Chuck size for bowls question

[Dan Forman]

I have both a 3 1/2" and 5" chuck (Vicmarc). For those of you who also have similar sized chucks, what size of bowl will inspire you go to the big chuck over the smaller one? Thanks,

Dan

[Mark Norman]

When the small one isn't big enough use the big one?

Reverse the logic with hammers...:p

[alex carey]

It's a little more complicated than that Mark, you can obviously make a really small tenon for a 20" bowl, its just not safe. For my talon the biggest I have made was a bowl 14" wide and 5" deep. I think this is about as big as you want to go, or at least as big as I want to go. BUT if you are making a platter that is 20" that is probably fine to. Any bigger than that though, you probably want to go with the bigger chuck.

This is just how I feel, I'm not sure what is considered "safe" but I haven't had any problems yet.

[Mark Norman]

I am a noob at turning and wish to learn.
I wonder whats too big for the 5" chuck and where do ya go from there? As for the threshold between 3-1/2" vs 5" I would guess about 12"~14" depending on the stability and balance of what is bein turned.

[alex carey]

yeah it definitely depends on what your turning, I'm not sure what's too big for a 5" but I'd sure love to find out one day.

[Dan Forman]

I'm just starting to turn bowls, have done about a half dozen small ones, from 5 to 7 inches diameter. I am now working on one about 11 inches by 3 1/2, which seems a lot bigger in comparison, but I suppose would still qualify as small to most of you. Anyway, I went ahead and used the big chuck just to try it out.

I've been mostly turning pens, so an 11" bowl blank to me looks like a lot of wood spinning around. :eek: I think I'm getting used to it though.

Is there a general guide for bowl size / tenon size? That would be handy to know for me. Thanks.

Dan

[alex carey]

hmmmm, it seems us three are the only ones who are insomniacs. I think I'll let one of the more experienced turners answer your question.

[Jeff Nicol]

Dan and Alex and Mark,

Sleep is a funny thing and I wish I had more fun doing it too! So here is the skinny on the chuck size thing. If you make the tenon 1/3 the diameter of the bowl that will determine which chuck to use. If you put on the #3 jaws on your smaller chuck that will give you the biggest most will go with the smaller chuck. I have a Oneway Stronghold chuck and with the #3 jaws one I will do anything I can get turned on the 3520B. When doing larger bowls HF's and vases a steady rest comes into play and that helps the operation and may let you go to a smaller tenon. But if you are in doubt it you are using a big enough tenon leave extra wood and turn down your piece using the big tenon and finish the base/foot last after you reverse the piece or part it off from the waste wood. There is a point where the foot/base can be to small for the turning and it will be top heavy so keep that in mind too while designing it. No matter what saftey first!

Jeff

[Steve Schlumpf]

Dan - Jeff offered some good guidelines to follow.

I have a Talon chuck and almost everything I turn (14" diameter and less) I use the #2 jaws to hold the tenon. On the very few large pieces I turn (14" to 16" range) I use the #3 jaws and they can hold a huge tenon! Remember to use your tailstock for as long as possible when roughing out your blank!

[Wally Dickerman]

More important than the size of the chuck is the size of the jaws being used. To get the best hold on a tenon the jaws should not be extended past the body of the chuck. Okay, a little is alright. If the jaws are wide open there isn't much contact with the tenon.

If the blank is very large, too large for the chuck, a faceplate is still the most secure way to hold a blank. That is also true for a a very deep piece. There is a lot of leverage in a deep blank.

Wally

[Dave Ogren]

Dan,

I also have the Vicmarc #120 or 5". I also have the Technatool Nova almost 4" chucks. I also am a new turner, having only turned 15 bowls ( 3 yesterday) My preference is for the Vicmarc 15 to 1 or more. I have only turned bowls from 6" to 14" so far. I am trying to develop a system that works all of the time. I have read a lot about the trunion, as Jeff talks about, but have never tried it. I think you have to have a tailstock assembly to use that method and I don't have that. Then you have to reverse the bowl to clean up the trunion area, and I don't want to do that. I have learned a lot from Reed Gray's (Robo Hippy) posts. I have been cutting a recess 2 5/8" to 2 3/4" and dovetailing it to mach the standard jaws. Rock solid, I have taken very large (deep) cuts, and nothing moved. I really like the Vicmarc 120, but also don't have any experence to compare it to. The idea of the base being 1/3 of the bowl dia works great from the 9" to the 14" so far. I also have the large jaws but have not used them yet. I hope this helps, and I really appreciate your posts and learn from them. Good luck, keep them spinning.

Dave

[Bernie Weishapl]

I have two of the Vic VM100's. I also have 3 of the Griz clones of the Vic. I use the #3 jaws on anything over 12" and up. Never have had a tenon break or fly off.

[Kaptan J.W. Meek]

I use the 1/3rd rule.. a 12" bowl gets a 4" tenon.. or close.. maybe a little less.. but close..

[Brian McInturff]

VicMarc has a 6" chuck out now the VM150 @ a whopping 369.00 weighs in at 10lbs. I've been wondering where someone could possibly need the additional inch. Maybe on Marks Monster lathe or on the VB36 I guess. Or a truck axle lathe. Whoops, off topic slightly. I have a VM120 5" chuck and 3 VM100's. I've used the VM120 only a couple of times. Both times the blank was in excess of 20" and way out of balance. If you don't plan on using the tailstock I'd recommend face plates for anything large and out of balance.

[Scott Conners]

I've heard the 1/3 rule a bunch...make the tenon 1/3 the diameter of the bowl. Generally I'd have no problem going to 1/4 if it's good wood and properly sized tenon. I use the tailstock as much as possible as well, and on really big stuff or tall stuff I'll add a steady of some sort.

[Reed Gray]

I have both sizes of the Vicmark chucks, and prefer a recess to a tenon. I will use the large chuck (jaws closed are 2 5/8 inches wide) for almost all my bowls, down to about 6 inches, and up to 18 inches. When I get down to the smaller bowls, the shoulder outside the recess is a bit small, but not overtightening is the biggest thing there to keep the bowl from flying off the lathe. Avoiding catches is the other thing. Less than 6 inches, and most of the time it is the small jaws, and less than about 3 inches, I will use a tenon, and yes, I do use a tenon some times. Generally, the recess will be between 1/8 and 3/16 deep. I can get away with less with dry wood, but with green wood, the wood can move so much that the recess can't be used again. I also do not use the tailstock when bowl turning. Just learned to do with out it as it is an extra step in production turning. I would not suggest that you do without it, but it can be done. With the tailstock added, you don't need as secure of a grip to get the bowl spinning, but a good grip is important with turning, but not so important when sanding as the pressures are less. The 18 inch bowls are maxing out this type of grip, and there is some vibration from the tool pressures at that diameter, but I can still be agressive when turning, and have no problems with coring. I have done a few bowls in the 20 inch plus range, and for those, I switch to the 5 inch jaws. For a tenon, I would use the standard set of jaws for tenons up to about 4 inches, which would be good on bowls up to about 12 or slightly more inches. Above that, I would switch jaws and use a bigger set. Your chioces here are to get a couple of chucks and sets of jaws so you can have them set up, or just change out the jaws as needed. I have a set of the step jaws and never use them. This is one case where specialized jaws work better than the combination jaws do.

A lot depends on the wood as well. Harder more brittle woods like Osage and Black Locust will tend to split out more than meduim woods like the fruit woods. The softer woods like Alder and poplar seem to hold great once, and then not well on another piece. I had some cherry that had sat for a year, and the sap wood was a bit soft. It split out fairly easily, and I had to make the recess deeper than normal.

When tightening, use both of the keys to tighten. Do not get it as tight as you possibly can, but get it snug in one key, rotate to the other key, and snug it up again, and go around a couple of times on larger pieces. If you tighten as much as you can, you can split out the shoulder or recess. You can also put so much pressure on it that if you have a catch, the grip will fail at the point of most stress.

robo hippy

[Dan Forman]

Thanks much for all of the info, most helpful!.

Dan