Holding mid sized rounds vertical in vmc

WILLEO6709 · Oct 2, 2017

I have a job coming up where it needs some Big notches put in the end of some fair sized “pins”, some might say sorta short shafts. Plan a is to mount up a front mount 3 jaw on a plate I already have, bore soft jaws for the dia. So no marks and go for it. Thing is I need at least a 4 inch through hole. The chuck is looking pricey but the job more than pays for it. Any reason I don’t want to do this?

Mud · Oct 2, 2017

I do that with fairly short pieces. I made an adapter to use a Kurt handle to open and close the chuck.

You might also consider using a milling vise turned up on it's side, make a special v jaw if needed.

mjk · Oct 2, 2017

Use a sacrificial piec 1/8"-3/16" sitting on the chuck face as your Z0
This will be your "shaft" support when clamping and you can partially bore into it

Or just find a chuck with a 4" thru hole to add your tooling arsenal

KMoffett · Oct 2, 2017

What is the length of the "short" shafts? That makes a difference.

Ken

WILLEO6709 · Oct 2, 2017

About 4 inch round x 14.5 inches long 2 inch slot 3 inches deep. Machine is a 50 taper box way beast. Plan is to get them choked up to be able to use the mill’s power (2.5 times lathe live Tool power)

706jim · Oct 2, 2017

I purchased a scroll plate (self centering style) 4 jaw chuck and mounted it on a 1" plate. Held this between two Kurt 688's for working on shafting on our VMC. Thinking the thru hole was more like 3-3.5" so maybe not practical for your setup. And make a loooong extension handle to tighten and loosen the jaws.

Zahnrad Kopf · Oct 2, 2017

L,

I do similar work fairly frequently. I'd be really very tempted to machine some steel blocks as a solid and a moving jaw and fashion an old style table vise arrangement. Machine the diameter pocket into those and clamp as needed. Water-jet the blocks to save time and effort. Would be a HECK of a lot cheaper and just as usable. Could also just make oversize jaws for a large Kurt or alternative. If the money is "stupid" and you can justify a throw away purchase of a chuck, then why not keep it as profit?

WILLEO6709 · Oct 2, 2017

I actually have another application for just such a setup right now- 3.5 inch k500 monel 12 inches long that gets tapped in the end.
There is a cheap d1-11 3 jaw with a 5 inch hole on eBay,,,,, but I need to maintain high quality alugnment, so debating if a cheap chuck is worth it

Vancbiker · Oct 2, 2017

You need a horizontal.

mmurray70 · Oct 2, 2017

Buy the chuck with a big enough through hole if you can. We used to do a similar job with a small chuck and it was a pain in the ass. Eventually we got a larger 3 jaw for the lathe and we now use that in the mill for this job and its much easier with the part passing through the chuck and the end closer to the jaws. Centers much better eliminating the need to pick up each part and its more rigid.

You may be able to clamp the chuck on top of 246 blocks or something to reduce stick out if needed. Good luck with it.

WILLEO6709 · Oct 2, 2017

Vancbiker said:
You need a horizontal.

The horizontal does not have the gonads the vmc does.

Zahnrad Kopf · Oct 2, 2017

WILLEO6709 said:
I actually have another application for just such a setup right now- 3.5 inch k500 monel 12 inches long that gets tapped in the end. There is a cheap d1-11 3 jaw with a 5 inch hole on eBay,,,,, but I need to maintain high quality alugnment, so debating if a cheap chuck is worth it

We've spoken a few times over the years. So I know that you already know the answer to that. Some times we just need to hear it from another to help settle our overactive brain buckets, so I'll entertain the concept - You are asking for trouble. See the part that I made bold print...

David_M · Oct 2, 2017

This is going to sound crazy.

You could make a fixture out of heavy-wall tube/pipe that gets the holding element up where it makes the most sense and use a Browning Flange type taper lock bushing as a collet. Mark it to always go in the same way and don't allow the tapers to scuff.

Jashley73 · Oct 2, 2017

WILLEO6709 said:
The horizontal does not have the gonads the vmc does.

A 1.5" high-feed mill would make quick work of a 2" wide x 3" deep slot, and probably be held much more rigidly than some hokey-poeky setup, holding a 14" shaft vertically in a VMC, and pounding on it...

Not trying to be a jerk, but having done lots of round parts before with a horizontal, and a vertical, I'd take the Horizontal every time - even if it was weaker...

kalim · Oct 3, 2017

hello Wille, depending on application, a normal chuck may get increased wear pretty soon, especially on the archimedean spiral

normal chucks loose power, because of their construnction ( also a hydra chuck looses power, but it has a much better randament, so it is more realiable ); they are ok for classical machines, as for mills, if you dont use it for series with high specs, than it should serve you well

also high vibrations will slowly weaken the chuck ( like high rpm + low doc, that creates that high frequency bee sound : zzzzz ); actually, such vibrations will affect whatever fixtures with weak points

how many times do you think that the chuck will keep griping parts with their axis vertical ? even a new chuck may require a hammer

you wont be able to rotate all the satelites of the chuck, unless you put it on rotary table, or on a high flange ( so to raise it from the table )

even if the price of the 4inch bore chuck is not a problem, please consider alternatives

all the best

ps : you wont be able to use that fancy 5BT mill of yours, at full power, if you use a classical chuck; unless you clamp hard the chuck on the table, and mill directly into the chuck body, so to turn it into chips; you need something stronger and more reliable

SeymourDumore · Oct 3, 2017

OT:

I am far far off base here, but ....

As per the title:

Holding mid size rounds

And then:

WILLEO6709 said:
About 4 inch round x 14.5 inches long 2 inch slot 3 inches deep.

Gotta ask: Just what do you guys consider ( on average ) a small, slightly small, normal, above normal, OK, above OK, bit large, large or HF large part in your shop?

In my case, anything which is 4 x 14.5 is in the HF large range, with or without the 2 x 3 deep slot!

Greg White · Oct 3, 2017

When the crane wont pick it.
Gw

machtool · Oct 3, 2017

kalim said:
hello Wille, depending on application, a normal chuck may get increased wear pretty soon, especially on the archimedic spiral

Smells like dead cat in here. How many times are you going to slime yourself back in after being banned?

plastikdreams · Oct 3, 2017

I'd make a fixture to hold it on the table before using a chuck. Cheaper, easier, much more rigid.

Aww here kitty kitty lol

HuFlungDung · Oct 3, 2017

If you put the chuck on a riser, you still need a centering gizmo on the bottom end of the shaft. This might be a close fitting ring clamped to the table, or even make use of a center hole. I think if you stabilize the lower end, then the chuck has a decent chance of holding the top in position, for as good as the chuck is at self-centering. You could then probe the top part of the shaft for centering, without suffering too much random error at the far end.

In my experience, a 12" 3 jaw has sufficient meat in the center to bore out to 4" plus a bit of clearance. They might come with a 3.5" through hole. I've done this 4 times at least, putting chucks on my Summit lathes with 4.1" spindle bore.

Holding mid sized rounds vertical in vmc

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