Why do my countersinks look horrible

[Martyb]

Building a Jim Chambers Lancaster Flintlock. I purchased a brand new set of Irwin metal countersink bits. Used the 1/2 inch one in my drill press with speed set at 540 RPM. The cuts look horrible…I’m a woodworker and have very little metal work experience…what am I doing wrong? I tried using a hand drill and got the same results.

 

[billraby]

It is moving around as you cut it. Mount the butt plate to a block of wood with shellac and hold it in a vise on the drill press.

 

[frankie]

One reason also, they use a drill bit instead of a real countersink.

 

[oldwood]

Standard countersinks will chatter like you show , due to not having enough cutting flutes. I do all my counter sinks with a standard variable speed electric hand drill , and get near perfect countersinks. I use a standard fluted cutter , then change to a metal cutter with a steeper angle , and with many more flutes. Makes perfect countersinks w/ no coarse chatter marks. The finer flute bits are available most machine tool catalogs. No special fixtures , or drill press needed........oldwood

 

[doubleset]

Also, not all countersinks are created equal. And how much runout does your drill have? But definitely for anything other that casual work, I'd go with the drill press suggestion (if it doesn't have excessive runout and has a good chuck).

 

[Rudyard]

Simple cure is to put a piece of rag over the hole and your C sink will run smooth as you have limited its ability to cut wildly .
Rudyard

 

[The Crisco Kid]

I've seen a skilled machinist cut a perfect countersink with single flute cutter and Bridgeport milling machine. I get the same results as the OP with my drill press. I haven't tried it but I wonder how a brace and bit would work?

edit: I mean using a brace to drive the countersink.

 

[bang]

Clamp part and use the stop feature on press to stop just short. The stop will hold bit depth position and allow the countersink to clean up the cut. Then bump the stop to desired depth.
Chatter with a countersink with a pilot happens when the hole is or becomes too big for the pilot, especially with thin metal. Clamp a piece of metal behind with hole size of pilot. Don't cut too much material at one time.
I use aircraft countersink stops. Provides real good end of cut control.

 

[bptactical]

Rigidity is key, keep things from moving and keep your speed as slow as possible.
More cutting edges = more chatter.
Single flute countersink.

 

[Metalshaper]

use a piece of stiff card stock or old jean material.. place it over the hole and run your countersink down through it.
the teeth of the cutter work through the card/fabric and engage the piece a bit more slowly and evenly.
you can even use this technique to clean up chattered attempts .. make sure the part is secure as vibration only
causes more problems.

single flute work a bit easier but it's what YOU do < or don't do > that can F it up.

 

[Rich44]

Clamp part and use the stop feature on press to stop just short. The stop will hold bit depth position and allow the countersink to clean up the cut. Then bump the stop to desired depth.
Chatter with a countersink with a pilot happens when the hole is or becomes too big for the pilot, especially with thin metal. Clamp a piece of metal behind with hole size of pilot. Don't cut too much material at one time.
I use aircraft countersink stops. Provides real good end of cut control.

Rigidity is key, keep things from moving and keep your speed as slow as possible.
More cutting edges = more chatter.
Single flute countersink.

Read these over and over, and cut that speed in half or more.
To clean that up now - Set the stop, Sharp single flute, Rigid mount, Slow RPM (100), and bump the stop. Meaning have the stop set for the slightest touch and come down positive and hold for just a revolution or two. Adjust stop a couple thousands and do again. Do not hold it down over a revolution or two. It is much harder to get rid of that chatter now that it is started. Short cut on any of the above and it will not get better.

 

[doubleset]

If you just need to smooth it out, you might at this point try a cone-shaped stone.

 

[2shute]

Consider a chatterless countersink-with random width flutes.

 

[Ponderosaman]

A little lube would probably help.

 

[ZUG]

SPEED is your enemy and that 540 RPM will give you chatter along with not having it clamped down using that drill press of yours. That drill press speed must be slowed down to around 100 - 150 RPM depending on the size of the countersink. If that can't be done then use a variable speed hand drill at LOW speeds. I've also used one of those "egg-beater" style hand crank drills with great success. Some have success with placing a piece of cloth or paper between the work and the cutter but I've not tried this so maybe it works . Some of the multi-flute countersinks have a very aggressive cutting attack angle on the cutting edge which is more for getting a rough surface finish than a cutter with only one cutting edge. I like the counter sinks with the hole that is at an angle to the center axis of the cutter. Also practice on scrap material before you use it on the finished material.
P.S. You can also try turning off that drill press and as the RPM's coasts down touch it to the work if you can't get the drill press speed low enough.

 

[user 34300]

I do not use countersinks on gun projects. I want the screw edge to be under the surface which requires a cutter that matches the screw in size and contour. So, I make piloted cutters that do that. I turn the basic form in the lathe then make the cutting flutes with a file of Dremil. Sometime the mill, but no usually. You could file the contour in a hand drill instead of the lathe. You can make the cutter so that you have two flutes, like a screwdriver blade with a pilot. If you have clearance behind the cutting edge it will work. The face of the cutter can be 90* to the work and it will make a scrape cut that tends not to chatter. Once made and sharpened I heat threat with a propane torch.

The key to not chattering, is to run very slow, in a rigid set up. I use a drill press that is set up to run very slow. With a close fitting pilot it can not chatter.
Hardware store countersinks are not precision cutters. The flutes seem to be equally spaced. This invites chatter. If you are countersinking a wood screw in an archectual project it does not matter. The single flute ones are better.

 

[Martyb]

You guys are awesome! Thanks so much for the help! I think I had the drill press set at the slowest speed, so I’m gonna try some of the other ideas presented here. Thanks!

 

[Martyb]

If you just need to smooth it out, you might at this point try a cone-shaped stone.

Great idea! I have a set that I’ve never used with my Dremel…will try that today!

 

[tallpine]

Lock the piece to be drilled in a drill press vice. Drill your hole. Without MOVING ANYTHING remove the drill bit and chuck up your countersink. Drill your countersink, it will be perfectly aligned. Use a light hand and a dab of beeswax. Best to run your drill press pretty fast. Works for me

 

[arjay]

Assuming a sharp countersink, chatter is caused by too much speed vs too little feed.