Replies

1. 
   IainEdwards | Oct 04, 2004 01:08pm | #1

   JP

   this is a first, I've never heard of the problem and I've been using Clico tooling for a long time in a sedgwick 571 mortiser. How big are the chisels?

   What may be happening, particularly in the harder woods and certainly on longer run jobs ....

   The drill bit subject to great heat and pressure as a by product of cutting, it will of course lose its edge quite quickly and become much less efficient.....As you're working and in the 'zone' you'll end up exerting even greater pressure to cut the mortise. This additional pressure might well have overcome the the grip the chuck has on the bit. This will force the bit further up the hollow chisel. You can see what's coming next.........The cutting face and spurs act as a wedge forcing the walls of the chisel out. This area of the chisel will have undergone a heat treatment at manufacture for the purposes of edge retention and consequently become more brittle so it is more likely to crack as opposed to bend.

   I'd check the drill bit for sharpness, and clean the drill chuck out ensuring no grease/oil on the jaw faces......you might even consider roughing up the drill shank to help the jaws grip..

   hope this helps 'cause those things aren't cheap take care Iain 

2. 
   JohnWW | Oct 04, 2004 09:49pm | #2

   Jason,

   Improper technique can put extra strain on a chisel and lead to the problems you are having. 

   A few weeks ago I wrote a lengthy reply to someone who was having a similar problem, the bits were overheating and snapping off.  If you set up the job the way I described in the earlier posting, it may solve your problem.  Go to advanced search at the top of the left hand column and enter message number 18964.11.

   One thing not mentioned in that posting is the need to keep the bit and chisel sharp, which can be a problem if the metal has overheated and lost its temper.

   John W.