Had a slip milling side of a shaft. Looking for suggestions for workholding

Vitran · Jan 15, 2018

I was doing a favour project for a neighbor on his car. More specifically, my boss told me to do it. Looking for some help on a better clamping setup for this.

A .75" shaft is machined on both sides to be .55". It seems very simple except for the clamping.

First I wanted to hold it in the T-slot grooves but the cutter doesn't reach that low. I then used a pair of V blocks and tightened it down as hard as I could with toe clamps where the shaft on the toe was right near the bar. I had the two V blocks about 18" apart and would shuffle the clamps along the bar to reduce chatter. Seems like the V blocks shifted and the bar got mangled. It was working for a bit, but not very long.

Any suggestions on better setups or what I could do? I am thinking getting some keystock and fastening a key to the bottom of the V blocks. My boss suggests to see if there is a V block with a hole through the middle to fasten it to the T slots but I have not heard of such a thing.

We have only one big machining vice. I would use a pair if I could.

michiganbuck · Jan 15, 2018

Guess you could have put V blocks closer to the work zone, put under blocks under. a bump block to the go side perhaps two places, and a hold down(bar pushing hard to the top.. some time a lath dog can be added to a work piece and a hold down on that if a job looks like it might wish to twist.not the case here..

Plus chancy set ups should have a slower feed rate, perhaps two passes and sharp cutter.

18" x 3/4 or 1/2 is a long part that would chatter down and away to the go side(the way the cutter tends to push). It would be difficult to even grind such a long part unsupported.

Even 10"long and 1/2" thick is a long part if unsupported to the go side and midpoint under.

*Guess if having a brass hammer.. and tapping a work piece to find it vibrates is a good sign the set-up is not good for milling.

You could set it long on a bar stock.. add hold downs to top.. add block in blocks to the go side having them to bump key slot keys.
yes the bar stock need be perhaps 20" to under support the work zone..for the flip add a strip or shims of 1/4".

Pathogen · Jan 15, 2018

Collet blocks with 3/4 collets

magneticanomaly · Jan 15, 2018

I believe this geometry is called, "double-Dee". Steering shaft out of a car? Liability? junkyard?

I think I would not try to mill both sides at once, but mill the first flat, then flip over and mill the second This would give more stability and less deflection between whatever kind of clamping you use.

If you need to keep feeding the shaft through your set-up due to length required, a shaft vise might give you sufficient access to the top surface with an end-mill Self Centering Shaft Vise

Peter from Holland · Jan 15, 2018

First I wanted to hold it in the T-slot grooves but the cutter doesn't reach that low.

Make that the cutter reaches that low
Extend the quill perhaps

BTW if you remove that guarding of the Z-axe you can get higher with your table a couple of cm

Peter

Richard King · Jan 15, 2018

If you had another vise you could put the V blocks in the vise turned 90 degree's and tighten the vises and they would be clamped against the 2 sides of the V Block and vise jaw. I am sure you would not have a problem. Also use V topped jack screws to support the flimsy shaft. Be sure to take light cuts too.

michiganbuck · Jan 15, 2018

Guess you may have put a lathe dog on the part and it touching the table just used as the locator then move the part supports(V blocks or what) close under milling a small section at a time.

Yes the dog touching the table would be the locator to assure the milled area would be returned to straight up as the supports were moved.. This could work with the mill vise in use with the part on a parallel so to be the same height as each section ( a vise width) would be milled.

the second side would have the flat to set on the parallel so the locator not needed if set in the vise..

Not much sense buying special holders if this is a one-up.

Likely there would be perhaps 200 lbs or more pressure from the force of a mill cutter so any opportunity to chatter and chatter will happen.Screw mill jacks will stop downward but not stop chatter in the go direction.

Yes you could sweep an indicator at each support move if it was a fussy part.

Tyrone Shoelaces · Jan 15, 2018

Whenever I used vee blocks on a machine table I tried to get the vee blocks that had tenons in the base. Even if the tenons were a bit small for the tee slots you can use slot pushers to push the vee blocks. Failing that you can put slot irons in another slot and use the pushers to push the vee block up to slot irons. I also used end stops to keep the shaft in place.

I'd also use screw jacks under the shaft, set them up with a DTI so you don't bow the shaft too much.

Every little bit of rigidity helps

Regards Tyrone

Tony Quiring · Jan 15, 2018

Simply do 2 things.

Get a new sharp end mill and take small cuts then the cutting forces will be small and it should be fine.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk

Bobw · Jan 15, 2018

magneticanomaly said:
I think I would not try to mill both sides at once, but mill the first flat, then flip over and mill the second This would give more stability and less deflection between whatever kind of clamping you use.

That's how I would do it also.. Another positive of doing it this way.. Location doesn't
matter at all, just tool height, and the height of the part.

Even C-clamp it to a piece of angle iron or something, just so you have support the whole way,
and already been said, but when you're trying to machine a banjo string, the smaller the cutter,
the less pressure you are going to have...

Marty Feldman · Jan 15, 2018

What is length of cut, material, cutter, cutter speed and DOC, and exactly what is slipping? Is it only the v-blocks, is the rod rotating?

Tough job the way it sounds like you're doing it, among the issues being the facts that this is a one-off and that your resources sound limited. Try to figure out a way to really securely immobilize the ends of the rod (one way is to make up 2 end clamps, each drilled through .750, with a horizontal side-slit parallel to the bore and going through one side of the bore, drilled & tapped for screws to squeeze the clam around the rod, and each end clamp also drilled for secure bolting down to your mill table) and to provide for support under the spindle axis as the rod moves along (one simple way if you can get away with no more than this is to make up a snugly fitting sliding block, which could at least prevent downward flex of the rod as it moves along under the cutter).

-Marty-

mfisher · Jan 15, 2018

Take two pieces of aluminum bar stock, bore a 3/4" hole in each, split them with the band saw so they can tighten around the shaft, then clamp them in the vise. Quick split blocks. If you can get a wide enough blocks so you can get the endmill between shaft and vise jaw, you don't even have to reposition the shaft.

You just need to make sure the hole is at the same place on each block.

Illinoyance · Jan 15, 2018

A long shaft, taking a cut odd each side, you are building a banana.

michiganbuck · Jan 15, 2018

Having 4 of the small V blocks and moving two of them along with the milling action for perhaps milling 6” of length ..then moving the two Vs for another 6” yes all 4 having hold downs and with never breaking all lose at the same time the up-side center would be maintained. 6” long x ½ thick x ¾ wide is a thin part…

How close need be the .550 finish size?

twin staged · Jan 15, 2018

Setup a couple of your vises with long jaws or just bar stock for make shift jaws and put the rod on parallels and do one side at a time. Use c clamps between the hangout of your new jaws. Might have to flip it a couple times if it curls, but I think it should be fine without knowing what you’re cutting.

Clive603 · Jan 15, 2018

Last time I did a one off, not high tolerance, job like that I simply wood screwed a few layers of waterproof chipboard under-flooring together. Strapped them down to the table good and tight then milled a suitable groove to locate the shaft using an ordinary cheap carbide router cutter. A few short bits of the underfloor wood-screwed across it did for clamps. Went fine in 6" ish bites. Up to you whether you re-do the groove before flipping it to do the flat. Make sure the battery screwdriver is well charged first.

Any of the high density "improved woods" will do. I used under-flooring 'cos that was what I had in suitable sizes. Needs to be better than common furniture grade stuff tho'. Messy as heck doing the groove, you need a assistant to hold the vacuum cleaner.

Way I see it you get the job done before the stuff figures out what's happening and gets round to distorting. Actually the good, high density, improved woods are pretty stable in the short term.

Posh boys use thick aluminium alloy bar but Mr Customer wasn't gonna pay for that.

Straight out of the bodgers book but, as I recall things, came out around 5 thou tolerance.

(Not the first or last time for that horrible trick. 9 ft long, 1 to 5 mm taper in the thin direction of 4" x 1/4" alloy bar coming up as soon as the weather warms up enough to work with the side door open so the bit that overhangs the Bridgeport table has somewhere to go! Whatever works.)

Clive

michiganbuck · Jan 16, 2018

Good for all new guys to think of the high pressure made by a mill cutter. To push off a perhaps .oo5 x 1/8 chip how much push do you think a one tooth file might need to push that much..likely 200 pounds down ward and in the direction of the push. So a work piece needs to be supported in those two directions..

Same goes with grinding.. look at the spark trail coming from a surface grinder heavy and light pass... then go to the bench grinder and Push a part to make the same spark trail..perhaps you can't push that hard..(yes be careful doing that..
So a held part has to be small brass hammer tap solid from vibration and lead hammer solid from moving IMHO.

Yes I know in a tough to hold grinding job you be sure you can't push it with two fingers then grind with space between your sparks and feed from the go side only.

Milling has a go-side..the way a lost part would go..that way..

and a shaper heavy pass might have near a ton of push..that is why the hold-in parallels are needed or you can't make the vise tight enough standing on it...

*Hope the OP Vitran posts a photo of the set-up that worked...

Yes another way for the Op'S part holding...first end in the vise.. mill jacks moved along under the mill zones as milling is done..with hold-down held block-in blocks touching the go side.. and a pair of hold downs to mill perhaps every 6" as that section is milled would do.

Again milling a part 1/2 thick and 3/4 wide is going to give way, bend and rattle if not supported near the point of cutter contact even if only 10" of length is not supported.
.
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SteveBausch · Jan 16, 2018

I’d use my wood shop and start with a length of 4x4.

Use table saw to rip a vee along one side

Use table saw to create a key on the opposite side

Countersunk holes for bolting to teenuts

Once it’s bolted to table, clean up the vee to desired tolerance

Clamps and indexing shouldn’t be too hard

redlee · Jan 16, 2018

McMaster-Carr
Might help.

Matt_Maguire · Jan 16, 2018

My possibilities would be v-blocks shoved against keys that fit the T-nut slots (well) or many small keys stuck in the T-nut slots and the piece part down on the table shoved against the keys in the slots & clamped.

As mentioned before it’ll likely need some straightening after face milling on it.

Matt

Had a slip milling side of a shaft. Looking for suggestions for workholding

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