Replies

1. 
   joinerswork | Jan 18, 2007 09:49pm | #1

   Arch,

   There is a lot of friction involved in getting all the waste thru the limited space between the bit and the chisel.  They always run hot, moreso the smaller the chisel, and worse with resinous woods.   Sharpening of both the bit and the chisel helps, as does application of a little wax from time to time.

   The cone shaped abrasive "wheels" are good, and need to be augmented with  a small tri-corner file to work into the inside corners.  Lightly dress the wire edge on outside of the chisel, and avoid honing a taper onto it, which will make it wedge in the hole.

   Sharpen the bit as you would an auger bit, with auger bit file, and hone with a carver's slipstone if you want to be real keen.

   Regards,

   Ray Pine

2. 
   jako17 | Jan 19, 2007 02:08am | #2

   I agree with Ray 's post.However to add a couple of points .Ensure that the ejection slot is facing the hole previously drilled and spray Dri-Cote on the drill through the slot.I also find that taking several plunges rather than one steady feed helps cut down on the friction

    

    

1. 
   philip | Jan 19, 2007 10:34am | #3

   Jako, spraying a lube of some sort may be a cure but it is prevention that is required and better in the first place.
   Assuming that the chisel and augur are properly set in relation to each other, i.e correct clearance, correct sharpness and the augur cannot move upwards in the chuck when under load, or the chisel be pulled down onto the shoulders of the augur when withdrawing, then there could be a hot spot-usually when the augur is bent or the chisel full of resinous material. A good cleaning and inspection will soon show where there is rubbing. Bent augurs need to be binned, and chsel bores need to smooth polished.
   They do run hottish at any time-far too hot to touch, but one cannot destroy them by heat unless the augur shoulders are pushed onto the chisel-and the noise this makes should be sufficient to cause one to stop and investigate- quickish.Philip Marcou

1. 
   jako17 | Jan 21, 2007 06:35am | #4

   Hi Phillip,  a belated happy birthday. I totally agree with you.The point I was making is that dri-cote reduces friction regardless of the internal polishing and also slows resin build up.I believe it is ptfe in a solvent which I prefer to the previous suggestion of wax.

2. 
   tinkerer2 | Jan 21, 2007 07:00am | #5

   What do you mean by "augur shoulder pushed onto the chisel?"  What little I have done, I try to set the bit slightly below the points of the chisel.  Is this what you are referring to?

1. 
   philip | Jan 21, 2007 10:32am | #6

   Depending on the type of chuck, the augur can be forced upwards in the chuck until its shoulders contact the chisel- it is fatal unless stopped in time. Those machines that just rely on a drill type chuck are liable to do this, they need to be very tight.
   Conversely, if the chisel is not securely clamped, it can be pulled down onto the augur when it is withdrawn-same effect.Philip Marcou

1. 
   tinkerer2 | Jan 22, 2007 05:04am | #7

   Now for the really stupid question, what is the shoulder of the bit?  I have an idea but I need to be sure.  My mortiser is a PM - a pretty good one, I think, but it does have the drill type chuck.  The first time I used it, I put a half inch chisel in and it went down about one eighth inch.  I just about bent the handle and it wouldn't budge.  Finally noticed it was against the stop.  Adjusted that and it worked great.  Had never tried a mortiser before.  It has worked fine for what little I have used it but I would like to avoid any future trouble.

2. 
   philip | Jan 22, 2007 07:30am | #8

   Not a stupid question at all-if you don't "get" it , it is a recipe for bad results.
   The shoulder I am referring to: take an augur and hold it so the point is up-that sloping part just below the knicker(s) where the fluting comes out is it. There should be some clearance between this and the coned part of the hollow chisel.
   The thing to note about the drill type chuck is that there is no depth stop for the upper end of the augur- it may happen that the augur is too short to be pushed right to the back of the chuck when one sets it up and that is when there is a chance of it being pushed up under load. If I had to use this arrangement and found that the augur did not reach all the way up the chuck I would braze on an extension so it could.
   Folk are shy of hollow chisel mortisers -because they are not paying attention to certain critical details.Philip Marcou

3. 
   user-211435 | Jan 22, 2007 08:21am | #9

   I use these on a regular basis, although not with a lightweight machine like you use, and find that the clearance that is set between the bit and the chisel to be very important.  You should experiment a little and you will know exactly how much is just right.  I personally make sure that the flat bottom of the drill bit is just a bit below the points of the chisel, but it depends on the size of the bit.  I have found that too much clearance allows the drill bit to bend a bit more and also allows larger chips to get stuck.  Less clearance seems so cause less heat but it becomes harder to push the chisel into the wood.

   One thing that helps with the heat is to drill faster.  There is actually a perfect speed that is right between too slow and too fast.  Try drilling faster than you are and you will probably see a decrease in heat.  You should drive the chisel in fairly rapidly.

   Another thing that I have started doing is turning the machine off between mortises.  I don't mean between each cut, but while shifting the board in your machine to the next mortise or maybe the other end of the board.  Leaving it running just keeps heating any debris left between the drill bit and the chisel.

   Hal

   http://www.rivercitywoodworks.com