-rigid setup (and machine), or, unless it's dull to the point where you're putting so much pressure on it that it's forming and not cutting (It will not chatter then, but you will get a nasty burr on top of the countersink). If you're using a drill press, you don't have a rigid enough machine, unless you have a really nice drill press, the kind most of us don't have at home.

Get yourself a single-flute one like you have, or, as suggested, get a 0-flute ("zero"), or, live with the chatter...

[KA9VQF]

My counter sink cutter looks just like yours. {except that mine is rusty}
It was made/sold by American Vermont tool company.

I'm with the 'its probably dull' group here.

I was able to dress up the cutting edges on mine with my generic Dremel tool and one of the small thin cut off disks. You have to be very careful not to roll the cutting edge at all.

I made a little wooden and steel jig to index the cutting surfaces and to hold the Dremel tool steady.

[K7RQ]

Google "Weldon" countersinks. I think they make those shown by KF5FEI above. No chatter, and a smooth job every time.

Hal, K7RQ

[KC9UDX]

A multi-fluted countersink will chatter *less* when dull, *more* when sharp. The tool is not responsible for the chatter, the machine is. Rigid setup in rigid machine means no chatter. Anything else and you're most likely to get chatter, unless the tool is dull.

[K6CPO]

In the aviation industry we used THESE to countersink holes in metal. They serve two three purposes: The pilot on the cutter keeps it centered on the hole, the cage keeps the cutter perpendicular to the surface and the cage allows a specific depth setting, allowing precision countersinking and consistency from one countersink to another (good if you're using the same fastener in multiple locations.)

[K8ERV]

What's wrong with a flute?

TOM K8ERV Montrose Colo