Centre finder.

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Derek Willis.

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West Oxfordshire, under the Cotswolds.
Been using one of my centre finders yesterday, marking up a number of mortise and tenon joints, certainly makes for ease and accuracy.
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Derek.
 
Hi there, any explanation on how this marks the shoulders? I can see how it marks the centre of any width rail / stile, but for shoulders, I'm lost... :oops:
 
Hi Derek - I can see that by slipping the block over a rail (for example), and rotating on the centre pin, that would show the centre of the rails width. How do you know where to place the shoulders (I'm working on a general 1/3, 1/3, 1/3 spacing)? :duno:
 
If you make a new guide, and put a nail at 1/3 and 2/3 across the gap between the guide pins, that will mark out 1/3 and 2/3 on the wood for shoulders. It works with any fraction. I don't know if it's any more useful then a mortice gauge though...
 
The thirds rule is fine but I generally set the mortise for the nearest chisel width to a third rather then an exact third. Unless it looks wrong of course in which case your thirds divider could be useful. I still divide up using a steel rule set at an angle.
 
I'm a bit of a heathen when it comes to Thirds. It always looks too thin, especially on ex-1" stock. I always err on the fat side (no making up your own jokes, please). So for nominally 1" boards (which, if I'm lucky have finished at 21mm) I would use 5/16 or 8mm tenons.

A jig like this is fine for finding the centre of a piece (provided you don't want to get too close to the end), after that, you do with it as you please :)

S
 
I was taught that the tenon/mortice should be slightly thicker than a third of the thinest component. Still whatever works.

xy
 
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