Factors affecting choice of wheel width.

[Tray]

There is plenty of good advice regarding choice of grit & bond but what factors affect the choice of wheel width? I have a choice of two 46 grit wheels both K bond one is approx 1/2” and the other 3/4” wide. I have a relatively low powered surface grinder but my friend has a J& S 540 would I be better passing the wider one to him?

 

[eKretz]

There is plenty of good advice regarding choice of grit & bond but what factors affect the choice of wheel width? I have a choice of two 46 grit wheels both K bond one is approx 1/2” and the other 3/4” wide. I have a relatively low powered surface grinder but my friend has a J& S 540 would I be better passing the wider one to him?

What is relatively low powered? And what kind of grinding are you going to be doing? For light finishing grinds, that little bit of difference in wheel width won't make much difference to the required power. Heavy roughing during slotting ops and you may even tax your machine with a ½" wide wheel.

 

[michiganbuck]

1/2 Hp is about the lowest I would like for a surface grinder...but 1/2Hp can use a 3/4 wheel Ok... can you change the motor to 1/2 or 3/4 HP?
1/2" wide wheels are common, do have one 1/4" very hard wheel fine gt for going into a small spec corner*, 3/4" can be better for down grinding and cross over a wider part and much safer for side/face wheel grind, and have a recess face wheel so you can face-grind below where your spindle nut sticks out...46K is a good choice (+HIJKL) but some wheels are made for longest wheel life and others for cool temperature grinding, each is good in its place but long life wheels may not be best for few-up grinding. White and pink Aluminum Oxide wheels are often my favorite, and wheels from an auction can fill a wheel cabinet at a low cost.

The now technique of large step-over was not common to older grinder hands.
With much of the wheel in the cut at one time it really stresses the HP and wheel RPM and changes the height of the wheel.. a much greater chance of burning the part, and not finding the finish size using the dial or DRO numbers....yes some caution hog grinding/down grinding hard parts because you can burn and warp the. Burns are to always to be avoided if possible.

The old small stepover method used the front/lead in edge of the wheel to break down and leaves the following to retain the wheel height and part size for a longer time.
The older grinding technique was to down-grind/ hog-grind to perhaps +.005/.008 and then dress and cool for the last incremental-cross step over for the finish...save the expected heat gain/expansion for finishing.
* To take .001 or .002 and cross over 20 or 10 times for .020 take, may be slower than take .015 and then.005 for two cross-overs...or down grind .015 and cross .005.

It is no wonder grinding takes so long nowadays. Grinding should be almost as fast as milling.
Another foolish notion is light tightening a wheel, it should be as tight as an average guy/gal can pill the wrench with one hand at bthe long end of the wrench..and then a little tighter. The notion one can not turn off the spindle because the wheel may come loose is dumb..how could one hog grind with a loose wheel?

*spec tight corner:
A 46-wheel is good for about .020" inside corners with having grits measuring about .015"..it is near inpossabl to get a dead sharp inside corner with a wheel. One may need to grind a angle off wheel and make a slight undercut in the corner..or pur a small bevel on the other part that needs to fit the inside corner.

Ops..long winding again.
Buck


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[stephen thomas]

Like Buck said, you have to figure out how you prefer to grind first.
If you down feed .0002 and step over 1/2", then the 3/4" wide wheel might be useful.

Like Buck, i am mostly working with situation where " a fair amount" has to come off, but not so much as to waste time milling it first. So i might set .012 or sometimes even .025 down, and .003 or .005 cross, and let it work while doing something else. The edge of the wheel wears, but barely at all behind it. So depending on material, grit, speeds, etc, you can do a lot of grinding in the sense of material removal before the wheel has a ramp in it and needs re-dressed. I have not found 3/4" wide on a 1HP 7" wheel grinder to be useful, the 1/2" wheels seem to be more efficient.

As the grinder gets bigger, wider wheels become more useful. I do use 3/4" & 1" wheels on the DoALL D1030 which has 3 HP and takes 10" wheels.

smt

 

[Conrad Hoffman]

1/2" is most practical on my Boyar Schultz 612. I use the "old" technique of small stepover. My guess is large stepover is only good if you have coolant.

 

[michiganbuck]

1/2" is most practical on my Boyar Schultz 612. I use the "old" technique of small stepover. My guess is large stepover is only good if you have coolant.

The below video is more step over than I usually use but for the non-Important side of a sine plate is justified. Down grind 7 to 10 thow, and then briskly step across. He could have down-ground .050 or .100 and stepped with smaller incremental steps.

The wheel width really doesn't matter as much as how much of the wheel is in the cut. Here Don may be pulling .050 ( crossfeed) of the wheel x the .007 or .010 depth of the grind into the wheel use. One big concern in the amount of stepovers is maintaining spindle RPM. Slowing RPM makes the likely hood of overheating more likely.
Good for a newbie to try different methods.

For Don's part making 4 separate down-grinds of .007 or .010 and then a step over pass was another Ok method.

surface grinding - Search Videos

www.bing.com

 

[michiganbuck]

Down grinding with a low HP spindle and a 3/4 wheel one might only use 1/2" or 3/8 of the wheel with each down-grind.
In incremental crossing, the wheel width is not as important as how large are the seep overs.

 

[AD Design]

Wheel width may not make much difference if you're just flat surface grinding but if you have to dress a form on the periphery of the wheel (radius, angle, "V", etc.) then the extra width may make a difference. Better to have it hanging on the wall unused than to need it and not have it. JMO

 

[michiganbuck]

As I said before, one should have 4 basic wheels a 1/2 wide, a 3/4 wide, a recessed face (so to grind past the spindle end nut ), and a narrow wheel perhaps 1/4 or 1/2 that is hard and a small grit to make a small radius corner (perhaps a 60 to 120 J), and a good size chuck use hone to hone the whole chucl\k lightly rather that spot-honing a chuck.

and I like wheels on a dust-covered peg board so they are easy to get with not going through a stack of wheels. The cover perhaps clear plastic so air contaminants cant fall on the wheels so to make the top-heavy out of balance, and they are less likely to be dropped. Yes on mounts for all the special dressed.

 

[Conrad Hoffman]

It took me years to learn this- don't be cheap. Buy some freaking wheel hubs so you can properly mount and balance wheels. Then it's a minor thing to change them and you don't lose a ton of wheel dressing them back to true. Either get the good Sopko hubs or an import. Some imports are pretty good, though the puller threads may be non-standard. Trivial to make a puller. The time you'll save with mounted wheels will pay for the hubs and much more.

 

[eKretz]

I like the Norton recommended way to store wheels but it takes up a bit of space. Forget where I saw it; one or the other of their grinding books I think. Basically like a bookshelf but instead of shelves just two wooden dowels left to right on the bottom with the grinding wheels sitting upright on them. Ready access to individual wheels that way. Can be made multiple levels high.

 

[CarbideBob]

Infeed amount per pass.