Turning a bowl tenon for chuck

[Chris Barnett]

Forgot what tool is suitable to turn a tenon :o Have only turned a few and they were a piece of cake, but my bowl gouge or parting tool do not seem to fit into root, unless a parting tool can be used flat, and a bit worried to use skew...they are looking so promising though. Had changed my bowl gouge from fingernail back to basic grind since I could not seem to duplicate the fingernail, so think I may have changed the tool profile that worked so well. You-Tube has been less than helpful on this one. Am embarassed to ask for help on something so simple...

[John Keeton]

Chris, I think you will get varied responses to this question. I normally use a 1/2" bowl gouge with deeply swept back wings, and a small working bevel of about 1/8" - 3/16". However, it would seem a parting tool would work fine.

You don't say what kind of chuck you have, but Nova (Teknatool) does not recommend a dovetail shaped tenon. For the Nova chucks, you need a tenon that is square edged, and not over 1/4" long for most purposes. In fact, the dovetail "crushing" action of the jaws really require about a 3/16" tenon.

[Hilel Salomon]

Hi Chris,
It depends on the chuck you are going to use. If it's a Oneway, then a straight tenon can be achieved with a parting tool, bedan or a finger nail bowl gouge. The Vicmarcs and Novas use an angled tenon and I've seen these cut using all of the above tools w/a turn at the end for the bedan and parting tools. I am going to get a lot of grief but I do use an angled skew almost all the time. I don't use the skew for much else and it works for me. I now don't cut too big of a tenon (depth wise or circumference) so a light plunging cut with the skew (when I've gotten to the right circumference) as the finishing cut to achieve the angle works just fine.

Hilel

[Chris Barnett]

Yes, I use only Nova II and Titan chucks but did not know not to cut a dovetail. Class I took had us cutting a dovetail on their Nova chucks. But if that is the case, I already have the square tenon cut. I could not get the tool into the corner without taking out the rear flat to support the chuck face, and thought the parting tool would maybe break or bend or catch if I used in flat, although it seems the perfect tool to use in that application. Will go ahead and chuck it up then see how it goes. The long sweptback wings is what I ground off.... I need to rethink my action. A reground bowl gouge to a point tool might be the ticket. Hilel, I can easily see how well a skew would work. I have three skews, two from a set, but have mastered none; I have used a skew but a few times...very carefully. Last time I used the larger skew...actually trying to cut the dovetail, I had a catch and it went back to the rack for a few more months.
Thanks.

[Jim Burr]

You can try a dovetail gouge...included in the CSUSA set I bought 10 years ago.

[John Keeton]

Hi Chris,
The Vicmarcs and Novas use an angled tenon....

HilelThis topic has come up several times, and while I have no knowledge of the Vicmarc chuck, the Teknatool manual is explicit on the formation of a spigot tenon - quote from page 13 -

Make the spigot as parallel as possible to maximise the efficiency of the clamping action. Only approximate sizing of the spigot is necessary, as the jaws will accommodate a wide range of spigot diameters within the spigot limits stated above. The 50mm standard jaw has a thin lip or shoulder at the front face. This is designed to bite into the timber as the jaws are tightened. DO NOT CUT A RECESS FOR THE LIP TO FIT INTO, AS THIS WILL REDUCE GRIPPING POWER.

When forming a "recess" (vs. a spigot), the process does require a dovetail recess, and that process is covered on pages 12-13 of the SN2 manual.

Again, other chucks may require a dovetail spigot/tenon, but the whole premise behind the interior dovetail on the Nova jaws is to compress the wood to achieve a "bite".

[Prashun Patel]

I just bought a 1/4" detail gouge that is perfect for this.

I use a 1/2" or 3/8" bowl gouge to get the rough depth of the tenon, then the 1/4" detail to sneak up on the fit.

Prior to this, I DID use a skew but only at the end, after I did as much possible work with the gouges.

[Sean Hughto]

For my one-way (straight NOT dovetail) chucks, I shape the square sides and small flat at the base of the bowl with a scraper (several shapes are suitable from spear point to square to slightly curved).

[Scott Hackler]

I might start the tenon with a gouge, just to remove some surrounding stock.... but.... 95% of the time I use a parting tool for the whole thing. Either coming in from the tail stock side (more difficult because the tail stock is kinda in the way) or if it's a spindle type turning I just part the end into a tenon.

I will also meantion that I made a crude gauge out of wood to see when I am at the correct diameter on my tenon. It doesnt look professional (I made it in 30 seconds on the band saw) but it works good and it was free!

[Jamie Donaldson]

Just whip out the parting tool and do it! Make sure that the tenon shoulders that meet the chuck jaws are square, and that the tenon is not so long that it bottoms out on the chuck. Don't get too confident with a short tenon either- it produces projectiles and other bad effects!

[Reed Gray]

A bedan, or sizing/beading and parting tool (wide parting tool actually) will work. A specialized dove tailed scraper will do if you need a dove tail. You can rough it in with standard gouges, and then clean it up with a spindle/detail type gouge which tends to be more pointy. You can use a skew like a scraper to clean it up. You do want the final cut to be clean, the bowl bottom to be square to the tenon, and the angles to match. I do tend to make a feather light cut, just barely touching the wood to remove most of the run out/bumps so when I reverse, it will mount more truly.

robo hippy

[Kyle Iwamoto]

Wow, I have Novas, and I've been cuttng a dovetail tenon for years...... I guess I better stop.

Who reads instructions anyways?

Oh, for ME, that's one of the uses for a skew. BUT since I no longer should cut a dovetail, I'd use a parting tool, and make a square shoulder. I guess I can retire my skews, since I can't think of another reason to use them... LOL

[Michael Mills]

I made my own dovetail tool but Nova does sell one. I made mine from an old bench chisel but a stout flat-tip screwdriver which has been ground on the side to the 15* angle works just as well. When and If a dovetail is suggested, I cut the tenon or recess with a parting tool. Once open a slight side movement (scrape) cuts the dovetail. You are removing a very small amount of wood.
That said, here are Nova instructions for forming a dovetail with a skew (when a dovetail is required). “The jaw dovetail has been designed for use with a standard skew scraper.” You will note they state also “Before scraping out the recess…”
Forming Recess http://www.teknatool.com/products/Chucks/SuperNova2/Downloads/SuperNova2 Manual Sheet_Jun07.pdf (http://www.teknatool.com/products/Chucks/SuperNova2/Downloads/SuperNova2 Manual Sheet_Jun07.pdf)

As far as length/depth of a tenon/spigot… and Jamie D.’s comment above … “Don't get too confident with a short tenon either- it produces projectiles and other bad effects!

I agree…
If you go to Nova’s jaw manual which John K. referenced above http://www.teknatool.com/products/chuck_accessories/General/downloads/Accessory Jaw Manual_Nov07.pdf (http://www.teknatool.com/products/chuck_accessories/General/downloads/Accessory Jaw Manual_Nov07.pdf)

Page 20 for the 50mm Jaw Set also states for a spigot
“Spigot Depth: The length of the spigot area must not be less than 16mm (5/8”).”

Page 36 for the Powergrip Jaws states for REVERSE Dovetails
“Spigot Depth: Always use the maximum spigot depth which is 12.5mm. ”At one time they gave the spigot depth in SPIGOT operation (not Reverse Dovetail operation) as a minimum of about 1-1/4” with the Powergips. They no longer list this data. However, on page 39 for the Titan Powergrip Jaws they state…” Always use the maximum spigot depth of 40mm (1.57”).”
You also do not cut a dovetail in the Spigot mode, only in the Reverse Dovetail mode with these jaws.

[Jon Nuckles]

+1 on Prashun's method. A quick rough size with a bowl gouge followed by a pass or two with a detail gouge from both directions toward the 90 degree corner of the tenon and bottom of the piece (along the side of the tenon and along the base of the piece) leaves a much cleaner seat than I can achieve with a parting tool.

[Jamie Donaldson]

Kyle- skews make great negative rake scrapers!

[Hilel Salomon]

INCREDIBLE!!! I mean my taking issue with Nova's instruction manual and even-to some degree- with far better turners than me. It isn't false modesty to preface this with a sincere admission that I am a very mediocre turner. But I sure have made hundreds of bowls. Nova says don't cut dovetails, and don't worry too much about the circumference because jaws can be rotated to larger diameters. Nova's jaws are dovetailed exactly in the same way as Vicmarc's. Everyone I have ever seen using Vicmarc chucks calls for making the tenon dovetailed. That's what I've been doing all along on both my Vicmarcs and my Nova's. True, I never make the dovetail quite as pronounced as the jaws, and I do look for the jaws to bite into the wood, but I do make the tenons dovetailed. Now I know that all the chucks can be made to accommodate wider tenons (spigots) than the smallest of their diameters, but again, every demonstrator I've seen has said that it is far better to have the chuck's jaws make a tight circle and present a greater percentage of metal on wood. It makes sense to me and that's what I've done. I used to make tenons as wide as possible and as deep as possible but, in my experience the tighter the circle the chuck's jaws make, the the better the grip. As for length of tenon, my experience is that the longer the tenon, the more torque and the more chance of the tenon breaking. Obviously, a lot has to do with the size of the bowl and the type and strength of the wood, but I generally make the length of the tenon about 1/2 the depth of the jaws. The variety of wood and the variety of sizes I make is one reason that I have so many chucks and so many jaws. Anyway, I have never had a problem using a skew to make the final dovetail cut and perhaps the reason for this is that I don't make the tenon too deep.
Truthfully, I am much more of a learner on this forum than an advice giver, so the above is offered with misgivings.
Hilel

[Rusty Smith]

Wow Hilel, I've been doing chucking the exact same way as you describe and for the exact same reasons. I use my skew as a scraper using the angle as the guide for the dovetail. Now I'm not sure what to think.

[Greg Just]

I have the SN2 and have always cut dovetail tenons with my detail gouge and I have never had a problem. This is how I was taught. Oh well!

[John Keeton]

Since I was the "quoter" or the manual, I guess I need to comment on the length of the tenon. I had never read that part, and developed my "short tenon" philosophy from the previous comments of other, more experienced turners. There have been numerous threads on this topic, including this one (http://www.sawmillcreek.org/showthread.php?148486-Broken-Tenon-s). I routinely use waste blocks approximately 2" in diameter, with a pre-cut 3/16" tenon on them. I make them in batches, and glue them on the bottom of wood with 5-minute epoxy, centered by a circle drawn with a compass on the bottom of the blank using the center mark from the tailstock or one made manually if the piece has not been on the lathe. I have had no problems with this method, and I have hollowed several pieces without a steady.

That said, I would have to acknowledge that apparently Teknatool recommends a 5/8" tenon, notwithstanding that I think it could cause issues as pointed out in the referenced thread.

[John Beaver]

I have an old parting tool that I grind with the same angle as the dovetail. It's fast, easy, and repeatable.
For making recesses with the tail stock in place, I made a tool handle with an allen wrench bent at 90 degrees and ground with the dovetail angle on it so I can get around the tail stock and center.
____________________________

The goal is to get the dovetail jaws as close to a circle as possible. This means making the tenon diameter slightly larger then the diameter of the jaws when they are closed. If you do this right you get maximum holding power with minimum marking from the jaws.
_____________________________

Vicmarc recommends "a dovetail tenon 5mm-10mm deep, or a dovetail recess with a minimum depth of 5mm-10mm."
I think you still have to evaluate the wood and determine if the tenon is capable of withstanding those dimensions.

[Jamie Donaldson]

There is 1 important fact y'all are overlooking when making the tenon as small in diameter as the chuck jaws, and that is the fact that a small diameter wood tenon is weaker than a larger diameter tenon. Which do you believe is the weaker material you are trying to grip, the steel chuck jaws, or the wooden tenon? I have been turning bowls of all sizes, with chucks of all sizes, on lathes of all sizes for 25 yrs. and can't honestly remember the last time I ever had a tenon break off. Most all chuck jaws allow a tenon max. length of 1/2," and the tenon should never be touching the bottom of the jaws. But a longer tenon reduces a tendancy for the blank to shift or torque sideways in the jaws, and I am certainly not a timid turner, especially when I'm turning natural edged pieces. I also turn lots of spalted maple, and the larger diameter tenon assures a more secure grip with #2 jaws. I make sure that the wood is sound before mounting, never worry about cutting a dovetail, and don't try to crush the wood with the chuck key when tightening. I rough out the form between centers, form the tenon, reverse mount in the chuck and secure with the tailstock while truing up the outside before going to the inside. I then remove the tailstock and shoooo away all potential catches, whatever they are, and remove the interior- no big deal!

[Mike Peace]

...If you go to Nova’s jaw manual which John K. referenced above http://www.teknatool.com/products/chuck_accessories/General/downloads/Accessory Jaw Manual_Nov07.pdf (http://www.teknatool.com/products/chuck_accessories/General/downloads/Accessory%20Jaw%20Manual_Nov07.pdf)

Page 20 for the 50mm Jaw Set also states for a spigot
“Spigot Depth: The length of the spigot area must not be less than 16mm (5/8”).”


I am with John K. in never reading the recommended spigot length. I tend to have mine at about 3/8". I wonder if this is another of Teknatool's documentation errors since the depth of the inside of the 50mm jaws I measure to be just under 1/2". You clearly cannot safely use a 5/8" tenon or it will bottom out!

[Scott Hackler]

I definitely make my tenons 3/8" tall and I know this because I use 3 widths of my 1/8" parting tool. I will say though that an extra large blank might get 3 1/2" widths of the tool and a light weight / thin platter might only get 2 widths!