Dovetail or tenon for bowls?

[John Torchick]

I'm sure this had been discussed but just got through finishing a small bowl that had a tenon during the process. What determines a tenon or dovetail for turning a bowl? Thanks.

 

[Roger Wiegand]

I much prefer tenons, having broken a number of bowls by expanding too hard in the recess. Tenons are easy to round up after drying a rough turned bowl for re-mounting. I find I have more freedom to design the bottom when I have the extra wood of the tenon, I can make the base whatever size I want. With a typical recess it's hard to make a base of the bowl smaller than the size of the recess, unless you leave a whole lot of extra wood. I find it easier to shape the bottom rim of the bowl if it's away from the chuck.

Though there is a very strong current thread of opinion that tenons absolutely must be sized to the minimum diameter of the chuck, it wasn't always so, and many thousands (millions?) of bowls have been made with the eight points of a chuck grabbing the tenon. With a recess that's not quite the right size you have two round surfaces interacting, a less stable situation, IMO, than eight corners firmly dug into the wood.

I've started making some plates of late, there I've been using a recess. It let's me get the most from a piece of 5/4 stock lumber, I already want a quite wide base for stability of the plate so the recess is usually smaller than the intended bottom rim of the plate, and a plate holds tenaciously on a vacuum chuck, making it easy to re-shape the profile of the bottom.

The other place I use a recess is while coring; I use a tenon to hold the log during coring, but I'll make a recess in the front side so that after I've made the biggest bowl I have a way to hold the core to make a tenon on its back side for the next round of coring. That way all my cored bowls have a tenon for re-mounting when they have dried and I don't waste wood.

 

[Randy Anderson]

Like Roger, I stick with tenons since it gives me a lot of access and flexibility for working the bottom of the bowl once dried. On natural edge bowls that can get to be a real challenge since they will warp and I can adjust the foot size to whatever works for how the bowl has changed shape.

Roger, I picked up a tip on your post - I usually (if I remember) put a tenon on the top side of the inner bowl when coring so I can flip it around and then work the bottom. I'll try a mortise next time and see how it works for me.

 

[hockenbery]

This is a frequent topic.
I much prefer a tenon for bowls. A recess is sometimes a good choice for platters
The tenon uses a lot less wood and is more compatible with the designs that interest me.
Expansion will split weak wood easily compression does not.

if I’m drying a bowl I can leave the center point in the the tenon. If the grain is balance the center point will be the center of the dried bowl. So much ever to true a tenon to return a bowl. Trueing a recess is difficult.

tenon size. The vicmarc #2 jaws have the perfect circle diameter of 48mm about 1.9” never want a tenon of smaller diameter.
I use a 2.5” tenon in Almost every green bowl I turn. This size tenon when it shrinks will always have a 2” tenon in it. Also my live center has a 5/8” cup. I turn a tenon an inch out from the 5/8 center and I always get a tenon close to 2.5” because over time I learned to judge an inch really good.

my first Chuck only did recesses. So I got a lot of experience with them.
Some people like recesses and the work well with their design choices.

 

[Emiliano Achaval]

I also prefer a tenon. That been said, I use a recess to do the outside of the bowl, so I can do a push cut without the tail stock bothering me. It takes an extra step, but sanding is not my favorite part of turning, so I like to leave as good of a surface as possible. For the hollowing, I always use a tenon. If your piece has a crack, maybe internal, and you apply pressure on a recess, chances are that bowl will explode. I'm extra careful when doing the outside with a recess, I make sure I see no cracks, anywhere. Also, a tenon gives you more options when reverse turning the bowl, more design choices. Watch Phil irons video, where he explains about using the large jaws and why NOT to use a recess. He is a professional woodturner, has done thousands of bowls, and his experience and advice are right on the money.
View: https://www.youtube.com/watch?v=lJesIjGrwKc

 

[john lucas]

I am also a tenon fan. Mostly because it leave so many options when I reverse turn the bowl. I can make the foot any size I want or no foot at all. I can turn a rebate (as long as I calculated that into the design while hollowing). I do use rebates on most of my platters. Even then I may reverse turn the platter and change the rebate shape or eliminate it.

 

[Dave Bunge]

The other place I use a recess is while coring; I use a tenon to hold the log during coring, but I'll make a recess in the front side so that after I've made the biggest bowl I have a way to hold the core to make a tenon on its back side for the next round of coring. That way all my cored bowls have a tenon for re-mounting when they have dried and I don't waste wood.

Roger, what's the advantage of a recess instead of tenon in this case? Easier to cut? Less diameter lost for the smallest core? I've always used a tenon on the front side, but that's from force of habit since it's what I use elsewhere.

 

[John Torchick]

Thanks to all. Looks like the tenon is the way for most applications.
Let me give a bit of my background- I have been around manufacturing for more years than I care to count. My first job was at a company that had one line of commercial air conditioners. Panels were pressed on a 12,000 ton press. Over the years I have seen a lot of lost fingers and hands due to careless people. Now...I'm a bit uneasy about getting the tool close to the live center or the chuck. What is your approach to turning down the tenon just before completing the turning? Again, thanks to all. BTW, does anyone have or recommend a video for the proper way to remove a tenon?

 

[Lamar Wright]

I use both also, really depending on the type bowl that I turn. I use a tenon more often though.

 

[Roger Wiegand]

Roger, what's the advantage of a recess instead of tenon in this case? Easier to cut? Less diameter lost for the smallest core? I've always used a tenon on the front side, but that's from force of habit since it's what I use elsewhere.

It probably doesn't make a ton of difference if you are able to dish the piece in within the diameter of the smaller bowl and make an inset tenon. If you don't do that you lose 1/4 to 1/2" of depth on all of your bowls. That may or may not matter to you. The recess just seemed easier to me. I only use it for a minute, forming the next tenon at small diameter. I also bring up the tailstock for most of that cutting, pulling it away just to take off the final nub (then hoping to remember to bring it back to mark the center for later!).

 

[Roger Wiegand]

. What is your approach to turning down the tenon just before completing the turning?

Lots of ways, depending on the piece. Most commonly, a combination of a friction drive and vacuum chuck. The vacuum chuck I have has a nice rubber collar I got from Rubber Chuckie that doesn't mar the piece, I apply pressure with the tailstock to hold it, turn away as much of the tenon and do as much forming of the foot as I can, then rely on the vacuum to hold the piece for shaping of the foot that can't be done with the tailstock in place and removing the nub. When the vacuum won't work due to the porosity or fissures in the wood I use the Vicmarc cole jaws with the pyramidal bumpers to hold the piece, working in the same way with tailstock support as much as possible.

There are some pieces where neither method works, then I start to rely on funky home made bent tools to try to work the inside edge of the bottom rim with the tailstock in the way of using conventional tools. I'm afraid I have something of a fetish about shaping and finishing the bottom of a bowl. I haven't yet made one of those doughnut clamp contraptions that would let me capture bowls that won't work with vacuum or cole jaws, but I probably should.

 

[Doug Freeman]

A dovetail can be used for a tenon/spigot or a recess/mortice. A tenon or recess can use a dovetail or be straight walled depending on the jaws - dovetail or serrated/oneway profile.

I use tenons 99% of the time, including coring, for all the reasons stated above. 3 main reasons I use them: prevent cracking, easier to true up, better realignment when rechucking a piece. I want marks on the tenon into the wood that I can find when rechucking. Never had a problem using jaws out near max clamp size except with very short tenons, 1/8”. . I do tend to make tenons ~ 1/2” larger than the minimum size for the jaws.

To turn the tenon away, I use a simple friction chuck (I have several profiles) that thread directly on the spindle, use the ts for pressure, turn it down to the nib and remove it with various methods - chisel, saw, sanding.

 

[John Torchick]

Thanks again. I have seen old knives cut and ground to make a parting tool. Might try it with an old knife that isn't used in the kitchen. Should work better for "detail" use. Present PT is 1/4 inch wide.

 

[hockenbery]

thanks to all. BTW, does anyone have or recommend a video for the proper way to remove a tenon?

.
There are lots of ways to remove the tenon. My method is pretty standard.

1. You might be interested in the video of the seed jar demo. The seed jar is a split hollowform - like two bowls glued together at the rims. Top and bottom are both hollowed using a tenons. The top tenon has the lip of the opening turned inside it. The face of the bottom tenon is con-caved and sanded. After the form is glued together the edge of the top’s tenon is turned away to finish the area around the rim. The edge of the bottoms tenon is turned to make the foot. — make 5 of these and you will be and expert on tenons.

View: https://youtu.be/i-odbgyJvrQ




2. In the demos I do for a natural edge bowl from a crotch and returning a dried bowl I show the removal of the tenon

Mounting and turning a dried bowl -

View: https://www.youtube.com/watch?v=sCZWsHB4vlM


NaturalEdgeCrotchBowlMay2014 -

View: https://www.youtube.com/watch?v=8jVoI12Kfug

 

[John Torchick]

HB, many thanks. Will take time this evening to view them. Nothing on TV worthwhile.

 

[Chris Lawrence]

I am also a tenon fan. Mostly because it leave so many options when I reverse turn the bowl. I can make the foot any size I want or no foot at all. I can turn a rebate (as long as I calculated that into the design while hollowing). I do use rebates on most of my platters. Even then I may reverse turn the platter and change the rebate shape or eliminate it.

How much do you get back on your rebates? I think you mean rabbets.

 

[robo hippy]

An old topic, and an older video that I did. Only time I would NEVER use a recess to expand into is when doing end grain like hollow forms. A tenon in this orientation is far stronger and expanding into a recess will try to split the wood.

View: https://www.youtube.com/watch?v=5KHkkws9lWA


robo hippy

 

[Roger Wiegand]

How much do you get back on your rebates? I think you mean rabbets.

John's usage is completely correct. I think the rabbet spelling is a corruption of the word that happened a hundred or two years ago. :

rebate2
Pronunciation /ˈrabit/ /ˈræbɪt/ See synonyms for rebate
NOUN

• A step-shaped recess cut along the edge or in the face of a piece of wood, typically forming a match to the edge or tongue of another piece; a rabbet.
  

 

[Dean Center]

Thanks again. I have seen old knives cut and ground to make a parting tool. Might try it with an old knife that isn't used in the kitchen. Should work better for "detail" use. Present PT is 1/4 inch wide.

John, you would not use a parting tool to take off the tenon. I suppose it could be done, but there are much better ways. A kitchen knife might make a skinny parting tool, but a little thicker steel would probably work better.

I hope it's clear from the above comments that to remove the foot, one way or another, you have to turn the bowl around (reverse turn). There are lots of ways to do that. Ernie Conover's book "The Frugal Woodturner" is a good resource for low priced ways to make accessories rather than buying ready made.

 

[John Torchick]

HI, Dean. This is a 10 inch chef's knife and the back is heavier than a paring knife, filet knife or veggie knife. I'll measure but looks to be about 1/8th inch thick. The closer to the handle, the thicker the blade. Should work OK.

 

[Bill Boehme]

The difference between rebate and rabbet (not to be confused with rabbit, a cute furry animal with long soft ears) is a couple thousand miles of ocean. Over there it's a rebate while it's a rabbet over here. Regardless of how you spell it, I believe that the pronunciation is more or less the same if we try to imagine normalizing accents. Maybe it's splitting hairs (or hares), but I think that "mortise" might be a more suitable name for the recess.

 

[Bill Boehme]

HI, Dean. This is a 10 inch chef's knife and the back is heavier than a paring knife, filet knife or veggie knife. I'll measure but looks to be about 1/8th inch thick. The closer to the handle, the thicker the blade. Should work OK.

That doesn't sound OK to me If it is tapered thickened thicker towards the handle because it could bind in the kerf.

 

[John Torchick]

I'll be cutting off most of the blade so the taper shouldn't come into play.
As for the rabbet/rabbit, we need to ask Elmer Fudd.

 

[Glenn Lefley]

I never think of which is better until the bowl is thin and I’ve made a recess and I’m re chucking it. I then wish I’d glued on a block or made a tenon as when I tighten chuck im praying I don’t hear a crack and when I’m turning I’m fearful I did make an unseen crack and it’s going to blow apart.

 

[Mark Jundanian]

The difference between rebate and rabbet (not to be confused with rabbit, a cute furry animal with long soft ears) is a couple thousand miles of ocean. Over there it's a rebate while it's a rabbet over here. Regardless of how you spell it, I believe that the pronunciation is more or less the same if we try to imagine normalizing accents. Maybe it's splitting hairs (or hares), but I think that "mortise" might be a more suitable name for the recess.

This cracked me up. And I agree it should be mortise, not rebate. But for that matter jointers don't join, they plane; and planers don't plane, they thickness.

 

[robo hippy]

How about ribbits??? I have been hearing the spring frogs lately. We did have a nice PIneapple Express move through, a warm rain front from the Pacific....

robo hippy

 

[John Torchick]

Hmmm.

 

[Bill Boehme]

This cracked me up. And I agree it should be mortise, not rebate. But for that matter jointers don't join, they plane; and planers don't plane, they thickness.

And the biscuit joiner must have been a British invention. If it had been invented in North America it would have been called a cracker or cookie joiner.

 

[John Torchick]

In the South, they are known as "cat heads." A properly made biscuit is shaped like a cat's head but tastes much, much better.