Easy Mitrelock Bit Set Up

simple steps to set up a bench mounted mitrelock bit

because of the accuracy required when making these measurements it is advisable to have certain tools

height guage and callipers

the more accurate these tools are the more they cost however there is a wide range available in the shops/internet so get what will suit you

(please note all measurements shown are from my cutter and will probably be different to your cutter)

set bit into router table and form a profile of the cutter into a piece of timber

from this point on accuracy is vital !!

measure the width of the tongue and the depth of the tongue and grove
record dimensions (needed each time this cutter is set up)

(measurements from my sample work piece)

tongue/grove depth = 7.44 mm

tongue width = 3.65 mm

measure the thickness of your work piece

(my sample)

thickness 14.83 mm

for the distance of the fence to the edge of the top tongue (cutter width)

add the thickness of the work piece to the tongue width measurement and devide by two

14.83 + 3.65 = 18.48 mm divided by 2 = 9.24 mm

height of cutter above table (cutter height)

for height of the cutter add the thickness of the work piece to the tongue and groove measurement and devide by two

14.83 + 7.44 = 22.27 mm divided by 2 = 11.135 mm

useing the depth gauge adjust the cutter height from table to the top of tounge as indicated

likewise set the fence back from the tip of the cutter as indicated

if the measurements taken were correct then the joint will fit first time

run 100mm sample cut off 50mm fit togeather as shown

joint should look like this
if not measure accross joint where shown

measurement greater than thickness of work piece

calculate difference between this measurement and thickness of workpiece

devide by 2

cutter height increased by this ammount

measurement less than thickness of work piece

calculate difference between this measurement and thickness of workpiece

devide by 2

cutter height reduced by this ammount

make new profile and recheck

if flush then height is correct

from this point do not alter height of cutter

run profile for right angle joint

picture one

measurement less than workpiece thickness

measure width where shown

calculate difference between this measurement and thickness of workpiece

devide by 2

fence position decreased by this ammount

picture two

measurement more than workpiece thickness

measure width where shown

calculate difference between this measurement and thickness of workpiece

devide by two

fence position increased by this ammount