I have to drill out some mortises that are NOT centered in table leg I am
working on. That means I can't press the bit down to make a hole and flip
the piece to see if the point goes into the hole I just made. I have been
experimenting on some scrap but I am always a little off. Why do I care?
Before I start I cut a line with a utility knife on the sides of the mortise
to "catch" my chisel blade but if I am a little off, I lose one of the
lines. Am I just being too picky or is there some tip one of you can give me
to get it dead center? BTW, the mortise is 1/4" wide.
I have a fence but even when I place the piece against the fence, drop the
tip of the drill bit down to just tap the wood and then snug the fence up to
the wood, I am still not getting the cut perfect. Maybe I should make fewer
holes with my drill press thereby leaving a bit of my scribe line to catch
the chisel blade.
I'm saying set the fence and test. If it's proud, adjust it back a
squinch. If it's now not perfect, it should be a little too far
back. If so, use a shim rather than fiddle w/ it unless have one of
the adjustable jobbies w/ the threaded positioner or have made
something similar yourself.
There is, of course, the alternative of locking the quill down and
measuring from the near side of the bit face to the fence w/ dial
calipers, but that would seem over kill...
Guess I'm not following.
Router bit is visible as it penetrates wood.
Jig lets you maintain registration form piece to piece such as table
legs, which will be more difficult trying to do on a drill press.
What I meant was that I can see the forstner bit as it enters the narrow
piece of wood. I have a good fence that I made for my drill press so I can
get repeatable results. This might just be psychological but it is hard to
see through the router base to see what is really happening. I supposed if I
used a router a lot for mortises there would be no issue. Clearly there is
much less chiseling required with a router and jig and maybe none if I round
the ends of the tenons to match the radius of the router bit.
Lew, would you mind telling me what jig you are using? I made one based on a
posting some time ago in this group. Did you make your own, and if so, is
there a link to it so I can see what you are using?
I modified this design:
All Stainless steel
1/4-20 x 2" HEX head bolts, flat washers and wing nuts.
10-32 x 1/2" flat head machine screws to attach jig to router base.
Maple 3/4 x 1-1/4 with 5/8" dia x 1/2" dp counterbore and 9/32' thru
hole for hex head bolts.
I refuse to use carriage bolts, the the counterbored holes above.
Assemble a washer under head of bolt and insert into counter bore and
snug up with another nut.
Pour epoxy fairing putty into counter bores a little proud and let
cure 24 hours.
1/4" plywood rather than hard board.
Get some 16x16 grid graph paper and glue it to the plywood with
contact cement of 3M spray 77.
Align the graph paper with a major grid line running down the long
(major) centerline of the plywood.
Working from the graph paper side, layout the slots for the 1/4"
bolts, 2" thru hole and your router base(Mine was a PC-90).
Using clear packing gun tape, cover the graph paper to seal and
Perform all machining operations including c'sinks from opposite side
to accept router body mount screws.
Remove 1/4x20 hex nuts used to sung bolts previously, while epoxy
Break any rough corners with some 150 grit, then seal all raw wood
with 3-4 coats of 1/2lb shellac.
(I get better results than with 1 coat of 2 lb).
Let cure a couple of days and have at it.
You may not have picked up on it yet, but using the graph paper to
locate the 3/4 x 1-1/4 runners, you need no other layout tools to get
dead nuts, repeatable mortises, piece after piece.
The only pencil layout required are the end lines for the mortises and
you will be able to visibly see the cutter come in contact with the
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