The Society of American Period Furniture Makers

Tools and Techniques => Power Tools and Shop Safety => Topic started by: bbrown on April 28, 2013, 08:46:28 AM

Title: mortise chisel bit source
Post by: bbrown on April 28, 2013, 08:46:28 AM
  I'm trying to find an inner drill bits for my Delta chisel mortise.  I snapped my 1/4 bit doing mortises in curly maple (for a sugar chest I'm doing).  I searched and could not find  just the inner drill bit.  I asked this on "Lumberjocks" and got no replies.  I don't need the whole thing, just the inner drill bit. 
        I figured Y'all are smarter and someone here would know    :)

    Also, along this line - what do folks recommend for mortise chisels?   Seems they should not be snapping when used properly.  I suspect there is much variation in quality as reflected in the wide range of prices I see.

   --Bill

 
Title: Re: mortise chisel bit source
Post by: msiemsen on April 28, 2013, 02:56:23 PM
Bill,
The darn things vary in diameter and length. I have a bunch of used ones and I could send you one if you want to send the broken one I could try and match it.
As to why they snap, do you have enough clearance between the bit and the chisel? If the bit stuck in the chisel it would snap. The rule of thumb is to stick a business card under the flange on the chisel and slide it in, put the bit all the way in and then remove the card and shove the chisel the rest of the way on. Bit could have been dull as well. I usually check sharpness first on just about any problem, check it second and third as well.
Title: Re: mortise chisel bit source
Post by: bbrown on April 28, 2013, 06:55:23 PM

  That's helpful - thanks Mike.

  It's a Delta benchtop mortiser; 1/4 inch bit needed; 5/8 inch shank.  I'll try to send a personal message with my address.  Really appreciate the help.

   I did not check clearance, and was probably hogging too much material at once.

   What do folks recommend for new mortising chisels? 

   I know I can do this by hand or with a router; I just like the ease of the  machine (and would love a heavy duty model some day).

  --Bill
 

 
Title: Re: mortise chisel bit source
Post by: Mickey Callahan on April 29, 2013, 10:16:26 AM
Bill,

If I were you, I'd replace the chisel also. More than likely when you broke the auger bit, the chisel was damaged also. Look for hairline cracks on the surface of the chisel. This is likely since you say you were not allowing for proper clearance between the auger bit and the chisel. I believe most of the bench top mortisers, such as Delta, Jet and General use interchangeable chisels and can be purchased either in a set or individually from Woodcraft and other suppliers of those machines.

Mickey   
Title: Re: mortise chisel bit source
Post by: bbrown on April 29, 2013, 10:29:25 AM

   But Mickey, I'm of Scottish descent: ie: thrifty.

But I do think I need to bite the bullet and spend the money to buy a set.

   Thanks for the reply,

          --Bill
Title: Re: mortise chisel bit source
Post by: wrduffield on April 30, 2013, 02:15:04 PM
You will break fewer hollow chisels and bits if you balance the lateral forces on them. This takes a little calculation, or at least finesse. When you plunge the chisel into the wood, the forces on the front and back of the chisel (from the side walls of the mortise) are in balance. When you make your first plunge, the forces on the sides of the chisel are also in balance. If you move over one mortise width and plunge again, the forces on the sides are very out of balance, since you have wood on one side and air on the other. This is what eventually breaks the chisels. So, instead of moving over the width of the chisel, move over about twice the width of the chisel, but no more. You want to plan this distance so that as you repeat these plunges, you last one cleans out the other end of the mortise. All of these cuts are balanced, since there is wood on both sides of the chisel. Then go back and cut out the remaining bridges. These cuts are also balanced, because they have air on both sides of the chisel.

William Duffield
Greenwich, NJ
Title: Re: mortise chisel bit source
Post by: bbrown on May 01, 2013, 08:19:46 AM
   Excellent points.   This is especially important for a small bench-top model like my Delta.

 Thank you William.
Title: Re: mortise chisel bit source
Post by: Mark Bortner on May 02, 2013, 12:32:53 AM
Watch ebay for Forrest City, Morris Wood Tool or Greenlee. Alot of the old Delta actually were made by Greenlee. Don't waste your time with anything imported. You can buy them new at crazy prices but the first time you use them you WILL see the difference!
Title: Re: mortise chisel bit source
Post by: bbrown on May 02, 2013, 07:30:07 AM

   Thanks Mark,
    Prices seem to vary tremendously.   You sometimes get what you pay for, but not always. I was looking for good quality at a decent price point.   Thanks a lot for the recommendations.  I was not familiar with any of these brands.

   -Bill




Title: Re: mortise chisel bit source
Post by: ttalma on May 14, 2013, 12:22:07 PM
Also I would add the mortising drill bits sold with the cheap sets are a brad point bit in a mortising chisel.

The ones mark mentioned are mortising bits. there should be no point in them and no screw at the end. You are trying to make small chips that are lifted out of the hole. The cheap sets can produce curls which get stuck in the chisel and heat up the bit and chisel.
Title: Re: mortise chisel bit source
Post by: bbrown on May 14, 2013, 06:34:53 PM

  Thanks talma.

  I found Austrian made Fisch brand mortise chisels on Amazon.  They are expensive I assume must be well made (?).
Whilst there I noted that the Delta brand got terrible ratings - seems they snap and break for others too, unless we  are all using them improperly.

   -Bill