Collets

[Susquatch]

They are both fast and accurate but the material has to be on size (to no more than +- 0.001" - with the 3C, 5C, R8 types) to not distort them when clamping stock.

There are prolly more than a few who disagree, but my experience backed by advice from several collet makers is more forgiving. My 5C chuck gets used more than all the others combined. My experience works for me and gets great results. But it's still just my opinion.

I find that 0 to -10 thou is usually good enough on the bigger collets. 10 thou is really only 5 thou per side. Smaller collets can sometimes need to be a bit tighter. On the really small ones I might shoot for 0 to -3 thou. I really don't think plus (+) anything is a good idea (despite thousands of web quotes to the contrary). Careful inspection of the collet fingers suggests that most collets don't handle expanding really well because it distorts the root of the gripping finger faces in a way that concentrates the forces and can damage the collet and potentially the collet holder. If the work doesn't slide freely into the collet, I use the next size up. I never force work into a collet.

5C collets are widely available in 1/64 increments, and you can get 1/128ths. You can also get custom sizes if you open your wallet enough. 1/64 is close enough to 15 thou (7 on a side). 128th is 8 thou (4 thou on a side). But a full set of 64ths or worse 128ths is just too much coin. Keeping in mind that 5C is primarily designed to hold stock, exact fits are rare. According to most of the manufactures, -8 thou won't hurt them. But it might not grip as tightly as desired. Therefore I often use shims.

A pop can wall is usually around 3 to 4 thou. So I like to use a wrap (or two) of a pop can wall (slightly wider than the grip length of the collet) as a shim to get a tighter fit on my 32nds collets when needed.

Never even once has a 5C collet of mine ever let go - even on the heaviest cuts I have taken. I have broken a few tools though.

Thats my experience for whatever it is worth, and that's my advice to others. Get a good set of 32nds and use pop can shims as necessary to get a good fit.

 

[darrin1200]

@Mcgyver That’s a lot of good info.
That is a really good deal on those collets. It’s a little out of my budget right now, but I’ll have to try and come up with some disposable cash.

 

[PowderPig]

@PowderPig - @YYCHM has the setup that will work for you. One other option would be to buy the "Tru-Set" chuck that will allow you to fine tune the runout of the chuck.

I have ER and 5C and find each have their place. ER collets are good on standard size round rods but if you need a square or hex collet 5C are the only ones I've found that do hex and square. One advantage to the ER collets is your stock can be .020 or more under size and still use the collet, AFAIK 5c collets are much less forgiving and only have a few thou leeway. One advantage with 5C is you can buy blank collets that let you make a oI'm inNorthernne off size for those specialty jobs.
When I needed a 3/16 hex I found a Hardinge 5C speed chuck at a decent price so I bought it and the hex collet.

For me the ER spends much more time on the lathe than the 5C but that may be that I bought the ER setup before needing the 5C.

@PowderPig - where are located? Maybe @YYCHM demo or let you try his setup.

I'm in northern New Brunswick.

 

[CWret]

what type of collet set I would need,

I’m glad you started this thread - it’s been a good read.

the 5C is primarily designed to hold work. Whereas the ER collets are primarily designed to hold tools.

I guess I could have guessed that by looking at how they are constructed - but now I better understand the differential.

I have the lever action drawbar which makes inserting and removing parts very fast, even with the spindle turning. Being able to insert a long piece of stock thru the spindle is a big advantage.

I guess I was lucky to find a similar lever handle drawbar type collet holder attachment for my Myford (Kijiji). It came with a basic set of collets to 5/8” - which matches the max size of this (relatively small) lathe’s spindle bore. This type of collet, I believe, is designed to hold the part. I have not used it yet, but I am looking forward to giving it a try. Here’s a pic of it:

If you are talking about collet brands the best are Hardinge or Royal or Royal/PBA or Crawford/PBA

In the pic above, these are Hardinge.

 

[YotaBota]

I'm in northern New Brunswick.

That makes it a bit of a nogo for coffee with @YYCHM. lol
Hopefully someone out your way can help with a demo.
Good luck.

 

[PeterT]

If you Google something along the lines of 'minimum diameter required to grip stock in 5C collet' you will get a wide range of answers. Unfortunately little to no authoritative information from a collet manufacturer. (If you do have a manufacturers link, please provide!).

From my own experience & readings, the rule of thumb is +0.0 -0.010", for example a 1/2" collet should hold 0.500 - 0.490" stock. Some argue +0 is not correct either. The reasons given is that a larger diameter does not seat the collet cone properly & risks gripping stock on the rear corner of the contact cylinder. What happens when you put lots of force on a contact point/line?

On the minus tolerance side, two issues. 1) excessive collet collapse can permanently distort the collet jaws. What is excessive? Another rabbit hole. Did you just bugger up an expensive 0.0002" collet that will no longer repeat, or is of no consequence on a cheapo model that will kinda bend back? 2) Contact area. You can visualize that the more undersize the stock is relative to nominal, the less contact area (grip) can be exerted on the part as the taper seat bends the collet nose inward. The radius of bend is dictated by the length of relief slits. Unlike an ER which is radially slit from alternate ends around its perimeter & collapses more radially, a 5C is basically 3 leaves which bends inward from a point about 2/3 from the nose. So at some point of excessive undersize, the contact goes from large area to small area to a line to no grip. So within this spectrum, one persons idea of sufficient grip may be different than another persons. Even the material being gripped factors in this.

The main takeaway point is just because you have a 1/32" (0.032') increment 5C set, does not mean you can accommodate all diameters just picking one collet or another. Its better to think: 'take 5-10 thou off each nominal diameter' & that is the bracketed range I can reasonably hold. (And that's not quite true either, smaller diameters have less tolerance). The big clue is they sell 1/64" & 1/128" increment or metric equivalents for a reason. Where people get into trouble is with a larger increment set like 1/16" set & attempt to gronk them one way or another.

 

[Ian Moss]

Anyone have experience with a Jacobs rubber flex collet chuck ? I missed one on Kijiji.
Martin

Hi Martin: I have a Jacobs rubberflex collet chuck and use it quite often. I find it very accurate, and of course will grip any diameter of work, not just discreet sizes like a 5C. I also have the key operated version that I can use in my 3 MT tailstock or 3MT geared head drill press. They seem to turn up regularly on eBay.