Easiest way to make balancing weights for grinding wheel hub?

ballen · Apr 7, 2018

I've got a couple of "new" hubs for my Studer RHU-450 grinder, but the balancing weights are missing. What's the easiest way to make new ones?

The wheels themselves are 300mm = 12" diameter, with a 127mm = 5" ID. The annular slot for the (missing) balancing weights is about 6mm (1/4") deep and has an inner radius of about 150mm (6 1/2") and an outer radius of about 165mm (6 1/2"). The slot is not tapered, it has parallel sides.

I was thinking about this for making the weights:

- turn a ring from 6mm steel which has the correct ID and OD to just fit into the slot

- cut off segments of the ring

- tap the segments for setscrews, using a taper tap but NOT going full depth, so that the threads are fully formed on the entry side but not on the exit side of the threaded hole

- slot the segments, with a slot that intersects the threaded hole

Is there an easier way? Will running a tap only partially in create the desired spread/lock action?

sable · Apr 7, 2018

The weights are usually a dovetail shape then the thread is between the two parts ,sounds like maybe you have something slightly different?

ballen · Apr 7, 2018

sable said:
The weights are usually a dovetail shape then the thread is between the two parts.

That's what I have on some of my J&S 540 surface grinder hubs. The set screw just pushes the weight in the direction out of the slot and locks it in the dovetail.

For these wheel hubs (Studer RHU 450 cylindrical grinder) there is no dovetail, the sides are parallel. So I need the setscrew to make the weight 'open up' the weight to lock it in place. What I have in mind is something like these ones:

Question is, how do I ensure that the setscrews spread out the slot?

sable · Apr 7, 2018

I have a Studer machine although completely different to yours ,I will have look.

SIP6A · Apr 7, 2018

Rather than deal with balance weights you should get a Balatron.

If your going to make weights use set screws and don’t tap the hole all the way through.

Red James · Apr 7, 2018

Use tapered pipe plugs instead of set screws.

stltoed · Apr 7, 2018

You are gonna need the weight of the original counterweights. You should make yours as close to the original as possible to make sure you get the range needed to balance a wheel that needs more. Let's face it, the fellas that made the hub put more thought and energy than most of us ever will.

Some counter balance weights use a setscrew pushing against a steel ball that pushes against the inside of the counterbalance slot. This works really well when the same wheel stays on the machine for a long time. The water, coolant additive, and grit tends to lock up the counter balance over time. A split counterbalance can be harder to remove in this situation. I don't believe a pipe plug would work very well in this situation.

ballen · Apr 8, 2018

SIP6A said:
You should get a Balatron.

What's a Balatron? I googled but didn't find anything relevant.

ballen · Apr 8, 2018

sable said:
I have a Studer machine although completely different to yours ,I will have look.

Thank you!

ballen · Apr 8, 2018

stltoed said:
You are gonna need the weight of the original counterweights.

I have one original hub with weights. I will use those as a model to get the right value. But the hub has a different design for the balance grooves.

Some counter balance weights use a setscrew pushing against a steel ball that pushes against the inside of the counterbalance slot.

Hmmm, I've got a good collection of bearing balls and some sharp point set screws. I'll experiment with this on some scrap.

CarbideBob · Apr 8, 2018

Are you sure there is no "dovetail" here? Often the angle is very light as you only need a very tiny bit.
You have to get the weights into the groove at assembly without notching the adapter which presents a design problem.
Bob

Plusminus · Apr 8, 2018

ballen said:
What's a Balatron? I googled but didn't find anything relevant.

A balantron is used for dynamic balancing.
So with the spindle running.
It measures vibration and had a diamond tipped device to remove pieces from the wheel.
You should be very close already so still needs weights.
Ill see if i can upload my manual.

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sable · Apr 8, 2018

I had a look at my machine and interestingly the weight are one piece and dovetail shaped ,they come in and out by removing a ring which forms one half of the dovetail on the hub ,it is held in place with screws.

No help to you Bruce but I learned something new.

michiganbuck · Apr 8, 2018

Like in post #3 and Sipga'S suggestion (post #5)set screws in holes not tapped all the way through to be spreaders seems an good idea.IMHO.

ole.steen · Apr 20, 2018

Bruce!
On my Studer RM 250 the groove is straight sided, the weight is 3/4 split, the screw has a conical head, and expands the weight in the slot when tightened. Have you removed a screw altogether, and examined it? These screws may probably be made from regular countersunk insex screws turned down. You will need a steeper than usual countersink cutter for the hole. Ole

ballen · Apr 20, 2018

Dear Ole,

ole.steen said:
Have you removed a screw altogether, and examined it?

I can't, because I do not have any balance weights like this. The hubs came without them, and my other hubs have a dovetailed slot, not parallel sided.

I did not realise that the expansion happened at the HEAD of the screw, and that the head was a countersink style. Instead I thought that the pointed tip of the screw was expanding the incompletely tapped hole. But what you are describing makes a lot of sense.

So please, could you take a handful of photos and post them here? Or if that's difficult, then just email them to me?

Thanks!

Bruce

Tony Quiring · Apr 20, 2018

ballen said:
That's what I have on some of my J&S 540 surface grinder hubs. The set screw just pushes the weight in the direction out of the slot and locks it in the dovetail.

For these wheel hubs (Studer RHU 450 cylindrical grinder) there is no dovetail, the sides are parallel. So I need the setscrew to make the weight 'open up' the weight to lock it in place. What I have in mind is something like these ones:

Question is, how do I ensure that the setscrews spread out the slot?

One could make the part with correct fit with slit in place.

Drill under size hole for screw through then correct size for short distance.

Then open the slit with say a screwdriver.

Drill correct size for screw and thread hole.

Remove screw and squeeze part back to original size then with bottoming tap re tap just the top of the hole that was drilled correct size to allow screw to start.

Screw should force it open but the above would require almost perfect guessing.

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ole.steen · Apr 21, 2018

This is what they look like. 3 weights in each wheel:

ballen · Apr 21, 2018

ole.steen said:
This is what they look like.]

Thank you! This is what I will do, it looks easy.

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dian · Apr 21, 2018

now the question: why would you need three weights?

Easiest way to make balancing weights for grinding wheel hub?

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