# CNC CHUCK HELP.  Where can I get a chuck like this??



## dfwcnc (Aug 24, 2014)

I am machining a watch case and this is the type of chuck I am going to need to get the job done.  Something that can internally hold a work piece that has a diameter of about one inch.  

I am banging my head against the wall trying to get this done .  Your help and insight is appreciated greatly.

Cheers~


----------



## Tony Wells (Aug 24, 2014)

Just an opinion, not being a horologist, but I would think a small manual chuck with machined soft jaws would be best for a watch case. I believe the lack of precise grip pressure would work against a precisely round watch part.


----------



## NightWing (Aug 24, 2014)

We need more info.  Is the 1" the OD or the ID?  Is the ID blind?  How long is the part?  Material, probably brass? 

If using a CNC machine, the chuck is probably hydraulic.  It should be able to have reverse chucking and a set of inside jaws, machined to suit, would do the job.  My concern is the hydraulic chuck might rip the workpiece apart.

An alternative, based on assumptions that this is a small part, might be to use a manual expanding mandrel held in the chuck.  Then, you could control the amount of gripping force.


----------



## DMS (Aug 24, 2014)

Steffan Pahlow has a series of videos on Youtube related to making a case for a pocket watch. I don't recall what he was using for workholding, but the videos are probably worth checking out.

Depending on the lathe you have, and what tooling you have, an expanding collet of some sort may work, or as Tony suggests, soft jaws are a panacea for difficult to hold parts. Depending on how much surface you have on the reference side, you may also be able to use a wax chuck (basically a faceplate where the work is held on by a wax-like substance). Pictures of the part and the operation you are trying to perform would help I think. Also, what is the material? If it is something soft like gold/silver/copper, you are going to be able to get away with a lot more than if you are working on stainless.


----------



## BRIAN (Aug 24, 2014)

Wax is the traditional way of holding weak or odd shape parts 

i have epoxy'd weak parts to a square block and mounted them in the 4 jaw to centralise the work. Ordinary epoxy loosens with the application of a little heat
so the part can be removed without damage.

Brian.


----------



## dfwcnc (Aug 24, 2014)

Yeah, I should give you more to go on.  

Material: Bronze (521)and Stainless Steel (316).  Have a look at the pictures and you'll understand what I'm doing...

I need a chuck that I can place on my CNC.  I may have to get creative since this is not mine.

- - - Updated - - -

Hi Tony, and thanks for your input.  These are large case, solid metal, not delicate pocket watches that would be better machined on a Sherline.  A four jaw may be best for the lathe, but for the cnc it wouldn't make much difference, it just needs to allow the tool to work around the work piece.  I'm sure the pics will help some.

I may have to make something.  I know there are some 5 and 6 inch table chucks that are out there, but their inner jaws are way too big to grip a 1 inch in diameter inside grip.  

I can always clean up any small details later on the lathe too. 

Your thoughts appreciated...



Tony Wells said:


> Just an opinion, not being a horologist, but I would think a small manual chuck with machined soft jaws would be best for a watch case. I believe the lack of precise grip pressure would work against a precisely round watch part.



- - - Updated - - -

As you can see from the pictures, the lathe is used to bore the inside hole, and the circumfrence of the what will be the crystal holder.  The hole that is bored on the lathe is used on the CNC to hold the piece, and it is a three jaw (non-hydraulic) chuck.  There is no hurry in machining these, so super strength isn't needed.  A small end mill is used to chew away, and an even smaller one for clean-up.  Hope this helps...


----------



## Tony Wells (Aug 24, 2014)

Internal pie-jaws on a manual 3 jaw, unless you can capture the piece with a spud and washer.


----------



## dfwcnc (Aug 24, 2014)

Finding a table chuck that size is the problem.  I can't find one anywhere.  

I just received a mail brochure from Ajax (no affiliation) that has a three and four jaw chuck with a 5 c attachment.  My experience has been **** poor with these, but if I just use it along with a table 5c fixture for the outer machining, tight tolerances are not needed--it isn't moving.  I just need to touch off it for the machine to know where it is.  What do you think?:thinking:

You may be onto something.  Maybe I make a riser out of a bar of aluminum, deep thread it, run a bolt down into it with a washer that fits right through that one inch hole.  It's crazy, but may work.  Hmmm.  I think the vibration and and end mill torquing would cause problems, though. 



Tony Wells said:


> Internal pie-jaws on a manual 3 jaw, unless you can capture the piece with a spud and washer.


----------



## Tony Wells (Aug 24, 2014)

With soft jaws, you just machine them as required to fit the id, so it's not so much a function of chuck size as getting jaws that close up tight, hence the "pie jaws".

I have even taken a piece of round, drill and tapped it about 1/2" deep with a taper tap and then cut slots across the face back past the shoulder I cut to butt against. Then running a soc set screw in swells it out like an arbor. Depending on now long a section of 1" bore you have, the grip may surprise you.


----------



## Kevin45 (Aug 25, 2014)

Machine the inside first, then make up a plug to fit the inside bore with a bolt hole through it, then bolt it to a piece of aluminum or steel to do the outside work. You can make a pilot on the plug long enough to ensure concentricity by counterboring the aluminum or steel piece. If this doesn't make sense, I can give you a sketch.


----------



## bloomingtonmike (Aug 28, 2014)

I'd try 5c.


----------



## dfwcnc (Aug 28, 2014)

I'm going to try this with some aluminum and see how it works.  



Kevin45 said:


> Machine the inside first, then make up a plug to fit the inside bore with a bolt hole through it, then bolt it to a piece of aluminum or steel to do the outside work. You can make a pilot on the plug long enough to ensure concentricity by counterboring the aluminum or steel piece. If this doesn't make sense, I can give you a sketch.



I have another 5c chuck on order, and am hoping it is better than the last.  Finding a 4 inch with a 5 c is difficult, especially a name brand one.  They way over-charge for the 5 c adaptor.  there' not a science behind creating it, but they charge like there is.  



bloomingtonmike said:


> I'd try 5c.


----------

