Turning on mortise or tenon?

[Alan Jeffers]

When I first got a chuck for my mini lathe, I was cutting a mortise in the bottom of the blank to hold it when turning the inner diameter. After watching a numerous of videos, it seems many turners prefer to use a tenon. Is there any advantage to one way over the other?

I've tried both ways. The one thing that made me favor the mortise was the ability to rework some of my earlier pieces that hadn't met my expectations. With a tenon, once the piece is parted off, I'm pretty much stuck with what I've got.

Still learning, and just wondering what common practice is.

 

[hockenbery]

I prefer tenons most of the time. More design options.
In many cases it saves wood. With a footless bowl the outside bottom of the bowl can be right at the top of the tenon.
With a recess you have cut that wood away so it can’t be in the form.

A few folks like recesses better. Most turners I know prefer tenons most of the time.

 

[Richard Coers]

Beginners seem to want to apply finish only on the lathe, so they prefer a mortise. But then the pictures of blown up mortises start to show up. Too little wood, too tight of chuck, and a catch will blow a side of the mortise right off the bowl. There is a Getting Started Forum here as well.

 

[Darryl Fective]

I feel like a mortise makes the bottom limit less visible and possibility a funnel more likely. It also seems more secure squeezing wood for grip instead of expanding inside it.

 

[Bill Boehme]

I feel like a mortise makes the bottom limit less visible and possibility a funnel more likely. It also seems more secure squeezing wood for grip instead of expanding inside it.

Maybe I am misinterpreting, but it sounds to me that your second sentence contradicts the first. I agree with your statement that squeezing the wood seems more secure which is why I prefer using a tenon.

For what it's worth, I also think that it is an unpardonable sin to leave a mortise (actually either method of holding) on the bottom of a bowl .. it's like quitting before you've finished. I don't want my method of work to be a component of the artistic statement.

 

[john lucas]

A mortiss gives you the option of re mounting the bowl weeks or years later for refinishing or whatever. However that can be done with a vacuum chuck with or without a mortiss. A mortiss limits the shape of the bowl. I often prefer a smaller bottom. I use mortisses a lot on platters. I almost always have a wide bottom so it's easy to leave enough wood outside the mortiss.
I prefer tenons mostly. I always reverse turn a bowl so reshaping or removing the tenon is simple. For bowls I feel a tenon is stronger. If your wood is too thin glue on a wasteblock to be used as your tenon.

 

[Doug Freeman]

Tenon ~99% of the time.
> For 2-turn items, a mortice is more difficult to true up
> Concern with splitting the piece - I prefer tight chucks
> I may remount a piece several times for numerous reasons. I want jaws to leave a mark to aid in realignment. The marks are easily visible on a tenon, cant see them in a mortice.
> For more artistic pieces I tend to make the bottom/foot smaller, and there is not enough material to support a mortice.

 

[Steve Bonny]

I always use a glue block. I prefer the clean look of the bottom when finished and (IMO) better holding power when turning. You can re-chuck later if you need to using a cushioned locating piece/jam chuck or just a plain disc of wood on a faceplate and tailstock support or vacuum chuck. My 2c!

 

[robo hippy]

One of the videos I did was Mounting things on the lathe. I am a once turned bowl person, and I use the recess exclusively. If I do hollow forms, then I will use a tenon. There is no advantage in holding power for either one, as long as they are made correctly. Main problem with the recess is that if you don't leave enough shoulder on the outside of the recess, then you can't apply much pressure or it will break. Never understood that idea that a tenon will save more wood than a recess. If both are the same size/depth/height, if you turn them off, there is no difference. When I sand my bowls, I use the extended jaws. If I wiggle the bowl around a bit, I can get 4 jaw contact, which is sufficient for sanding forces. 3 jaw contact does have a tendency to work loose. You do not need the power grip that is necessary for turning, and half of that power grip is just in case you have a catch. I always sand at 10 to 15 rpm. If I go faster than that, with my warped bowls, I can not keep the abrasives on the wood. I do not have or use a vacuum chuck, though I can see them being handy some times.

robo hippy

 

[Alan Jeffers]

Maybe I am misinterpreting, but it sounds to me that your second sentence contradicts the first. I agree with your statement that squeezing the wood seems more secure which is why I prefer using a tenon.

For what it's worth, I also think that it is an unpardonable sin to leave a mortise (actually either method of holding) on the bottom of a bowl .. it's like quitting before you've finished. I don't want my method of work to be a component of the artistic statement.

I agree with you about finishing the bottom of my bowls. I recently bought a set of flat jaws for my chuck so I could clean up the bottoms of my early pieces.

 

[Michael Anderson]

I prefer a tenon. To be honest I’ve only use a mortise a couple of times. Furthermore, I also prefer a separate should above the tenon. I think this is very helpful in giving you the most flexibility with foot design. It also makes it a heck of a lot easier to visualize and turn a nice curve if you’re making a bottomless bowl (calabash, for example).

 

[hockenbery]

Never understood that idea that a tenon will save more wood than a recess. If both are the same size/depth/height, if you turn them off, there is no difference.

Reed, Here is one example. I turn Seed jars as split hollowforms. The surface of the opening and foot are turned inside the tenon.
I suppose it would be possible to do these with recesses to prove it could be done but it would take twice as long.
Turning away recess Wood much more difficult and getting an even thin wall with the recess wood is hard to do and well beyond the skills of many. Both have been done by advanced beginners in workshops using tenons.

This is a typical seed jar with the rim and opening
The rim of the opening is turned and sanded inside the tenon

After hollowing the top is glued to the bottom. you can see the opening was enlarged during the hollowing by turning near the rim from the inside.

The tenon is blended into the curve of the rim and the jar

If you want to see more there is a thread in the tips&techniques

Turning a seed jar - split hollow form

I turned one of these for after dinner entertainment at SWAT-2017 along with Trent Bosch. Trent turned a traditional hollow form in an informal race and finished first. A fun time. Since then I have done several of these in club demos and also did a club workshop where students turned them...

www.aawforum.org

 

[Randy Anderson]

Tenons 99% of the time. Just easier for me to shape and use. I trust them a bit more. I've lately used a few mortise mounts on some small hollow forms thinking that minimizing the wood thickness on the bottom helps the drying process and reduces the potential for cracks. I find mortise mounts using my dovetail jaws provide more consistent remounts when doing things like platters where I mount, flip over and remount a number of times.

 

[Alan Weinberg]

with only 6 months and two dozen bowls under my belt, my opinion carries little weight. I was using tenons until I watched robo hippy videos and have since used and liked a recess, especially on a plate or shallow bowl where it can be incorporated into design and one loses less wood. I’ve broken a couple tenons, turning technique to blame more than the wood. Both tenon and mortise seem secure. Final judgment reserved.

 

[Darryl Fective]

Maybe I am misinterpreting, but it sounds to me that your second sentence contradicts the first. I agree with your statement that squeezing the wood seems more secure which is why I prefer using a tenon.

For what it's worth, I also think that it is an unpardonable sin to leave a mortise (actually either method of holding) on the bottom of a bowl .. it's like quitting before you've finished. I don't want my method of work to be a component of the artistic statement.

When you're expanding inside a mortise, you can't really see your chuck jaws. You have to remember how deep inside the bottom you went and try to visualize your final shape while accounting for that depth. You also have to leave enough wood around your mortise. Peel away too much and it can become weak.

If you're squeezing a tenon, it feels more secure to me, but maybe it's really no stronger. The advantage is that you can plainly see your jaws and how much wood you have left. You can cut right down to them and it really doesn't weaken the hold.

 

[Gerald Lawrence]

I use both it just depends on what form I am turning. Yes you do need to remember how deep you cut the mortise , for me no more than 3/16. The shoulder should be at least a half inch. Also grain orientation is important. Like Reed I have never seen the logic in saying that it wastes wood .

 

[john lucas]

No reason to guess where your jaws are with a rebate. You slide the rod inside your bowl. The distance between the base of this device and the block shows the exact thickness.

 

[robo hippy]

I quit 'guessing' the thickness of my wood bowls years ago. Not accurate. One video I did was 'finding the bottom of the bowl. I always stop a bit short and then measure. Been a long time since I went too thin.

robo hippy

 

[Leo Van Der Loo]

I have been turning since the late 50ish, first without the 4 jaw wood chuck that were not build/sold yet, used a 3 jaw metal lathe chuck and found it's limitations.

Most all blanks were started on a faceplate, and I lived with the limitations of that, most secure hold though.

When Oneway started making their chucks, I got a stronghold, later got the talon and bought some more Oneway chucks, learned the chuck's uses and limitation and the wood holding.

Used tenon and recess, and learned that a recess is the more secure way to hold most woods and shapes, unless you are ham fisted.

As for wasting wood with either manners of holding, I'd say that a tenon that is removed from the turning is wasted wood, shaping the wood so that it incorporates a recess is the least wasteful.


Depending your blank, as shown here, the area in the center can either be a tenon or recess, depending what you turn away, if made into a recess you have a larger amount of wood holding the blank on the chuck than with the tenon




If you like the turning to have a base to sit on, then you can make it large or small, does not need to be deep, as you can see on these bowls, or can tell if either tenon or recess is used.



Or nothing if you want a wobbly bowl


And yes I do use a recess any time I can, and that is almost every time.

 

[Darryn Achall]

No reason to guess where your jaws are with a rebate. You slide the rod inside your bowl. The distance between the base of this device and the block shows the exact thickness.

I like it! Will make one of these over the 4th of July holiday.

 

[Rusty Nesmith]

I prefer a tenon. You can’t split your bowl in half by over tightening on the tenon. Don’t ask my how I know this.

 

[Leo Van Der Loo]

I prefer a tenon. You can’t split your bowl in half by over tightening on the tenon. Don’t ask my how I know this.

Well I have never split a bowl in half by hamfisted over tightening, but seen tenons broken off the turning,

Like this one, (not mine)

 

[john lucas]

I've seen a ton of bowls with mortisses blown up. Mostly on beginner sites so I guess tool control was a considerable factorm

 

[robo hippy]

Either joint can fail. I have blown up recesses from overtightening. I have blown them up from nasty catches, and a slightly too small shoulder. I have also ripped tenons off as well, mostly from catches. Some times I will blame the softer woods, and woods that are more brittle. Kind of depends on the situation. For me, if I have a problem of some sort, I get obsessed with figuring out what the problem was, and how to fix it and/or figure out how to prevent it from happening again. It is a journey.

robo hippy

 

[Leo Van Der Loo]

I've seen a ton of bowls with mortisses blown up. Mostly on beginner sites so I guess tool control was a considerable factorm

I can believe that John, that is where hamfisted comes in to play, seen a turner use a piece of pipe on the handle to tighten it some more , and then they are blaming the wood or tenon /recess or the chuck.

 

[Thomas Kila]

Because I turn mostly end-grain bowls, I prefer to use a tenon.

 

[Lennart Delin]

I use both mortise and tenons depending on bowl size and shape. Also, I almost exclusively rough turn, dry and finish turn. When finish turning I start with completely finishing the outside. A foot or tenon is turned to final shape and used to finish turn the inside. With rhis foot I make a constant wall thicknes, including bottom, regardless of mortise or tenon. This is a more complete description of how I chuck bowls.

 

[JeffSmith]

I also use both, but find that a tenon is most often on most bowls. I think its interesting that we spend so little time discussing the ‘ham-fisted’ approach used by many turners - mostly on the newer side. Thanks Leo for pointing that out. Without actual numbers to back it up, I feel that many, if not most of the failures of either tenons or recesses is caused by people thinking they need to make certain the chuck has a good, tight grip, use both hands, brace their legs and try hard to strip the key when tightening their chuck jaws.
over tightening can actually cause the wood to fail by exerting force in the wrong direction.

Make a clean tenon shape, check that the face of the jaws meet the wood squarely and you only need one hand to tighten the jaws - nuf said - rant over…