Newbie Collet Question

G

G8R151

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Hello all. Need some help with collet choice. I'm new to machining and need some help figuring out what type collets I need. I have a PM 1236 lathe and for now I'm tinkering with stock 2 inch or smaller. I have made some things I thought turned out really well, but when I finished most of the work then flipped it over in my 3 jaw chuck it scratched the finish I had on it. I have always been self taught, but I'm having trouble figuring out what type collets I need. Any help would be greatly appreciated.
 
Tough to say for the size of material. Most collets go up to around 1" plus a little. How about making, or buying, some soft jaws for your chuck? If you have two piece jaws this would be a good alternative.
 
Collets are nice for certain work holding, but they are not a game changer. I got along very nicely for 30+ years before getting a collet set up. They are handy, but they don't really add to your capability (in my experience). Why don't you use the 4 jaw chuck? As Paul said, soft jaws are great, also really planning your work steps. Can you leave the work piece long and machine it all in one grip, then cut the "handle" off? Can you machine that component between centers? Have you tuned your chucks (what sort of runout are you getting)? How good do you need? Collets are not perfect either.

There is often more than one way to get the job done.
 
Your lathe has a MT5 taper spindle so you would typically use 5C collets, which limit you to 1 1/8" max diameter basically. But it looks like the spec sheet for your lathe lists a collet chuck, instead of a drawbar, but you are still limited to 1-1/8" 5C collet size. You would need to determine if you want to buy a couple of 5C collets based on the common size you turn or a set (increments in 1/8", 1/16", 1/32", 1/64" or metric), it's a matter of cost.

As Paul posts, need to make or buy soft jaws for your chuck. I just insert 3 pieces of aluminum to keep my jaws from digging in, unless I can use my collets.

As you gain more experience, you will learn how to sequence your machining to lessen the chance of marring the piece. Also better ways of holding the work to lessen it as well (soft jaws, centers, drive plate, and dogs, etc.)
 
I would go with ER collets, simply because of their much greater clamping range and improved accuracy over the 5C system. Either will hold a work piece without too much damage to the surface finish and chucks are available for both types. ER-40 will go up to an inch and ER-50, while more expensive, will go larger.
 
If you are doinga lot of repetative ops the collet is the way to go. The ER 40 or the 50 will be better than the 5C.
 
If doing multiple parts a collet with a stop in it is the way to go. There are also 5c collets that go bigger than 1 1/8" but you have to bore them for what your part diameter is. there are also square and hex colletsin 5c.
It all depends on what you need.
 
I'd go 5c, because of the step collets, allowing up to 6 inch in diameter I believe. I have a 5c chuck, my friend with a real machine shop uses 5c because of the step collets....
 
i'd go 5c myself because of the wide range of sizes that can be held and they can be had pretty cheap used if you are vigilant in your searches.
i have purchased new and used collets of all sizes, new and import, step and button.
a clear advantage is through feed, that you can't get from an ER holder.
your situation may differ from mine and an ER may suit your needs.
i have one, an ER 25, it holds nice and is easy to use- but i prefer the 5c- i guess i'm just old fashioned...
just another FYI,
they do make 5C emergency collets that come in scratch resistant materials like nylon, brass, & aluminum.
it may even be a nice project for a budding hobby machinist to reproduce a 5C collet from scratch in a scratch resistant material...
 
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