# 1/4" vs 3/8" loose tenons



## JollyRoger808 (Jan 25, 2012)

When creating loose tenons on 3/4" stock, I see people either use 1/4" tenons or 3/8" tenons. Which is better? I intuitively thought 1/4", because of the 1/3 rule, or is there something I'm missing?


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## cabinetman (Jul 5, 2007)

JollyRoger808 said:


> When creating loose tenons on 3/4" stock, I see people either use 1/4" tenons or 3/8" tenons. Which is better? I intuitively thought 1/4", because of the 1/3 rule, or is there something I'm missing?


I don't think you're missing anything. I don't know about any "rule". I use ¼" for tenons in ¾" stock, and ¼" for splines. I guess I just have ¼" stuck in my mind, as I use that dimension for rabbet and dado depth for ¾" stock.

IMO, leaving ¼" for wall thickness affords adequate strength.









 







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## Dave Paine (May 30, 2012)

I have also read the 1/3 rule for mortise and tenon joints, although I would be pressed to find the reference.

If the tenon was going to be a tight fit, then once glued in place, either 1/4in or 3/8in would work, since the tenon would be attached to the surrounding wood of the mortise, so the joint would be strong.

I would not use a 3/8in loose tenon in 3/4in stock, I would be concerned at the thin 3/16in wall of the mortise. This can be overcome by using a gap filling glue like epoxy.

Personally I prefer to use the yellow glues where possible. Easier for me to deal with.

I would therefore use a 1/4in loose tenon.


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## Steve Neul (Sep 2, 2011)

If I am making a tongue and groove joint on 3/4" stock I make the tenons 1/4". If I am just making a mortise and tenon joint I use 3/8" tenons. I worked for a company one time that made the faceframes for their cabinets with a mortise and tenon joint and they used a 1/4" tenon. It was a daily experience for someone to break off the tenon handling the cabinets. Then it had to be repaired with corrugated fasteners. Eventually they changed to a 3/8" tenon and the breakage stopped.


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## cabinetman (Jul 5, 2007)

Steve Neul said:


> If I am making a tongue and groove joint on 3/4" stock I make the tenons 1/4". If I am just making a mortise and tenon joint I use 3/8" tenons. I worked for a company one time that made the faceframes for their cabinets with a mortise and tenon joint and they used a 1/4" tenon. It was a daily experience for someone to break off the tenon handling the cabinets. Then it had to be repaired with corrugated fasteners. Eventually they changed to a 3/8" tenon and the breakage stopped.


Sounds like just poor craftsmanship.








 







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## Midlandbob (Sep 5, 2011)

I like Steve' reply. It depend on the engineering. Where the joint is.
If you are reducing 3/4 stock to 1/4 by a thin tenon in a critical stress bearing joint, the priority would be to maintain as much wood carrying the load so go with 3/8. If it has a twisting force, then the cheeks would be mor important to preserve.
Most rules are guidelines.
Bob


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## Steve Neul (Sep 2, 2011)

cabinetman said:


> Sounds like just poor craftsmanship.
> 
> 
> 
> ...


 Hardly, It was a factory producing custom cabinets for 15-20 houses a week. The faceframes were mostly solid ash and the 1/4" tenons were just smooth breaking off.


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## cabinetman (Jul 5, 2007)

Steve Neul said:


> Hardly, It was a factory producing custom cabinets for 15-20 houses a week. The faceframes were mostly solid ash and the 1/4" tenons were just smooth breaking off.


How does that happen? The mortise is cut, the tenon is cut, the parts get glued and the tenon gets inserted in the mortise. What am I missing?









 







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## Steve Neul (Sep 2, 2011)

cabinetman said:


> How does that happen? The mortise is cut, the tenon is cut, the parts get glued and the tenon gets inserted in the mortise. What am I missing?
> 
> 
> 
> ...


The thin 1/4" tenons were breaking in two. Like everyone else there I thought when they changed to a 3/8" tenon it was asking for more problems but it worked. There were no more faceframes being broken from normal handling of the cabinets. It was primarily the top rails on long base cabinets that didn't have center dividers.


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## cabinetman (Jul 5, 2007)

Steve Neul said:


> The thin 1/4" tenons were breaking in two. Like everyone else there I thought when they changed to a 3/8" tenon it was asking for more problems but it worked. There were no more faceframes being broken from normal handling of the cabinets. It was primarily the top rails on long base cabinets that didn't have center dividers.


They don't break all by themselves.:no:









 







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## jschaben (Apr 1, 2010)

There is normal handling and there is NORMAL handling. I used to work in a furniture factory and dropping a sofa 4-6 feet was NORMAL.:yes:


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## Steve Neul (Sep 2, 2011)

cabinetman said:


> They don't break all by themselves.:no:
> 
> 
> 
> ...


 The 3/8" tenons didn't break at all.


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## cabinetman (Jul 5, 2007)

Steve Neul said:


> The 3/8" tenons didn't break at all.


That's fine and dandy. I prefer to have at least a ¼" wall thickness for ¾" stock. You won't have that with a ⅜" tenon.









 







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## Brian Hinther (Aug 5, 2008)

FWW did a joint test a few years ago in which they had to go to a 3/8" tenon to get the joint to perform better than a Beadlock or Dowelmax. The 3/8" m&t withstood over 1400 pounds of stress--very close to the half-lap and bridle joint winners. The 1/4" variety was only good for around 700 pounds, barely ahead of pocket screws.


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