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2 techniques for the trade
A simple jig for mortise Locks
by Miles Davey
Jig making is an essential part of routing and for repetitive operations offers savings on both time and productivity . One example of this is shown by making a simple jig for cutting a lock mortise and the shallow recess to take the lock face plate .
When fitting a number of locks of the same type and size , the jig can be fairly simple . However , a more sophisticated jig can be designed to accommodate different lock and door sizes .
The template face is secured to the jig cheeks using machine screws and threaded inserts . The recessed slots are cut parallel to the top and bottom and allow the cheeks to be set to suit any door thickness . The length of the slots together with the notched sides of the template face give sufficient clearance for the router base when routing the key slot and spindle hole .
The Trend mortising cutter ( Ref . 5 / 52 ) is ideal , having a plunge cutting depth of almost 70mm and good chip clearance characteristics to remove waste material quickly . If a deeper mortise is required , a chisel or drill bit can be used to increase the depth .
Please note : Before cutting the mortise and face plate recess , work out the margin between the outside diameter of the guide bush and the outside diameter of the cutter . Margin Formula = Deduct diameter of cutter from outside diameter of guide bush and divide by 2 .
A 38mm x 134mm slot is required . This will enable the face plate to be routed with a 1 / 2 ” cutter and a 26mm guide bush . By inserting two packing pieces , one at each end of the slot , a 32mm guide bush can also be used to rout the mortise .
The cheeks have apertures to accept the same diameter guide bush to rout the key slot and spindle holes on either door face . The jig cheeks are wide enough to support the router for this purpose .
Generally a mortise lock body is around 19mm thick , with a face plate width of 25mm .
Routing the Mortises
Centre the jig across the door edge and secure it using Gripper clamps .
Insert the packing pieces into each end of the slot , and with the larger guide bush fitted , rout the mortise first . Cut in a series of shallow steps , re-setting the depth of cut for each . Cut to the full depth of the lock body plus extra depth to allow for the recess for the face plate . Then remove the packing pieces , fit the smaller diameter guide bush and cut the shallow face plate recess . Carefully square the corners of the mortise and recess using a sharp chisel .
Still using the same combination of cutter and guide bush rout the hole for the handle spindle and the slot for the keyhole .
Materials for making the jig
Template Face Cheeks Machine screws Threaded inserts
1 x 1 / 2 ” x 350 x 190mm MDF 2 x 18 x 350 x 210mm MDF 4 x M6 x 16mm panhead 4 x M6 for wood
Autumn 1998
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