What tenon sizing to fit your chucks......?

[Odie]

I am using three stronghold chucks, and for correct tenon sizing to fit the #2 and #3 jaws, they must be from 1 7/8" to 3 3/8", and 3 3/4" to 5 1/4" in diameter.

You can see there is a gap between 3 3/8" and 3 3/4" where a tenon within this range simply won't fit my chucks. That you know of, are there any other options for me, that I'm not thinking of, that will enable me to use my Stronghold chucks for tenons that are within this unusable range?

For those of you who are using other makes of chucks, are you experiencing similar gaps in sizes of tenons you cannot use?

Which brands of chucks, and available jaw sizes fit tenons between 3 3/8 and 3 3/4" ?

ko

 

[john lucas]

That's one of the reasons I chose the Vicmarc. My jaws actually overlap slightly so if the tenon doesn't fit one it will always fit the other jaws.

 

[Richard Coers]

I don't understand the issue. You are cutting the tenon, just measure and cut the diameter that fits. I much prefer to work on the smaller size range of the jaws. I feel that the grip is better when the jaws grip in a near circular pattern instead on points.

 

[Gerald Lawrence]

I have 50 mm and 100 mm nova jaws and see some of what you express. Would like a 75 however the Nova 75 is made differently and not sure that is what I want. A thought occurred to me and I have used is the expansion mode. In my jaws using either expansion or compression will give a broader range of sizes on the bowl bottom.

 

[Odie]

I don't understand the issue. You are cutting the tenon, just measure and cut the diameter that fits. I much prefer to work on the smaller size range of the jaws. I feel that the grip is better when the jaws grip in a near circular pattern instead on points.

Well, Richard......I rough nearly all my own bowls from a solid block of wood, and there is no problem, if I am the one cutting a tenon. On occasion, I purchase a kiln dried roughed bowl, and the tenon sometimes is within that dreaded "dead zone". Once in awhile I have to pass on one that looks like it could be an outstanding bowl, simply because the tenon isn't usable.

The purpose of this thread is to probe a little bit, and see if anyone else is faced with the same issue.....and found a solution. I love my Stronghold chucks, but if no solution to this comes up, I may be looking for another chuck, just for this particular need. Darn it.....I sold both my Vicmarc chucks, and a Nova long ago when they were replaced by the Stronghold chucks! They sure would come in handy now! 🙄

ko

 

[Bill Boehme]

That's one of the reasons I chose the Vicmarc. My jaws actually overlap slightly so if the tenon doesn't fit one it will always fit the other jaws.

I have both Vicmarc and Oneway chucks and feel just the opposite. While there is some overlap in range with the Vicmarc chucks, when they are expanded very much from the perfect circle diameter, they are only contacting the tenon at eight points whereas the profiled jaws on the Oneway chucks provide much more contact area. However for precision alignment for final turning, I feel that the Vicmarc chucks are better provided that the tenon diameter is very close to the perfect circle diameter.

Regardless of which chuck you are using, I think that it makes a lot more sense to size the tenon for the best fit with whatever chuck is being used rather than making an arbitrary sized tenon and then discovering that it either doesn't fit or poorly fits the jaws that you have. Since getting a couple Vicmarc chucks I am even more aware of proper fitting than when all of my chucks were Oneway Talons and Stronghold. I also have some dovetail jaws for my Stronghold chuck which works nicely for tenon sizes that aren't a good fit for my Vicmarc jaws.

EDIT: Odie, I see that you sometimes get a bowl with an off-sized tenon. Maybe contact the seller and let him know about the problem. It might be something that he hasn't considered and would appreciate knowing about it.

 

[hockenbery]

Well, Richard......I rough nearly all my own bowls from a solid block of wood, and there is no problem, if I am the one cutting a tenon. On occasion, I purchase a kiln dried roughed bowl, and the tenon sometimes is within that dreaded "dead zone". Once in awhile I have to pass on one that looks like it could be an outstanding bowl, simply because the tenon isn't usable. The purpose of this thread is to probe a little bit, and see if anyone else is faced with the same issue.....and found a solution. I love my Stronghold chucks, but if no solution to this comes up, I may be looking for another chuck, just for this particular need. Darn it.....I sold both my Vicmarc chucks, and a Nova long ago when they were replaced by the Stronghold chucks! They sure would come in handy now! 🙄 ko

I start turning my dried bowls by rechucking them over the slightly open jaws of the chuck.
The center of the tenon against the tailstock center the chuck against inside bottom of the bowl.
No padding is used unless the wood is exceptionally soft.
The tenon always needs to trued as it warps along with the bowl.

I find the center of the tenon end grain to end grain side grain to side grain ( I usually leave the center point from the rough turning and that works)
I balance the bowl on the chuck before turning.
They usually line up well by themselves but I check and loosen the tail stock and move the bowl to get it even if necessary.
With symmetric grain I get the two high spots on the rim even distance from the head stock and two low spots even distance from the headstock.

If the grain is not even I try to get opposite sides of the bowl even distant from the tool rest.

Then I first true the rim with cuts straight toward the tails stock.
This balances the weight fastest. Then I return the outside to round, true the tenon and the put it in the chuck and hollow.

Al

 

[Odie]

EDIT: Odie, I see that you sometimes get a bowl with an off-sized tenon. Maybe contact the seller and let him know about the problem. It might be something that he hasn't considered and would appreciate knowing about it.

Hi Bill.....

Yes, I've contacted the seller earlier this year, and he has accommodated my request somewhat. Still, some of his KD roughed bowls have tenons in that "dead zone". I'm sure he has his own needs, and it's certain he has other customers to think about, too......so, he may not be able/willing to tune his operations to my needs, all of the time.

ko

 

[Sergio Villa]

Real dove tail chucks, like vicmarc, when close to perfect round grip 100 % of the circonference: perfect fit and grip. With the eight shaped jaws of the oneway type, you alwaus have eight and only eight points of contact. Much less than perfect.
Not only with the real dovetail jaws near the perfect round you do not marr the tenon and can grip with 1/8 inch tenon. Done with 17 inch overhand or 18 inchbowls without any problems.
By the way a vicmarc jaws close perfect round at 84 mm which is 3.3 inches. I only wish they had a perfect round at 2 1/2 -2 3/4 inch.
I have two small oneway chucksfor small things and there is a huge difference in favorof the real dovetail jaws.

 

[hockenbery]

Real dove tail chucks, like vicmarc, when close to perfect round grip 100 % of the circonference: perfect fit and grip. With the eight shaped jaws of the oneway type, you alwaus have eight and only eight points of contact. Much less than perfect. Not only with the real dovetail jaws near the perfect round you do not marr the tenon and can grip with 1/8 inch tenon. Done with 17 inch overhand or 18 inchbowls without any problems. By the way a vicmarc jaws close perfect round at 84 mm which is 3.3 inches. I only wish they had a perfect round at 2 1/2 -2 3/4 inch. I have two small oneway chucksfor small things and there is a huge difference in favorof the real dovetail jaws.

ONEWAY has dovetail jaws too. I use them a lot. I prefer dovetail jaws for short tenons.
I like the Vicmarc better than the strong hold because of the mass and the hex key.
I don't use the dovetail in my final designs so I haven't found the circle closing useful. It is a neat property.

Dovetail jaws hold really well but the eight wide parts of the standard ONEWAY jaws will hold just as effectively provided the tenons are close to a half inch long and have parallel sides. Turn a taper or a dovetail on the tenon and you loose the grip of the jaws.

My experience in teaching is that dovetail jaws are vastly superior to the standard ONEWAY jaws in holding a sloppy tenons.

 

[Grant Wilkinson]

Odie: You could look at the #2 tower jaws for the stronghold. They open to 3 3/4" according to the Oneway site.

 

[Fred Belknap]

Odie I use Stronghold and Talon chucks. The Talon with #3jaws would work in this range, I usually cut my tenons 3 1/8" for the Talon with the #3 jaws. If you don't have a talon chuck this info is kind of useless.

 

[Odie]

Good morning, all....... 😀

Odie: You could look at the #2 tower jaws for the stronghold. They open to 3 3/4" according to the Oneway site.

Hello Grant.......Matter of fact, I have a set of #2 tower jaws, but mine only open to 3 3/8 for a spigot.....same as the standard jaws. It would make sense that would be the case, because if both sets of jaws have the same minimum dimension, which they do, they both would only open the same distance. I suppose it's possible the current #2 tower jaws have been redesigned to open wider, but if that were the case, they wouldn't have the same minimum specifications as the standard #2 jaws. I don't believe I've purchased any new Stronghold jaws since I bought my first Stronghold chuck in the early 1990's, so that's entirely possible.

I do know that the Stronghold chuck has had some redesigning in that time gap between when I bought my first Stronghold chuck, and sometime about a dozen years later, when I purchased two additional Stronghold chucks. (I now have three Stronghold chucks.) Within that time frame, the Stronghold changed the gearing, and the chuck key I have for my first chuck, will NOT fit the two chucks I bought later on, and vise versa.......

Odie I use Stronghold and Talon chucks. The Talon with #3jaws would work in this range, I usually cut my tenons 3 1/8" for the Talon with the #3 jaws. If you don't have a talon chuck this info is kind of useless.

Well, Fred.......I don't have a Talon chuck, but that information is still useful to me, because it's in the plans to someday get some other chuck that will fill the need I have to cover the "dead zone" for spigots I cannot accept with my Stronghold chucks......thanks! 😀

ko

 

[Ron Solfest]

I don't have th experience that som of you do, but I don't see any of the issues talked about here:
1. Dead zone - I do like Al says and I st turn a true tenon by placing the open bowl against partially open jaws. Not an issue at all, certainly wouldn't cause me to pass on a blank.
2. Stronghold serrated grip depth - I routinely use about a 3/16" tenon for finishing up dried blanks previously turned to ~1" wall thickness. When originally turning green I use ~3/8" tenon, sometimes 1/2" on a large (15") bowl.
3. Stronghold 8point - I haven't had any issues, nor noticed a difference whether tenon is near min or max dimension. I even often have a very slight dovetail on the tenon. As long as the tenon isn't tapered backwards, doesn't ottomh out, and there's a good shoulder to seat I find the chuck holds very well (couple of strongholds and a talon).
YMMV
Ron

 

[Bill Boehme]

I don't have th experience that som of you do, but I don't see any of the issues talked about here:
1. Dead zone - I do like Al says and I st turn a true tenon by placing the open bowl against partially open jaws. Not an issue at all, certainly wouldn't cause me to pass on a blank...

I agree that there are various solutios. I typically start with the dried bowl between centers and true up the tenon which usually has gone oval shaped. As Odie mentioned, he was just probing for various ways to skin that cat ... oops ... wrong metaphor.

... On occasion, I purchase a kiln dried roughed bowl, and the tenon sometimes is within that dreaded "dead zone". Once in awhile I have to pass on one that looks like it could be an outstanding bowl, simply because the tenon isn't usable...

 

[Odie]

I don't have th experience that som of you do, but I don't see any of the issues talked about here:
1. Dead zone - I do like Al says and I st turn a true tenon by placing the open bowl against partially open jaws. Not an issue at all, certainly wouldn't cause me to pass on a blank.
2. Stronghold serrated grip depth - I routinely use about a 3/16" tenon for finishing up dried blanks previously turned to ~1" wall thickness. When originally turning green I use ~3/8" tenon, sometimes 1/2" on a large (15") bowl.
3. Stronghold 8point - I haven't had any issues, nor noticed a difference whether tenon is near min or max dimension. I even often have a very slight dovetail on the tenon. As long as the tenon isn't tapered backwards, doesn't ottomh out, and there's a good shoulder to seat I find the chuck holds very well (couple of strongholds and a talon).
YMMV
Ron

I agree that there are various solutios. I typically start with the dried bowl between centers and true up the tenon which usually has gone oval shaped. As Odie mentioned, he was just probing for various ways to skin that cat ... oops ... wrong metaphor.

Yes......I was enquiring to see if anyone else had other solutions to this.....(skin the cat is fine with me! 😀)

A KD roughed bowl doesn't have that much appeal to me in the first place, because I have an inventory of roughed bowls that are ready to finish turn, and I'd much rather naturally season them, if I have a choice in the matter. I want to be the one who is in full control of the roughed shape and size of the tenon. There are exceptions to that, of course, and if I feel an exceptionally promising KD roughed bowl comes along, I'd much rather put it in my chuck and do some manual adjustments by eye before proceeding. If the tenon falls within that "dead zone"......well, I think you can understand what it is I'm attempting to avoid. Dry KD, or seasoned roughed bowls have warping and distorting, and to add another procedure to the process adds yet another element of variable.

All of this is of little consequence anyway......because I don't acquire very many KD roughed bowls.....maybe 2 or 3% of what I purchase, at the most. It seems to me that the best solution for my needs, is to get a chuck that covers the size tenons my Stronghold chucks don't.

ko

 

[Owen Lowe]

Matter of fact, I have a set of #2 tower jaws, but mine only open to 3 3/8 for a spigot.....same as the standard jaws.
ko

Odie,
I’m assuming you know this already, but perhaps you hadn’t remembered...

The Oneway chucks have limiting grooves milled into the body and a matching pin in one of the jaws. One groove allows greater opening diameter than the other. If you are using the short groove, this may be the reason you aren’t getting the wide-open diameter that others are.

 

[hockenbery]

Odie, I’m assuming you know this already, but perhaps you hadn’t remembered... The Oneway chucks have limiting grooves milled into the body and a matching pin in one of the jaws. One groove allows greater opening diameter than the other. If you are using the short groove, this may be the reason you aren’t getting the wide-open diameter that others are.

I have set with no pins thanks to a bear of a student who was stuck like Kelly with a tenon too large. Sheared the pin right off....
Actually the pin is in there it is just now flush.

ONEWAY advertises the # 3 Strong hold jaws closing to a 3 7/8 tenon and the #2 Stonghold jaws opening to 3 1/2 inches
A tenon 3 5/8 or 3 3/4 is Too big for #2 and to small for the # 3 jaws.

The standard solution of truing the tenon to a size to fit the chuck is not one that Kelly uses.

Al

 

[Odie]

Odie,
I’m assuming you know this already, but perhaps you hadn’t remembered...

The Oneway chucks have limiting grooves milled into the body and a matching pin in one of the jaws. One groove allows greater opening diameter than the other. If you are using the short groove, this may be the reason you aren’t getting the wide-open diameter that others are.

Thanks Owen......

My chuck jaws are always set to the long groove in the chuck body.

As for the specs.......just because a chuck will open to the manufacturer's maximum specifications, doesn't mean it's always practical at that diameter. I've trimmed all my maximum tenon specs a small amount, in order to avoid the probability of encountering additional conflicts. If a tenon is cut to the maximum diameter possible for a given chuck/jaw combination, it will fit under the most ideal circumstances. Since there is wood movement between the time the tenon is cut on an unseasoned roughed bowl, and when it's fully seasoned, the most ideal circumstances are good on paper, but in practice there are times when wood movement becomes an additional obstacle which prevents the absolute maximum diameter tenon to be a practical diameter to use.

I have been using the specifications I have written down in my shop for reference. They are the specifications I've been using for approximately 25 years, and if I went out to the shop and physically measured the maximum opening using #2 jaws, that measurement would probably be closer to 3 1/2". To tell you the truth, I had not remembered about this when I started this thread, but would have made no difference in my needs, or what it is I'm trying to accomplish with my methods.

ko

 

[hockenbery]

If a tenon is cut to the maximum diameter possible for a given chuck/jaw combination, it will fit under the most ideal circumstances. Since there is wood movement between the time the tenon is cut on an unseasoned roughed bowl, and when it's fully seasoned, the most ideal circumstances are good on paper, but in practice there are times when wood movement becomes an additional obstacle which prevents the absolute maximum diameter tenon to be a practical diameter to use. I have been using the specifications I have written down in my shop for reference. ko

I do all my rough turned tenons with #2 jaws at 2.5"
I do my bowls from half logs with the grain centered.
The tenon does not shrink in the vertical axis of the tree growth the line to the the two end grain sides ( longitudinal shrinkage)
It does shrink roughly at the radial shrinkage of the wood species in the other direction to the two side grain sides.

A 2" or larger tenon can always be turned from the dried tenon that was 2.5" in the wet wood.
The long axis of the dried tenon will be 2.5" the short axis of the dried tenon will be 2 1/4" if the wood had 10% radial shrinkage.
At 20% radial shrinkage the short axis is still 2". Most of our domestic hardwood have radial shrinkage of less than 10% and all are under 13%.

So a 2.5" wet tenon will always have a 2" round tenon in the dry wood.

Al

 

[Odie]

I do all my rough turned tenons with #2 jaws at 2.5"
I do my bowls from half logs with the grain centered.
The tenon does not shrink in the vertical axis of the tree growth the line to the the two end grain sides ( longitudinal shrinkage)
It does shrink roughly at the radial shrinkage of the wood species in the other direction to the two side grain sides.

A 2" or larger tenon can always be turned from the dried tenon that was 2.5" in the wet wood.
The long axis of the dried tenon will be 2.5" the short axis of the dried tenon will be 2 1/4" if the wood had 10% radial shrinkage.
At 20% radial shrinkage the short axis is still 2". Most of our domestic hardwood have radial shrinkage of less than 10% and all are under 13%.

So a 2.5" wet tenon will always have a 2" round tenon in the dry wood.

Al

Your findings, and my findings are not the same, Al.......

What I've found is the tenon will significantly reduce in diameter with the long grain.....same as you......while the diameter will increase a very minute amount at the end grain. If the tenon is cut to the maximum possible diameter the chuck/jaw combination will allow, it become problematic to re-install it. In this case, one method of remedying this, is to re-turn the tenon, such as you are doing.

If the tenon was originally cut significantly into the unusable "dead zone", such as those KD roughed bowls I purchase on occasion, I was hoping to find someone on the forum who has found some method of dealing with it without re-turning the tenon. This is what I was originally trying to find out.

Regardless of that, I thought I had already mentioned that I'd rather not re-turn the tenon, if there were any choice in the matter....since it does introduce another variable. No tenon I originally turned has ever been so far out of round that I couldn't reinstall it on the chuck/jaws it was originally turned on. That is, since that time long ago, when I first adjusted for the variables. I have reduced the problems to be minimal by adjusting the parameters I allow.

ko

 

[hockenbery]

Your findings, and my findings are not the same, Al....... What I've found is the tenon will significantly reduce in diameter with the long grain.....same as you......while the diameter will increase a very minute amount at the end grain. If the tenon is cut to the maximum possible diameter the chuck/jaw combination will allow, it become problematic to re-install it. In this case, one method of remedying this, is to re-turn the tenon, such as you are doing. If the tenon was originally cut significantly into the unusable "dead zone", such as those KD roughed bowls I purchase on occasion, I was hoping to find someone on the forum who has found some method of dealing with it without re-turning the tenon. This is what I was originally trying to find out. Regardless of that, I thought I had already mentioned that I'd rather not re-turn the tenon, if there were any choice in the matter....since it does introduce another variable. No tenon I originally turned has ever been so far out of round that I couldn't reinstall it on the chuck/jaws it was originally turned on. That is, since that time long ago, when I first adjusted for the variables. I have reduced the problems to be minimal by adjusting the parameters I allow. ko

Kelly,
Wood does not stretch as it drys. Longitudinal shrinkage does occur but it is very small much less than 1%. virtually 0.

The larger lengths you observed may be the result of some tension wood movement in the tenon or a tenon compressed by the chuck returning to its length.
In some cases the tangential shrinkage could push the endgrain out slightly from tension it creates.
Also a slightly over sized green tenon can be wedged into a chuck that cannot be wedged in when it is dry.

In any event if you turn green tenons at 2.5 " diameter for #2 jaws they are always going to fit in the number 2 jaws and they won't be round and there will not be a flat surface for the tops of the jaws.

I reverse chuck dried bowls between centers using the center of the tenon, line up the rim, returning the outside and returning the tenon gives me the largest outside diameter bowl and allows me to follow and refine the nice curve I put on my roughed out bowls. I used to return a small bowls 10" or so without reverse chucking. The small bowls don't have the mass to create a lot of vibration.
Reverse chucking over the open chuck is so fast and easy I do it on all bowls. Turning the outside with the rim facing the headstock gives me the best view of the curve. Your woodfast has a good locking tailstock and is quite capable of turning between centers.

With your focus on precision, I would think you would reverse chuck to turn an accurate tenon, minimize vibration, and take advantage of the curve in the dried bowls.

Al

 

[Grant Wilkinson]

waste blocks?

KO

I wonder if one solution may be to use waste blocks for your tenons, instead of the wet blank. I've done a few pieces from wet where I did not want to lose even the small bit that I would lose when I turned off the tenon. I flattened the bottom where I would have usually cut the tenon and attached a waste block. Then, I turned the tenon in the waste block. At that point, I could use either a chuck or a faceplate, obviously. I've been lucky, I guess, that when the blank dried, the waste block held. Since the waste block I used - and I've used the same one a few times now - was dried wood, I was able to rechuck it months later when the blank had dried.

Just a thought ....

ps: KO, your PM inbox is full and can't received any more PM's

 

[hockenbery]

KO I wonder if one solution may be to use waste blocks for your tenons, instead of the wet blank. I've done a few pieces from wet where I did not want to lose even the small bit that I would lose when I turned off the tenon. I flattened the bottom where I would have usually cut the tenon and attached a waste block. Then, I turned the tenon in the waste block. At that point, I could use either a chuck or a faceplate, obviously. I've been lucky, I guess, that when the blank dried, the waste block held. Since the waste block I used - and I've used the same one a few times now - was dried wood, I was able to rechuck it months later when the blank had dried. Just a thought .... ps: KO, your PM inbox is full and can't received any more PM's

I do the same but a bit differently. Glue blocks are great for saving wood, especially crotch figure.
What glue did you use?

I use thick CA with a waste block of dry wood and green wood blank. Both glue block and waste block have slightly concave surfaces turned in them. I have a small center hole through the glue block and make a small indent in the center of the bowl bottom by twisting a small drill bit in my fingers. A straight piece of coat hanger lines them up. Two beads of CA on the waste block, accelerator in the bowl, slide the waste block down the coat hanger and twist. The twist is critical; it spreads the glue out into the matching concave spaces making a wide glue area with a lot of contact. Without the twist the CA will dry in the beads and just contact on the top of the beads and fail.

This method can be about as fast as using a chuck and it saves wood. I take the waste block off before drying. A flat chisel in the glue joint fractures the CA( one of the few glues not stronger than the wood) A CA glue block will come off with the first wood movement so l do all the wet turning in a half hour or so.

I do this mostly with wood I will turn once but it is easy to true the mounting surfaces and reattach the glue block using CA.
Glue block just needs the glue turned off to re-use them The glue block will last for a hundred bowls or so.

AL

 

[Odie]

KO

I wonder if one solution may be to use waste blocks for your tenons, instead of the wet blank. I've done a few pieces from wet where I did not want to lose even the small bit that I would lose when I turned off the tenon. I flattened the bottom where I would have usually cut the tenon and attached a waste block. Then, I turned the tenon in the waste block. At that point, I could use either a chuck or a faceplate, obviously. I've been lucky, I guess, that when the blank dried, the waste block held. Since the waste block I used - and I've used the same one a few times now - was dried wood, I was able to rechuck it months later when the blank had dried.

Just a thought ....

ps: KO, your PM inbox is full and can't received any more PM's

Thanks, Grant.....I just cleaned out my inbox.

I'm not having any problem with any tenons I make, as long as I make them to the specifications I've allowed myself. The only problem I've ever had is making the tenon to the absolute maximum diameter the chuck will allow, and after seasoning not able to get them back in the chuck. Regardless, this is such an insignificant problem, because I've covered this aspect by making tenons just a bit smaller.

Every one of my bowls eventually get a waste block prior to finishing the bowl.....it's my standard. I've never had much success gluing a waste block to an unseasoned roughed bowl, due to the uneven drying of the two pieces of wood. If I'm not mistaken, I believe I've heard someone say they used a super glue for doing this....not sure about that. Regardless, I'd rather use a tenon on the wet wood, until after the seasoning process is completed. After stabilization is completed, I then attach the waste block. Never has been a problem gluing up, at that point.

Curious, though......What kind of glue were you using to attach your waste block to wet wood?

ko

 

[robo hippy]

I think dimensional lumber moves differently than bowls. The 10% rule works on some woods, but not others like Madrone, which is my favorite just because it is so weird. I turned one bowl that came off the lathe at 22 inch diameter. When it was done drying, it measured 27 by 17 inches. The recess, of course, went oval as well, and pretty much 'expanded' along the end grain line. I wouldn't think of trying to use a tenon on Madrone because the extra thickness would most likely make it split. The excessive movement could make it impossible to return the tenon to fit the same jaws that were originally used. With lumber, there is always minimal movement along the end grain, and much more along the side grain.

robo hippy

 

[hockenbery]

I think dimensional lumber moves differently than bowls. The 10% rule works on some woods, but not others like Madrone, which is my favorite just because it is so weird. I turned one bowl that came off the lathe at 22 inch diameter. When it was done drying, it measured 27 by 17 inches. The recess, of course, went oval as well, and pretty much 'expanded' along the end grain line. I wouldn't think of trying to use a tenon on Madrone because the extra thickness would most likely make it split. The excessive movement could make it impossible to return the tenon to fit the same jaws that were originally used. With lumber, there is always minimal movement along the end grain, and much more along the side grain. robo hippy

Reed,
Madrone is another beast entirely. Madrone does obey the shrinkage laws as best it can. Madrone has a tangential shrinkage of 12.4% and a radial shrinkage of 5.6%. Maybe the largest difference in any wood commonly turned. That huge radial shrinkage creates a lot of stress. Thin work bends to relieve the stress; thick work dries and if the stress is too much cracks, If you had a foam bowl and pushed opposite sides down toward the bottom to simulate the radial shrinkage, the two opposite ends would push out like your bowl,

With thin work another phenomenon, telescoping, takes place. The outer growth rings squeeze the inner ring out. If you took a look at the video of my demo on natural edge crotch bowls I show a pith in crotch bowl about an 1/8" wall thickness. The three piths all poke out in a bump about a 1/2".
This can only happen in thin work maybe a 1/4" wall at most.

The grain direction of crotch bowls provide an interesting study of wood shrinkage. In the half log bowls the tangential shrinkage takes place around the three piths that form a Y. The inside center of the bowl rise up in a bump.

Also keep in mind that the percents in tables are the expected shrinkage for the species and an individual tree may shrink more or less than the average..

Al

 

[bowlman]

What size tenon ...

I am using three stronghold chucks, and for correct tenon sizing to fit the #2 and #3 jaws, they must be from 1 7/8" to 3 3/8", and 3 3/4" to 5 1/4" in diameter.

You can see there is a gap between 3 3/8" and 3 3/4" where a tenon within this range simply won't fit my chucks. That you know of, are there any other options for me, that I'm not thinking of, that will enable me to use my Stronghold chucks for tenons that are within this unusable range?

For those of you who are using other makes of chucks, are you experiencing similar gaps in sizes of tenons you cannot use?

Which brands of chucks, and available jaw sizes fit tenons between 3 3/8 and 3 3/4" ?

ko

For those blanks where the tenon falls in the gap, do this ...

Mount your chuck on the lathe. Place the bowl inside bottom against the jaws of the chuck. Bring the tailstock up to as close to center of the tenon as you can get. (If the dimple from roughing out is there, use that). Tighten the tailstock and the live center down. Start at 0.0 rpms, slowly increase speed, and resize the tenon yourself, to fit your jaws. Easy as pie!

 

[Odie]

For those blanks where the tenon falls in the gap, do this ...

Mount your chuck on the lathe. Place the bowl inside bottom against the jaws of the chuck. Bring the tailstock up to as close to center of the tenon as you can get. (If the dimple from roughing out is there, use that). Tighten the tailstock and the live center down. Start at 0.0 rpms, slowly increase speed, and resize the tenon yourself, to fit your jaws. Easy as pie!

Howdy bowlman.......You are not the first to suggest this. I was hoping to find some creative alternatives to re-turning the tenon, which subsequently alters the original orbit. This will make little difference for a bowl that has very little warp, or could be more so with a warp that is significant. How well the operator can adjust for the original orbit, could be a factor, as well. Unless there are any viable suggestions to come up, it looks like I may be chasing a ghost!

It's always much less difficult to do what others before you have done before......but, what is most challenging, is to do what very few, or nobody has done, or thought of before. Until someone does what is generally thought to be impossible, the general consensus is that it IS impossible! 🙄

ko

 

[hockenbery]

Again,

I mount the dried bowl between centers with

1 the tail stock in the center of the tenon ( rough turned center ideal) and
2. The chuck pressed against the inside bottom with the rim adjusted so the two high points of the rim and the two low points of the rim are in the same plane equal distance from the headstock respecively.
Then true the rim, true the tenon, true the notion of the foot( to be finished last) , turn the curve from foot to rim.
Mount in the chuck, ( true outside if necessary), turn the inside, reverse turn to finish the foot.

Not sure how you might get closer to the center of the bowl that is in the warped bowl than that. If you find a way share it with us.

Mounting the oval tenon in a chuck doesn't work nearly as well, I used to do that.


Al