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Thread: Collet chuck for A2-8 spindle
03-11-2007, 03:43 PM #1
Got a question.
My new lathe is on it's way. It has a 10" chuck that I'll be using for most of the larger jobs, but I'm also gonna get a collet chuck for barfeed work.
The machine has an A2-8 nose, and would like to get the most versatile collet setup.
5C I have for the other 2 lathes, so that's a no-brainer, but it's limited to 1 1/16. I'd like to get up somewhere 2" or so, along with the ability to have soft collets or pads for second op-s.
I know that collet prices will be substantially higher than 5C, but that's OK. Never had the need to look into them deeper until now, so just fishing for some advise.
And while we're at it, Royal has a 50% off on their quick-change chucks. I was thinking about an 8" chuck just in case I'll have clearance issues with adjacent tools on the turret. Does anyone have experience with the quick changers? Do they repeat well? Not too sure about those keyed chukjaws, I'm sorta partial to the serrated ones.
03-11-2007, 03:56 PM #2
S-20 will get you to 2 inch. I think S-26 is 2.5 or 2.625. We have a S-20 on our Hardinge. I like it pretty well. I have yet to put the 3-jaw on the machine. The Hardinge collet pads are a breeze to change.
03-11-2007, 03:58 PM #3
If i had to do it over again I would buy a collet chuck that holds 22j collets. They have a capacty up to 2 1/4 . I have a 16c collet setup on my lathe and every time i have to machine something bigger than 1.625 I have to change to a less acurate standard chuck .
03-11-2007, 04:31 PM #4
For bar feed, a dead length master collet with jaw pads is good. Hardinge makes interchangeable pads that you can get in 64ths. They have serrated, smooth, hex, square and machinable emergency pads. Very durable and repeatable enough for bar stock. If you want to make sure you are holding true to the diameter, the emergency pads are machinable and use loading pins. The machinable pads are not as durable, because they are not hardened. I like using small pieces of key stock for loading pins, because I can re-turn the machinable pads as needed by using progressively thinner pieces of key stock. The dead length (push forward to close) collets are great for bar feed as they will not pull the stock away from the bar stop.
03-11-2007, 04:45 PM #5
One more thing...the only down side to dead length collets with bar feed is that gripping is about 8" or so from the face of the head stock which can add to whip and vibration causing your parts to be a little out of round and out of flat. Because of that, I went to 6' bars from 12' bars in a hydrostatic bar feed.
03-11-2007, 05:43 PM #6
03-11-2007, 07:10 PM #7
Those S26 collets seem very tempting.
Great collet selections from Hardinge for round and hex stock, stubby and short pullback design.
Question: If you guys had machined those for 2nd op, do they hold concentricity?
03-11-2007, 08:33 PM #8
Not bad...gotta adjust pressure depending on material, but if turned properly, hold well. What's your tolerance, 'cause I've held +/- .0001 runout from bore to o-ring groove in that set up.
03-11-2007, 09:24 PM #9
I can easily live with a few tenths. I was just curious if those rubber molds between the segments were reliable enough for repeatability.
03-12-2007, 04:13 PM #10
I HATE Hardinges dead length B65 (?) chucks! They are stock on my machine and I had nothing but issues with them in real world machining!
They are designed the same as what B&S and Greenlees have ran for decades - 'cept the automatice used mechanincal closers as opposed to the hydro on the CNC's, and they both had chip/coolant evac holes drilled in the caps that let excessive fine chips out of the assy. As stock on the B65 there is no ports for the fines to get out and contimue to build up - eventually limiting the travel of the push sleeve and hence - limiting the grip on the part at that piont due to travel limitations.
Now I think a feller could bore a few holes in the cap and help that issue out - and depending on what materaila and job you are running - chips getting in there may not be as much of an issue as other jobs. ??? (I will be puting them back on my machine this afternoon for a certain job.)
One other thing that I hate aboot the dead length chucks is that do to the fact that the actuator pushes forwards - any Z thrust is pushing against the actuator and lessening the grip - resulting in pushed back bars.
Now I have a small actuator on my machine as it is a twin spindle/twin turret and space is limited - and also has an A2-6 rather than your 8 - so you may have more actuator pressure than I do? But I don't like'm.
I had some pull backs made for mine in S-26 form. Handing off or pulling with the sub and reclamping on rough bar can be an issue with pull backs. I will uncouple the "Z" on my sub if I try it on rough bar. It is harder to hold hand off lengths using the pull backs as compared to the dead lengths too of course. +/- .007 seems to be the limitations of dbl pull backs - depending on the conditions of your workpiece and bar. Usually it holds better than that - but don't want to bank on it all day.
A chumm bought a set of dead length S-26 chucks from Royal for his machine. He tells me that they are designed in a fashion that allows the chips to evacuate better. (I have not seen them apart to see how they work.) He has not had any chip issues in a yr with them and aparently no thrust issues either - but his is only a single turret machine - and may [once again] have bigger actuators than mine. ???
The Hardinge B65's only take S22's that git you to 2.25" and from there on up you use solid collets. Of course they have solid collets for smaller sizes if you preferr too I am sure.
I would highly recommend an S-26 setup of some sort for your machine. If you do not run a subspindle - I would HIGHLY recommend going with a pull back design from Hardinge or any other. For barfeeding - set your Z stop to Z+ .07 to .1 and the collet will pull it back some - again - how much will depend on bar straightness, surface finish, and fit of spindle liner.
Hardinge = 800-843-8801
Think Snow Eh!
03-12-2007, 06:08 PM #11
you could change to a chuck that accepts collet pads.... my 12" Cushman takes Warner swasey #5 ( also known as 471 pads) collet pads and works fairly well as a general purpose machine. I rarely run the top jaws as the pads go to 2-1/2 with a 3 inch collet pad bore.
03-12-2007, 07:02 PM #12
I figure a collet chuck is easier to handle when trying to get close to the chuck. I use collets wherever I can.
Thanks for the info. ATS-s chucks seem very reasonable, but want to check out MicroCentric as well.
S26 pullbacks looks to be the ticket.
03-12-2007, 08:17 PM #13
I do prefer pullbacks...unless I am machining a short part, say less than 3/8". The pullbacks can "spring" the bar out if the bar stock is small diameter and hard, generally less than .5 and tool steel or stainless. If you use a bar stop or puller, that won't be a problem. It is an issue with auto feeds like the LNS Quick Six. Great feeders, but have to use bar stop on the small hard stuff. They don't tell you that when you buy one...
03-12-2007, 09:46 PM #14
As a side note. We get our S20 pads from Hardinge. They are quick to ship. We usually get them next day. The S pads are reasonably priced too. Customs are only a couple weeks or less. [img]smile.gif[/img]
03-13-2007, 02:48 PM #15
I always use a bar stop on my LNS Quickload Servo and S2.
Think Snow Eh!
03-13-2007, 10:36 PM #16
I don't use a bar stop on the heavier and bigger diameter stuff (can only go to 1.5") just because it saves time and a turret station. Those servos are very accurate, if "no spring". Gotta use bar stop on the LNS Super Hydrobar...not a servo...uses constant pressure.
03-13-2007, 11:25 PM #17
I just use a trigon. The servo doesn't snap the bar. Not sure if I have aver damaged an insert in the last 9-1/2 yrs. I have one of the first batch of "servo" units. Before the S2's. I like the S2 a lot better. It is a MUCH heavier duty machine! I feed to 2-1/2" too.
I s'pose if you set the feedout distance too long it would hit it a little harder? But it would fault out anyhow...
Think Snow Eh!
03-14-2007, 12:57 AM #18
The LNS Quick Six is relatively new. They are hardy and can handle much bigger stock than I needed. Programmable and accurate. Want to get rid of the Super Hydrobar and get another Quick Six for the 2.5" machine. $40,000 is a steep tag, though.