Countersink woes

[eagle24]

I'm having problems cutting clean contersinks in metal.  I guess it is chattering, but instead of a smooth countersink, I'm getting a 6 sided bevel to the hole.  What causes this problem or how do I keep it from doing that?  The only ones I have done so far are the Tang bolt and Tang screw (southern rifle).

[Long John]

There are others here that are true machinists and they will probably give you better advice than I can.  I am just an amateur. 

I have had the same problem when using the countersinks that have a bunch of cutting edges on a conical portion.  I think those countersinks are intended for wood and when used on metal, especially with a hand drill, they bounce up and down while you are drilling with them and yield that multi-sided pyramidal depression rather than a smooth cone.  For metal I use a countersink that has a single cutting edge like a single flute drill bit.  Those countersinks cut a nice smooth conical hole in steel but don't work well at all in wood.

Best Regards,

John Cholin

[Acer Saccharum]

Try one of these countersinks:


The trouble with the six sided is that they start to set up harmonics, and before you know it, you have chatter.

With a single flute tool, you don't get that chatter. I also mount this in my brace and can take metal off one side of the hole if it needs to move over a touch. Do this by partial rotation of the brace.

Plenty of pressure and low RPM combats chatter and gives the best finish. Run a countersink as low rpm as possible. Cutting oil helps, but don't use oil if the metal is in the unfinished stock.

Look in McMaster-Carr or MSCdirect.com or Enco for these tools.

[Tom Cooper]

I use a six flute countersink purchased from the machinist shop here in town and have no problems.
I think that the speed that the tool is turning is the issue here, I do use a drill press though, and have used a handcrank drill to go to finished depth.

[AndyThomas]

I use one of those single cutter units like Acer recomends, which I got from TOW. It solved the problem for me. Also, as Acer notes using a brace, although slower, is ideal, you can "fit" the countersink to the job easier. On a butt piece, for instance, you want the screw to push a little harder on the side of the countersink toward the front (or bottom) of the BP. It's take a little off and check it, etc, etc.

Hope this helps,
Andy

[eagle24]

Thanks All!  I was using a countersink that is designed for wood.  I'll try one of the single cutting edge designs.

[T*O*F]

If you use one of these to drill your initial hole, you solve both problems.  They are available in various sizes depending on what size screw you're using.

I find that I can then hand-hold one of these, or a 6-flute to adjust my angles and final depth.

[Acer Saccharum]

What you show Dave is called a 'combined drill and countersink'

They can be had in 60 deg and 82 deg cone taper. Get the 82 deg for standard flathead screws.

I find that these tend to chatter once the tip goes thru the metal. I don't like them as much as the single flute csk.  Again, use slow speed and plenty of pressure.

Tom

[Metalshaper]

Old machinist trick, from out of the 40's or 50's

Place a stiff piece of card stock between the countersink and the hole.
<  Manila folder works great >  the card stock only needs to be a bit larger than you intend to go. start the counter sink and let it work its way down through the paper and into the metal.  this technique works by easing the bit/flute(s) into the metal and helps eliminate some of the harmonics and resulting chatter.

It can also be used, to clean up a countersinck after it has started to get 'chattered',, if your careful!

Hope it helps

Respect Always
Metalshaper

[Acer Saccharum]

Great tip, metalshaper.

By the way:
American standard flathead angle: 82 degrees
European std flathead angle: 90 degrees

[BobT]

What you show Dave is called a 'combined drill and countersink'

Actually it's a 60 deg. center drill, designed to drill center holes in stock to be turned between centers on a lathe. It also makes a pretty fair "spot" drill. They come in various sizes but are best used in a drill press or a mill if you are going to countersink with them. I will try to scrounge up a selection of countersinking tools and post a photo after I get to work. I have a hand held one that works great for cleaning one side of a hole.

Bob

[Tim Crosby]

 I had no less than 5 old counter sinks around here and couldn't get any of them to do a decent job. So I threw them all in the trash, that is not easy for me to do cause i use things way past their life span and then some. Anyway since I trashed the old ones I bought a new one it has 5 cutters and cost 9 bucks. It is nice and sharp and boy does it get the job done.

Tim C.

[Scott Bumpus]

The 2 biggest causes of chatter are dull tool and lack of rigidity in the set up.  The dull tool is easy to fix, the rigity is more difficult when cutting by hand ( as when not clamped in a drill vise or mill table).  I have found the center drills and the style countersink that acer showed to be best.  If you are using a drill moter or brace try to set up as firm and rigid as possible, such as bracing your arm or body against a firm objest like the bench or vise.  Just some of my experience shared.   SCOTT

[Randy Hedden]

Tim,

I have been using the same chamfering tools for well over 15 years. When they get dull, I sharpen them. I don't use any of the multi-flute chamfering tools, preferring the uni-flute tools. BTW, the uni-flute chamfering tools come in two standard sizes, 90 degrees and 82 degrees. The 90 degree ones are used for chamfering and deburring a hole and the 82 degree ones are what should be used for countersinking a hole to receive a flathead or oval head screw or bolt.

Randy Hedden

www.harddogrifles.com

[B.Habermehl]

When I drill the pilot hole for My tang bolt or any other hole I need to countersink I use a 5/64 dia drill. Check your centering now. If needed you can do a bit of fudging by notching the side of the hole you need the countersink to drift to with a small cold chisel. Remeasure and repeat as needed. Next I will rough countersink to just under finished dia. I never have countersink chatter with a little bitty pilot hole. Next drill your hole out  to finished dia. The drill will center it self just fine in the funel shaped hole left by the countersink.

[Roger Fisher]

I must remark that all the information freely given on this subject illustrates once more the value and importance of this site. 

[don getz]

Metalshaper.....while I have never tried this, I did hear about using "toilet paper" over the hole and it would eliminate the chatter.  Apparently it does the same thing as your card stock......Don

[LRB]

  I believe Tom Cooper has the real answer. Speed is what seems to screw up a counter sink, regardless of flutes. I have used both, and find the muti-flute better for me, but it must be used at a slow speed.

[D. Taylor Sapergia]

My countersink(s) have three flutes and I place a doubled cleaning patch over the predrilled hole before cutting the countersink.  It fills the flutes and allows just the edge to engage the metal, and leaves a very clean unchattered countersink.  One of the hardest to do nicely, is thin metal with a large hole, such as patch box metal.  It's easy to get a three or five sided hole if everything isn't solid and the speed is too high.

[Evil Monkey]

I did hear about using "toilet paper" over the hole and it would eliminate the chatter.  Apparently it does the same thing as your card stock......Don

Hmmmm, "useing toilet paper over the hole" isn't a new concept however, doing it to "eliminate the chatter", well, that's a new one on me. Even in the outhouse in -30 it don't "eliminate the chatter". I don't think toilet paper and card stock are all that interchangeable either.......but that's just me. BTW, what does this have to do with countersinking?? Strange way to highjack a thread Don.

[Stophel]

I countersink holes with a brace turned by hand.  If the countersinks had unevenly spaced flutes, they couldn't chatter....hint to toolmakers.  I use two different countersinks.  One is 5 flute, one is 3 flute.  When one begins to chatter, I simply change to the other, and the chatter marks are cleaned up, and it cuts smoothly again. 

The single flute cutters simply don't work for me.

[Kentucky Jeff]

Had the same problem as you a while back when I first tried using my countersink bits.   Like you I posted the question to the forum.  The answer that I got back that worked for me is Speed.  Keep your speed as low as possible and go EASY on the downward pressure.  Mine cute nice and smooth now using my hand drill.  

[davec2]

I use Metalshaper's method with either card stock or even a rifle cleaning patch between the counter sink and the hole, but I put some good cutting fluid (i.e.Tapmatic, etc) on the patch or card stock first.  I don't know why it works, but it works.

[flehto]

When I was in the toolroom never had faceted bevels and used 5, 6 and single fluted ctsks. The drill presses had tight spindles, the workpiece was clamped in a vise which just sat on the DP table and the slowest speed was used. Too high a speed and  a "wiggly" workpiece ensure a faceted bevel. I ctsk the holes in the BP heel using a DP  and because of the tall, unstable block needed,  I got faceted bevels. The block is now clamped securely and the faceted ctsks are no longer a problem. Presently use a single fluted ctsk w/o any problems whatsoever....Fred

[George F.]

I just got back from the tool supply and picked up a few items. A single flute countersink/deburrer, a 10/32 and 8/32  countersink/82 deg. step drill, and a  82 degree center drill. The countersink actually shaves the metal instead of those cutter teeth,. I had a single cutter counter sink and it didn't work worth a @!*%.  But this baby is the cat's meow.  ...Geo.