# Tenon Thickness Suggestions



## jamesmayson (Apr 21, 2008)

Is there a golden rule for working out a mortise thickness, relating to the size of timber you are using?

I am currently making a window frame for a flush window, the frame size is 95mm, I was going to make my tenon thickness 25mm, does this sound okay?

Also is there a preference between 25mm, and 1''?

Many Thanks


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## Roy Harding (Jun 8, 2008)

Rule of thumb is tenon approximately 1/3 the thickness of your stock - so you're a little shy there.

Doesn't matter if you work in imperial or metric. But work ONLY with one measuring system for each project - mixing the two only guarantee's mistakes. For instance - 1" is NOT 25 mm - it's 25.4 mm.

As a Canadian of a certain age (I'm 48), I grew up with the Imperial system, we switched to metric in my teens. Consequently, I'm comfortable in either system. When I do my own designs, I use metric (I find the math quicker), when building something that someone else designed in Imperial - I leave it in Imperial, I don't convert. I have both Imperial and metric markings on all my fences, etcetera.

Whatever system of measurement you use, and however thick you make your tenons (I'd suggest 32 mm), have fun.


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## jamesmayson (Apr 21, 2008)

Sounds good,

Many thanks for your advice :thumbsup:


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## joiner boy (Aug 13, 2008)

on my flush windows at work they are 95mm, with a 15.7mm tennon, so its a 63mm rebate "6mm for draft strip making the rebate 57mm" then a 15.7mm tennon then a 16.3mm ovolo or flat ect, the sahes are 57mm


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## Tony B (Jul 30, 2008)

*General rule of thumb is*

the mortise/tenon should be 1/3 to 1/2 the thickness of the wood.


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## Handyman (Jan 2, 2008)

Roy Harding said:


> Rule of thumb is tenon approximately 1/3 the thickness of your stock - so you're a little shy there.
> 
> Doesn't matter if you work in imperial or metric. But work ONLY with one measuring system for each project - mixing the two only guarantee's mistakes. For instance - 1" is NOT 25 mm - it's 25.4 mm.
> 
> ...



What he said


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## Roy Harding (Jun 8, 2008)

Seeing as how somebody bumped this: 

For jamesmayson - how'd you make out? Did all go according to plan? Got pictures?


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## jamesmayson (Apr 21, 2008)

It's on the production line now, my frame rebate is going to be double stepped, to try a hide the weather seal, and friction stay hinges the best I can, so my tenon is going to be located on the higher rebate step, I'm going to try using a 25mm tenon, on 95mm timber, I know this is less than the rule of thumb I asked you for, but I think it's still a decent enough size, should have some pictures at the end of the week

Thanks again


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