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  • Carbide Insert Pocket

    I'm wanting to make up a handle for a woodturning tool. It will be a round carbide insert sitting in a pocket on a square steel shank, which goes into a long wood handle. The insert I have is flat topped, but tapered: 0.550" dia on the top, and 0.500" dia on the bottom. So, it would be nice to make a nice tapered pocket in the shank.

    However, I'm having trouble figuring out how to make this pocket given the manual tools I have available. I suppose I could angle the mill head to the proper angle, and run the shank around with a rotab. But, I'm wondering if I even need to worry about all that. Would a cylindrical 0.563" pocket be just as good? Seems like unless it is perfect, it won't give much support to the insert anyway. Given that it is woodworking, the loads on the insert are relatively minimal.

    Has anyone done this before?
    If ignorance is bliss, why aren't there more happy people?

  • #2
    I make my own carbide insert mill and lathe tools sometimes. I have found that it's best not to make the pocket quite all the way to the top of the insert on positive rake inserts. If the pocket is full depth it leads to chipped edges when the insert is pushed back into the pocket. For an oddball size of round you can cut it with an endmill, then bring it to size with a boring bar.
    What I do is mill the pocket to about 3/4 depth of the insert, then set the insert in the pocket and find the center of the insert with the pointed end of an edge and center finder and call that X and Y zero. Then move .003 further into the pocket and drill and tap for the insert screw.
    When the screw is tightened it pulls the insert tight into the pocket for a secure hold. This works for square, round, diamond and any other shape and requires no complicated calculations of where to put the screw.
    Last edited by Toolguy; 06-01-2013, 07:07 PM.

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    • #3
      Tapered endmill and a rotary table, HSS tapered endmills are reasonable in cost, and available in pretty much every insert relief angle.

      Or you could just buy one.

      http://www.thingswestern.com/3.html

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      • #4
        Coming at this from my blacksmithing background I would make a punch for the arbor press that looks like the carbide insert, set up some stops to locate the carbide tool holder and then heat it and drive the forming tool into the hot tool preform. Don't know if it will work, but it will be quick.

        paul
        paul
        ARS W9PCS

        Esto Vigilans

        Remember, just because you can doesn't mean you should...
        but you may have to

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        • #5
          Make a sanding jig for the final fitting. Just turn a short length of aluminum (or wood) to the correct diameter and taper (allowing for the thickness of the sandpaper).

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          • #6
            Originally posted by elf View Post
            Make a sanding jig for the final fitting. Just turn a short length of aluminum (or wood) to the correct diameter and taper (allowing for the thickness of the sandpaper).
            Please elaborate. I understand about making the jig, but how do you hold the sandpaper on the taper?
            If ignorance is bliss, why aren't there more happy people?

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            • #7
              I have two round insert holders at work,neither of them have a tapered pocket.
              I just need one more tool,just one!

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              • #8
                Why have I never thought about a carbide insert for woodworking? DUH? I think I will make one, seems it would save a lot of gouge sharpening. Back to the thread, it seems a center cutting end mill would make a workable pocket for an insert. Bob.

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                • #9
                  Originally posted by sbmathias View Post
                  Please elaborate. I understand about making the jig, but how do you hold the sandpaper on the taper?
                  You can use PSA sandpaper or 3M - 90 spray adhesive. The 90 holds quite a bit better than 77. Double sided tape will also work. It's also very handy for holding wood workpieces on the lathe. The professional grade has a lot of holding power. I know one turner that does 24" platters and only uses double sided tape to hold them on the lathe.

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                  • #10
                    Originally posted by wierdscience View Post
                    I have two round insert holders at work,neither of them have a tapered pocket.
                    Theres acouple lathe tools at the place i work for that are also straight... but the inserts used are not positive rake (not saying positive will not work or fit) which might be the reason behind the strait walls, they are more versatile.


                    Originally posted by Bob Fisher View Post
                    Why have I never thought about a carbide insert for woodworking? DUH? I think I will make one, seems it would save a lot of gouge sharpening.
                    It does... made one a while back, took some getting used to though... cant control it the same as you do with a fluted gouge... also took a piece of a broken carbide boring (for get the size, maybe 5/16 or 3/8) and sharpened a flat on the end kind of like a flat head screw driver (using a wet tile cutting saw) and stuffed it in the end of a 5/8 or 3/4 bar stock and use it to rough out a vessel... boy does that thing work good and stays sharp.

                    _
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                    • #11
                      I would take a 5/8 or 3/4 rod of tool steel or 4140 and turn a little taper at the end of it, so that it matches the shape of your insert. Then mount this rod in the mill and chop off half the tip so that the cross section looks like a D. Then harden it. You now have a tool that can cut pockets just like your insert. However, it has no back relief, but whatever. Since this tool is not quite center cutting, drill your hole first, and then move over by about .001-.003 like toolguy said. Plunge slightly past depth with a 1/4" end mill. Then plunge to depth with a 1/2 end mill. Then use this tool.

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                      • #12
                        I don't really think you would want tapered walls, With a posative rake insert, straight walls, but shorter then the height of the insert would contact the (softish) steel ridge to the (hard, brittle) carbide side, providing decent support and location without risking damage to the insert.

                        For a negative rake (0 clearance) insert, I think you would want sort of 'dovetail' walls, maybe with a small recess milled in so that the cutting edge corner of the carbide does not touch the insert holder at all and it is only supported by contact with the flats.
                        Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                        • #13
                          Originally posted by elf View Post
                          You can use PSA sandpaper or 3M - 90 spray adhesive. The 90 holds quite a bit better than 77. Double sided tape will also work. It's also very handy for holding wood workpieces on the lathe. The professional grade has a lot of holding power. I know one turner that does 24" platters and only uses double sided tape to hold them on the lathe.
                          Still not sure this would work - after all, the insert is only about 1/8" thick. Trying to glue sandpaper to this small area would seem to be a challenge. I may try beanbag's approach of making my own limited-use tool to cut the recess. If I can just find something that will hold up to a cut or two.
                          If ignorance is bliss, why aren't there more happy people?

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                          • #14
                            Originally posted by sbmathias View Post
                            Still not sure this would work - after all, the insert is only about 1/8" thick. Trying to glue sandpaper to this small area would seem to be a challenge. I may try beanbag's approach of making my own limited-use tool to cut the recess. If I can just find something that will hold up to a cut or two.
                            You can make the taper as long as you like to hold the sandpaper. It doesn't need to be only 1/8" wide. Actually you don't even need a pocket for woodturning. The pocket is mostly for ensuring the insert stays in the same place when rotated or replaced. Neither of these is very important in a hand-held tool. I'd probably worry more about the wood chips jamming in the cracks than the support.

                            If you want to use the tool for deep hollowing consider mounting the insert on the bottom of the shaft after milling the shaft to the centerline. The top of the shaft will act as a chip breaker and also limit the depth of cut in case of a catch. It also gives you the minimum size opening. This is the way I've made most of my deep hollowing tools, but I've used HSS ground to various shapes instead of inserts.

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                            • #15
                              I just realized that if you have a 4 jaw, you can mount your tool holder on the lathe and make your tapered pocket that way. Set your compound at 7 degrees.

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