Question about large jaws on a 5" chuck

I have a 5" HTC125 chuck, which came with standard dovetail jaws. When I bought it, I figured I would buy the large dovetail jaws for it, later, when needed. At the time, I wasn't turning anything larger than about 13", and the standard jaws were adequate for that.

Well, now I need them, but I can't find them anywhere. The thewoodturningstore.com site has a listing for them, but you can only put them on a wish list, not in a purchasing cart. I called, they said they don't have them and have no information about future availability. Amazon had a listing, showing "currently unavailable," with no other information. Now that listing is gone completely.

Both sites offer large jaws, but only in "serrated" form, not dovetail. My impression is that dovetail jaws hold better than serrated jaws, of the same size, so I would prefer the dovetail type. But I can't find them.

At the moment, my immediate need for the large jaws is to attach a couple of really large bowl blanks that a friend cored for me, which have large dovetail tenons on them. The blanks are about 18" diameter, 9" tall, with thick walls, and quite heavy. They'll be lighter, of course, after they dry some, but still, they're BIG!

So here are my questions:

1. Does anybody know of a place that is selling a set of large dovetail jaws for the HTC125 chuck?

2. I suppose I could take the large blanks when they are ready to be finish-turned, put them on a really big jam chuck, convert the dovetail to a straight tenon, and then buy and use the large serrated jaws to hold them. Do you think that would work okay? Or, would it be better to use a 6" face plate, since there's quite a bit of extra wood on the bottom, to turn away the screw holes later? Any other suggestions?

Robert

After they dry they'll probably have warped so much you'd have to jam chuck and true up the tenons before you could mount them, anyway.

I don't really like serrated jaws but they'll probably work fine if it comes down to it.

If those cores are recently cut wet wood, you have plenty of time to make a decision. If your thickness is 1.75" to 2" you have a good 1 1/2 year wait to dry. I'd think the jaws you want will be in stock before then.

Glue block them--no sweat.

I have the large serrated jaws for my HTC125- it does a great job of holding. I would not be afraid to use them for coring, which is the most stressful work a lathe does, IMO, but YMMV. I think the HTC chuck design is strong, and would have no pause.

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Originally Posted by Robert Marshall

Both sites offer large jaws, but only in "serrated" form, not dovetail. My impression is that dovetail jaws hold better than serrated jaws, of the same size, so I would prefer the dovetail type. But I can't find them.

At the moment, my immediate need for the large jaws is to attach a couple of really large bowl blanks that a friend cored for me, which have large dovetail tenons on them.

Robert

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Can you borrow your friends chuck with big jaws?

I would stay with dovetail jaws instead of a straight tenon or serrated jaws, even if that means buying a Vicmarc chuck and Vicmarc Mega dovetail jaws. Others will undoubtedly argue with this, but I was told by a professional turner that serrated jaws are more for end grain (spindle) work. When used on side grain, the serrations can dig into the side grain more than the end grain, which can affect how "equal" it holds. As a result the piece can move and loosen, requiring that you continually check and re-tighten the chuck. Dovetail jaws will hold equally no matter the grain direction. Straight tenons just don't make sense to me, especially for holding power.

Robert,

You haven't said what diameter the tenon actually is but there is some overlap between the HTC large and super large jaw sets. Looks like the biggest style is in stock if you need something soon and don't want to wait. If the tenon is better than 5 1/4", they would work. Just for kicks for everyone else, here's pics of the 3 different sizes they offer. The super large is truly a big honking set of jaws.

Attachment 378944Attachment 378945Attachment 378946

I ended up ordering both the extra-large dovetail jaws, and the large serrated jaws (no one having the large dovetail jaws for sale). David Delo is right; the extra large IS a big honking tool!

And, proving that it's better to be lucky than to be good, the large serrated jaws that I ordered (while really regretting that no-one had the dovetail type in stock) came in a box that said "large serrated" on the outside, but the box actually contained the large dovetail type. Which was what I really wanted, but thought no-one had!

So, it all worked out just fine!

Robert

Stuart Batty gave a talk at our club stating that if you pull a bowl out of dove tailed jaws, the tenon will not separate from the blank. If it is secured in serrated, the tenon will be torn away from the bowl. To me this suggests that the serrated jaws grip so well that the tenon will break.

Quote:

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Originally Posted by Bob Bergstrom

Stuart Batty gave a talk at our club stating that if you pull a bowl out of dove tailed jaws, the tenon will not separate from the blank. If it is secured in serrated, the tenon will be torn away from the bowl. To me this suggests that the serrated jaws grip so well that the tenon will break.

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To me it says that the serrations are digging into the tenon and compromising the wood fibers. Instead of having solid wood around the outside edge of the tenon, the serrations have created small thin ridges that will break away.

Batty’s slant on it was that the tenon was still intact and he could remount the blank. I have found it more important to not leave too much gap between the jaws. I agree that when a serrated jaw clamps down on the end grain it could act as a smaller leaver to separate end grain. I have found less problem of tenon failure in large bowls than smaller ones. I believe both jaws systems work well and it is more personal choice. I think about back to the day when we’re using three jaw machine chucks or collect check?

To me a recess is stronger and safer than a dovetail tenon, ever seen Robo Hippy’s way of holding large blanks, I also never use a dovetail tenon, but hold in a recess with my Oneway profiled Jaws.

Here’s a good solid held dovetail, the bowl isn’t :eek:

Attachment 382524