Thread: Cylindrical square theory

unless it bends afterwards from stress being relieved from the grinding process.

If the diameter is the same, the sides are straight and parallel. But the ends may not be square to the sides I guess.

Hmm definitely some food for thought, I have some mystery alloy steel about 80mm dia off a bulldozer, already centre drilled on the ends about 300mm long as well as a stash of 80mm dia 1045 steel round, I supposed I could rough grind and then shove it in a friend's furnace until it's been warmed up orange hot, to cool over an hour or so.

I can use the same mate's TOS 2UD cylindrical grinder to grind and then use the sides of the grinder wheel to gently kiss some machined rings on the ends to hopefully be square. The best I've got from it is 0.001mm over 200mm for the steel mandrel I made for machining a bronze bush on.

Hi
What diameters are you talking about?
It doesnt tell you much about the ways (at least not the way I see it)
If the work was 50mm and the wheel 100mm my math says that 0.5mm wear in the ways would give an error of something less than 0.0017mm(edit, my math was incorrect, I think that number should be 0.005mm). Which you could fix by moving one of the centers. Then........... well I havent got that far yet, I'm not sure what shape you would end up with.

Stuart

Originally Posted by Stustoys

Hi
What diameters are you talking about?
It doesnt tell you much about the ways (at least not the way I see it)
If the work was 50mm and the wheel 100mm my math says that 0.5mm wear in the ways would give an error of something less than 0.0017mm. Which you could fix by moving one of the centers. Then........... well I havent got that far yet, I'm not sure what shape you would end up with.

Stuart

The TOS's grinder wheel is about 400mm diameter and the steel bar is 80mm dia. It seems to be grinding straight not curved tapers so way wear doesn't seem to be an issue for the available measuring equipment. At this stage it's just getting it parallel that's the fun part.

Originally Posted by Graziano

The best I've got from it is 0.001mm over 200mm

And you want it better than that? How are you going to reliably measure less than a micron?

Originally Posted by Bryan

And you want it better than that?

Hells yeah!, I want it to be so parallel that it glows and a heavenly choir singing "Hallelujah" can be heard faintly every time you open it's box.

Originally Posted by Bryan

How are you going to reliably measure less than a micron?

I can't at the moment measure better than 1 micron using the Mitutoyos and I don't have one larger than a 50mm which is a hassle. But say I did have one to measure 75mm down to a micron, if my cylinder was parallel to one micron over a length of 400mm, then it would have to have a taper of half a micron over 200mm.

Once it's ground I guess you could muck around with an interferometer setup with a 532 nanometer laser to get down to 1/4 wavelength, say a bit over an eighth of a micron .

Graziano
When it comes to grinding the ends of the cylinder, at the same set up after the parallel OD grind, its best to have the sides of the grinding wheel dressed by a diamond dresser to relieve the wheel. Then its only grinding on a small say 1/8" wide rim, on the wheel periphery.
This will ensure a flat face square to the parallel portion of the OD.
regards
Bruce

Originally Posted by Abratool

Graziano
When it comes to grinding the ends of the cylinder, at the same set up after the parallel OD grind, its best to have the sides of the grinding wheel dressed by a diamond dresser to relieve the wheel. Then its only grinding on a small say 1/8" wide rim, on the wheel periphery.
This will ensure a flat face square to the parallel portion of the OD.
regards
Bruce

Here are a couple of Cylinder Squares I made during apprenticeship 52 yrs ago.
( I could not be that old)
They are made from SD51 a case hardening steel, hardened then ground on mandrels held between centres, using the relieved grinding wheels to touch each end after parallel grinding.
Its important to have the cylinder machined so that it only rests on a small peripheral land, as shown. The same applies when making Toolmakers Buttons.
Hope this may be of assistance.
regards
Bruce

Hi Bruce, I did plan to machine the rings on the ends of the cylinder with say a 5mm+ undercut and a 5mm or so ring width. I'm a bit wary of dressing the side of the grinder wheel, I was hoping to slowly approach it and just kiss the ring until spark out. I expect there'll be a bit of unevenness to the sides of the wheel.

Originally Posted by Graziano

Hi Bruce, I did plan to machine the rings on the ends of the cylinder with say a 5mm+ undercut and a 5mm or so ring width. I'm a bit wary of dressing the side of the grinder wheel, I was hoping to slowly approach it and just kiss the ring until spark out. I expect there'll be a bit of unevenness to the sides of the wheel.

Graziano
I reckon that should work as it only requires a light pressure to grind the ends, & allowing it to spark out should be fine.
regards
Bruce

Hi Graziano,

Just getting within 1 micron, is pretty impressive stuff.. the number of little subtle details that have to be just spot on and then you have to hold your tongue just the right way... dress the wheel just so, don't stop it after it's dressed... spark out just right... keep the door closed, temperature control just right...

Then remember that steel expands at 13 microns per meter per degree C, so over 100mm it's 1.3 microns per degree C, so light breeze wafting through the door, that cools one end a little more than the other will throw you out by about a micron anyway... ( that's on the length) if the diameter is 50mm you can handle a 2 degree temperature gradient....

Then there's the issues of how to measure cylindricity, I seem to remember GQ has some fancy metrololgy for measuring cylindricity...

Regards
Ray

I ground two more spindle shafts today.....and do you think I could get them parallel with any ease??.........must have been a Friday arvo thing as I got particles in between the centre drilled holes and the centres, issues with wheel dressing, the table moving around and so on...... The last two times must have been a dream run of some kind as now it was a major effort to get a decent grind.

Hi Ray, I have been drowning things in coolant as I go which seems to help with the the temperature and switched to an aluminium oxide wheel which wears a lot less than the previous silicon carbide one which required constant dressing. I don't know about all those other precautions, I have to reverse the spindle to dress the wheel properly as the Makino diamond dresser points upwards into the wheel. I did find that a fresh dressed wheel without any glaze seems to heat a lot less which I do for the final pass of 0.01mm and then feed across the shaft very very slowly. I can't stick the tongue out at the side as the coolant is a bit rank at the moment .

Hi Graziano,

The wheel dresser sounds strange, got a picture?
Do you have another wheel dresser you could use for the last dressing?

Not sure that the very very slow feed is such a good idea. Many faster passes might work better.

Stuart