Countersink bits, does more flutes mean less chatter?

Do you prefer single flute bits or does it matter?
I use all styles, that is what I have acquired over the years. The problem with a 6 flute countersink is that it needs to be fed 6 times as fast to get the same feed per flute as a single flute cutter. Most aluminum and plastics are easy, work hardening steels are another thing altogether.
 
I use MA Ford 3 flute countersinks. I have found that firm pressure and low rpm works best. Usually, the countersink is the last operation which increases chances of chatter. If the countersink is done first, or only a small pilot holes is drilled, the chatter is reduced significantly or eliminated entirely.
The down side is a screw can't being used to check for proper depth of the countersink. I invert the screw to check depth. It isn't quite as good but it works. I find that the cylindrical section of the flat head varies from one brand or size to the next but if a guesstimate of that height is made, the maximum diameter of the countersink would be the major diameter of the screw head plus twice the cylindrical section height. In any event, a trial run could be made on some scrap material.
 
Hi Ken,

The picture that you show, is a "Weldon" countersink and available in 82 and 90 degree versions. I use nothing else !
I have picked up one or two in the local scrap yard, and even have a tool for sharpening them.

As others have said slow speeds and firm pressure. I use a piece of hardwood to get an idea of the depth needed for any particular size screw.
 
. Usually, the countersink is the last operation which increases chances of chatter. If the countersink is done first, or only a small pilot holes is drilled, the chatter is reduced significantly or eliminated entirely.
I have to try that.
 
I have picked up one or two in the local scrap yard, and even have a tool for sharpening them.
I thought a rolled up sandpaper wrapped around a dowel/rod would be my tool of choice, what tool are you using to sharpen these bits?
Thanks.
 
Hi Ken,

I find that if I countersink a hole that I am going to tap, any burr raised when threading, tends to collapse and grip the screw when tightened down. Some times this damages the thread on the screw when it is removed.

Weldon countersinks can be sharpened that way. A round stone is better.
 
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If I can lay my hands on the sharpening tool, I'll take its photograph and post it.
 
I have even turned my drill press and mill spindles by hand at times to countersink with them, which works, but is slow and awkward. Make sure you see real chips when countersinking. A depth stop helps a lot, you can push harder and not overshoot the chamfer size.
I have used this process on thin sheet metal. The sheet metal is on a plywood backing plate and I lower the quill to create downward pressure, then turn the spindle mnanually until interference has been eliminated or the proper depth is reached. It gives a clean countersink.
 
If I can lay my hands on the sharpening tool, I'll take its photograph and post it.
Thank you, I have sharpened the single flute once or twice in the past and the result was just acceptable to be honest but sharpening these CS bits is one deciding factor ,the zero flute is a different story though.
 
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