Bad Parting

[Jerry Marcantel]

I was wondering how many of you use a jam chuck to part off your tenons when done turning? I use to use a donut chuck until it exploded and that made me somewhat nervous of using anything not between centers. Now, between centers I'm having about a 75% success on parting off the tenon. Yesterday I was parting off a bowl that I'd been working on and off for a couple of years now, and when I thought I was done, my tool grabbed and broke off the 1/4" nub that the live centerd was contacting. After it broke, the bowl got caught between the tool rest and one of my screwless chuck plates that I'm using as my jamb chuck. Before I could get the lathe shut down, the CP burned a groove in the bowl bottom.
That got me to thinking, and I would like some of you to explain how you remove the tenon from the bottoms of your pieces...... Any help would be appreciated... ..... Jerry (in Tucson)

[Curt Fuller]

I like to turn off my tenons between centers using a jamb chuck. But I don't part it completely off anymore because I've had the same experience as what happened to you. I get them down to that 1/4" size or even larger sometimes and then stop the lathe and cut the last little bit with a small Exacto hand saw. Then I just sand off the nub. I haven't made the leap to a vacuum chuck yet, but I think that's the direction I'm heading. I think that opens up a lot of opportunities to finish the bottom completely while still on the lathe.

[Bob Bergstrom]

Light touch. Be gentle with the tool. Use a spindle gouge to cut across the tenon. Use duct tape or Saran wrap to help act as a safety belt on the jam chuck and bowl. Keep the tail stock in the piece till close to finishing off the tenon. I use a 3/8" spindle gouge to work on the bottom of all my bowls.

[Roger Chandler]

I have a vacuum chuck, but I like using a jam chuck a lot..........I have a live tailstock center with a 1x8 tpi thread on it that I got when I had my old lathe........I threaded a piece of maple and then cut the thing down to about 1/2 inch in diameter and it will not mar the bottoms as it turns in sinc with the spindle............

I also use a 60 degree cone center a lot..........if I have enough wood to work with, I just snug it up to the bottom and reverse turn till I get to about 1/8th to 1/4 inch and then stop the lathe like Curt does above.......I then use a very sharp chisel and cut it flush.........a quick sand and it works slick as a ribbon!

My new favorite is to use my rubber chucky - reverse chucky as the jam chuck and use the cone center...........talk about slick and not having to do a lot of adjustment to get the thing to run true..........this is for boxes and vases..........for bowls I use a large jam chuck with a piece of mouse pad to protect the inside and either the cone center or the maple on the threaded live center.........the larger surface on the maple gives me more area to apply pressure against the bottom.

http://www.pennstateind.com/graphics/100px/LTCA18.jpg this is a picture of the live center with threads.........I got it from Penn State Industries.

[Dale Miner]

From your post, it sounds like you are using a parting tool to remove the tenon. If so, that is a method with a high likelyhood of failure. Do like the others have suggested; With the bowl jammed chucked against a piece of wood (jam chuck) with padding in the bottom of the bowl, turn the bulk of the tenon off. You should end up with a small nub just larger than the cone of the live center where is makes contact with the live center, with the nub tapering to whatever diameter you feel comfortable with at the bottom of the vessel. Typically, I turn the taper to about 1/8" or so, and shut the lathe off. I then use my skew and turn the vessel by hand to cut the nub smaller, or at least ring the nub heavily about 1/32" away from where the bottom of the foot will be. At that point, the vessel is removed from the lathe and the last bit of unsevered wood is snapped off where it has been ringed with the skew, and the bottom of the foot sanded. On smaller well balanced vessels, the nub can be turned down to a smaller diameter than on larger or out of balance pieces. The more acute bevel angle of a spindle gouge makes it more suited for this operation.

The block of wood (jam chuck)that is used to jam the bowl against should be fairly large diameter, and make contact with the bottom of the bowl at the outside edge of the jam chuck. Be making contact at the edge, it provides a more stable mounting, reducing the chance of the nub breaking prematurely. If the tailstock and the headstock do not line up fairly well, this method will not work. The constant scrubbing action of the misalinged centers will cause the nub to break when it is still fairly large.

[James Roberts]

Jerry, I've only used a jam chuck 1 or 2 times. Most of the time I use a donut chuck or I place the bowl against the flat faceplate of my donut chuck - a piece of 3/4" plywood attached to a face plate with a foam padding added - and hold the bowl in place with tail stock and live center (helps to have the original live center dimple), then use reinforced packing tape, the kind with the fibers running through it. Tape the bowl firmly to the faceplate with numerous pieces criss-crossed over the bowl with ends stuck to back side of plate. After that, I run a piece of tape around the outside of the faceplate as insurance against the tape letting loose. This usually centers pretty well and I take light cuts to remove tenon/nub.
I have built a vacuum chuck system but only recently got it back up and running (vac pump got flooded last September during TS Lee before I could try it out:mad:) so I look forward to using that as my go to method.

[Thom Sturgill]

I go with Bob except I use blue painters tape instread of duct tape - no residue. Also I mostly use a detail gouge.

[Roger Chandler]

+1 on the detail gouge..........I forgot to put that in my post above............if you have it nice and sharp you can turn the tenon to a very small nib with a cone center for support.

[Thomas Canfield]

I use a jam chuck with rubber shelf liner and the live center for almost all piees to remove the tenon. I turn tenon down to about 1/2" to 3/4" or even larger on some very large pieces using a spindle gouge for the last 1/16" or so of the tenon and to get the recess on the bottom. I then use a piece of plastic with notch and a flexible flush cut saw to cut the nub for final clean up. A carving chisel or just sandpaper on disc in angle drill smooths out the bottom. That method has worked on 19" diameter pieces. One caution is to not use too much tailstock pressure if working with small diameter dub or you can punch a hole in the bottom or spring the bottom on thin bottom pieces.

[Jim Burr]

Almost always. I learned in person from an acknowledged artist so that's all I know. Toss a chunk of woven shelf liner in the middle and get busy!

[Steve Schlumpf]

Jerry - depends on the turning. Bowls and wide HFs get vacuum chuck when they are solid wood. When there are voids - then I use the donut chuck system. Vases I use the jam chuck method and leave 1/4" or so of wood in the tenon before I remove it from the lathe, saw the remaining tenon off and sand.

[Scot Roberge]

+1 on not attempting to remove the tenon with a parting tool. Learned that the hard way. I'm curious what caused your doughnut chuck to explode. Did something come loose? I have been cautioned that a doughnut chuck is a low speed fixture, so I keep mine at 600 RPM or less. It is now my prefered fixture for completing bottoms. Either way, I have had zero mishaps using a sharp spindle gouge, low speed and a light touch.

[charlie knighton]

Jerry, on vases i use craft supplies woodchucker mandrel and bowls i jam chuck, i do it down to about 1/4 tendon and then cut off and sand like Curt said, i had lost a few before i started using this system, when the tendon gets small, you need to loosen the tailstock up some so the tendon does not break too soon

[Michael Mills]

I leave a small tenon (1/4 - 1/2) and sand off as many others do.
Vince sells the 1” disc in lots of 50 but he made a smaller kit for me (he doesn’t offer a starter kit for the 1”). I went with 100,150, 220, 320, and 400.
This allows you to sand the bottom of a small item (vase, toothpick holder, etc) or add decorations to a larger base and not mess up your decorations with a 2” pad.

[Prashun Patel]

IMHO, a parting tool pushes INTO the tiny spindle that's created when parting, and makes it easier to break. When I get smaller than 1/2", I use a small scraper or detail gouge to shave UP the tenon. I find cutting towards the bowl - instead of at right angles to it - lets you get very thin (1/4-3/8"). Also, make sure yr live center's not so tightly chucked that the wood wants to rive and split when it's thin. Perhaps it's not my angle of attack, but the fact that those scraping cuts are gentler than the parting style cuts.

To remove the tenon, I cleave a little scoring line with a chisel, then use pliers to break off the tenon, and finally a chisel to clean up the bottom.

[Jerry Marcantel]

Thanks for the replies folks.. I'm pretty much doing it the way you guys are suggesting.. Some of my problems stem from the wood I'm using. It's usually local wood that's been dead for 25-50 years. Some I can actually get the year thast the tree was pulled out of the ground.. Mostly Mesquite, and since I've discovered that Palo Verde has some good spalting and character, I'm going to start checking into that wood when I get back out to that ranch. Their trees were pulled in the late 60's and very early 70's.....


, when the tendon gets small, you need to loosen the tailstock up some so the tendon does not break too soon
Charlie, I do that and like how it works. I can't always do it on all pieces..


I use a jam chuck with rubber shelf liner and the live center for almost all piees to remove the tenon. One caution is to not use too much tailstock pressure if working with small diameter dub or you can punch a hole in the bottom or spring the bottom on thin bottom pieces.
Thomas, I did use some rubber shelf liner once, but it left an oily oil ring on the inside bottom of my bowl,, I also went through a couple bowls by turning the nub too small. pretty dissappointing to make that last cut and mess up the piece. It's kind of like flintknapping. You don't really want to get to the point where you end up saying, "One more flake and I'm done!". Then you have 2 points to finish now. It never fails.... ....... Jerry (in Tucson)

[curtis rosche]

design your bowl to have a foot, or use a reccessed grip instead of grabbing onto a foot,,,

[Tom Winship]

I've had good success using double sided Duck Tape on a jamb chuck. I turn the nib down to about 1/4" and then back tailstock away and remove remainder of tenon. The DSDT holds pretty well, to the extend I have had to use pretty good force to remove the piece.
This is a method I learned from Kathy Marshall, and she got promoted on here, so I guess it is good.

[Jim Colombo]

I also was having the same problems when I first started turning so I bit the bullet and built a vacuum system. It's been a bed of roses since then. I used the plans on this website to build the the system.