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Brass 5c collet durability?

turnworks

Cast Iron
Joined
Dec 12, 2018
Looking to streamline/organize some second lathe ops on my products and trying to do away with collect stops. I'm looking to getting some brass emergency collets and just boring them to the size and depth I need for each part but I'm not sure how well they will hold up over time.

Lathe is cnc with pneumatic closer. Any guess on how many cycles the brass will hold up to? I'm sure steel emergency collets will hold up a lot longer but prefer the brass plus it will save me the time of making more split brass bushings. Parts are cosmetic so avoiding marks and scratches are a must. Material being held is 6061 and 7075.

TIR will need to stay under .0025" so not very critical. I'm guessing the Z depth of the brass collet will change with wear over time which I can deal with.

Thanks in advance.
 
With AL, they should be more than adequate for a few thousand cycles at least.
I mostly use brass collets for 2nd ops when I have to hold on a threaded portion of the part or when I have to cut a profile into the collet, but they do last quite well even on steel parts.
 
I have no brass collets so I have no clue how long they last. Putting a one off part in the HLV-H I just wipe the spindle and collet off before installing. Any production job I lube the collets with moly grease before installing them. I know the collets and spindle surfaces show a lot less wear because of doing this. I can see no reason doing this would not extend the life of a brass collet.
 
Agree with Sami that nylon won't mark but I'd be worried about cold flow shifting the machined in end stop over thousands of cycles in a production environment. Nylon does move a touch but that matters not a jot with a conventional separate end stop. Perhaps put a steel insert in after machining to better define the stop position.

Brass collet wear is most likely to be a function of work surface finish and edge sharpness. It's pretty obdurate stuff and needs a sharp edge to make serious marks or damage. We all learned "use your new files on brass first" which is basically the same thing. If the job goes in cleanly with no sharp edge or burr at the entry end odds are the collet will loose its spring and not open properly before objectionable wear takes place. When it does stop opening properly so the job "scrapes" in its going to wear like fun.

Clive
 
On reflection I'm not sure where the great gain from machined to size collets will come from.

Have you considered making a bench mounted holder so you can easily set a standard end stop to the right position without groping right down the spindle.

I'd be thinking in terms of "5C spindexer meet hacksaw, depth gauge and two offcuts of tooling plate". Or a stop and made to size length bars might be more robust.

Clive
 
OT: we did not all learn to use a new file on brass first. I'm late to the game. Will someone explain this to me and others please?
 
Even with a brass collet, your length may vary depending on your collet holder. Is it a dead length type holder (taper moves forward) if it's just a pullback holder, the length of the part will vary about 3:1 as holding diameter varies. I think the best bet would be to get a dead-length type emergency collet.
 
Thank you for the replies. Currently using regular 5c collets then a brass split bushing insert into the collet along with a threaded stop with aluminum tip. I have a variety of different aluminum tips for all the parts.

That has worked for me to make my products. I could stop there and be done with it but as my product line grows I noticed I'm spending too much time trying to keep everything square in my head. I have made notes and pictures for each set up and it helps but would like to off load things I need to remember so that's where the idea of the brass collets come from.

I just wasn't sure if the brass would hold up very well over time but it sounds like I'll get a good life span out of them with periodic checks to the part lengths. Dead length set up would be great but I don't believe its an option unless I custom make something and since my length tolerance is pretty open I can't see it being worth the effort but might be wrong.

I do have some nylon collets but never used them. I was able to get around any marks or scratches with brass and figured brass was more durable than nylon.

Again thanks for the replies.
 
I've never used brass collets. I do use emergency collets when needed. 5c brass collets are about twice as much as steel. Are you sure steel will scratch if nicely machined and deburred? I run mostly highly finished stainless steel parts and don't have any problems. I do use a fair amount of care.

I have run into a lot of emergency collets that were not properly made and when the boring pins were removed they did not spring open, so they constantly grabbed the part. A small push with a tapered point in the arbor press opened them up and they worked fine.

Another thing about brass may be it is soft enough to embed any bits of grit that happen to be around. And stay away from the india stuff. It is well crap.
 
Hi turnworks:
A lot depends on how much of the part is captured by the collet and how much is sticking out, exerting leverage on the collet clamping surface when you put a tool onto the outboard end of the stock.
The diameter of the part you're clamping also matters...I aim for a 1:1 depth to diameter ratio in the collet if my stickout is anything more than about 3:1.

I recently ran a job turning down some M1.6 setscrews initially in a threaded brass sleeve held in the 4 jaw chuck.
I soiled my panties a bit when it ripped the end right out of the sleeve and bounced off my nose.
I was holding onto it by something like 1.2 mm and it was sticking out almost 4 mm.

I had to go to a hardened tool steel sleeve to successfully hold those tiny screws.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
 
OT: we did not all learn to use a new file on brass first. I'm late to the game. Will someone explain this to me and others please?
Less than really sharp files tend to skid on brass rather than cut. Old ones pretty much don't cut any sense at all although you can force them to work after a fashion.

Steel rapidly takes the very sharp edge off new file teeth but continues to cut well, some even claim a better finish, with the slightly less sharp tooth. Unfortunately the slightly less sharp teeth don't do well on brass.

Hence using the nice new files on brass first before relegating them to steel was always considered best practice. It doesn't take long before a file looses its aggressive cutting ability on on brass.

Being machinists rather than hand tool workers I guess most of us carry on using files far past their best. I know I'm always surprised how well a new one cuts and vow to swop for a new one a bit sooner next time. Something I've been saying for the best part of 50 years with no visible effect.

Clive
 
Thank you Clive. I too own some and still attempt to use some files that would be better off turned into drift pins. Hard for me to accept they are worthless as folks although I know they are.
 
The Nylon 5C collets I bought have about 1/2" more meat in the center compared to a metal collet.
They also have Nylon wedges that are to be used in the slots. I have not used wedges before.:willy_nilly:
 
Looking to streamline/organize some second lathe ops on my products and trying to do away with collect stops. I'm looking to getting some brass emergency collets and just boring them to the size and depth I need for each part but I'm not sure how well they will hold up over time.

Lathe is cnc with pneumatic closer. Any guess on how many cycles the brass will hold up to? I'm sure steel emergency collets will hold up a lot longer but prefer the brass plus it will save me the time of making more split brass bushings. Parts are cosmetic so avoiding marks and scratches are a must. Material being held is 6061 and 7075.

TIR will need to stay under .0025" so not very critical. I'm guessing the Z depth of the brass collet will change with wear over time which I can deal with.

Thanks in advance.
I think you should just try using a steel emergency collet. I have ran thousands of parts with steel soft collets. They cost so little and work so well it just makes sense to try one. Doing production work I ran thousands of parts with bored stops and spring loaded ejection springs and never had problems with the finish even when we didn’t stop the spindle when loading parts. And I don’t think part length will change much IF the stock od does very a lot. And I never had the stop length give me trouble. And the Hardinge type soft emergency collets are dead length anyway.
But the Hardinge dead length are pricy. And I think only made with steel. So I only used them if stock od veried a lot. You could also buy a brass collet to see how they compare. When you think about it you can’t hardly make a one off bushing for less then a emergency Collet.
In fact I don’t think you can buy a piece of brass for price of store bought ones.eBay has 10 collets for less than 16 bucks ea with free shipping.
jimsehr
 

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