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Tenon or Recess? (Read 508 times)
 
Allan Miller
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Tenon or Recess?
Feb 28th, 2018 at 5:43pm
 
What is everyone’s preference? After having a tenon snap off on me, granted it was a bit small for the bowl size since my large jaws are still on a ups truck, it got me to thinking is a recess better. To me it seems that a recess would put outward pressure on the entire bowl possibly encouraging a small crack to grow causing failure. As long as the tenon is large enough to support the piece it seems compression on the tenon would be better.
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Don Stephan
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Re: Tenon or Recess?
Reply #1 - Feb 28th, 2018 at 6:01pm
 
In three or four years I think I have made one recess and hundreds of tenons.  With a Vicmarc 120 chuck and jaws I am very confident in the holding power - on small bowls the tenon is little more than 3/32" long, and even on large bowls I seldom make a tenon as long as 1/4".  I remember having one break, but can't remember if it was due to a major catch or perhaps tightening the jaws too much and weak grain.
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George Hurlburt
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Re: Tenon or Recess?
Reply #2 - Feb 28th, 2018 at 6:47pm
 
Go with the tenons. When I have used the recess, I tend to get a depression in the wood at the bottom, it is also easier to go through or get it too thin at the bottom. I will use the recess to do vase or box  lids and that's about it.
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Glenn Roberts
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Re: Tenon or Recess?
Reply #3 - Feb 28th, 2018 at 7:16pm
 
Does a recess have a tendency to split an end grain bowl? And does a tenon have have a tendency to leave a side grain bowl?
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Arlin Eastman
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Re: Tenon or Recess?
Reply #4 - Feb 28th, 2018 at 8:06pm
 
I have done a recess, tennon and nothing and feet on a bowl which is a tendon with spaces taken out.

To me it just depends on how I feel with the turning.

I have not had a tennon or recess break out since I started eight years ago buy others telling me what I did wrong and it was good advise.

I will now cross my fingers.   Grin Grin Grin
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Louie Powell
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Re: Tenon or Recess?
Reply #5 - Feb 28th, 2018 at 8:53pm
 
The big technical argument between recess and tenon has to do with the relationship between the direction of stress imposed on the blank relative to the direction of the fibers in that blank.  That is, using a recess on a spindle turning tends to separate the fibers along the length of the spindle, while using a tenon on a face-grain turning tends to pull the tenon off the turning (and that problem is aggravated if the jaws concentrate that stress at the point where the tenon meets the bottom of the turning).

So that almost sounds like a Ford versus Chevy situation (or, if you wish, boxers versus briefs) - its your choice.

But there is another factor - some turners tend to favor a recess because it can be left in place, while using a tenon requires an additional step to remove the tenon.  And my non-scientific research (looking at turnings for sale in galleries and shops while shopping with my wife) leads me to suspect that production turners who make a living from turning and are concerned about volume tend to use recesses. 

I've also noticed that turners in Ireland and the UK also often leave a recess on the bottom of their bowls and platters.
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Steve Kniffen
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Re: Tenon or Recess?
Reply #6 - Feb 28th, 2018 at 9:44pm
 
I choose the one that seems to fit what I'm turning the best.  I probably use more recesses than tenons.  I don't just leave a recess there, though, I reverse it and make it concave to cover the shape of the recess. 

I have never had a recess split an end grain turning.
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Rick Caron
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Re: Tenon or Recess?
Reply #7 - Mar 1st, 2018 at 9:04am
 
I like a recess,  so i don't have spend time removing a tenon.  Of course i power sand the sharp edges of the recess with bowl off the lathe,  then sign and date, then seal.       You will need an inch of wood around the recess for support or you may split the bowl.
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Ed Weber
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Re: Tenon or Recess?
Reply #8 - Mar 1st, 2018 at 9:48am
 
First off, let me say, it's entirely up to you.
The actual holding power of the connection to the chuck is the same in either direction.
A recess has more wood to support the connection so it may be considered "stronger" than a tenon but this is due to the strength of the wood not the connection to the chuck.
The connection strength, or lack of is dictated by the turner that fashions the tenon of recess.
Over or under tightening, poorly matched radius and/or jaw angle contribute to the connection failing, this is operator error and has nothing to due with the strength of a tenon or recess.

For a tenon or a recess, you need to,
1. Make it the proper size for the object you're turning,
2. Make it the proper size for the jaws you're using
3. Be as certain as possible the the wood is capable of holding.
4. If you're not confident as to the strength of the tenon or recess, use the tailstock for support as much as possible
Tenons "usually" fail due to being too small or being cut from weak wood.

Glenn Roberts wrote on Feb 28th, 2018 at 7:16pm:
Does a recess have a tendency to split an end grain bowl? And does a tenon have have a tendency to leave a side grain bowl?


You shouldn't use expansion (recess) on spindle or end-grain orientation,
A tenon can break off from a bowl but again this is usually due to a combination of factors.

This is not a one size fits all, every piece of wood is different.
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Al Wasser
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Re: Tenon or Recess?
Reply #9 - Mar 2nd, 2018 at 2:29pm
 
Some things to remember re chuck.  Any chuck has its maximum holding power when the jaws make a perfect circle.  Usually that means the jaws are open about 1/16 in.   Problems start to occur when you open the jaws much wider that a perfect circle.  If you open the jaws up and grab a well made tenon  you are grabbing with 8 points of the jaws.  Open the jaws up in a recess and you may only be actually holding with 4 points so with a tenon it is critical you are close to a perfect circle.  The other thing to always avoid with a tenon or recess is to never have your jaws grabbing directly to end grain.  Hope this helps.  I have heard 2 pros say that a recess is the strongest.  I tried a recess when I was a beginner and had a lot of failures but now use a recess most of the time.
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Ed Weber
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Re: Tenon or Recess?
Reply #10 - Mar 2nd, 2018 at 4:49pm
 
Al Wasser wrote on Mar 2nd, 2018 at 2:29pm:
I have heard 2 pros say that a recess is the strongest.  I tried a recess when I was a beginner and had a lot of failures but now use a recess most of the time.


When I responded earlier I suppose I should have said "properly made" tenon or recess.
For a recess this "usually" means a minimum of 1" of material surrounding the recess.
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