Why Is It So Hard To Decide?

[kcmillin]

I am having an incredibly difficult time deciding/finding what I am looking for in an ER collet Set.

My frustration is with the Tolerance. I can find the cheap ones to be about .0005-.0006 T.I.R. I would like to get this down to .0002. I found a good set of ER32 collets with a .0002 T.I.R, but cannot find a suitable MT4 mount chuck to go with it. Most if not all of the chucks I find are .0005 T.I.R.

Does this mean that the worst it would be between the Chuck and collets is .0007 T.I.R.? It seems like a lot.

Is this acceptable?

I am looking for an accurate way of holding work in the lathe, I have an MT4 mount on the lathe, and would like to use it, as opposed to using a 4 jaw chuck to center a straight shank.

I want to be Chuck-Less.

I would like to find a good quality MT4 mount chuck in either ER32 or ER40.

Am I asking for too much. Is this type of tolerance necessary. I am currently only doing model engines, but would like to expand to paid jobs at some point, So quality is important to me.

I see alot of collet holing on the lathe, and for the most part are used when extreme accuracy is needed. Like making valve seats by flipping the valve and having it concentric, (For the most part)
I found a Bison straight shank chuck and ER11 collet set for $166 on E-bay. I cannot get the tolerance of this, but I have heard that Bison is of decent quality.


I am kind of rambling here, I have looked through just about all the posts on this subject and still cannot come up with a conclusion.

has anybody been in this situation?, if so, what did you go with?

Kel

 

[cfellows]

I'm working on putting together some tooling using er20 collets. I'm noodling around with the idea of making my own er20 collet chuck for my mini lathe. I bought a cut off chuck from ebay and I'm thinking of making a backplate to fit my mini lathe, then boring a hole in the center and silver soldering the chuck I bought into the backplate. I think if you can get a combined TIR under .001" between both chuck and collet, your home free.

Chuck

 

[shred]

A couple guys in the club have made their own ER holders and say it's pretty easy.. it's the collets and nut that are the tough bits to make.

Maybe a custom holder will help. What are you looking to do that needs better than 0.001" repeatability?

A friend in the machining business (he's got a room full of CNCs punching out parts day and night) had a scribble on one wall where he'd explained things one day to a novice. Not all their work is like this, but a whole lot of it is:

0.1234"
 ^---- hundred thou
  ^--- ten thou
  ^-- thou
   ^- don't give a sh**

 

[Lamachina58]

I use a lot of ER16 and 32 collets from Maritool. The nuts are balanced and holders too. This is CNC stuff meant to be balanced at 25000 rpm,but I am going to make some holders for the lathes (I teach at a community college) for the same reason you want too. I will post what I am doing, it may be winter semester though. We don't have 5C or any collets for our CNC lathes so it is kind of the same problem.

At home I use end mills down to .010 diameter and spin up to 15000 rpm so balanced and accurate collets are important just like when you are doing the small work you described on models. I often load the tool and indicate the flutes. It is surprising but if you are out a few tenths, I loosen the nut and rotate the piece 90 degrees. I can usually get things closer that way. It must be a stack up of many tolerances but they can cancel each other as well.

I think you are on the right track, make your holder, they are very expensive, do a good job and it should run true. The nuts and collets are less expensive than the holder.

If you don't have a collet lathe I often make "soft jaws" of aluminum or Ledloy ( aka 12L14 steel) so they run true and grip what I want. I will take a picture monday, we are doing a project at school with them.

 

[quinette7]

I have only a little professional experience with ER collets, but I'd have to think that you MAY be asking too much. ER collets are designed and used much more commonly for milling (rotating tool) applications than turning (rotating workpiece) applications. Milling adapters that hold the tolerances you desire are more commonly found than MT adapters. My "Machinery's Handbook" gives tolerances for milling holders, but no tolerances for MT tooling, which makes me think that the limiting factor for you is the MT itself. ER collets were patented in 1973, whereas MT tooling is several generations older than that, when the .0002" TIR you seek was pretty rare commodity. It is my understanding that MT tools were used primarily for inward thrust (drilling, reaming), while ER tools excelled at side thrust (milling) and concentricity. Iscar/ETM makes this adjustable ER holder that can probably meet your demands, but I'll bet it is a pricey option.

http://www.iscar.com/Ecat/familyHDR.asp/fnum/2047/app/110/mapp/IT/GFSTYP/M/type/1/lang/EN

Bob G

 

[doc1955]

You need to remember that a .0007 t.i.r. means a run out of only .00035 of the center line.
You can lightly tap what ever you are clamping in the collet to get it right on if necessary.
I believe even the best quality collets will not be much better than the .0007 if any.

 

[Blogwitch]

If you need to get accuracy from your lathe, the only real way to do it is to make the tooling yourself, on the machine you are going to be using it on.

For fairly short piece work, you can't beat a set of soft jaws, if you can get a set to fit your chuck. If you are going to ever invest in a new self centring chuck, either 3 or 4 jaws, buy one that you can get the soft jaws for.

Now to solve your ER problem, I am sending you to two posts about jobs I have done for my lathe, where I made interchangeable tooling to fit onto my lathe or mill RT.

This first part shows how I made a 5MT adapter for my lathe, then cut a Myford thread onto it. With yours being a 4MT, it is just a matter of angle changes whilst cutting. You can ignore the nose threading bit, and go onto the second posting and cut an ER thread onto it.

http://madmodder.net/index.php?topic=1993.0


This is how I cut my ER thread and taper onto the nose. It is very easy really, if you take your time.

http://madmodder.net/index.php?topic=2249.0

So you should end up with a dedicated ER collet holder for your lathe that has almost undetectable runout.


Bogs

 

[wheeltapper]

my lathe has a flange on the mandrel.
so here's the one I made, it's er32.

and with the closing nut

I can move it a fraction on the flange before bolting up and can get damn near zero runout.

I bought the nut by the way.

Roy

 

[gbritnell]

Here's my experience with some ER collets and holder, ER32 to be specific.
My mill has R8 holders and it's cumbersome to change them by hand so I thought a set of ER collets would do the trick.

Having read many stories about the accuracy or inaccuracy of these things I wasn't sure which way to go.

I found a lightly used set on Ebay and the bidding was extremely low so with some reservations I contacted the seller prior to bidding. I asked if he had checked the runout and his reply was he had only used them a couple of times and hadn't done so.
I put in a bid and eventually won the set.

When I received them the first thing I did was clean them up and mount them in my mill for checking. I put in a hardened tooling dowel and set up my indicator. The dowel ran out almost .003. I loosened the nut up to release the collet and repositioned it for a recheck to which I got the same reading plus or minus.
I then took them to my buddies machine shop where he has some very nice tooling and we checked them again with the same results. He said that he didn't have any type of arbor for holding an R8 adapter but if I made one we could mount it in his set true chuck and regrind the collet taper to be concentric with the R8 taper.
I did and we did.

Now the moment of truth. I put in a .375 collet and a hardened tooling dowel and I still got .0015 runout. I then put in a .500 collet and repeated the test, it was worse.

I have come to the conclusion that buying these import collets and holders is a real hit and miss proposition.
Should I spend a lot of money and buy what is supposed to be a 'better set' only to have similar problems? I don't think so.

For the time being I think I'll stick with the R8's.
gbritnell

 

[mu38&Bg#]

I try to plan my machining such that I don't need to rechuck a part. This isn't always possible. Besides, ER won't work well for parts that don't fully fit the grip length of the collet, I understand making a slug to fill the collet is the answer. When you're dealing with an adapter from MT4 to ER you may want to mark it go get best runout in the spindle. As mentioned clocking the MT adapter and regrinding the collet taper will give the the best results.

Good luck buying cheap import collets that actually meet he spec. I bought some CTC ER16 straight shank holders that had virtually perfect collet tapers with virtually no noticable movoent on a 10ths incidator. The supposedly .0004" collets don't appear to meet spec, but I haven't measured them yet. I'm sure the quality brands are better, but spending 200-300USD on a ER16 collet set isn't something I'm going to do right now.

I have a 5C chuck on my lathe and don't regret it. I made the backplate for it and ended up 2/10ths out and repeatable. 1-1/16" through spindle capacity is great if you need it. Patience on Ebay will net you a full set of collets in short order at a reasonable price. 5C dividing heads and indexers are also very common and useful. I just received material to make a 5C spindle for a 4th axis for my CNC mill. I also have a 5C spindle to make a small CNC lathe. Going 5C makes you pretty committed however, and it you like metric sizes doubles your collet collection.

 

[kcmillin]

Thanks everyone for your advice. Your thoughts are appreciated, nothing like a few un-biased opinions to help your decision process along.

I am strictly going to use the collets in the lathe and possible R/T. My R8 collets work great on the mill, plus keep everything nice and tight to the spindle.

Here is the ER 32 collet set I am looking at.
http://cgi.ebay.com/18-Pc-Close-Tol...ork_Holding&hash=item1c10738121#ht_4555wt_764
I cannot find a manufacturer, but it says there is an average .0002" T.I.R. This is about the best I have found, even with the Lyndex and Bison.

I figure if I get good quality collets, and make a collet chuck on the lathe,(Like the one Bogs Made) this will give me the best chance of repeatability.

Bogs, my lathe has a threaded spindle, I think I will use this to mount the collet chuck, instead of an MT4 adapter. Your posts have been more than insightful. Also, what is the final height of the collet off the chuck face? I seen you used an ER32 collet holder to get this dimension, but I do not have an ER32 chuck to measure of off. Can I get the dimensions of the chucks working faces somewhere?

I have some 2" and 2.5" round steel bar, I believe it is Mild Steel. Will this material choice be good enough? Or do I need to choose a harder steel to make the chuck out of? Perhaps I should practice with the steel anyway, I have never cut internal threads before, and the thread on my lathe is 1-3/4"x8 TPI, so this might be a challenge. But worth it in the end.

Kel

 

[rake60]

Little Machine Shop offers a good set for a little less $$$.
ER-32 Set of 18

Rick

 

[Deanofid]

Kel, a while back I made a collet chuck for my little Atlas. It has a threaded spindle nose, like your lathe,
though smaller in diameter, the same TPI. I think if my 6" Atlas will cut that, you should have no problem.
I bought cheapo collets from CTC, along with an MT2 adapter, but had planned from the beginning to
make the chuck myself. Mainly got the MT adapter because it came with the closer nut.

When it came to cutting the ER25 taper, I pretty much followed John's way of doing things, which turned
out very well. The runout is right at .0005", and this is a 60 year old lathe with bronze bushings. I did
replace the bushings a while back, but still the same old spindle, and as long as I have the bushing caps
snugged up right the collets run out at .0005" except for a couple that do .0006-.0007".

I have a build article on my website, if you'd like to see it for the spindle thread part:
http://www.deansphotographica.com/machining/atlas/ER25/ER25.html

I'm quite happy with this, considering the age of the lathe. Was a full day of shop time, the way I work,
and I think well worth it for the convenience of collets.

When you speak of tolerances for doing outside jobs, I wonder how many you would get that need
better than these collets offer, really? Half a thou should do you well for the great majority of what you
would need to do. It's not often we need that even for making the small parts for our models, and
when parts get bigger, tolerances often do too. When you make your collet chuck to match your lathe,
I think you will do fine in that department.

Good luck with it. Hope you show us what you make.

Dean

 

[mu38&Bg#]

If I was going to go the ER collet route I would certainly do as Dean did and make it to fit the spindle threads rather than a taper adapter. This will allow you to use the rather large through spindle capacity an MT4 spindle should offer. I like the ability to put a 3 foot bar of 1" through the spindle to make a part and part it off in the lathe.

 

[kcmillin]

All this talk of making a Chuck has given me the itch.

Although I do not have the collets yet I thought I would start on the chuck.

I began by making the threaded end first, with the register. Using basicly the same method of Bogs and Dean. I do not have an internal threading tool, but I do have some small indexable triangle inserts and holders.

I cut one of the holders to fit a single point cutter holder I made for the mill awhile back. As you can see it is mighty rigid.

This was my first try at internal threading, and only the second time I have ever made successful threads on the lathe. I could not be happier with the result.

Kel

 

[steamer]

Good for you Kel......Don't let that thread scare YOU......machine that Sumbi(#& into submission!

And a Karma for ya!

Dave

 

[kcmillin]

Thanks Dave!

I wasn't sure how well the cutter was going to work, I thought it might shatter from such a deep cut, but it went quite well.

Since I made this out of CRS (I think), I have heard about the internal stresses and so forth with CRS.

Is there anything I can do to help relieve this stress before I cut the final taper in it?

Since there is already a hole through the entire part, I was thinking about throwing it in the freezer for a day and then let it warm up to room temp, and maybe do this a few times.

Is this wishful thinking?

Will it do anything at all?

Should I go with a higher temperature swings?



Kel

 

[don-tucker]

Here is my twopenneth,I bought a er 25 collet chuck on a backplate from one of the cheap sources,on mounting it in a faced plate in the lathe it was a mile out,I turned a 5/8" stub and gripped the collet chuck to it using a 5/8 collet then faced the plate and returned the register.I then refaced the lathe backplate and turned the recess to fit the collet chuck register,it now runs very concentric.
I told the company the problems and they refunded me £10.
Don

 

[Blogwitch]

Sorry Kel,

I have only just noticed that you asked a question a few posts back.

These should answer your question.

I measured a few collets, and these were the low and high figures obtained, so somewhere in between, say 0.555" would be just fine. It shouldn't make that much difference as they have a fairly long tightening range.

Hope it helps


Bogs

 

[steamer]

Actually Kel, I think a round part such as that should stay pretty stable...even in CRS

I'd leave it be and just finish it...


Just my Opinion.

Dave