Chuck remount question

Yes, you should tighten down the chuck jaws so that the blank does not come out. And when you have a lathe on which you can turn bigger stuff, you REALLY don't want anything to come out of the chuck. You should not plan to be able to accurately rechuck anything, whether you are using smooth jaws or the Oneway style.

Now, what to do with the marked up bottom? Turn it off. Reverse the piece onto a jam chuck, holding it there with vacuum or (for a lot less money) the tailstock. Remove any sign of the tenon and make the bottom look good. If you are using vacuum you can finish turn and sand the bottom. If not, then you leave a little bit in the center which you will carve off and sand.

Bill

Rob McC> Ok, I do have a serious question now. All joking about my blowing up bowls

Hey, Bill; I am sure you mean well, but in this instance you seem to remind me of the cow that forgot how to be a calf:-)

I'm still one of the "cheap" turners who still do not own all the gadgets, and I still - when I get good pieces of advice about _not_ doing something - still bite my teeth together and scowl: Why the hell _not_!!

Rechucking is made difficult for two reasons: The chuck deforms the wood when you tighten it, which you must. Because the wood is of different consistency or density as opposed to metal or plastics, the blank will "always" twist a little out of line as you tighten the chuck.

Even if you rechuck in the exact same "toothmarks" the second time, you find that the piece has changed when you worked on it, due to further drying, or maybe from release of tension in the material.

Personally, I find this effect to be much reduced when I use a Forstner-bit to make a recess and use the "inside" grip.

This goodlooking piece of advice makes me ask in earnest:

- How many of you guys out there own a vacuum chuck?

(Am I really that far behind?)

Bjarte

I got a really cheap chuck, and it works pretty well- provided it grips on the ID. It's certainly no Oneway, but it does allow for accurate remounting. Perhaps the problem is that you're turning a tenon for the piece, and not a recess? I know that gripping a tenon with a chuck is standard procedure for a lot of folks, but I've had no luck with it at all- gripping the inside of a recess works really well, though.

Gripping in the ID keeps the chuck marks where they can't easily be seen.

You're doing what you can with the equipment available. I hope the war does not reignite, but there are good, non-destructive ways of mounting out there, and none of them involve serrations or non-circular "grips."

Use an interior or exterior dovetail for your mount. Size the recess or tenon slightly larger than the first point of circularity, and _snug_ , do not tighten to hold. You want to make a good shoulder for reference and loading when using the dovetail. This means a flat area inside, with no sanding trash packed in the corners, or a flat area outside to meet the _face_ of the jaws. Use your third hand if available - tailstock - to help in hold and center as you snug the hold. The dovetail will draw the piece back into the chuck.

Here's an important point. With the dovetail, you don't have to settle for close. If you cut it flat, and your jaws are flat, it _must_ center. If it doesn't, it's time to loosen the hold and make sure the faces meet cleanly. Don't let your experience with destructive mounts temper your judgment here - these will mount both circular, and with no runout.

That is why I suggested a jam chuck and even noted that it would cost a lot less money than vacuum chucking. In fact, it can cost you nearly nothing if you make it yourself. And, if you make it such that it mounts in your chuck, you don't even need to dedicate a faceplate to the jam chuck.

I use a piece of 4" schedule 40 joint which costs about $0.80. My Stronghold chuck expands into one end and I've trued the other end and glued on a piece of gasket material. I use a piece of paper towel between the gasket and the bowl to keep the bowl from getting marred. I try to use the same piece of paper towel over again so as to keep the cost down.

And, even though I use vacuum chucking, frequently I turn thin enough that I cannot pull a vacuum on a piece so still use the 'carve the bottom and sand' method.

So, what did I forget about being a calf?

Bill

Bjarte Runderheim wrote:

Hey Bill, A great idea! Reuse paper towels and save enough money to buy a Stubby...or a fatted calf. ;)

I once had a thrifty neighbor lady who carefully hung her used paper towels out to dry. Not a pretty sight in the eyes of some fancy beholders. ( go barefoot or wear sandels at the beach... never at the lathe)

Turn to Safety, Arch Fortiter

You must not be using much tightening force at all. I can't believe anything that fits on a 10" mini being held by a Stronghold would come loose if properly mounted. Proper tightening is one aspect but the tenon must not be too long such that it bottoms out on the bottom of the jaws. The points of contact are the jaw grips and the front face of the jaws which must contact the bottom of the bowl. The latter is very important as it helps keep the bowl from twisting out of the jaws with cutting pressure. The tenon is cut parallel with the axis of rotation, not tapered. Your Stronghold manual gives the dimensions of valid tenon sizes. I have seen some large bowls mounted with tenons no deeper than about 1/8".

I have remounted bowls using the regular Stronghold jaws and the odd time it is perfect but usually it is out a little. If you think that you want to try dovetail jaws you can get them from Oneway for your chuck. I always use an external tenon and I do not consider the bowl finished if it has anything looking like a tenon sticking out the bottom no matter how smooth it is. Internal, unsmoothed, tenons are not elegant either. My methods for finishing the bottom are vacuum chuck (lately), jam-chuck/tailstock, or donut/compression chuck.

Billh

Bill.. I'm still new enough to remember stuff that you probably have selectively remove form ram.. *g*

I have knocked several items out of the grip (not out of the chuck though) of the Talon on a Jet mini... and always using the same method, the dreaded catch..

I find that now that I have a lot more experience and a little more skill and technique, I somehow seem to have far less catches and most things stay true in the chuck for a whole turning..

I also remember starting out with fairly large turnings and since every catch means remounting and re-truing, the turning gets smaller and smaller.. *g*

mac

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Mac, I haven't been catch free for all that long that I'd forget but I won't deny it doesn't happen. I learned bowl turning on a cheapie Jet 1236 look-alike lathe with a rotating headstock. I had a cheap dove-tail jaws chuck like the ones sold by Grizzly which cost about $50US. A reasonably good catch with that chuck used to typically knock it out of true (or way out of true) with the rare one coming right out. However, I tightened the chuck very tightly and had the bent tommy bars to prove it.

When I got my Stronghold I found that the catches didn't really knock the bowl out of alignment in most cases. Yes, by that time the bad catches were less frequent. I tighten my Stronghold and Talon firmly since I don't care about what the tenon looks like. At our club, people demonstrating chucks recommend that for the best grip you tighten in each key hole in the chuck - the same as I was taught a zillion years ago in grade 8 shop class when tightening a drill in a Jacobs chuck on a drill press. I don't have the same feeling as really reefing on the Oneway but the key/gear does give a 5:1 mechanical advantage.

Another thing that might help if severe catches are a problem is to loosen the drive belt if possible so it acts like a clutch.

Billh

Now you're talkin'! I withdraw evrything to do with bovine elements, and note things behind my ear for the future.

But what I meant, was that us calves need things explained just a little more than your first try, and more in the direction of this second try.

No offence meant:-)

Bjarte

Two points, guys. First, the tenon should be just a smidgen larger than the smallest opening on the jaws. In other words, if the jaws come together and measure 2" across (on the inside of the jaws), then make the tenon 2 1/8" to

2 1/4" in diameter. This way, you have the maximum amount of the jaws in contact with the tenon.

Second point. Take the point of a skew or a narrow parting tool and sever the fibers on the tenon right up against the bottom of the bowl. 1/16" deep is probably enough. What this does is allow the fibers all the way across the tenon to be compressed evenly. If you fail to do this, the fibers right next to the bottom of the bowl are supported more than the fibers at the end of the tenon, and when compressed, the tenon tends to end up tapered away from the bowl.

If you try these two things, I bet your problems will be (mostly) solved.

Regards, James R. Johnson

Hey, I resemble that remark! If they're only wet, they've still got life in them. Thank me old Scottish mama for that one.

snipped-for-privacy@yahoo.com (Chuck) wrote in news: snipped-for-privacy@news.capital.net:

Perhaps she had been using BLO, and was hoping to avoid spontaneous combustion problems?

Patriarch

same procedure here, bull.. I used to do recesses a lot more before getting Bill Grumbine's video.. now I do a lot more tenons.. I doubt that it makes much difference if I tighten the Talon from both sides, but I do anyway.. Like Bill says in the video, you can apply too much jaw pressure to a recess, but it's hard to break a tenon...

I haven't looked at the belts on the new 1442, but on the mini, I kept the belt loose enough to stop the spindle if (ok, when) I got a bad catch.. (are there any GOOD catches?)

mac

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James.. to "expand" on one of your points... The smaller the diameter of the tenon, the more the chuck is "closed", which means less spinning metal on the back of the jaws..

mac

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Normally, bowls are held in a chuck by a tenon that is later turned away, removing any jaw marks.

This doesn't really relate to your question, but with a Stronghold on a Jet Mini................the flywheel effect must be considerable. You've got a little too much chuck..........or.............not quite enough lathe. You might want to consider a Talon or a bigger lathe.

Barry

I'd recommend getting BOTH.. *g*

Get a bigger lathe for the Stronghold and a Talon for the mini..

mac

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