Lathe hard jaws for turning small OD's?

Schjell · May 31, 2021

Hi,
On my 10-inch chuck I've got two set of hard (grip) jaws for various OD spans, but I can't go below 18mm OD. This is driven by the width of the jaws, which is 40mm in my case.
Is anyone here aware of commercially available hard jaws that are more narrow towards the chuck center end? - they would then in theory be able to grip onto lesser OD's.

I have played with the thought of using a 3-jaw drill chuck of sorts and gripping this with my jaws, but it sounds like an accident waiting to happen.

It's a shame that collet chucks require removal of jaw chuck - for my work flow this would be wildly inconvenient since we have usually have one or two off's and no series.

I thought about using soft jaws and drilling a hole in the center, but would prefer a harder and serrated jaw that will not slip so easily once I stray away from the drilled hole size. I don't want to have loads of softjaws drilled for everything between 17 and 10 mm if you get my drift. I already have 19 sets of machined soft jaws on my shelf (where I use most of them regularly btw).

Thanks for all ideas, I hope there's an easy fix out there!

Screwmachine · May 31, 2021

I think the easiest would be to hold a smaller chuck in your 10". You could make a backplate with a convenient male diameter to grip in the 10"; turn the register for the sub-chuck, and mark it so it goes back in the 10" the same orientation each time and concentricity shouldn't be an issue.

Schjell · May 31, 2021

Thanks for the advice - will give it some thought.
What I'd really like are some grip jaws that are more pointy, ref. picture of soft jaw options below.

Scottl · May 31, 2021

I wonder if one idea might be to make jaw inserts of steel angle that would go over the nose of each jaw. They could be grooved and then casehardened after grinding for proper alignment and of course numbered for the jaw they are fitted to. They would need some kind of tab to go over the face of the jaw, probably with a small magnet to hold in place before tightening.

Since the stock jaws are already fitted, perhaps rig one up at the proper angle on a surface grinder and grind all 3 in sequence so they are the same thickness.

May sound a bit off the wall but would be easy to install and remove when needed.

The other option would be to fit a smaller back plate and chuck to your spindle but that would be a PITA to swap.

cyanidekid · May 31, 2021

that is what smaller diameter chucks are for. you simply can't expect one chuck to do everything.

a 150MM or 125MM chuck will handle that. D1- mounts allow quick chuck swap outs, but if you have one of the inferior antiquated mounts, the "chuck in a chuck" technique Screwmachine outlined (very well I might add) will work.

a quality chuck, so mounted and used within reasonable limits will provide good service, and you can set up a few different types in the smaller sizes.

P.S. you will generally want to use lower profile lighter duty chucks for "chuck in a chuck" to keep the weight down and closer to the spindle, and likewise, keep the work "light and close". or just change chucks, that's the right way to do it, after all.

Nmbmxer · May 31, 2021

I’ve made mounting plates that bolt to the front of large chucks (manual and power) to hold smaller ones over the years. Lots of 4 jaw chucks have t-slots or tapped holes for counterweights that work great for mounting a small chuck. You can also mount the small chuck to some 6” material 6” long and just chuck that. I like the 5-6” set-tru type for for the sub chuck.

Watch out for chuck key clearance, I’ve made several long keys so the handle clears the larger chucks OD. This is usually the aggravation if you directly chuck and small one in a larger one.

Delw · May 31, 2021

Schjell said:
Hi,
On my 10-inch chuck I've got two set of hard (grip) jaws for various OD spans, but I can't go below 18mm OD. This is driven by the width of the jaws, which is 40mm in my case.
Is anyone here aware of commercially available hard jaws that are more narrow towards the chuck center end? - they would then in theory be able to grip onto lesser OD's.

I have played with the thought of using a 3-jaw drill chuck of sorts and gripping this with my jaws, but it sounds like an accident waiting to happen.

It's a shame that collet chucks require removal of jaw chuck - for my work flow this would be wildly inconvenient since we have usually have one or two off's and no series.

I thought about using soft jaws and drilling a hole in the center, but would prefer a harder and serrated jaw that will not slip so easily once I stray away from the drilled hole size. I don't want to have loads of softjaws drilled for everything between 17 and 10 mm if you get my drift. I already have 19 sets of machined soft jaws on my shelf (where I use most of them regularly btw).

Thanks for all ideas, I hope there's an easy fix out there!

get a set of these type of Jaws.StackPath

blot then on and go

Triaged · May 31, 2021

Get a 5C collet setup and chuck it up in the big chuck. If you aren't doing more than a couple of pieces it isn't too bad. Very inexpensive and doesn't every shop have some 5C collets already?
McMaster-Carr

Schjell · May 31, 2021

Delw said:
get a set of these type of Jaws.StackPath

blot then on and go

Outstanding, thank you very much!!

Fancuku · May 31, 2021

Yeah, collet pads are your best bet.

Triaged · May 31, 2021

I've never seen one of these in person but it's another option. Does anyone have any experience?
CNC Collet Chuck System - NUB TOOLS

Schjell · May 31, 2021

That one looks even better! Prob. some runout, but more than good enough for my use! Thanks!

Triaged · May 31, 2021

I'm curious if it would damage the collets if you closed it without something in the collet.

Nmbmxer · May 31, 2021

I’ve got a set of soft jaws that hold 5c collets, works quite well. No way would I spend $900 of them. The set I made was 1/16”x90 for a power chuck, I’ve been meaning to make a set for my manual lathe’s 3jaw. Easier than swapping chucks out.

Scruffy887 · Jun 1, 2021

This is an easy solution if you have a set of jaws for 1.25 shank. And straight shank ER holders are made in a ton of shank/collet sizes.

ER32 1.25-4.0 Straight Shank Collet Chuck - Made in USA MariTool

vw_chuck · Jun 1, 2021

Yes use an ER collet holder in your current chuck.

Schjell · Jun 1, 2021

Scruffy887 said:
This is an easy solution if you have a set of jaws for 1.25 shank. And straight shank ER holders are made in a ton of shank/collet sizes.

ER32 1.25-4.0 Straight Shank Collet Chuck - Made in USA MariTool

Thank you all for good suggestions, but the ER32 shank solution must be the way to go - brilliant! You just saved me 900 bucks as well, owe u a beer if you ever come to Norway:-)

nateacox · Jun 1, 2021

We use these and love them. About 10 mins for a full changeover.

EnderDRM · Jun 1, 2021

Or make your own...

Philabuster · Jun 17, 2021

Schjell said:
Hi,
On my 10-inch chuck I've got two set of hard (grip) jaws for various OD spans, but I can't go below 18mm OD. This is driven by the width of the jaws, which is 40mm in my case.

I wanted to have my 10" hard jaws grip on 12mm OD rods. What I did was mill away some of the 60° angle on the nose of the jaws so the jaws could collapse closer together before they touched. Carbide endmill in the Bridgeport and I was done in no time.

Lathe hard jaws for turning small OD's?

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