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Thread: 1/2" vs 1/4" shaft router bits

  1. #1
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    1/2" vs 1/4" shaft router bits

    Do 1/2" shaft stay tight better then 1/4" shaft bits. I been cutting dove tails and have hasd several times where the bits have come loose in the middle of cutting dove tails. They are 1/2" 14* bits with 1/4" shaft. The router is a Milwakii 5614-24 and it is almost brand new and I tighten the dickens out of the collet. It would make sense to me since you have 4 time the surface area to grip.
    "There’s a lot of work being done today that doesn’t have any soul in it. The technique may be the utmost perfection, yet it is lifeless. It doesn’t have a soul. I hope my furniture has a soul to it." - Sam Maloof
    The Pessimist complains about the wind; The Optimist expects it to change;The Realist adjusts the sails.~ William Arthur Ward

  2. #2
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    I have had the same thing happen.

    Now I tighten the c##p out of the 1/4 collet - then part way into the dovetail cutting I will retighten again.

    I got a 1/2 bit - but it will not fit with the collet, so I couldn't use it.

    And based on the laws of physics - the contact area of a larger bit has nothing to do with holding power. The holding power is directly a function of clamping pressure.

  3. #3
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    Might be worth taking the collet out and cleaning it with some mineral spirits. Use something like a .22 gun brush to make sure there's no grease or sawdust in the collet. Give the shaft of the bit a good cleaning too...
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  4. #4
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    Couple of issues here, Don.

    1/2" before 1/4" if it is available in the profile you want and if it fits the jig you are using it with; not the least of which is the amount of metal that comes in contact with the collet when mated up into the machine.

    But your issue is not with the diameter of the shank. It is with the bit creeping out of the collet. Yes?

    Bit creep, in my experience, has always been a matter of dirt. The collet, nut, socket, and shank must be operating room clean. All that keeps things together here is a mating of dry, clean metals.

    First check the shank. Clean with solvent and allow no residue. Then check for any burrs from bit spinning. If you find them you get to trash two items, the bit and the collet.

    Then clean the collet/nut and socket. No left over residue. No lubricant of any nature. Dry, clean mating. This is how it was designed.

    Collets are consumable items, not permanent tool fixtures. Over-tightening them will also render them unfit for duty. Over-stressed metal is distorted and applies pressure unevenly.

    Dirt and burrs detract from a clean, dry. tight mating of the metal of the shank and collet. A 'tight' collet is loosened when the dirt is smashed further into a pancake due to the high speed spinning of the bit and the lateral stress placed on the cutter when routing. Its not much but it certainly can be enough for things to creep.

    Now before you guys line up to shoot me and pepper me with "but" stories, there are exceptions to everything - for a while. My observations have been over the years with many, many students - not just my own experience. And I have a story about a newbie student, a new pair of jeans, and a router bit that came out of the collet at full speed. But I'll save that for my safety demo! Suffice it to say that shorts were stained. And the collet and socket were dirty with dust and pitch.

    One more thing with regard to technique; allow the cutter to cut. Do not force the cutter. That problem is more likely with a scraping type cutter in the collet. A cutter than presents its cutting edge to the wood fibers blunt, straight on is a scraping type cutter. A dove tail bit is an example. A shear type cutter presents its cutting edge to wood fiber at an angle, like a spiral bit.

    FWIW, a dove tail cutter presents another problem. It is an undercutter. That means the swarf cannot easily get out of the cut. That combines for two things - heat and a small amount of pressure. The heat serves to more rapidly dull the cutter. The pressure is minute but comes from swarf trying to get out of the cut. Slow down the rate rate of travel, but not so slow as to unnecessarily "dwell" in the cut. That overheats the cutter as well.

    All these little things can add up to trouble. Big things in life take care of themselves when the little things are carefully attended to.

    This is the retired Router Lady breaking her own rule about answering router questions on an open forum. Be kind.

  5. #5
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    Quote Originally Posted by Leo Voisine View Post
    And based on the laws of physics - the contact area of a larger bit has nothing to do with holding power. The holding power is directly a function of clamping pressure.
    I don't think this is correct. I believe what is happening is the 1/2" dia of the cutter is just to much for that little 1/4" shaft. the radius of the bit 1/4 inch is twice that of the radius of the shaft. The 1/2 collet is 4 times the area to grip the torque that the 1/2 bit transmits to the shaft would be distributed to much larger area. The collet is like brand new, I've only used it for a few practice dovetails. I have the 1/2 collet so I think it's worth a try. The only thing that I can see is the guide won't be necessary sine the jig is designed for a 1/2 dovetail. The contour will change.
    "There’s a lot of work being done today that doesn’t have any soul in it. The technique may be the utmost perfection, yet it is lifeless. It doesn’t have a soul. I hope my furniture has a soul to it." - Sam Maloof
    The Pessimist complains about the wind; The Optimist expects it to change;The Realist adjusts the sails.~ William Arthur Ward

  6. #6
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    Thanks Carol, I was hopping youd see this. The collet like I said is new as was the cutter. I'll check them out as you suggested.
    I'm still gonna pick up a 1/2 shaft bit..
    "There’s a lot of work being done today that doesn’t have any soul in it. The technique may be the utmost perfection, yet it is lifeless. It doesn’t have a soul. I hope my furniture has a soul to it." - Sam Maloof
    The Pessimist complains about the wind; The Optimist expects it to change;The Realist adjusts the sails.~ William Arthur Ward

  7. #7
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    one thing i didn't see mentioned.......do not bottom the bit in the collet before tightening.
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  8. #8
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    Quote Originally Posted by tod evans View Post
    one thing i didn't see mentioned.......do not bottom the bit in the collet before tightening.
    No tod, thats one thing I always check on but it is a good thing to point out for others.
    "There’s a lot of work being done today that doesn’t have any soul in it. The technique may be the utmost perfection, yet it is lifeless. It doesn’t have a soul. I hope my furniture has a soul to it." - Sam Maloof
    The Pessimist complains about the wind; The Optimist expects it to change;The Realist adjusts the sails.~ William Arthur Ward

  9. #9
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    Could be an undersized bit. I have seen that on some import bits and even on a Whiteside once.
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  10. #10
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    Quote Originally Posted by Jay Caughron View Post
    Could be an undersized bit. I have seen that on some import bits and even on a Whiteside once.
    After I saw your post I put the mic on it, nope.

    After what Carol said I took the collet apart and it looked good but there was some dust in the slits and the shaft was buggered up on the bit so I'm just gonna scrap the bit. I cleaned the collet and will get a new bit. Think I'll go with the 1/2 in shaft though.
    "There’s a lot of work being done today that doesn’t have any soul in it. The technique may be the utmost perfection, yet it is lifeless. It doesn’t have a soul. I hope my furniture has a soul to it." - Sam Maloof
    The Pessimist complains about the wind; The Optimist expects it to change;The Realist adjusts the sails.~ William Arthur Ward

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