Countersink in existing hole with drill press

[Franko]

Every now and then I have to make a counter sink in a preexisting hole and I'm unable to clamp it because of the size of the part.
Invariably, the countersink tool chatters and I end up with a six sided countersink.
I've tried every speed and feed with no success.
Doing some research, I've seen recommendations that a single end countersink will work.



Does anyone have any experience with these, and do they work as claimed? Are there any tricks to it?
I'm open to any suggestions.

How about a single flure countersink? Any better? I used to have one of these bt it's disappeared.

 

[mikey]

If the existing hole is gnarly, I use a Uni-bit to take off the ragged edges first. Then I use a zero-flute countersink like the first pic above. The single flute in the second pic also works but I prefer to use them when I have a clean hole that I drilled myself. They cut really nicely if you keep speeds on the low side and feed a bit heavier. The best of these is made by MA Ford.

 

[Aukai]

I learned from him^^^^I have the Keo set of counter sinks

 

[JimDawson]

I normally buy the 0 flute, but have a few of the single flute also. Both work well if you buy M.A.Ford or Keo brand. Have not had good luck with the ones from the big box stores.

 

[stupoty]

I use the single flute and find they allow me to make counter sunk holes as apposed to the hexagon shaped depressions the multi flute ones sometimes do

 

[darkzero]

I've got that same KEO set pictured above. I also have the KEO set in 6 flute also but they mostly just sit in a drawer. Only got it cause there was a seller on ebay selling the sets brand new for $50 shipped.

I use the single flutes more than the zero but are the only 2 styles I prefer to use. Mainly cause I own more single flutes in different angles, bought a box of cutters from a local retired machinist that worked at Boeing but I have bought a few singles new. The zero flutes I only have in 90°. I have some cheap 4 flutes that don't work all that well but then again they are no name brand that I use as beaters in a cordless drill.

I find that single flutes work better for me when making actual countersink holes for countersink screws. I tend to only use the zero flutes for chamfering holes.

I find it funny that some manufactuers call the 6 flutes chatterless yet they say to use zero or single flute when the multi flutes give you chatter.

 

[extropic]

Franko,
I bought something recently that had a severely lobed countersink like you described. I "needed" to clean that up but I was away from my shop so, how to do it? All I had to work with was a multi-flute (6 I think) countersink (not new by any means) and a cordless drill. No real help so far. I rigged up a clamp arrangement that held the countersink/drill into the existing mess real solidly. In other words, the countersink "had to" cut those lobes off because it was axially rigid. It worked perfectly. Cleaned it right up without going oversize either.
The bottom line is that multi-flute countersinks need an axially stiff setup to cut cleanly in metal.
YMMV. Good luck.

 

[mikey]

You eventually need an assortment of countersinks for different flathead screw styles. I have zero flute in an assortment of 82 degree, 90 degree and 100 degree. The latter two are for metric screws. I use zero flutes for most countersinking because they don't chatter, cut accurately and are easy to sharpen. I use my MA Ford single flutes for precision countersinks where the geometry matters. I guess we use what works for each of us but I for sure avoid those multi-flute cutters the woodworker guys seem to use.

 

[projectnut]

I normally buy the 0 flute, but have a few of the single flute also. Both work well if you buy M.A. Ford or Keo brand. Have not had good luck with the ones from the big box stores.

I've used the single flute almost exclusively for over 35 years. On occasion in the field I've used 6 flute, but they're best when used in a rigid setup like a mill or lathe. The 2 brands I have in the shop are MA Ford and Keo. I bought he MA Ford set in the mid 1980's. They've been used to countersink and deburr thousands of holes in 316 stainless, 6061 aluminum, 1018 and all sorts of other alloys. I highly recommend both brands.

We used MA Ford exclusively in the shop at work and never had any problems. Mine have only been sharpened once in all that time. It's getting near the time to sharpen them a second time. To do the job I bought a MA Ford Unicam sharpening fixture like this about 15 years ago:

Welcome to CECS OF CT LLC - High-Performance Manufacturing & Metalworking Tools

At the time I paid less than $50.00 for it. I see the price has gone up a bit since then

 

[Liljoebrshooter]

One trick i figured out with my very low quality drill press for using a countersink is to turn the power off and turn the spindle by hand. I just pull the feed lever down and twist the spindle with my left hand. It only takes a couple revolutions. And no chatter.
The zero flute ones almost eliminate this.
Joe