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wheel for cylindrical grinding

dian

Titanium
Joined
Feb 22, 2010
Location
ch
im looking to get 2-3 wheels for an od grinder im refurbishing. the size is 250-300 mm. my supplier recommends:

80 (grit), h (hardness), 8 (structure), no prosity data.

the mixture is a propriatary "93a". rep sais this will grind soft and hard steels (whatever that means), so i dont have to get two wheels.

any thoughts? im afraid the wheel will be too fine and too soft, although the stuff i will be grinding will come from the lathe usually, so just finishing, machine is manual anyway. i have no idea what the wheel is that was on there.

for non ferrous metals he recommends:

15c80h15.
 
80 H would be on the finer and softer side of my selection for surface grinding...but have used that wheel on OD grinders and surface grinders..

Most likely the rep knows the machine and the material, and has other customers doing similar so a good idea to go with his recommendation for a starting point. If not getting a price break for buying three wheels you might just buy one and test that wheel for surface finish and holding up to your part.
QT: [the size is 250-300 mm.] near 12" ...is that the part or the wheel size..
Buying used wheels you take chances because saving great amounts of money. Buying new wheels it is best to stick with one manufacturer because the hardness factor can be better selected for the next harder or softer. for instance going from a H wheel to a J wheel, and changing the manufacturer at the same time the J may be the same hardness as the other manufacturer's H.
 
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12" wheel....Then perhaps around 2000RPM..good for spindle bearings and for a cool part.
Grinding method is also important. Going right and left with cross in feed is common..but for some work slow constant plunge to + .003 or so then travel left and right can save wheel and time..The wheel peripheral makes the strongest grind but few use it as much as it could be used. like going into a corner/shoulder with a dressed Od and a dressed corner/side/shoulder with turning the wheel head, many just side wheel....Yes in most cases wet is best.

Below 10" (back in the day) we would kick RPM to 2500 but now the rule is go by the label as per OSHA...

there are some handy grinding tricks on youtube.
How to remove the taper from an O.D. Grinder without grinding the part. - YouTube
 
so don has put up some new vids since the last time i looked. i wonder how his slit arbor doesnt expand from being ground on centres.

anyway, can you recommend some norton wheels (i can get those too)? soft, hard, non ferrous. not concerned with finisch too much as it will probably depend more on the machine than the wheel. 250/300 x 20/25 x 51.8 mm.
 
I get this question all the time from my customers. And my answer is always the same: just about any grit type will do. White, pink, brown, mono, NQ. And just about any wheel grade will do: H, I, J. What matters most is grit size. The very common mistake that is responsible for 80% of the burn, chatter and size-holding issues in cylindrical-grinding is to choose too-large a grit size and dress the wheel dull (with a slow diamond traverse) to achieve surface finish. Don’t go this route. Choose a reasonable grit size (or close, it’s not an exact science), and you’ll find a lot of your other problems go away. Here are some guidelines:

Ra=32, 60 or 80 mesh
Ra=24, 100 mesh
Ra=16, 120 mesh
Ra=8, 150 or 180 mesh

These mesh sizes will see too fine. Do it anyway, and then dress with an Overlap Ratio of 2-4 (if you don’t know Overlap, take my course or watch my videos).

We could also get into wheel speeds, plunge speeds and workpiece RPM, but the most important thing is grit size. Finally, if you’re doing cylindrical-traverse, choose a roughing traverse speed and workpiece RPM combination such that you use 50% to 80% of your wheel width each workpiece revolution. (Very relevant to roll-grinding.) I’ve gotten customers using the right grit size and traverse speed and seen their cycle times cut by 75% (and general headaches go away). But they must first understand the fundamental concepts of dressing overlap and grinding overlap. Once they do, everything else usually takes care of itself.

I hope this helps.

Jeff
The Grinding Doc

Jeffrey A. Badger, Ph.D.
The Grinding Doc
Expert in Grinding
Independent Consultant
Making grinding solutions practical & simple
+1 512-934-1857
[email protected]
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hi doc

i have seen a lot of your vids and its the best source of info on the net for beginers and pros. you wouldnt believe how many times i impressed grinder hands with the coolant velocity stuff i learned from you.

however, you seem to be making this simpler than it is. there are so many grains and mixtures lately, so that i would like to use the latest technology. all that stuff is propriatery to the manuf., and therefore diffucult to analyse.

i have a real difficulty to find a wheel of the 250/300 x 20/25 x 50.8 size for od grinding. i thought i would need three: soft, hard and grey iron.

if you can help i will appreciate it. im based in switzerland, so norton, 3m, tirolit, krebs etc. are an option.

i undestand you want a harder wheel for od as compared to surface, because the contact is smaller and gritt breaks down easier. however about structure and porosity im not sure, controversial info from manufs., probably due to differen types of grain.

so where do i get my wheels?
 








 
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