Countersink bits, does more flutes mean less chatter?

Ken from ontario

H-M Supporter - Silver Member
H-M Supporter - Silver Member
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Hi all.
I need to get a countersink bit with a body diameter of minimum .775" for the M8 screws that I'm planning to use in aluminum and mild steel.
The 3/4" bit will be too small so I've been searching online for a good 7/8" or 1" countersink bit,
I have never owned a zero flute bit, all I've used have been single flute and a couple of 6 flutes, which all performed equally well ,what's confusing is what 's called "chatterless" countersink bits ,it seem to suggest the more flutes a bit has the less chatter it'll produce but on the other hand I have read posts here praising the zero flute countersink bit as the better performer , so here's my question: do I stick with a single flute bit since I know what to expect or do I get the zero flute and hope it'll cut a smooth CS ?
I looked around ebay and amazon, there's a lot of cheap bits for sale and almost all claim to cut metal but one item I found that sounds good is KEO brand :
https://www.amazon.com/gp/product/B00947BU22/ref=ox_sc_act_title_1?smid=ATVPDKIKX0DER&psc=1
71tTYGu1FeL._SL1500_.jpg
Please let me know what you think.
 
No expert BUT I have all kinds that I purchased from the swapmeet and I like the one you are showing and it seems to do a nice job and with less chatter for me
 
The single flute or O flute that you show above are the only countersinks I use. KEO is a top brand, I like the M. A. Ford brand for the single flute. I have had nothing but trouble with multi-flute countersinks.
 
I have a multiflute chatterless countersink as well as several other types. The multiflute produces more chatter than any of the others! Perhaps in a large rigid machine it performs better but it is terrible in a drill press or small mill.
Robert
 
Thanks for your replies so far.It sounds like the 6 flute CS bits are the ones to avoid.The few times I used them the 6 flutes did alright if the workpiece was firmly clamped with the RPM of around 100, that's in my limited experience using one but in general they are not they type I was considering to buy.
 
I find the secret to good countersinking is a really low speed and a real feed. Too high a speed and too low of a feed nearly always causes problems. Remember that the larger the cut diameter, the faster the surface speed of the cut for a given rpm. My mill only goes down to 250 rpm, and my drill press to 215 rpm, and that definitely causes problems with bigger countersinks, like my Union 1 1/4" single flute when used near capacity in steel. My lathe, which goes down to 70 rpm, never causes problems with countersinking. 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 a 6 flute mounted in a old school manual crank type drill. It works wonderful for deburring holes and even countersinking if wanted. Couple turns of the drill perfect every time. Higher speeds will cause problems.
 
The speed was likely my issue. Thanks guys. I will try slower.
R
 
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.
Hi Bob, that's one thechnic I never tried in metal, thank you for mentioning it.
Do you prefer single flute bits or does it matter?
 
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The speed was likely my issue. Thanks guys. I will try slower.
R
I totally dislike to countersink,it is the least enjoyable operation for me.
 
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