Boring pulley wheel

Could do Neil, really depends if there is any draft angle on the boss, looks to be a cast flywheel so not ideal to hold the angled surface

Edited By JasonB on 16/08/2016 20:39:39

No Neil I don't think you are,your comment seems sensible to me,think this has got a bit too complicated

Mick

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Not sure, but; it seems likely that the boss has a casting draft angle.

... This might complicate things.

MichaelG.

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< Jason beat me to it >

Edited By Michael Gilligan on 16/08/2016 20:43:55

The rim would be ok for getting it central if it's been machined and the V ok for wobble when it is running true. That's assuming they did make it in one setting. The V would be like clocking an ellipse if it's not true in both plains so something else as well will correct for that.

I'd just hold the boss in the 4 jaw as by the time I had it running true it would likely to be very tightly held.

If I wanted to do it in a rotary table I would face off the boss first and if the table was too small drill fixing holes in the pulley itself.

The OP needs to look and see what has been machined and use the most appropriate surfaces for setting it up. The V and the bore probably have been machined - od maybe not. Outer rim maybe not.

John

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The Vee is likely to be flat bottomed so clock bottom of Vee to get concentric and then one side of vee to check wobble

Would be easier to make one out of a slice of foundry cast bar tbh. Needing to consolidate for accuracy on a casting is a nightmare in the works. I mean, if the vees are that badly out it defeats the point of casting them on it, really. Like i said before, so long as everything is cut from the same position, concentricity issues are non-existent. 

I'd just take the plunge and turn it, save the chatter, make the mistakes and see what happens rather than waiting on forever to come round. 

Michael W

Edited By Michael Walters on 16/08/2016 21:27:01

Few more pics.

Some Picadore's are cast all round Andy. If so a split line can usually be seen in the V some where. If none I think you can assume that the V has been machined.

John

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Hi Andy

I have assumed you have a 4 jaw chuck big enough to hold the outer edge of the pulley with the jaws turned outward and that the jaw faces run true within thou or two.

Also I assume you want to enlarge the bore?

Just mount the pulley in the chuck then using a dial indicator mounted on the cross slide check the bottom of the V with the dial indicator, set the indicator and the cross slide dial to zero, then withdraw the slide so you can rotate the spindle then feed the cross slide back in until it is again at zero and recheck the pulley for run out, repeat for all four positions until the pulley is centered.

To protect the paint you may wish to use a layer or two of copy paper between your pulley and the jaws. I use it all the time for light work. also good for wrapping black bar for the first clean up cuts. in this case to protect the chuck jaws.

Then gently rebore to size.

Regards
​John

Personally I would hold it via the boss. Too much risk of damaging the outer rim if held there.

The only tricky aspect clocking it up is that the dti needs to be near horizontal when clocking a side of the V for wobble. And near vertical for getting it to run true. The 2 readings will interfere with each other to a certain extent.

I've done one or two. It's a fiddly job and setting up can take longer than resizing the hole.

John

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But quite often the boss is tapered... Is it not ... & cannot be turned as it often has a projection for a grub screw over the woodruff key

As for damaging the rim one might also suggest that if it is a V belt it runs inside the V not on the rim.

I would also ask if a properly fitted V belt actually sits on the flat part or does it ride between the sides, which is what gives it the friction so clocking the flat might seem correct , & who am i to disagree , but if the belt does not run on it is it the part to clock. But in answer to that question then one might ask what the h.ll does one measure. However, symetry would not depend on the flat only the acuracy of the V's and the gap therein

But considering the wear on a V belt & the speed it is designed for such accuracy is hypothetical anyway

Edited By Sam Longley 1 on 17/08/2016 20:54:01

I think Picador pulleys are die cast so draft is minimal and bit of thin ali packing should do the job if needed.

Neil

Who cares about draft angle? It's mazak, not HT steel. Grab it by the boss in the 4 jaw, clock the groove true and bore it out.

Thats the spirit, have at it!

Michael W

Neil & Duncan, material and casting method were unknown at time or mentioning draft angle so it could have been sand cast iron

Thank you all for the help.

The OP will be holding it tightly of course. That generally happens automatically when final tightening is used to get what ever it is running dead true. If it doesn't then make it so.

John

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Edited By Ajohnw on 18/08/2016 10:40:56

Edited By Ajohnw on 18/08/2016 10:41:26