Expansion Jaws Less than 1 Inch

[Scott Grossman]

Can anyone recommend a chuck/jaw combination that has a minimum expansion less than one inch? It would need to fit a 1 1/4 X 8 TPI spindle.

When I turn peppermills the top has a hole that is 15/16 in diameter to accept the Crush Grind top. I used to use a MultiStar Titan that could expand into a hole this small. Oddly, the threads on my new lathe are just enough different I can't mount this chuck anymore. I have three choices:

1) Have the Titan chuck machined to have slightly looser tolerance. That won't be cheap, and it may not work.
2) Come up with a different way to securely mount the top on another chuck. That will be tricky as the smallest chuck I've come across is 1 inch, and even a 1 inch hole will not always be one inch after wood has dried and warped.
3) Find a new chuck/jaw combo that can go this small.

Other ideas are welcome!

Thanks,
Scott

[John Keeton]

I use the 20 mm jaws on my SN2 to turn lids for bowls and other tasks. It fits nicely into a 7/8” hole.

[Leo Van Der Loo]

Can anyone recommend a chuck/jaw combination that has a minimum expansion less than one inch? It would need to fit a 1 1/4 X 8 TPI spindle.

When I turn peppermills the top has a hole that is 15/16 in diameter to accept the Crush Grind top. I used to use a MultiStar Titan that could expand into a hole this small. Oddly, the threads on my new lathe are just enough different I can't mount this chuck anymore. I have three choices:

1) Have the Titan chuck machined to have slightly looser tolerance. That won't be cheap, and it may not work.
2) Come up with a different way to securely mount the top on another chuck. That will be tricky as the smallest chuck I've come across is 1 inch, and even a 1 inch hole will not always be one inch after wood has dried and warped.
3) Find a new chuck/jaw combo that can go this small.

Other ideas are welcome!

Thanks,
Scott

Oneway have the step jaws for the Talon and the basic chuck that go down to ⅞”, and the spigot that have the minimum of 1” on the Talon according this chart.

https://oneway.ca/products-category/chucks

[John K Jordan]

Can anyone recommend a chuck/jaw combination that has a minimum expansion less than one inch? It would need to fit a 1 1/4 X 8 TPI spindle.

When I turn peppermills the top has a hole that is 15/16 in diameter to accept the Crush Grind top. I used to use a MultiStar Titan that could expand into a hole this small. Oddly, the threads on my new lathe are just enough different I can't mount this chuck anymore. I have three choices:

1) Have the Titan chuck machined to have slightly looser tolerance. That won't be cheap, and it may not work.
2) Come up with a different way to securely mount the top on another chuck. That will be tricky as the smallest chuck I've come across is 1 inch, and even a 1 inch hole will not always be one inch after wood has dried and warped.
3) Find a new chuck/jaw combo that can go this small.

Other ideas are welcome!

Scott,

Recommend? - make your own! I don't know this would work for you, but when I wanted jaws to expand precisely into a 22mm hole I modified some 25mm pin/spigot jaws on one of my Nova chucks. I wanted them to be a perfect 22mm diameter for the best fit with the smallest amount of force. Since I mostly use these jaws in the contraction mode for small spindles, no function was lost by changing the outside. (I do have several sets of these if I do want to use the original size in expansion mode.)

I used a Thompson scraper on the wood lathe and turned the steel jaws down to the size I needed. I've turned quite a bit of aluminum and brass on the wood lathe but this was my first time with steel. Cutting down the steel jaws was not real fast but it worked better than I expected. I did have to sharpen the scraper several times.

turning-steel_IMG_20170605_081521_124.jpg

For the most accuracy and least runout I 1) used a chuck I could dedicate to these jaws, and 2) turned them on the wood lathe where they would be used. If I had turned them on my metal lathe I would have had to deal with all the issues of holding and centering the threaded chuck and account for any lack of precision in the chuck's machining. I also came up with a method to take up any play in the expansion direction to maximize precision.

Here's a thread where I described this in more detail: http://www.sawmillcreek.org/showthre...odturing-tools

There may well be suitable jaws for other chucks but all mine are Nova and I didn't want to buy anything.

I've also made jam chucks for special hole sizes. That would be a lot easier to make if it would work for your pieces although smaller chuck jaws might be worth making if you plan to make a lot of the peppermills.

Also, I wonder if a machine shop could do something very cheap for your existing Titan chuck such as running a tap into it.

JKJ

[Tim Boger]

Check this tool out ....

http://www.bealltool.com/products/tu...ix_collets.php

[Scott Grossman]

This is really thinking out of the box, at least for me. Sounds like you have a machining background. Perspective helps.
I think I'll give this a shot. Worst that can happen is that I spend a couple trips to the grinder to resharpen my gouge with nothing to show for it!
Jam chucks are not reliable in the general case, due irregularities. So the expandable jaws are a better option.

John and Leo had suggested jaw combinations that would fit the hole, but the top is too close to the chuck for me to do any meaningful shaping of the lower part of the object. The pin type jaws allow me to move it out away from the chuck.

I see Tim has suggested the Beall expanding collet. I was just looking at those and will give Beall a call tomorrow. I understand the expansion range of collets can be small, so I don't know if their 7/8 inch collet will tighten something that's 15/16. That approach also allows the bottom of the object to get shaped, so that's a good option too.

[John K Jordan]

Those expanding collets look interesting. I've made similar expanding jaws from wood with saw cuts and a bolt to expand, held in a standard chuck. Here's an extremely simple one but this one can only be tightened from the front (you probably don't have a thru hole in your lid so yours would probably need to expanded from the back, not as simple.)

wood_expanding_chuck.jpg

I'm wondering how robust the Beall collets would be with the 1/2" shafts - I'd like to try them (and the contracting collets). The combination of both sets (I'd want the full sets) would be pretty expensive though.

As for the size, you could probably easily reduce the diameter of the 1" expanding collet to work with 15/16".

For on the cheap you could probably make the equivalent from a tough wood like lignum vitae fairly easily: bore and tap a socket for your lathe's spindle, mount on the lathe and turn a 15/16" cylinder (minus a little bit), bore a center thru hole with a short taper at the front, make saw cuts most of the way through the cylinder to allow some "give", then taper a threaded standoff (or even a nut) to fit and use a socket screw accessible from the rear to tighten the taper and expand the thing into the 15/16" hole. I've used lignum vitae to make a number of functional things that would normally be made from metal. HDPE would work too, as would materials like delrin. It would be a fun project!

I do have a couple of small metal lathes and mills (and welding equipment, etc) and a variety of stock on hand, so useful to make and repair things on a whim. I learned from books but I found it pretty easy and quite rewarding.

JKJ

[Marvin Hasenak]

Read the post I made on this thread. https://www.sawmillcreek.org/showthr...pindle-turning I have turned all kinds of things including pepper mills with these. Since this sounds like an ongoing turning project, it is best if you drill and tap your drive mandrel so that it stays on center. This is a cheap, and very accurate method of turning pepper mills. There is enough info there, but if you need more let me know. John Jordans pic will work, but in no time the 4 jaw chuck will crush it off center and you will need another. I would also recommend drilling and tapping the end and using a pipe plug instead of the small screw. It will give you more expansion. If I was going that route, I would take a 3/8 diameter lag screw and screw it in to the back of a blank and cut off the head. Then use a drill chuck or collet chuck to drive the mandrel. The jaws of the chucks will not change the diameter or crush the lag bolt.

[John K Jordan]

John Jordans pic will work, but in no time the 4 jaw chuck will crush it off center and you will need another. I would also recommend drilling and tapping the end and using a pipe plug instead of the small screw. It will give you more expansion....

I should have mentioned that the wooden expansion thing I showed was a quick experiment from soft wood for one-time use. It worked and proved the principle but it's not something I'd use repeatedly, especially not gripped with a scroll chuck. I decided to make the steel jaws after this proved to work.
Here's the same block when I used it as a jam chuck which worked but didn't hold as securely as I wanted since the jam part needed to be slightly tapered. Making it into an expandable version let the contact surfaces be straight instead of tapered and the hold was more secure with less outward force.

FidgetJam2IMG_20170621_110135_790.jpg

As mentioned later, for repeated use I would drill out the end of some suitable material and tap it to screw onto the lathe spindle then turn it for concentricity.

However, in my case what I was turning was thin and accessible from the front.

It was not clear to me if what Scott needs is open through the middle to allow using a tool from the front to expand the "jaws". If not, any means of tightening would need to be from the back with a tool inserted through the hole in the scroll chuck (most likely before the chuck is mounted on the lathe!)

Hey Scott, I just remembered I forgot about an easily made and time-proven method to hold things like this! - a pin chuck.

These are very simple to make - all you need is to make a mandrel with a flat spot and a small round pin. You also need a way to hold the mandrel. Most pin chucks are small diameter but a large one works the same way. You make the mandrel to snugly fit the hole and rotating it against the pin holds very securely. As before, it could be made from metal, tough plastic, or lignum vitae, perhaps from a block drilled and tapped to fit the lathe spindle threads. It could easily be turned from a piece of aluminum rod and held in a scroll chuck.

Here are some examples:

https://www.youtube.com/watch?v=Odu1cT3AwUE
www.penmakersguild.com/articles/pinchuck.pdf
http://www.finewoodworking.com/2005/...king-pin-chuck

I don't see where you live but if anywhere near here drop by and we can make one. I have all the stuff and I'm not afraid to use it.

JKJ

[Scott Grossman]

Hi John,
Modifying the pin jaws was really simple. I used one of the EasyWood carbide tools I sometimes use for nasty stuff like black palm. It took less than ten minutes and I only used one face of the carbide head. I put a slight roundover on the top to make it easy to get into the hole and its very, very subtly tapered. It really works great.
The top of the peppermills are closed so mandrels won't work. And as I said, my design for the top is like a Russian onion dome (no other way to put it), so I need to get under it to round the bottom and there is some substantial wood removal that takes place on the top. So the fitting has to be able to expand to accommodate some wood warpage (holly is terrible), the piece has to be a bit up away from the chuck, and it needs a firm purchase. Your suggestion of slightly milling down the pin jaws worked great.
This is somewhat liberating, as I could see how modifying the Beall IX expanding collet would be a cinch. They're aluminum.
I live in Hopewell, NJ, so not that close to you. But I appreciate the offer, and of course, the good recommendation.
Scott

[Brice Rogers]

Congratulations of your successful machining of the pin jaws.

I'm curious with your comment: "Oddly, the threads on my new lathe are just enough different I can't mount this chuck anymore." What is your new lathe model?

[Marvin Hasenak]

To make the expanding collets like Beall sells, look for concrete expansion anchors. I believe the Red Head brand has the bolt that has the tapered head on it. Drill a blank to fit the bolt, turn to size, and split one end like a collet. From the Red Head anchor bolt, throw away everything exceptthe nut and bolt. The bolt head will expand the fingers of the "collet". These are an example of the ones I use. https://www.homedepot.com/p/Red-Head...1018/100009902

[John K Jordan]

Hi John,
Modifying the pin jaws was really simple. ...

Yea! Pictures, pictures! As machined and in use.

JKJ (registered photograph addict)

[Scott Grossman]

A Robust American Beauty. I had a Powermatic 3520. I wrote to Brent English (owner of Robust) and got the following reply:
"All of thread sizes are standardized. Unfortunately, not everyone follows the standard !

Powermatic spindles are way undersize. Ours are a little undersize. That is by design. That way they can accommodate the wide variety of tolerances other manufacturers use. Your Titan is obviously a little on the tight size."

I'll try a tap as Brent suggested, but I'm not optimistic. The Titan was snug on the Powermatic and I get very little on the spindle of the Robust before it completely stops.

[Scott Grossman]

Okay, pictures. Two of the milled chuck and the first top I finished on it.Milled Chuck.jpgMilled 2.jpgAt work.jpgThanks everyone for your generous time and suggestions.
Scott