ER Collet Chuck Back Space seems excessive

[UptownSport]

ER collet protrudes from chuck with a considerable length unsupported.

Also,
In drawing rendering AND measurement specified a considerable distance to spindle nose.

Would the collet compress this much to accommodate it's smallest size?

(There is a small mark on collet at top of caliper at 50mm dia that's obscured by slide)

Is this correct or am I way off on something????
Thanks in advance

 

[Mtndew]

Would the collet compress this much to accommodate it's smallest size?

You say it's an ER50 collet by the title of your photo?
If so, then the range of that collet is approximately 2mm smaller than the stated size. Never go larger than it's rated for.
So, a 12mm collet for example can hold on to anything from 10mm-12mm.

 

[UptownSport]

ER50

~1/2" backspace before spindle nose seems excessive.

Collet small end is slightly smaller than Lathe Spindle bore, and would be compressed even smaller at minimum grip range, so i'm thinking of taking 3/16 or so off the backspace

 

[Mtndew]

Oh.
Then I'm not entirely sure I fully understand what you're asking.
You're wanting to modify the lathe spindle bore? The collet chuck? To accept an ER50 collet and it would still hang out unsupported?
If that's the case I personally wouldn't do that.

 

[sfriedberg]

UptownSport, do you have the actual chuck in hand? Planning to make the chuck? It's not clear to me what you are actually measuring or planning for.
I suspect an actual chuck screws on to the spindle threads, then the body of the chuck supports the ER50 collet, which is closed by the nut which turns on a separate set of threads (on the chuck, not the spindle). So concerns about unsupported length might be unwarranted. Concerns about stickout or "gage length" would definitely be warranted, since you can't bury the collet very far into the spindle.

 

[BajaFire]

Uptown - It sounds like you're saying the collet chuck you have holds the collets out ridiculously far from the spindle, correct? And you want to knock some thickness off the backside of the chuck (between the chuck and its backplate, perhaps) to allow the spindle to swallow the tail of the collet, leading to more rigid setups. Am I in the ballpark?

 

[UptownSport]

I'm turning one.

It's Highlighted area I'm concerned about.

IF i'm calculating correctly, it is about .500 !

I have no way of calculating how far a collet, compressed to it's minimum, would stick out.

 

[BajaFire]

8* rise/run = .141

So, if the collet shrinks 2mm = .080" in dia, that's .040"/side. So, it will go into the bore .040/.141 = .285 from uncompressed to fully compressed

 

[UptownSport]

You, Sir, are awesome