Round Magnetic Transfer Parallel ???

[JoeLee]

What does this part look like? Why is a round parallel a necessity?
Can't just block the part on the chuck with two Vee(s) of scrap steel?

OK, here is the part and this is the reason I need to do it this way.

These are my balancing hubs. Still working on them, decided to make a couple more while the process is in my head. What happens is when I part them from the round they move slightly. So after careful measuring and indicating and seeing what is changing and how much I've come to the conclusion that the only way to keep them true is to grind the back side off of the inside recess of hub flange. This is the spot that doesn't seem to move or change after parting.
What I've been using is the round disc in the picture behind the hub. The dot in the center is so I can keep an eye on it when grinding. If the hub starts to slide I'll see it.



So in order to keep the flange flat the back has to be ground off the opposite side. This is why I need the round magnetic transfer block to set the hub on. Then everything gets trued up from there. Think of the center of the hub as being my datum point.
So far I've just set these on a ground disc. It transfers just barely enough magnetism to hold the hub in place. I have to be real careful. I have one more to do.



JL.................

[754]

Why cant you run 6 equal length pins in the circular groove ? Might hold it.
Or use shims and 4 jaw chuck, should get within 1/4 thou or better, then work off by hand.

[Mcgyver]

grinding washers shapes and spacers etc is common....afaik SOP is what Reggie and I said - put some packing forming a V downwind of the chuck to act as a stop.

Also afaik, you cannot redirect the magnetic lines of force unless you change the magnetic source itself

[Dan Dubeau]

Superglue. Yes, superglue. Still block in your part as normal, light cuts etc, but mag transfer blocks are great, but superglue also works great for odd, shapes, and other hard to hold stuff.

[Jaakko Fagerlund]

As the magnetic fields go from pole to pole and they prefer steel in that path, you have to arrange your transfer block(s) such that it transfers both poles to your part. If you have it sitting on one pole only, all bets are off if it will ever hold.

If your spacing is larger than the inside of the hub, just make a round brass block with two pins in it the size of your poles with the spacing of the poles and then turn down the OD from one end so it can fit inside your part.

Or just use superglue like suggested. In any way you hold that piece, block it off or your butt muscles will never relax after the grind.

And if you want it done fast, just chuck it up in a lathe and face the end. Turn a piece of stock in the jaws to fit your part over and face the end so you have a flat place for your reference. Then press the part against it with your tailstock center fom that hole and face it to as near the center as you like and finish the job by chamfering the hole or turning it separately a little under the faced end.

[CalM]

OK, here is the part and this is the reason I need to do it this way.

These are my balancing hubs. Still working on them, decided to make a couple more while the process is in my head. What happens is when I part them from the round they move slightly. So after careful measuring and indicating and seeing what is changing and how much I've come to the conclusion that the only way to keep them true is to grind the back side off of the inside recess of hub flange. This is the spot that doesn't seem to move or change after parting.
What I've been using is the round disc in the picture behind the hub. The dot in the center is so I can keep an eye on it when grinding. If the hub starts to slide I'll see it.



So in order to keep the flange flat the back has to be ground off the opposite side. This is why I need the round magnetic transfer block to set the hub on. Then everything gets trued up from there. Think of the center of the hub as being my datum point.
So far I've just set these on a ground disc. It transfers just barely enough magnetism to hold the hub in place. I have to be real careful. I have one more to do.



JL.................

Joe
A procedure idea for the "Next time".

IF one of your first operations is a parting cut to a diameter that is just smaller than the through hole of the completed part, then you can machine the entire piece all over and still have the work securely attached to the original round stock. With a final operation to "drill and bore the through hole, very little change in the material would occur.

I prefer to drop a part onto a boring bare rather than right off the parting tool. With a little thought and tooling, you might even drop the part on a back chamfer operation. Very little material removed for the final release of the finished part.

[Mark Rand]

That sounds like a good way to do it. If the finish from parting isn't good enough, it can still be cleaned up on the surface grinder. If no surface grinder were avaiable, enough cuts with a parting tool will remove sufficient stock to face the back of the part with a right hand facing tool.

[JoeLee]

CalM, I did think of that, and I did try it.........but I can't part anything that deep.
Almost done with my last one, might as well finish up the way I've been doing it.
There are just a lot of unknowns that happen when you make something like this.
If I had know all this before I started I cold have saved myself a lot of time and headaches.
I'm not sure what the material is that I used. The smaller one machined a little bit easier than the bigger one.
I'm guessing that the smaller dia. stock was 12L or something similar. The bigger one machined nice too, I'm guessing 1215 maybe??
I figured I would use what I had lying around in the shop. Had I known I would have bought some kind of stress relieved material.
But when done it doesn't matter. After it's parted it doesn't move any more, even after 15 min. in the blue tank.

JL..............