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Question about recess for Oneway Talon smooth dovetail jaws...

B

Barry Larson

Joined
Jan 23, 2023
Messages
194
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316
Location
Calgary, AB
Hi.
Before I re-embark on the process of re-learning some turning skills that have been unused way too long I have a rather simple question. Let me start by saying I have been away from turning for the better part of 25 years - long story, but primarily day job got in the way! Back then the few bowls I turned were done with faceplates as that was the technology I was familiar with and possessed. That said, times have changed and it's time to embrace some different technology - hopefully easier and better. The bowl blanks I have are small, approx. 6 inches in diameter and 1-1/2 inches thick - big enough for a couple of small, shallow bowls for practice. Because of the thin material I will use a faceplate and glue block on what will be the top of the bowl and turn the bottom/sides to finish and create a recess for #2 smooth dovetail jaws (Oneway Talon chuck) to turn the top and inside. My question is how deep to turn the dovetail recess for the jaws? The dovetail portion on the jaws appears to be about 1/4 inch, so is this the right depth for the recess or should it be more? Less? How critical is the depth - is there a rule of thumb for depth vs bowl size? How does my procedure sound overall? I guess this ended up being more than one question! Any and all advice is appreciated. Thanks in advance.
Barry W. Larson
Calgary, Alberta, Canada eh!
 
I don't very often use a recess but I'd think you'd only need a depth of maybe 1/8th inch for a recess on a small bowl like that, maybe a little deeper while you're freshening your skills. You will want to ensure that there's a decent amount of wood surrounding the recess so you can't overtighten and split the blank. Others will be along with a far better explanation in sure.
Have you looked into the wood turners guild down there in Calgary?
 
What is more important than the depth is how much wood is outside the mortiss. Also the size of the piece. 1/8" deep is fine for platters. For a large bowl probably not.
 
Thanks guys. I'll go with about 1/8" to 3/16". The blanks are pretty small and since I'm rusty at this I'll take it slow to start. Another question just occurred to me. If I was to use a tenon instead of a recess (I can't on these blanks because of thickness) what's a good length for a tenon, either with the smooth, dovetail jaws or with the serrated jaws?
Cheers. Be safe and stay well.
Barry
 
Tenon and recess depth can be the same. On blanks the size of the ones you have, and I guess they are dry, I would use a glue block and paper bag glue trick to max out the thickness. Finish turn the outside, glue the waste block on, then turn the waste block true, then reverse and turn the inside. Like John said, having enough shoulder is at least as important as is having the correct depth. With a 1/2 inch wide shoulder, you would have trouble destroying that one unless you were turning at super sonic speeds and had the mother of all catches....

robo hippy
 
Barry Larson said:
length for a tenon, either with the smooth, dovetail jaws or with the serrated jaws
Click to expand...
A ftat ring around the tenon that sits on the tops of the jaws adds lots of stability.

with dovetail jaws 1/8” tenons work well for me.
With serrated jaws and ONEWAY profile jaws I like the tenon length to be in the space below the teeth. If the top of the tenon is even with a tooth the closing jaws a can push the tenon up over that tooth. The top of the tenon should never touch the jaws.
 
Thanks again.
Reed. Thanks for the thought on the glue block - actually you turned my original thoughts on the glue block around, but I believe your suggestion would allow some flexibility with turning the base of the bowl - a design opportunity! I have two blanks and could make more so I think I'll experiment a bit. I won't be doing any supersonic turning - at least not in the near future!
Hockenbery, thanks for the tenon advice. Just so I am clear. The top of the tenon (furthest from the base of the turning) should be below the last serrations on the serrated jaws if using, but not so long as to hit the jaws where they attach to the chuck body? I assume it is ok to have the body of the turning resting fully on the top of the jaws?
Guy. Nice piece. Once I get more comfortable with turning again I may try something similar.
Be safe and stay well.
Barry
 
Barry Larson said:
Just so I am clear. The top of the tenon (furthest from the base of the turning) should be below the last serrations on the serrated jaws if using, but not so long as to hit the jaws where they attach to the chuck body? I assume it is ok to have the body of the turning resting fully on the top of the jaws?
Click to expand...
Yes
And a flat resting on the top of the jaws isgood
 
Ah yes the power of a splitting wedge. I'm familiar with the concept in other areas of woodworking - like putting in screws and threaded inserts!
Thanks. Be safe and stay well.
Barry
 
Barry Larson said:
I assume it is ok to have the body of the turning resting fully on the top of the jaws?
Click to expand...
Not just OK, it's ESSENTIAL. For these small blanks, it probably wouldn't make a difference, but as you go bigger, it becomes critical. The flat surface of the jaws against the flat surface of the wood is what gives the connection it's strength and stability.
 
The OneWay chucks usually come with a wood worm screw and that can be useful in two ways; first install the screw in the jaws then measure the diameter of the jaws, which should be about 2 3/8", and make a sketch of a recess with that dimension. Next drill about a 1" deep 3/8" hole into the wood that will become the inside of the bowl and mount the blank on the screw. Turn the outside of the bowl including the 1/8th to 3/16" deep recess to the diameter previously measured, dismount from the screw, remove the screw from the chuck, close the jaws, place the blank over the jaws and open the jaws until they grip the blank. The true circle will firmly hold the piece without excessive (splitting) force.
 
Thanks to all who responded. I'm in the process of applying the advise I received. Stay tuned for further developments!
Cheers. Be safe and stay well.
Barry
 
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