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Thread: Mortising bit gets stuck

  1. #1
    Join Date
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    Mortising bit gets stuck

    I just purchased a bench top delta mortiser and went to try it out to make sure everything worked ok. I had borowed the same machine from a friend to make a bed for my grandson and it worked pretty well so I decided to get one of my own since I have orders for two more beds (granddaughters). Set the machine up, put the drill and chisel in like I did with my friends machine and when I started drilling the bit would not come back out of the wood (white oak) I tried some soft red cedar, same result. Tried to sand the bit with some 600 grit wet dry, same result. What's going on fellas?? My friend said he never had this problem. I have to actully take a hammer and knock the bit out of the wood. Help me!

  2. #2
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    I would try honing the bit more. I bought a cheap set of woodcraft bits when I bought my mortiser, and they came with noticable machining marks on the sides. They wooked decent that way, but since I have honed them to a mirror finish they work much better. If your bits are smooth I would still try to get them as smooth as a chisel or plan iron.

  3. #3
    I slightly bevel the sides of the bit (like hollow grinding teeth on a saw). Remember that if the chisel isn't really sharp the wood will bend into the cut before shearing. This leaves a Chinese finger trap-like effect and will jam the bit if the bit is tight in the hole.
    .
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  4. #4
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    If you have an accurate set of calipers or a micrometer, measure the chisel and make sure it isn't tapered. Then make sure the drill bit is adjusted about the thickness of a dime below the bottom of the chisel. If you want to hone the chisel, start with 220 grit and work your way toward 600 grit being careful not to taper the chisel. Of there are rough machining marks on the outside of your chisel it will tend to stick in the wood.
    Lee Schierer
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  5. #5
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    +1 on your honing method. Did you use a flat stone to hone the sides? I use an oversized diamond plate although anything that will allow reliable, controlled contact with the abrasive should be fine. Like Lee says; a mic will tell you if you have developed a trumpet or 'flared' bit. On square chisels the mantra seems to be sharp, sharp, sharp.
    Last edited by glenn bradley; 11-28-2009 at 11:43 AM.
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  6. #6
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    Lightbulb a few HC mortiser thoughts...

    Hi Ray,
    I'll toss in my 2cents.
    I prepare for hollow chisel mortising by:

    -sharpen the auger in 3 places which are obvious
    [LV will sell you an auger file, which cuts on only 2 faces at a time, to protect adjacent]
    -hone the 4 chisel sides
    -cone hone the chisel inside
    -deburr the chip ejection port
    -my General Int. does Not want the auger dropped a bit which is the standard HCM advice, mine performs best fully seated
    -ensure the chisel is plunging square both ways or suffer jamming
    -I touch the hot chisel with a bar of parrafin wax to keep it lubed, and also to shush any banshee screeching
    -if you do the classic bit slight drop... and leave too large a gap...
    you will cut a square hole with a circle bit out of it, no good - scallops
    -by the time the chisel in in a state of readyness, it is treacherous to handle - like a handful of razors -the spurs bite! (bleeding sucks)

    I have covered such points more thoroughly in the GMchair thread, but it
    has become huge and unwieldy, to try to find a specific reference...

    *edit*I braved the big thread and found a relevant posting*
    which includes pics of my first through mortises, which were a scalloped mess
    http://www.sawmillcreek.org/showpost...1&postcount=91
    There were many other such mortising references in the monster thread.

    good luck with it,
    let us know how you make out
    Walt

    ps My early results in dense white oak were not terrific, but time and effort seem to have improved them
    Last edited by Walt Caza; 11-28-2009 at 1:15 PM. Reason: found a link...
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  7. #7
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    Just to clarify, when guys talk about honing the chisels they mean the outer surface of the chisel, right? Can this be done in the same manner as one would lap the back of a hand chisel or plane iron?

  8. #8
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    Wink yes outer, and yes inner too...

    Quote Originally Posted by Walt Caza View Post
    Hi Ray,
    I'll toss in my 2cents.
    I prepare for hollow chisel mortising by:
    -cone hone the chisel inside
    Zach,
    Yes, the outsides are honed on four sides as a flat chisel would be.
    As I said in post #6, the inside of the hollow chisel is also honed,
    with a pair of abrasive cones.
    (you can see them in my link in that posting, there's a photo of cones)
    good luck with it,
    Walt
    There are no shortcuts to anywhere worth going! WCC

    Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind - Dr. Seuss

    Crohn's takes guts. WCC

  9. #9
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    Hey Ray,

    Don't you have a hold down that will hold the wood down as you retract the chisel?

  10. #10
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    Quote Originally Posted by BOB OLINGER View Post
    Hey Ray,

    Don't you have a hold down that will hold the wood down as you retract the chisel?
    That was my question as well. My Delta mortiser does stick a little no matter how sharp the chisel points are (inside and out) and how smooth the outer 4 sides of the chisel are.

    If I don't use the hold down, the workpiece will lift off of the table and hang off of the bit.

    I still use the cheap bits/chisels that came with the mortiser as well. I figured this is normal (otherwise a hold down wouldn't be included).

    I've never had to use a hammer to separate the workpiece from the bit though... if you can't pull it off by hand, something seems wrong.

    Is the bit 90 degrees to the table?

  11. #11
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    Jan 2005
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    Central Kentucky
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    Well as a last resort I'm going to call Dewalt in the morning and tell them my problem. I;ve tried everything that was suggested, sanded, honed, polished, adjusted and it still sticks in the wood, and have to pound it out with a hammer!!! And ,yes it has a hold down which does not help. I used a c clamp thinking that would help to no avail. I'm starting to think the chisel is going in at an angle, the table is not flat or the head is crooked. I've tried all the different chisels that come with it,same result, I,ve tried all the chisels on my friend,s machine and the only one that worked was the 1/2 in. that he had used to make a futon and a crib (wore out?) Thanks for all your help fellas, I'll let you know how I come out.

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