Author Topic: Lathe chucks (Read 11462 times)

rleete · « **on:** July 26, 2009, 09:35:02 PM »

I have a Homier 7x12 "Speedway" lathe. One of the chinese clones. It came with a 3" self-centering 3 jaw chuck.

Recently I obtained a small piece of DOM tubing in 3" ID. Just barely too big for my 3" chuck to hold. Pity, as it would make excellent rims for flywheels. So, I started looking at getting another chuck.

LMS and others sell a 4" and a 5" version. The price difference is minimal ($95 vs. $105). Both include the adapter at that price. Is there any big disadvantage to getting the larger one?

bogstandard · « **Reply #1 on:** July 27, 2009, 02:32:47 AM »

Roger,

First off, couldn't you use the normal jaws for holding the tube internally?

I personally wouldn't go too large, just because it fits, doesn't mean it is right. I could, in theory, put a 17" chuck on mine, but I think the lathe would disintegrate when I turned it on.

A couple of reasons, the first being the larger the chuck, the more mass on startup to get it turning. I know nothing about your lathe, but if it uses those electriconical circuit board thingies, you might just overload it and burn it out. The same goes for actually turning, the larger the item held and turned, the more loading on the motor and board.

The second is actually the mechanical bits of your lathe. These machines are usually made down to a price, and everything on them is designed to do the job and not much more, bearings, gears etc.

So looking at it, go for a larger chuck, but don't push it by going too far.

With the few bucks saved by going for the smaller of the two, look to see if you can put it towards buying a set of soft jaws for the chuck you buy, that will really help improve your tolerances greatly.

I hope this helps

John

foozer · « **Reply #2 on:** July 27, 2009, 03:31:26 AM »

Quote from: rleete on July 26, 2009, 09:35:02 PM

I have a Homier 7x12 "Speedway" lathe. One of the chinese clones. It came with a 3" self-centering 3 jaw chuck.

Like the man said, bigger not always better. I have a 6 inch faceplate 1 inch thick AL for my AA109. No way, no how do I crank the speed up, just to much rotating mass. Fitted a 3 inch Taig soft jaw chuck and its pure heaven. Has low mass so can crank it up over 3000rpm with little worry. Can make the jaw pieces for those times when the part is just a tad too big. They virtually eliminate any chuck runout, need to face off flywheels, wonderful tool for that.

Check out Bogs Making a Flywheel post, the pics explain better than I. Cant take hard cuts with em, but then the little lathes argue that point anyway. Was money well spent.

Robert

Stilldrillin · « **Reply #3 on:** July 27, 2009, 03:50:46 AM »

I now have a 4" chuck on my Churchill 7 x 20.

There is a very noticeable difference in rotating mass, overcoming the starting, & stopping inertia.

I mostly use the lower gear ratio (to 1,100rpm), but always build up the revs over a couple of seconds, or so.......

David D

Darren · « **Reply #4 on:** July 27, 2009, 03:53:48 AM »

Hi Roger, there is another issue I believe with the larger 5" chuck.

You can't open the jaws out fully as they will hit the bed, so no real gain over a 4" size.

The extra mass would be my biggest concern though as has already been mentioned.

rleete · « **Reply #5 on:** July 27, 2009, 08:01:08 AM »

Quote from: bogstandard on July 27, 2009, 02:32:47 AM

First off, couldn't you use the normal jaws for holding the tube internally?

I tried. The ID is just a tad smaller than the chuck itself. Therefore, I was gripping on the very back edge of the jaw; not the part that is meant to be used, but the part that dovetails into the chuck. I didn't think that would be very secure! I also tried the outside jaws, and they barely held on, being right at the hairy edge of engagement of the scroll in the chuck. Once again, not very secure.

I'll take a pic later if this isn't clear.

Darren, I hadn't thought of that. Could be an accident waiting to happen.

I guess I just have to tell the wife I need a larger lathe...

Bernd · « **Reply #6 on:** July 27, 2009, 12:00:29 PM »

Quote from: rleete on July 27, 2009, 08:01:08 AM

I guess I just have to tell the wife I need a larger lathe...

I've been telling mine that too. If you suceed in getting one let me know how you did it.

I've got a requisition in for a 13 X 40 Gear-head floor lathe from Grizzly, but the finance committee says there's no money available. Dam!

Bernd

foozer · « **Reply #7 on:** July 27, 2009, 01:38:33 PM »

Shot of 3 1/2 inch flywheel made using the soft jaw approach. Something my regular 3 jaw couldn't handle. Bored the jaw faces to give grip to the inner rim. Cut em to the same dia as the piece to be held for good contact area. Holds well enough so long as aggression is applied only to the wood pile. Haven t tore one loose yet.Still have plenty of room for larger dia tubing (pucker factor exponentially increases with size) Very handy and useful tool.

Robert

rleete · « **Reply #8 on:** July 27, 2009, 02:38:01 PM »

Okay, so where do you get soft jaws (or blanks) for the standard 3 jaw chuck? Making them from scratch is a bit beyond my capabilities at this point.

foozer · « **Reply #9 on:** July 27, 2009, 03:05:00 PM »

Quote from: rleete on July 27, 2009, 02:38:01 PM

Okay, so where do you get soft jaws (or blanks) for the standard 3 jaw chuck? Making them from scratch is a bit beyond my capabilities at this point.

That's the 64 dollar question. The Taig chuck (3/4 X 16 mount) is nothing more than flat faced steel jaws for the scroll part to which the AL bits bolt upon. Would think that a set of regular jaws could be flattened, drilled and tapped to achieve the same.

Maybe someone who has done it will chime in while i go actually try it on an chuck

Robert

bogstandard · « **Reply #10 on:** July 27, 2009, 06:58:30 PM »

There was an article in Model Engineers Workshop (a UK mag) a few months back about how to use them, and in the second part, how to make them for your chuck.

If you are interested in finding out about soft jaws, I might be able to give you a good link if you PM or email me.

We in the UK seem to be very lucky, almost all cheapy chucks you can buy, you can also get soft jaws for them.

http://www.arceurotrade.co.uk/Catalogue/Chucks/Lathe-Chucks

Normally around 20 squid a set (about 25 bucks US)

It seems your US suppliers are about 20 years out of date in knowing what the modern machinist requires.

I suppose if you have one of those wierd chucks that the jaws bolt onto the front of the scroll pieces, it would be very easy just to make soft iron or ali jaws to bolt on.

Bogs

rleete · « **Reply #11 on:** July 27, 2009, 07:56:11 PM »

These: http://littlemachineshop.com/products/product_view.php?ProductID=1688&category=1022859368 are what the jaws look like. There is also an outside set, which I have. I believe they're hardened, but I haven't checked.

At this point, I'm either going to buy a larger chuck, or figure out a way around my workholding problem.

bogstandard · « **Reply #12 on:** July 27, 2009, 08:22:09 PM »

Roger,

Bad news, those are just standard hardened jaws. LMS don't do any chuck soft jaws at all.

You have to be very careful when buying any replacement jaws for chucks. You have to get exactly the right jaws for your particular chuck.

The different manufacturers will use similar, but not exactly the same scrolls in their chucks. So it might look like they will fit, but 9 times out of 10 they won't. They are like threads, metric looks similar to UNC, but the nuts are not interchangeable. It is the same with chucks.

That is why you should always buy spare jaws when you buy the chuck. You are guaranteed then to have them fit correctly.

John

rleete · « **Reply #13 on:** July 27, 2009, 08:52:07 PM »

Well, it came with the lathe (but no faceplate, go figure), and so I had no choice. Plus, until I joined here (more than a year later), I didn't even know about soft jaws. Live and learn. I'm still researching chucks, and when I find one, I'll try to get it with soft jaws, or the kind you can bolt on your own.

Right now, I've put that particular one aside for the moment, and started yet another. I have big plans for this new project, and it's all based on things I know I can do with the tools I have already.

bogstandard · « **Reply #14 on:** July 27, 2009, 09:57:30 PM »

You are doing it the right way, never push yourself financially if at all possible, try to come up with ways to use what you already have.

I did it for many many years, as I am sure a lot of us had to do.

It is only recently that I am now in the lucky situation where I can afford the silly little playings I always dreamed of, but if a situation does occur where I don't have the right bit of equipment, I still improvise, and get more enjoyment doing it that way than taking the easy way out, waiting for the postman.

I still scrimp and save wherever I can, and turn nothing away that will save me money in the long run. I think that once improvisation and scrounging gets into your blood, it is there forever.

John

Darren · « **Reply #15 on:** July 29, 2009, 03:09:19 AM »

Roger,

I found a chart here.....http://images.google.co.uk/imgres?imgurl=http://www.mini-lathe.com/Mini_lathe/Modifications/Brass_gibs.jpg&imgrefurl=http://www.mini-lathe.com/Mini_lathe/Modifications/modifications.htm&usg=___T1EPj_FVXdiXPGB2Bzostu4Hys=&h=412&w=490&sz=31&hl=en&start=17&sig2=SoltdlFxHj1dGDhlvij_-Q&um=1&tbnid=Ua_L2XcFkCd8VM:&tbnh=109&tbnw=130&prev=/images%3Fq%3Dadjusting%2Bbox%2B%2Bgibs%26hl%3Den%26safe%3Doff%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26sa%3DN%26um%3D1&ei=LO9oSpWUEeGRjAeVk-SyCw

There is a chart showing the capacities of different size chucks. ..

rleete · « **Reply #16 on:** July 29, 2009, 07:18:20 AM »

Thanks. I already read through that section before I posted, but it's nice to know that we're both on the same page (no pun intended).

I think, for the sake of safety and to prevent overloading the lathe, I'm going to get a 4". I need a 4 jaw anyway (just the 3 jaw has been very limiting), so getting one just a bit larger ought to be good.

Stilldrillin · « **Reply #17 on:** July 30, 2009, 03:36:43 AM »

Quote from: rleete on July 29, 2009, 07:18:20 AM

Thanks. I already read through that section before I posted, but it's nice to know that we're both on the same page (no pun intended).

I think, for the sake of safety and to prevent overloading the lathe, I'm going to get a 4". I need a 4 jaw anyway (just the 3 jaw has been very limiting), so getting one just a bit larger ought to be good.

I was very surprised, a 3" chuck wouldn`t hold a 3" flywheel.......

The replacement 4" has done all asked of it, so far!

David D

28ten · « **Reply #18 on:** July 31, 2009, 03:25:51 PM »

I have been using 4 inch chucks without problem in my minilathe, but i'm not taking deep cuts or turning long bar stock.
I found soft jaws rather elusive but I eventually found Chester stock them for 80mm and 100mm 3 jaw chucks. I got a set for the 80mm chuck that comes with the lathe and they will stay in there permanently as turn a lot of shallow wheel castings, or at least I will do when the bed is sorted

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Author Topic: Lathe chucks (Read 11462 times)

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