Is there such a device?

[Maria Alvarado]

Hi Folks,
The problem: I had a frustrating time this weekend trying to get a large bowl to stay centered in the chuck (SN2, powergrip jaws). I had roughed out using a faceplate on top, then turned a tenon. It went much faster than previous sessions between centers (this is a green maple log) so I was pleased with that, but putting it in the chuck just became a study in re-truing a steadily diminishing bowl. The tenon was not bottoming out, and I think I had decent shoulders on the bowl, but of course that could still have been the issue. The intent was to create a nested set, using the still attached faceplate to hold the cores while creating the tenon, but I gave up on that and just stuck with roughing the large bowl.

My question: Is there a device that allows one to hold a chuck or faceplate in the tailstock for more accurate attachment to the workpiece. I'm sure I have read about something like that, probably here, but I can't seem to come up with it in a search. Thanks for your help. (apparently my sig line does not always ring true!)

[David E Keller]

Yep... Seems like csusa was the source. Recently discussed but can't remember which post.

[Steve Schlumpf]

Maria - here is one source: http://www.packardwoodworks.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=packard&Category_Code=lathes-acc-tlstkadp

Here's the one from Craftsupplies: http://www.woodturnerscatalog.com/store/Lathe_Accessories___Spindle_Accessories___Reverse_ Chucking_Alignment_Adapter___reverse_chuck?Args=

[Thom Sturgill]

Penn State (PSI) also sells one, theirs have bearings. http://www.pennstateind.com/store/LTCA18.html

[charlie knighton]

best wood tools has one for a faceplate, but for a bowl to be turned around i do not know, i was using it with hollow forms

you might improve your drive center and rotating center, there are a world of difference in some centers that come with some lathes

i discovered this when i upgraded my lathe, not the onlly difference in lathes but one that was very noticeable

[Don Geiger]

I make one that is available in 3 popular sizes (1" X 8, 1-1/4 X 8 and 33 mm). I use it every time I turn open forms and hollow forms.

How it differs from other system is: when you position your turning against a jamb chuck or vacuum chuck, there is no hardware attached to your work piece. A drill bit, drill stop and a device that screws into your face plate or chuck that supports a hardened drill bushing is provided to enable you to drill A 3/8" hole into the exact center of your waste stock. A 3/8" diameter pin is supplied that fits into your live center. This pin, when pushed into the drilled hole, accurately rec-centers the piece and holes it while you remove the waste stock.

I was told I can't post my web site so I hope I'm not breaking any rules by suggesting that you Google: Geiger's Re-Centering Solution.


Don Geiger

[Maria Alvarado]

I'll check all those out (even Don's ;)). I see now why searching "tailstock chuck thingy" might not have gotten the desired results!

[Mike Minto]

OneWay sells them, too - fits onto their live center, which you must have to use it. Is small, would introduce very little error, I'd think. I have one and like it.

[GLENN THOMAS]

With my experience it is not uncommon to have to true up a bowl somewhat after turning it around and putting the tenon in a chuck. If fact is seem to happen more often than not, especially with really green wood. I think in some cases wet wood warps just that fast. In fact I have left of bowl on the lathe that was perfectly round and come back to it a little later only to find it warped, and I didnt even flip it over. I have even seen videos where this issue was discussed so I dont think its that uncommon.

Just my 2 cents worth.

GT

[Bernie Weishapl]

Maria I use those also. One thing I have found as Glenn said the wood will sometimes warp that fast in some woods. When I turn a bowl around I just get it to kind of a rough shape and no more then cut my tenon. I turn the bowl around and finish turning the outside to shape. Then I avoid what probably has happened to you. I think we get them down to final shape and when turned around have to reshape and true them up which means taking off more wood.

[Hilel Salomon]

Maria,

As I understand it, your concern is that after you make a tenon, when you put the blank's tenon first into the chuck, it is still in need of truing. The sites offered include devices which are useful for reverse turning... that is finishing the bottom after you have finished most of the bowl.
I think that Glenn is right. Almost any chuck when you first put the bowl's tenon on, will require some additional truing. One way to reduce the amount is to use a live center on the tailstock, using the hole in the center push the bowl onto a chuck which is not yet tightened. Then tighten it. This will help but not eliminate some truing. Another factor is how quickly you put the blank w/tenon onto the chuck. If you wait, even a few hours, green wood will have begun to move and the truing will be even more pronounced.
Also, different chucks have different degrees of accuracy and repeatablity. In my experience, for example, the vicmar chucks have the greatest degree of repeatability--- that is, when properly marked, if you take the piece off the chuck, and put it back on, there will be less need of truing the piece.
The problem with using the commercial tailstock chuck adapters, is that taking the blank off the headstock, assuming you haven't used a screw to hold the original blank, you will have exactly the same problems as if you put it on directly to the headstock.
Lastly, if your concern is how much wood you have wasted, don't complete the roughing process until you have put it on the chuck.
Good luck, Hilel.

[Don Geiger]

Please look at the attached files. These are excerpts from a presentation I use when I do my demo: "Mastering the Side-Ground Bowl Gouge". I hope this is of some help to you.


Don Geiger

[Maria Alvarado]

Thanks again guys,
I checked out the various options and it looks like there are a couple of choices in the 1-1/4 x 8 TPI category to consider.

I know there is always truing to be expected, but since I was leaving my faceplate on it made it difficult to use the tailstock to aid centering in the chuck (risk of marring the threads) and the result was pretty wonky, especially since it still ran true re-mounted with the faceplate. So I don't think it was "that" green. I had actually started roughing it a couple months ago, so some of the water has evaporated. At any rate, it got me thinking that there were some situations where having the tailstock be able to hold the chuck could be useful. Thanks for the links and advice!
Happy Turning,

[Reed Gray]

Maria,
If you had left it for a couple of months, then the tenon should have been trued up again. Even 'dry' wood will adjust. The final cuts on a tenon or recess should be like finish cuts, with the steel just barely touching the wood. I prefer a scraping cut here with a skew or dove tailed scraper. There will always be some bounce from the way the cutting edge goes through end grain and side grain. By taking a very light cut, you can true it up. Also check for any shavings in the chuck jaws as even tiny ones can throw it off. Some times the screws on the jaws will work loose, and this can make things wobble. You can take the bowl off the lathe, and put the chuck onto the tenon while the bowl is on your work bench. This works for big heavy blanks that you can't hold up there. You can rotate the bowl blank 45 or 90, or 180 degrees, and some times this makes things better. There is an art to making the bowl refit and run true.

After reversing the bowl for coring, you can remove the face plate, engage the tailstock, and cut a recess for remounting the core. Then when you remove the core, it will center on the recess when you remount it. With a properly made recess, it will hold fine, but you can use the tailstock as added security.

robo hippy

[Maria Alvarado]

Reed, you're a genius! After posting the reply below, I checked out the chuck and lo and behold, one jaw was wiggling, with the screws having loosened (or not been tightened enough) by about half a turn. I find sometimes they stick going in, so next time I will be a bit more aggressive with my tightening. That certainly contributed to the lack of holding power and no doubt to the truing issue. Thanks!

Thanks Reed,
Yup, I did true everything up (I had left the faceplate attached while the bowl sat). I reduced the tenon to the appropriate size, tried to create a good flat surface for the jaws to rest against and had the bowl, but upon reversing it, I just couldn't get it to spin quite true in the chuck. Had I removed the faceplate, it would have been easier to use the tailstock to help center it in the jaws, and that's eventually what I did. The goal of leaving the faceplate was to have a way to mount cores after using the Kelton. It may also be that I needed a longer tenon for a bowl of that size, particularly for coring. The jaws were not gripping well enough for me to core so I think a little bit of everything contributed to this particular experience :rolleyes: I guess it's one way to get the gremlins out!

[charlie knighton]

good diagrams, Don

[Mauricio Ulloa]

I just bought the centering device recommended by Steve from Packard... This is the problem when a woodturning shop-aholic reads these threads..... :cool:

[Thomas Canfield]

Maria,

Trying to mount a large piece in a chuck installed on the lathe can be difficult. A video (I think Nick Cook that came with my Powermatic) recommended removing the chuck and setting it on a surface so that the piece to be mounted was sitting on the chuck and get a better seat. Also applying thin CA to the tenon will help sometimes to harden the tenon and prevent crushing which can cause alignment problems when doing additional tightning during turning. The pictures show a jig I made to hold chuck or donut chuck faceplace for mounting.

[Reed Gray]

Maria,
I think it is more a case of been there and done that a couple of times rather than genius.

When I turn and core (I use the McNaughton), I never use a face plate. Forstner bit to drill a recess on the top, and then turn a recess on the bottom for reversing. This way, I don't have to use a face plate which is an extra step for me. I remove the biggest core first, then finish that bowl. I remount the core to turn it by using the recess that is already drilled in the top of the blank.

You really don't need a tenon more than 1/4 inch for just about any bowl size you make. Depth doesn't make it stronger, and in a workshop I took with Stewart Batty, he told me to round over the end of one that I made that he said was too long, even though it didn't bottom out in the chuck jaws. When I use a recess, the one I drill in the top is about 1/4 to 3/8 inch deep. The ones I cut into the bottom is 1/8 to 3/16 (note, I never measure, just cut it by eye). I can get away with less, but with my green turned bowls, some times they warp so much, I can't get them back on any chuck for sanding.

robo hippy

[Maria Alvarado]

Great suggestion Thomas, I'll try that next time.

Reed, what diameter recess (jaws) are you using? I have the McNaughton and was thinking that a larger tenon in the powergrip (3.5 inches I think?) jaws would be necessary. Also, I understand you have a video on the McNaughton system. Could you PM me with details at your convenience?
Thanks!

[Reed Gray]

Maria,
Most of the time I am using my big Vicmark, and the jaws closed are just under 2 5/8 inch diameter, which probably means a metric size, but the 2 5/8 Forstner bit works fine. I use this chuck for bowls up to about 18 inches. I do have a smaller Vickmark, and those jaws are just over 1 3/4, and I use them on bowls 6 inch and under. For bowls, you want a tenon about 1/4 or so the diameter of your bowl, so a 12 inch bowl should have a tenon about 3 or more inches diameter. With a recess, you want the fit as close as possible, so for 2 5/8 inch, you want 2 3/4 inch max diameter recess, and dove tail hold better than straight. With a tenon, you can stretch the jaws out more than the actual diameter of the jaws, so jaws that close down to 2 inches can be expanded out to 3 or so inches, but again, the closer the fit, the better the grip.

PM is being sent.

robo hippy

[Don Geiger]

Thanks Charlie!

The two graphics are part of over 150 slides I developed for training woodturners on setting up a sharpening station, sharpening various tools, using a bowl gouge, and turning a natural edge bowl and a smooth edge bowl from selecting the blank from a log through the finished product. I've tried to cover several options for using chucks and faceplates and provide tips on each option. They include re-centering, jamb chucking and vacuum chucking for finishing the bottom. I've worked on this presentation for several years.


Don Geiger