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Countersink bits, does more flutes mean less chatter?

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Ken from ontario

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#1
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.
 

Ed ke6bnl

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#2
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
 

JimDawson

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#3
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.
 

rwm

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#4
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
 

Ken from ontario

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#5
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.
 

Bob Korves

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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.
 

Cadillac

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#7
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.
 

rwm

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#8
The speed was likely my issue. Thanks guys. I will try slower.
R
 

Ken from ontario

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#9
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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Ken from ontario

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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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Bob Korves

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#11
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.
 

RJSakowski

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#12
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.
 

BaronJ

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#13
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.
 

Ken from ontario

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#14
. 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.
 

Ken from ontario

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#15
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.
 

BaronJ

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#16
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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BaronJ

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#17
If I can lay my hands on the sharpening tool, I'll take its photograph and post it.
 

RJSakowski

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#18
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.
 

Ken from ontario

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#19
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.
 

Dabbler

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#22
Sorry to be late in on this, I have 6 flute, 5 flute and Weldon countersinks. I have recently moved to carbide insert chamfering mill cutter for my larger countersinks (1/2" and larger, though it could go smaller). It does a better job than anything elsie I have used. No chatter!!!

When I have smaller holes to countersink, I'll try to report back to this thread.
 

Ken from ontario

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#23
Thank you all for your posts, keep it coming ,
Bob, thanks for the video, it's now clear how it's done.
 
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BaronJ

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#24
Hi Guys,

I'll probably get blasted for this, but never sharpen a Weldon countersink with a Dremal ! You cannot get the edge angle correct. Yes as demonstrated it will cut, but it won't cut well.

Use a round stone, by hand, from the inside out towards the cutting edge. Never the other way !
If that edge is damaged you definitely need to use a jig to resurface the outside surface of the cone.

Weldon countersinks are quite easy to make, but you do need to be able to harden the drill rod and you do need a jig to sharpen them properly.
 

mikey

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#25
Ken, the link in your first post is for an 82 degree countersink. I suggest you purchase a 90 degree one for metric screws instead to ensure full contact with your M8 screw.

Keo, Weldon and MA Ford make some of the finest zero-flute countersinks in the industry. In fact, anything that MA Ford makes is top shelf but you can't go wrong with any of them. I highly recommend staying away from the Asian versions.

I've been using and sharpening these zero flute guys for a very long time. I use a hand drill, not a Dremel, but I use Dremel stones and sharpen from the back side of the hole. Conveniently, the inside of the hole acts as a nice guide to position and maintain the proper angle on the stone and allows you to sharpen the front cutting edge quickly and easily. You just keep the whole length of the stone against the inside of the hole and go around the cutting edges. Takes a few seconds to do and you have a sharp tool. I like the lavender colored Dremel stone, not sure of the grit. I use a hand drill or a Foredom - Dremels go too fast.

Zero flute countersinks actually run well at higher speeds. The small ones can be use at speeds of about half or more of normal drilling speeds. However, they last longer and cut just as well at low speeds, between 100 and 250 rpm.

When the hole is freshly drilled and gnarly in steel, with all sorts of hard stuff sticking up, I use a hand-held zero flute bit in a handle to knock those bits off before using a sharp countersink. Lasts longer that way.

For the single flute bits (I really like single flutes from MA Ford), use them at low speeds and feed hard enough to make sure they cut continuously. When I need a really nice countersink, like one that has to locate a tool, I use a sharp single flute bit from MA Ford. I have never had an MA Ford countersink chatter this way and the finish is excellent.

Multi-flute bits are horrible. I only use them in wood and plastics and only hand held in a handle.
 

Ken from ontario

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#26
Thank you all for helping me with my question , you have also helped me make the right choice even though there were more than one .
I went ahead and ordered the zero flute by KEO. , the price was just right and I thought I couldn't go wrong with that type of countersink bit.
Mikey, thank you for all the info in your post, I did order the 90° since almost all my screws are in metric so that was a very good recommendation.
As far as sharpening of it goes , I'll( very carefully :))follow your suggestion which is almost like the video in Bob's post. but I am now really curious to know the sharpening method BaronJ mentioned . being a lefty, I may find one method easier to follow than the other.

You all have great day now.
 

ezduzit

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#27
I have found that an 82* single flute is by far the most useful.
 

stupoty

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#28
I have a single flute counter sink which is my prefered counter sink, I also have a couple of two flute ones that are also very good, I find the 6 flute ones prone to bouncing and not making a nice counter sink.

:)
 

Ken from ontario

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#29
I have found that an 82* single flute is by far the most useful.
I've read that Metric flat head screws have a different angle and the 90° CS bit is often mentioned when using metric . for my hobby use I shouldn't be too fussy .
 

mikey

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#30
Standard countersinks: 82 degrees for Imperial FH screws, 90 degrees for metric FH screws, 100 degrees for BSW and aircraft screws.
 
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