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  1. #21
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    They doo make piloted c'sinks.....

    How is the OP making the holes ?
    Or are these done with waterjet/laser/plasma ?

  2. #22
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    Quote Originally Posted by Terry Keeley View Post
    Not sure what countersink you're using but I've had great success with these:

    Series Display - M.A. Ford
    I love Ma [sic] Ford, but not the six-fluters. What I really liked was their M42 grade of single flute tools, which they seem to have abandoned.

    To the OP - buy a single flute, cobalt countersink of good quality like this: McMaster-Carr, and use in at the 500 rpm.

    Cobalt ctks are tougher than carbide, and will take heat better than the regular HS steel ctks you're using now. Since I don't know the quality of the one you're using, I can't say if it's inherently bad, but usually a good single flute will give better results in "iffy" setups.

    Don't rub, cut. Make sure to match pressure to the chip being generated, so low, more, more, tail-off as you're at full depth, retract. Ensure the tool is tight in the chuck, don't let it spin.

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  4. #23
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    Ill second the 6 flute MA Ford ones. I have some single flute and some 6 flute. If I'm just chamfering a hole ill use the single flutes. If I'm countersinking a flat head allen screw I will go for the 6 flutes. You need slower speed. Do you have a slow speed hand drill?

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  6. #24
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    Quote Originally Posted by ferrretcatcher View Post
    Ill second the 6 flute MA Ford ones. I have some single flute and some 6 flute. If I'm just chamfering a hole ill use the single flutes. If I'm countersinking a flat head allen screw I will go for the 6 flutes. You need slower speed. Do you have a slow speed hand drill?
    Argh!! Six flute and HAND DRILL?! What did the OP ever do to you? Steal your truck AND your dog?

  7. #25
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    As a bit of anecdata, I worked as an aircraft assembler. Using piloted c'sinks in a cage, I noticed that chatter most often happened right at the end of the cut. Crowding the bit seemed to help.

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  9. #26
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    We use a mag drill and a ground a flat spot in the shank of a 6 point countersink. It takes a lot of downward force but countersinks large holes beautifully.

    Until someone doesn't push and just lets it burn up.

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    You guys missed the part where he was using a 45 degree tool for a 82 degree fastener

  11. #28
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    I guess he only said a 3/8" hole so he could be using a metric fastener

  12. #29
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    That may work with a multi-flute countersink and even a single flute but it won't work with an O-flute one because they do not cut at the center.

    And I would think that you would need a pilot hole with any of them. Unless you like a lot of smoke.



    Quote Originally Posted by jscpm View Post
    Countersink the cone first, then drill afterwards. Do not apply a countersink to an already drilled hole.

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  14. #30
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    Well I reread all of his posts and the reason why I and all the rest of us missed it is because he never said anything about an 82 degree anything.

    What he did say was that "45 degree" was what the customer called out (on a print?). To me that sounds suspiciously like a chamfer specification. And using a 90 degree countersink is one way to do this. They also make milling cutters that have 90 degree angles at the tip but he does not have a milling machine so I would not suggest them.

    Only the customer knows what that hole is for so there is no basis for questioning the 90 degrees.



    Quote Originally Posted by garychipmaker View Post
    You guys missed the part where he was using a 45 degree tool for a 82 degree fastener

  15. #31
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    I have seen a bad finish on a CS many times. One observation I have made is this can occur in the final stages of drilling/cutting them. When I have cut CSs by hand I have a tendency to go in with a lot of pressure for a fast feed at first but then back off as it nears the proper depth so I do not go too deep. As several others above have said, the chatter occurs in that final stage.

    One really good way to avoid this, after getting a single flute or O-flute countersink that is dead sharp and using a good cutting fluid (TapMagic is my favorite), is to have and use a solid depth stop on your drill press or mill. Here is one that I installed on my bench top DP.



    That is a push button nut and it allows both rapid, coarse setting by using the push button and accurate setting by rotating it.

    Before I installed this depth stop, I almost never used the depth stop because twin nuts were just too time consuming first to get the correct setting and then, after the job was over, to return them to the maximum setting for the next job which probably did not require them. Now, with the push button nut, I use the depth stop all the time and that is great.

    One of the most frequent uses is for countersinks. On most jobs that need a CS, there are multiple holes where the identical CS is needed. So I set it once and then the remaining holes are a breeze. And yes, they do hold the setting very well. It is also great for just chamfering the edges of drilled holes.

    This good depth stop, which can be adjusted very accurately, allows the final few thousandths of a CS to be drilled with the same pressure and feed rate as the beginning. And that helps to provide a good surface finish.

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  17. #32
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    Get a Microstop countersink tool. It's made for aircraft rivets. I don't remember if they're 90° or 82°.

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    Quote Originally Posted by Koloa View Post
    Yeah, I would try 200 but 500rpm is the lowest I have. I'm going to have to slog through this job and just feel bad about it cause they want them right now. I don't want to do this again though.

    Oddly there is no difference when I clamp the work down or just press it against a solid stop. Thinking It really must be my speed, not enough rigidity, and then maybe I'll try one of those zero flutes next time.
    only option you have now is to farm it out to someone with a more qualified machine.

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  21. #34
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    It's jenky but if you need lower rpm often you can easily add a jackshaft for further belt reduction.

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    For the record, 3 flute c'sinks are the worst of the worst IMO. Once chatter starts, you'll likely never get it out with one of those. Zero flute, piloted, or single flute all the way. Severance (are they still around?) made great 6 fluters, but I heard they are a proprietary grind (dunno for sure) and can only be sharpened by them to still cut and not chatter?

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    Quote Originally Posted by steve45 View Post
    Get a Microstop countersink tool. It's made for aircraft rivets. I don't remember if they're 90° or 82°.
    That’s what I was going to suggest, you can set depth to a thou, use in a drill gun, I have a few flea market ones, nylon face, calibrated collar nice finish, no chatter low speed
    Mark

  25. #37
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    Put a rag between the cutter and the work and countersink through the rag. For the last 0.050 shut off the machine just as you apply pressure then release the pressure just before the spindle stops. Use cutting oil.

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    Try a Weldon style, and as was suggested shut off and finish while coasting.

  27. #39
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    First off I agree with those that say the speed is excessive. I usually countersink at 200 rpm. Secondly I do prefer the MA Ford single flute countersinks for most operations. I've used them for over 30 years and haven't had any problems as long as they are sharp. If they do get dull chatter is imminent. Ford used to make a fixture for sharpening them on a surface grinder. I have one and have used it a number of times over the years.

    When depth is critical I use a cage. I have a number of different sizes made by Magnavon. There are currently several listed on eBay

    https://www.ebay.com/sch/i.html?_fro..._odkw=magnavon

    They make countersinks in a number of different angles. I currently have 45*, 60*, 82* 90* and 100*. The only drawback is they are specific to being used in a cage. They are screwed into the shaft with a 1/4"-28 threaded stud, and require a pilot hole. MA Ford, Mores, Briles, and others make replacement cutters.

  28. #40
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    Your post 14 comment about the c/sk on final depth.Think its a bit like a parting tool once the tool is cutting dont stop it go to final depth.As has been suggested a pipe on your handle so you can get a steady feed to depth and WD40 WILL help.This sounds like a light weight machine and if your forcing the tool in the light weight table often will push away.So have a bottle jack under front table so it cant push down when pressure is at its peak as you near the final depth


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