Thursday, 7 August 2014

Pattern Routing Work Holding Jig

Fine Woodworking magazine for the month of  July/August 2014 issue 241 has plans for a Smart Jig for Pattern Routing by Tim Celeski to hold a template and work-piece when pattern routing. Over the years I have made occasional jigs to do such things but they have always worn out, broken or fallen by the wayside. So I decided to make the one described by Tim in the magazine. Credit for the design goes to Tim and full details are in the magazine.


Essentially it comprises:

  • a base 10" x 17" made from 18mm plywood (preferably baltic birch 3/4")
  • a clamp plate 8" x 17" made again from 18mm plywood
  • a hardwood fence, in my case an oak scrap, glued onto the clamp plate
  • 8 off 3/8" captive T nuts
  • 4 off 10mm (3/8") washers
  • 2 off 3/8" star knobs
  • 2 off self adjusting toggle clamps
  • 8 off M5 x 40 long countersunk head socket screws with nuts and washers(or equivalent imperial).

The hardwood fence is glued to the top plate and cut away to clear the star knobs when they are in the forward position.
Drill 2 columns of 4 holes (8 in total) for the T-nuts in the base plate. These start 3-3/8" from the front of the longest edge of the base plate on 15" centres. The remaining  3 pairs of holes are drilled inline with the first two on 1-1/4" centres.
Next counterbore these holes on the underside of the base plate with a Forstner bit to clear the head of the T-nuts. Then the T-Nuts are inserted from the underside and hammered home.

Underside of base plate showing the
counterbores for the heads of the T-nuts

The two slots in the clamp plate are routed to line up with the base plate holes again on 15" centres as clearance for the threaded shafts on the star knobs.

Top view of  the full assembly
Note there is no workpiece shown here
The toggle clamps are positioned on 18mm spacers centrally in 7" centres. The spacers are glued and pinned to the clamp plate. The clamps are bolted permanently onto the clamp plate after drilling for the 8 - M5 screws. The holes for the M5 screws are countersunk on the underside of the clamp plate.

In the article Tim suggested using captive T-nuts on the underside with screws holding the clamps from the top but I didn't have any small T-Nuts so used the method above.

A hole is then drilled to hang the jig up.


Section through the jig
In practice you can position the work to be routed complete with its pattern onto the baseplate. You then adjust the fence by positioning the star knobs into whatever hole is suitable and finely adjust the clamp plate on the slots. Tighten the star knobs and tighten the toggle clamps. You can then use a pattern routing bit to follow the profile of the template and cut the work-piece to shape.
(photos below taken from the article while viewing it on an ipad)

Photo of jig in action

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