any advice on tenons?

[Bob Bachynsky]

Hi all,
Just thought I'd see if anyone has any tips on making tenons easier. I'm pretty new at this but it seems like no two of mine are alike lol. Sometimes I nail it and my project stays on and steady other times i feel like I'm picking my piece off the floor a half dozen times. Are there any tricks, maybe a jig or something, to help a newbie make good tenons?

[John Keeton]

It may be helpful to know which brand of chuck you are using?

[Bob Bachynsky]

I have a Barracuda 2 (PSI). Same style as a nova for the most part although it doesn't have the dovetail angle.

http://www.pennstateind.com/store/CSC3000C.html?gclid=CjwKEAjw2ImsBRCnjq70n_amv14SJA ChXijNLSepRFJSX306NSjUO-3pOq0DjsoMoEVAtjgZN7zCkxoCy0Lw_wcB

[Peter Blair]

Bob. Check out this thread
https://www.youtube.com/watch?v=5KHkkws9lWA
Reed Gray does excellent videos.
Wish he was doing them when I started turning.
Would have saved me a bunch of time on the old 'learning curve'!

[Peter Fabricius]

Bob, there is a UTube video by Mike Peace and he goes through all (?) the possible methods of "work holding" I think that is the title of the video.
Normally for your Profile style jaws the tenon should be about 3/8" long and a "slight" taper / dovetail will not hurt, it might improve the hold. Just be sure the work piece is seated against the face of the jaws and DO NOT bottom out inside the back of the jaws. Tighten the jaws occasionally to make sure they are not working loose, especially in softer woods.
If you are loosing your work across the shop floor it is possible that you are taking too deep cuts or you are getting catches??? Review your tool presentation with a mentor and always stay out of the line of fire.
Peter F.

[Thom Sturgill]

I had a lot of problems with the Barracuda chucks when I started. There were two issues - me and the jaws. Learning to get the tenon face FLAT and making the tenon shallow enough to not bottom out is important. The other was swapping the default jaws for the optional dovetail jaws PSI sells. The default jaws have two small ridges on the inside. They are just not deep enough to get a good bite, IMHO.

[Dan Forman]

I think I can see the source of your difficulty in the pic in the link you posted. This is a takeoff on the Oneway profiled jaws, however there is a big problem here, as they have omitted the primary characteristic that makes the Oneway jaws so successful. If you go to this link, and click on the zoom icon, and compare the geometry of the jaws interior surface to that of the Penn State jaws, you will be able to see the difference, and what Penn State omitted on their version, which may be a patent issue. Oneway Talon Chuck System - Rockler Woodworking Tools (http://www.rockler.com/oneway-talon-chuck-system)

The Oneway jaws have two relatively flat sections milled into the interior face, which allow for a very firm grip on the tenon. These do not seem to be present on the Barracuda jaws, which appear to be just milled in a circular fashion. This means that unless the tenon is cut to the exact size of the jaws, the jaws will only be able to make contact with the tenon on the very corners, giving a very small surface area of grip. Even if you could manage to cut to exact size, the wood would compress and become loose eventually, and if turning green wood, you would have to return the tenon after it dried, and it would no longer hold.

The Oneway design has a much greater grip area and thus holding power, regardless of the tenon size. Dovetail jaws have the same limitation - only contacting the tenon at the jaw corners, but because they are dovetailed, they will have more holding power than your Barracuda. If you want to keep the chuck you have, and keep pieces on your lathe, I think you will have to exchange the profiled jaws to dovetailed jaws. If you like the idea of making straight tenons, I would highly recommend the Oneway Talon with their profiled jaws. You will find they are a world apart from the jaws that are currently on your chuck.

Here are a couple of photo's to illustrate.

The first is what I would expect a tenon coming from your chuck jaws to look like, (only paying attention to the pencil marks). I suppose in reality they would actually be a bit farther apart. The second pic is the same tenon from my Oneway with the jaw marks highlighted in pencil. You can see that no matter the size of the tenon, they will have a lot of contact area, and hold quite firmly.

Dan

[Michael Mills]

I don't know of many jigs. The video by Reed Gray (ref Peter Blair) shows laying out a tenon or recess using divers which a lot of people do; this is about the 7min 30 second point.
Here is the link to the video referenced by Peter F by Mike Peace. If you haven't watched it already, it is worth the time (about 1.5 hours); at about the 1 hour, 5 minute point he shows a "go, no go" jig which is the max and minimum for each set of jaws. Similar to a set of open end wrenches.
https://www.youtube.com/watch?v=aUXil-5dEeo

Terminology may vary for the jaws. For me the "face" is the interior/exterior which tightens against the wood, the "top" of the jaws are what seats against the wood. The top of the jaws should sit flat and tight against the work. If the curve of the bowl continues all the way to the tenon then it can rock and not be supported making it much easier to orbit. IMHO this fit is more important than the fit of the jaws size.
In Mike Peace's video above he shows this about the 59 minute point.

Before everyone screams I do think the fit of the size tenon to the jaws is also very important. If you only have one set of jaws you may need to make the tenon 3/8" larger than optimum for the initial turning in order to re-true it for final turning. I have different jaws so I may cut the tenon to optimum size for 70mm on rough turning and resize down to 50mm for final turning. This allows a complete grip for each turning.

Another group of excellent video's which are about 10-15 minutes each are by Stuart Batty. Look for the ones on chucks, tenons, recesses, and similar...there are three in this group of about 35. He is very detailed as to how and why.
https://vimeo.com/woodturning/videos/sort:alphabetical/format:thumbnail

[Reed Gray]

I think it was on a Glen Lucas video where he had marks on his tool rest for tenon sizes, very efficient. There are many ways to mark them. Most of the time, I think there is not much of a trade off with a 3 inch tenon that is grabbed by jaws that close down to 1 1/2 inches. However, you have to be more delicate in your cutting, and no catches. Over sizing is necessary in twice turned bowls, or you have to have multiple jaw sets to cover every situation.

robo hippy

[Bob Bachynsky]

Great! You guys have given me plenty to look at and I will (plus a couple of youtubers I hadn't stumbled across yet). Thanks so much :)

[Thom Sturgill]

Capt Eddie also has a video, but the main thing is his go/no-go gauge for sizing the tenon or recess. If I remember correctly, it simply a notch on one side that the tenon should fit into giving the maximum opening for the jaws and the maximum depth without bottoming out. The other side is a 'tenon' of minimum width and maximum depth for recesses.

[Mark Greenbaum]

I just watched Robo Hippy's video, and learned quite a few new things. Thanks.

[robert baccus]

Or just buy a bottle of thick CA!!

[nelson lasaosa]

Hi Dan,
Excellent tec review , and for us newbies a free tutorial. Thanks !

[Dan Forman]

You're welcome.

Dan

[Geoff Whaling]

Bob, It pays to learn a little about the history of chuck design & the differences in chuck jaw profiles as each has a different requirement for tenon shape/profile to be ideal for a specific jaw design. Some rely upon a friction fit only & others have varying "mechanical" gripping designs i.e. "shark jaws."

I prefer to use mostly Vicmarc chucks with dovetail jaws with a single taper which I think may be about a 1:6 taper. My Nova midi chucks have a two "taper" system which is basically a mini dovetail and a pretty straight/parallel taper section. If I use my Escoulen chucks they come with a set of go/no-go gauges to size the taper required and rely on friction only by driving the work piece into the "mortise" of the chuck. So it is a case of making chuck/jaw specific tenons, “Vicmarc” design tenons don’t work so well in Nova chucks, & vice versa.

Next bit to understand is how the work piece "registers" into the chuck. The most simple tenon design to make is a long parallel tenon to fit a simple cup or socket chuck, but it has no additional mechanical gripping and the tenon diameter must be very precisely made to fit. Either it fits or it doesn’t and an allowance for compression of the timber must be made. Different timbers have different crushing strength. The registration surfaces are the tenon & chuck side wall. The next logical evolution / variation is tapered tenon & tapered cup chuck sides which still has the same registration surfaces but the added advantage that the tenon no longer has to be made so precisely. With both the work piece is driven into the mortise & really requires tail stock support or they will work loose.

Then wood turners started using metal machinists independent 3 jaw chucks with parallel jaw set designs, which still had the same short comings of using a parallel sided tenon. Turners evolved & adapted machinists chucks with dovetail jaw sets then moved to wood turning specific 4 jaw scroll chucks. Patent development, protection & licensing means that chuck and jaw designs vary across manufacturers, hence the different tenon design/making requirements.

Photo below is from an older acquaintance who modified this machinist chuck for recess holding in the 1970's.

So for 4 jaw woodturning scroll chucks the “registration surface/s” depend upon chuck/jaw design. For Vicmarc dovetail jaws the registration surface is the front of the jaw face and the "gripping" surface is the dovetail surface so it pays to cut a parallel matching surface on the rear of the bowl or spindle blank to match the jaw face, and a crisp corner and a matching dovetail. It is very important not to have the dovetail bottom out (i.e. to long a tenon) and that the rear or bottom of the tenon is fairly parallel to the registration surface. If they are not parallel it can/may cause wobble as the timber compresses at slightly different rates pushing the blank slightly off axis.

Scroll chuck jaws also have an ideal gripping range which gives maximum holding power, precision alignment & minimal problems with potential variations in crushing timber a different rates (think soft/hard, early/late growth rings etc). The ideal diameter is open slightly wider than the “perfect circle diameter” of the jawset. This is a whole subject on its own and a very contentious subject. Note that traditionally chuck jaws are manufactured in the “round” then sawn/machined into four jaws. Some newer jaw developments are cast.

Many turners rely upon the crushing power of shark jaw designs, personally I don’t like them for a number of reasons but mostly because I do not wet or green turn.

A couple of tips for making dovetail tenons, make a go/no-go gauge for each jaw set for the typical tenon diameter you prefer, and work out the jaw dovetail profile taper and match it “closely”, doesn’t have to be perfect. Pay attention to tenon diameter and to grain direction at the tenon, particularly how and in which direction it runs relative to the jaws or jaw dovetail. Max strength is spindle orientated grain, weakest is face plate (bowl) orientation with to small a tenon diameter for the bowl blank size. See SAWG "Spigots" tip, link below.

Glen Lucas & Mike Mahoney have excellent bowl turning tutorial DVD’s; Keith Rowley’s “Woodturning, a Foundation Course” & Mike Darlow’s books give pretty good advice and some history on chuck development. Another good reference source is the South Auckland Woodturning Guild (SAWG) website. http://www.sawg.org.nz/tipsnjigs/

[Bob Bachynsky]

See now I should have started this thread before ordering my barracuda :) lots of good info here. Thanks for the detailed explanation Geoff, I think I am starting to get the idea although I'm going to read it a few more times.

BTW for others here is the capt eddie vid:
https://www.youtube.com/watch?v=qATykxAuZ-E

[Geoff Whaling]

Stuart Batty has a very good series of videos - https://vimeo.com/68649130. Technically very accurate & professionally done videos. Stuart has an excellent pedigree as a turner & demonstrator.

[Jeffrey J Smith]

Looks like you've gotten good information here- I've found that, for my work (lots of greenwood and twice-turned bowls) smooth dovetailed jaws seem to hold best. I saw a video that Glenn Lucas had done where he showed a jig that was attached to his tailstock that sized his tenon consistently when he's production turning. As I recall, it was just a simple outrigger that indicated the correct diameter. He seems to work in large runs of similarly sized bowls, so the jig allows him to determine a standard size for the tenon to optimize the grip of a single set of jaws.
One thing that I haven't seen mentioned is the importance of a flat face or 'step' that contacts the front face of the jaws when the tenon is fully gripped. That flat face adds holding power and helps resist racking forces that can pull the tenon out of the jaws in the event of a catch. Ellsworth has a good description of this 'step' in his book. Also, make certain your tenon does not bottom out and contact the inside face of the jaws.

[Dan Forman]

One thing that I haven't seen mentioned is the importance of a flat face or 'step' that contacts the front face of the jaws when the tenon is fully gripped. That flat face adds holding power and helps resist racking forces that can pull the tenon out of the jaws in the event of a catch. Ellsworth has a good description of this 'step' in his book. Also, make certain your tenon does not bottom out and contact the inside face of the jaws.


That step not only needs to be flat (not curved), but also to be 90 degrees or less to the tenon. Because it can be hard to tell if the face is truly flat or perpendiclar to the tenon surface (the part the jaws clamp on), and a very small error can cause a relatively larger problem, I generally angle the face in toward the headstock a tiny bit (a degree or two shy of 90) as I am cutting to ensure a sound registration against the jaw face. This way, only the outside edge of the jaw face will contact the bowl or whatever you are chucking up. An error in this direction (receding) has no ill effect, whereas if the face is curved (not flat) or angled toward the tailstock (greater than 90 degrees), the jaws can not register correctly. I learned this from Ashley Hargrove, a student of Stuart Batty.

Dan

[Geoff Whaling]

I learned this from Ashley Hargrove, a student of Stuart Batty.

Dan

You might be thinking of Ashley Harwood though she may be using her married name now? Stuart explains how to make tenons and what happens if tenons are poorly formed in the clip https://vimeo.com/68649130

[Dan Forman]

My memory being what it is, I'm sure you are right about the name. I knew it was Har something. :)

Dan

[Geoff Whaling]

My memory being what it is, I'm sure you are right about the name. I knew it was Har something. :)

Dan

Ashley demonstrated at our Turnfest symposium on the Gold Coast. She is an excellent demonstrator plus having Stuart Batty as a mentor means she has had excellent training. Only wish we could tempt Stuart to attend & demo one year. :cool:

[Bob Bachynsky]

Just wanted to say thanks again. After going through these vids and reading the helpful posts I re-evaluated my chuck. I ended up ordering a G3 as I think it will work better for what I do.