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[4]

Talk about a total fail...

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Hukshawn

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#1
I made an ER collet chuck for my lathe a while back, finally put it to an actual use today.
Apparently when I bored it out and turned it to size, I left nothing but a HAIR of metal left. I chucked up a piece of 3/4" bar, just TOUCHED the tool to the metal and *boink* just fell off... Can't win lately.

IMG_20171028_122244.jpg
IMG_20171028_122237.jpg
 

rgray

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#2
ARRR missed it by and 1/8 right!
Since you would need to remove the chuck to use that ER anyway, it is about the same trouble to just chuck what you have left there in the 4 jaw when you want to use the ER.
 

rgray

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#3
Or bore the base piece and press the ER end into it and weld it up.
 

Hukshawn

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#4
Yeah but then it would be a nightmare to get it's run out back to nothing.
I'll just make another one. Now that I have the big mill, I'll make a lathe chuck and a hex collet block for the mill... The project list piles up lol. So many things, so little time.
 

Hukshawn

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#5
Well, I could salvage this maybe. There's enough threads on the collet side that if I welded the pieces together, I could just return the taper and threads. Hmm. That'll be a lot easier and faster since I sorta need this now. Haha
 

Hukshawn

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#9
Yeah, for sure gonna make another one. Probably tomorrow morning.
I tried welding it together, I got the taper resquared, but there wasn't enough meat left to redo the threads cause I cut clearance behind the thread. Yaaarbage.
 

tweinke

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#10
On the bright side, in a way you sucessfuly parted on the lathe. :cower: Really though I'm sure you learned a thing or two also.
 

brino

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#12
It doesn't apply here but same concept; Lee Valley used to have a tool for wood turners to avoid thin section break-thru when making vases, etc.
It consisted of a laser pointer held on an arm over top the work that you would adjust to point and the end the turning tool.
Then when the tool is deep in the hollow cylinder you had a laser dot on the outside side-wall to indicate where the tool tip was.
Obviously if the laser dot ever got to the front face of your work you would break thru.

I wanted to provide a link, but I don't see that offered any more........

Rockler has this:
http://www.rockler.com/carter-hollow-roller-laser-guide
but no picture of it in use!

okay here's one being used......
http://www.woodturningvideosplus.com/hollowing-tools.html
it's huge system to hold the tool "flat" since if you roll it you would change the angle of the laser and the dot would lie to you.

-brino
 

Hukshawn

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#13
Oh man, at first glance it looked like that guy was in traction, turning a vase. Lol
Neat idea. A much smaller rig could be built on a tool post since all the tooling is rigid. But you know, I could also just be more careful with my calculations. Haha
 

woodchucker

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#14
Why neck it down, you only need to neck down the thread area. There's no harm leaving i wider, and it probably absorbs more vibration. The original design with full size out to the threaded area seems like the best solution, you are turning on the spindle eliminating as much of the runnout as possible.... And if you feel for looks you must neck it down, the taper it to remove the stress riser.
Just my two cents.
 

Hukshawn

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#15
I created the relief behind the thread because I cannot use my half nuts when threading. I have to forward and reverse the lathe. Definitely not an exact science for start and stop positions.
 

woodchucker

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#16
I created the relief behind the thread because I cannot use my half nuts when threading. I have to forward and reverse the lathe. Definitely not an exact science for start and stop positions.
I was not talking about the threading, you reduced the material quite alot and quite quickly. What was the need to do that?
If you redo it again. only reduce it near your threads for the collet. And when you do taper it, you will have a much stronger tool, and it will have mass that absorbs vibration better. And you eliminate the stress riser.
 

Hukshawn

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#17
I think I see what you're saying, just leave more meat. If I have to have a relief, make it shorter closer to the thread?
Maybe I'm missing what you're saying.
My plan now is to leave it beefier. More material left on the piece
 

Bob Korves

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#19
There are these really high tech tools to help prevent going through the walls of your work. They are called "spring calipers". They can be sprung to get into or out of a tight space without changing the nut setting, then allowed to spring back to the nut for measuring the gap between the measuring surfaces. Extremely easy to use, and quite accurate after practicing a bit with known sizes and then getting the "feel" of the proper contact pressure into muscle memory. They can also be used to check wall thicknesses of things like bell and vase shapes with compound curves if the caliper shape will fit the spaces. It helps to have a number of these calipers in different sizes and shapes to fit oddball stuff. Firm joint calipers are another version of this tool type, also very useful at times. Old school machinists used spring calipers constantly while at the lathe and while doing other work. Quickly, too. Too bad those useful skills have mostly passed into memory, but the good side is that these tools are now available quite inexpensively, including beautifully made vintage Brown & Sharpe, Lufkin, and Starrett ones. They are just as useful today as they were 100+ years ago, no batteries required...
https://www.bing.com/images/search?...ers&qpvt=spring+firm+joint+calipers&FORM=IGRE
I have about 20 of them, so far, and am always looking for others at a good price and in decent condition that I do not yet have.
 

Hukshawn

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#20
Yeah, I have a bunch of those. I just generally refer back to mics and telescoping guages.
 

mmcmdl

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#22
LOL . Huckshaw , I would have sold you 2 collett chucks plus the colletts for $50 + other related pieces . I have them still , but a learning experience is priceless in the making of a fixture . I have had many a failure also , but we as machinists call our mistakes ECNs . ( engineering change revisions or notices ) . Machinists can never screw up a G job , only improve on our prototypes ! :eagerness:
 

Hukshawn

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#26
So how much run out is too much in a collet chuck?
I chucked up a 1/2 end mill and gorlt .0015-.002 run out then tried a newer 1/2" end mill and got .001 @ about 1/2" from the chuck. And compounds as you get further out. Couldn't test too far on account of short end mills. So the first end mill either was bent or sat differently than the second. I do not have dowel pins to test better.
What do you think?
 

rgray

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#27
Thing about an ER collet is it needs to have more length into it to grip correctly.
You might need a longer test piece.
TIR of .0006 would be my choice for an ER collet chuck.
 

Hukshawn

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#28
So some drill rod for a better test. I also noticed it very much depends on how about you get the nut too.
Maybe it would be worth taking another swing at the taper. Or maybe a cleanup pass over the thread.
I did use some sand paper inside the taper cause my compound isn't the smoothest it seems. It's ripe for a rebuild and some bearings.
 

rgray

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#29
Tool post grinder would be nice. Compound would still need to be smooth though.
Drill rod is not always straight either. You could mark it and release and turn and measure again to verify.
If the rod was straight the reading would never change.
 

Hukshawn

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#30
I have a Dremel with a wand I could cobble together into the qctp.
What would you suggest is the preferred test medium?
 
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