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Thread: Drill and countersink

  1. #1

    Drill and countersink

    We are running a bunch of hard maple solids. We are flipping parts after first side and doing a drill/countersink on the second side. Seems most combination bits are adjustable but the depth is too deep at the shallowest set screw depth on the countersink portion of a bit like this" https://www.toolstoday.com/v-9965-55608.html

    I dont want to do this in two operations (tool change). The setups we have been using the set-screw countersink tends to slip over time. (surely the countersink is getting hot and the set screw loses its grip).

    Anyone know of another option that will allow a single operation? We are just poking a clearance hole for the screw and the countersink for a screw and hardwood plug on the second side (.8125 thick). The .8125 seems to be the issue in that if I retract the bit that far up in the countersink and grab on the outer diameter of the pre-drill, it just slips. Even the high end pre-drills have flats milled on the flutes for the countersink but they still dont hold.

  2. #2
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    Are you doing this on a cnc? Most wood cnc router spindles cannot go slow enough for unbalanced bits like a countersink. Try using a one piece drill/countersink (like a centerdrill). Items such as these
    http://www.harveytool.com/prod/Doubl...rsinks_42.aspx
    Colorado Woodworkers Guild
    Colorado CNC User Group

  3. #3
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    McMaster Carr has some one piece pre-drill + countersinks, but the drill is likely too short for what you are doing. Anyway to bond the top to the drill? I would suggest braizing, but the top part of those is usually some sort of pot metal. I could find you a $400 custom bit. hahahaha

  4. #4
    Quote Originally Posted by Richard Gonzalez View Post
    Are you doing this on a cnc? Most wood cnc router spindles cannot go slow enough for unbalanced bits like a countersink. Try using a one piece drill/countersink (like a centerdrill). Items such as these
    http://www.harveytool.com/prod/Doubl...rsinks_42.aspx
    Yes, on a cnc. We are boring now with a similar bit to the one in the link at 3k rpm. Spindle slows a bit when it plunges so id guess its a bit less than that. It works fine but after several holes the counter sink slips on the bit and the countersink slides up the bit so then there is no countersink only a predrill. We then have to countersink by hand which is handy to have the predrill but still sucks.

    I'm contemplating running a kreg style drill bit and seeing how that works. I have an.albrecht chuck on an iso30 taper. May give it a go in the AM. The kreg bits tend to really pull which makes me nervous on some.small parts that may lift off the table.

    The center drill idea is a life saver.
    Last edited by Mark Bolton; 03-20-2018 at 8:52 PM.

  5. #5
    These might work for you, you would still need the adapter shank and then the proper sized drill, but shouldn't be too hard to figure out. We used to use a similar style counterbore version in the machine shop all the time.

    http://www.telconpcd.com/aerospace-t...hangeable.html

    On edit... these are PCD (polycrystalline diamond tipped) and are probably high dollar, there should be carbide tipped versions out there too. You didn't say what sizes you need, but say you wanted the 3/8" body, which has the 1/8" center hole, you can get a 5/32 or 3/16 stubby drill with a turned down shank to fit the 1/8" center hole.
    Last edited by Brian Lamb; 03-20-2018 at 10:10 PM.
    Brian Lamb
    Lamb Tool Works, Custom tools for woodworkers
    Equipment: Felder KF700 and AD741, Milltronics CNC Mill, Universal Laser X-600

  6. #6
    Brian Lamb
    Lamb Tool Works, Custom tools for woodworkers
    Equipment: Felder KF700 and AD741, Milltronics CNC Mill, Universal Laser X-600

  7. #7
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    Location
    Rochester NY
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    147
    Can you make a sleeve to go over the drill shank between the countersink and the collet to keep the countersink from sliding up? Could be a piece of copper tubing or whatever is handy. Or braze it on to the drill shank.

    If you have a metal lathe (or a friend with one) you could make a tool holder bored to house the drill with a shoulder to stop the countersink. i think everyone should have at least a little bench lathe, so handy for making custom tools, jigs, gizmos, etc...

  8. #8
    Thank for all the input guys.

    I am looking at a couple options similar to your Brian. I guess at this point Im getting a little concerned with any set screw option though as you say a stubby bit and possibly a ground dimple in there may be a better option. Thinking about it a bit more I worry that the countersink, if its loosening to the point of slipping up the bit it could also loosen and fall off.

    Richard, Really like the idea of the tube sleeve if I can keep the countersink tight. Brazing it on would definitely be an option if they were cheap enough to just toss out. I do have a small bench lathe in the shop that is a fossil but it gets me through. I watch endless metal machining channels on Youtube and dream of getting a nicer lathe and a small bridgeport one day but the cnc has me brain at full capacity as it is lol.

    On this job we are just running drill/countersink in some solid maple parts for commercial shelves. They are assembled conventionally with a blind dado and then screwed from the exterior side and plugged. Weve been running every operation on the CNC including flattening the glue-ups and its really heaven. The RO sanding after the parts come off the machine is virtually zero but a good bit of that is because they are just getting clear, no stain. Working out very well.

    Thanks again for all the input.

  9. #9
    Another option, there are plenty of places that will custom grind a step drill bit. I found a place on the net, you input what you want and they email you a price. Might be worth a shot, or look for a local tool grinder...

    http://www.valleytool.net/build-step-drill.php
    Brian Lamb
    Lamb Tool Works, Custom tools for woodworkers
    Equipment: Felder KF700 and AD741, Milltronics CNC Mill, Universal Laser X-600

  10. #10
    Join Date
    Dec 2007
    Location
    Rochester NY
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    Mark, I had another thought. It's been a while, but as I remember that drill/countersink combination does a poor job of clearing chips and the flutes tend to get jammed up, probably because the drill flutes coninue up into the bore of the countersink. That would contribute to both heating up and increased lateral force on the countersink. Argues strongly for a combined drill/countersink if you can find one, or maybe filling the flutes in the bore with JB Weld to promote better chip flow.

    on edit - fossil metal lathes are perfect for woodworkers! can be plenty accurate enuf, we're not in a hurry for these one-off parts. Get yourself tooled up and you can solve all sorts of problems.
    Last edited by richard newman; 03-21-2018 at 12:24 PM.

  11. #11
    Thanks again guys. The step drill was the option I was thinking of with the kreg style bit. I didnt try it today because all the sides that need boring are done, only shelves remain. I will keep you all posted to my attempts. Im sure there is a solution out there that doesnt cost an arm and a leg.

    Im leaning towards this:
    https://www.toolstoday.com/carbide-t...5896BA37EDDF90

    I post a lot of amana stuff but its only because I have one of their big catalogs sitting on the desk lol so they wind up getting a lot of my tooling business.

    That looks like a pretty stout setup and the flute on the main body are deep because they are intended for pocket holes. Plus it would still leave me the flexibility of how deep the pre-drill would be.

    On this job the pre-drill is just through he unit side (total thickness of .8125) so drilling deep enough for a plug and a screw the pilot/clearance hole for the screw is probalby less that .200" but its still nice to have it in here on assembly because the screw doesnt twist any trash into the blind dado when it comes out the back and allows you to draw them together super tight.

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