From: tip@lead.aichem.arizona.edu (Tom Perigrin)
Newsgroups: rec.woodworking
Subject: Re: Handcutting Dovetails
Date: 24 Jul 92 01:28:15 GMT
Distribution: world, na, usa
Organization: University of Arizona UNIX Users Group

Okay, a number of people have asked in e-mail about my mixed power tool
hand dovetails,  so I'll do it again.   Maybe this time I'll be smart enough
to save a copy?

The idea is to use power tools to hog out most of the wood, leaving just little
bits to clean up afterwards.   I looked at the tails, and decided that they
were the best candidates for hnad finishing, since thy have those acute 
angles in the corners.   If you look at the pins, you notice that the bottom
of the gullet meets the pin at a 90 deg angle,  offset from the face of 
the board.   Since somebody asked about the definitions, let me give some
ascii graphics:


	tail                                            pins

  -----------------------------                -------------------------
  |        |         |        |                |       /      \        |
  |        |         |        |                |      /        \       |
  -----------------------------                -------------------------

                                           
            ----------                         ---------        -------
            \        /                         |     | |        | |    |
             \      /                          |     | |        | |    |
   -----------      ----------                 |     --------------    |
   |                         |                 |                       |





So,  I use my table saw to cut the pins first.    I turn the miter gauge to 
the desired angle,  and set the blade hieght to the thickness of the boards.

Now, imagine taking the pin board, and placing it against your miter 
gauge, and running it through the balde once.   You get



  -------------------------
  |       / /             |
  |      / /              |
  -------------------------

                                           
  -------------------------
  |     | |               |
  |     | |               |
  |     ---               |
  |                       |

Do this a number of times  (or use a dado blade)  until you get:


  -------------------------
  |       /       /       |
  |      /       /        |
  -------------------------

                                           
  ---------     -----------
  |     | |     |         |
  |     | |     |         |
  |     ---------         |
  |                       |




This is all the further you can go with this setting of the miter gauge.   Do
the rest of the pins,  to this half way stage.    Now,  flip the mitre gauge
around to the other angle,  and clean up the last triangle, which is marked
with x's below.



  ---------------------------
  |       /       /x\       |
  |      /       /xxx\      |
  ---------------------------

                                           
  ---------     -----------
  |     | |     |xxx|      |
  |     | |     |xxx|      |
  |     -------------      |
  |                        |



This gives you your pins.    Clean up with a chisel to desired 
degree of smoothness.   Although I have illustrated only two pins per
board, you can make any number you want.  Fist cut all of the "left slants",
flip your miter cgauge, and cut the remaining triangle n the "right slant".


Now use these pins to mark your tails.  I then use a 1/8'th or 1/4 inch
band saw blade to cut most of the tail out.   On this simple graphics
example you just cut to the line.    But when you are workinging between
two tails on a board, it is a little more work.   I need to use four cuts...
the first is a long slope from (say) upper left to middle bottom, and 
then straight to lower right.   This doesn't free any wood.   I then cut 
the right hand side line to the corner.    A largish chunk falls out.
Then I go back and cut from middle bottom to lower left.  This doesn't 
free up any wood.  I then cut the left hand line.  The remainder falls
out.   Since you have cut to the INSIDE of the line,  you now pare to the line
with your chisel.   Or if you are VERY good wsith the band saw,  you can try 
to cut to the line.  I do that for wood boxes and rough stuff.

Note that there are some strict limitations.  Not all widths and sizes of
boards fit nicely on the band saw.  You need to use a thin blade, or be 
prepared to do a lot of chisel work.  This technique needs to have the tails
spaced at least 2* or 3* as far apart in the gullet as your blade is wide.
So a 1/4 blade means you need to have at least 5/8 width in the gullet.

I find that I have to spend some attention to clean up the gullets of 
the pins if I make them with multiple passes with a normal blade,  but the
sides are smooth enough.  The tails need more attention, since my old Sears
bandsaw wobbles and leaves a rough surface on the tails.   So I think I save
about 50% to 75% of the time compared to doing them by strict hand mthods,
unless I am just building a crude step stool for the garden or something, 
in which case I just saw to the line and bang it together.  Then this is
a clearly faster method.
Newsgroups: rec.woodworking