Replies

1. 
   derekcohen | Jun 08, 2008 06:41am | #1

   Hi Brian

   I have published two such jigs ..

   http://www.inthewoodshop.com/ShopMadeTools/AJigforParingDovetailBaselines.html

   http://www.inthewoodshop.com/ShopMadeTools/ANewJigforParingDovetailBaselines.html

   Hope this is what you are looking for.

   Regards from Perth

   Derek

2. 
   rwdare | Jun 08, 2008 07:00pm | #2

   Brian, your problem is probably caused by taking too large of a bite with your chisel. After cutting your tails, use a coping sae to remove all but an 1/8" of the wood. Then pare the remainder in THIN shavings. If you try to chop the waste with a lot remaining, the bevel forces the chisel to undercut.

   Dick

3. 
   AdamCherubini | Jun 08, 2008 07:45pm | #3

   Brian-

   If you don't cope out or try to pare the waste bit by bit, a jig won't work. What you need to know is how chisels work (not how to use them). Chisels work by either paring or chopping.

   Paring- I define a pare as the removal of waste so thin that it exerts no significant pressure on the chisel.

   Chopping- In a chopping operation (whether you are using a mallet or not) the waste is so big that it exerts significant (or equal) pressure as the non waste side.

   Here's what you need to know. If you take a chisel that is beveled on one side, hold the flat side perpendicular to the wood and push straight down, the chisel will under cut (move toward the flat side). The reason for this is that the wood doesn't care what direction you want to go. All the wood sees is a wedge and wedges exert equal pressure on both sides.

   So here's what you must do:
   1) forget the jig. It won't work, except for a pare and you don't need it for that.
   2) When you chop out dt waste, set the chisel on the waste side of the line, and pull the handle back a little over the keep side. As you chop (or push) the chisel will naturally cut straight down and back to the scribed base line. I often hold my handle perpendicular to purposely undercut between the tails.
   3) The other choice is to cope out or pare bit by bit.

   This all just takes practice and a little mindfulness. Try it, pay attention, and examine teh results carefully.

   Good luck

   Adam

4. 
   Samson | Jun 09, 2008 06:13pm | #4

   If you are talking about the baseline, then an angle is of no consequence.  Indeed, most of us purposefully bevel from the baseline to the middle fo the board on each side.  This end grain portion doesn't add to the strength of the joint anyway, so having the undercut helps the fit and doesn't undermine the strength. 

   To chop out the waste, place the flat back of the chisel three thick pencil lines away from your scribed baseline on both sides - perpendicular to start - subsequent chops at a slight angle to create the slight V I mentioned.  After the bulk of the waste has been removed, go back and carefully pare the modest waste you left to achieve a perfect fit. 

5. 
   MikeHennessy | Jun 10, 2008 03:26pm | #5

   Ditto what Samson said -- exactly.

   If you want a great primer on dovetail joints, pick up Frank Klaus' video on dovetailing drawers. He does a great job of explaining what you need to sweat and what you don't. Well worth the $$$ IMHO. One of the best instructional pieces I've ever seen for someone just starting hand dovetails.

   I'm not sure what you mean by needing to use a chisel to "fine tune" the tails. If you mean your saw cuts aren't square, you might wanna work on that rather than finding a jig to square your chisel.

   Mike Hennessy
   Pittsburgh, PA