grinding wheel nomenclature - how to you remember it?

I'm not as old as I once was, and sometimes my memory fails me. I get by OK like most people. But dang it, I just can NOT remember whether A is hard and Z soft or the other way round.

Do you have a clever mnemonic you use to remember this?

metalmagpie

Don't even try to remember it. Get it on paper or bookmark a web page. If I recall Machinery's Handbook has that info. Make up a binder of frequently needed information.

How to Read a Grinding Wheel Spec

H to L are most common. (H softer / L harder)
Grits 32 to 60 most common.
46 grit is my first choice for much SG work.
Grit size can deremine the corner made with often .005" larger part corner that grit size.
Also course grit can grind faster with rougher surface finish.
Mesh Size | Mesh - Micron Comparison chart | Kramer Industries Inc

As long as I'm at it, my surface grinder uses 8" wheels. What width wheels do you recommend in general?

Side wheeling is some times needed and less than 1/2" wide needs more caution so I recomend 3/4" wide first choice, so one can side dress it and still be safe..

Plus one 1" recess so one can side wheel skim a part with not the wheel nut hitting the part.

Plus a 80 grit perhaps an L to go into a corner where a small corner is the spec.

Yes we grinder hands may side grind with a 1/4 wide but we are more carful that most...ofted dishing the wheel side.

on a good day one might make a .010 inside corner with an 80.

A dead sharo inside corner is near impossibl becaus that fine a wheel tends to burn..

Grinding incremental down os the fastest way to remove stock. Then dress and incremantal crossing for surface finish.

Say you have a 3" wide part so you down grind to + 006 in 4 down passe ..dress add then incremental cross the part.

With the right wheel and a grinder strong enoug to pull the wheel..along with the quick set-up of tha magnetic chuck one should equal or near eqial milling the part.

michiganbuck said:

I recommend 3/4" wide so one can side dress it

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OK that leads to ANOTHER question (sorry): how exactly do you side dress a wheel? By hand with a dressing stone?

metalmagpie

Clamp your diamond bar holder vertical to an angle plate with two C clamps or the like. Bring the parked wheel too the wheel just below the blotter for a light touch feel and note the number, back away and return to .005 short of the number, travel to the right away from the blotter to see that it does not touch the wheel. Travel all the way across to see nothing bumps the parked wheel..
Fire up and travel to the right direction and back to center feeding the cross by small feed .001 or so until the diamond starts dressing the wheel. continue with .001 or so to dress the wheel. never in feed cross on the left side of the wheel.

You might long travel all the way across the full wheel to see that your wheel head is square with the travel of long travel.

*Practice number of times coming to you wheel to get that feel so it requires little thought before you try to dress for the first time...

To side grind a part you do the same. Come to feel the part with a parked wheel / note that cross number before you fired up, be .005 away at fire up, travel past to be sure you are clear. Side grinding requires a very small feed and little take-off. Many grinding advices says Do Not do This. But it happens that it will be needed for some work.

*Don’t even try side wheel grinding when you are new to grinding. You need to know your hand wheels well before you try side grinding.

Method in above post is what I've always done too. I also dish the wheel by hand a small amount with a Norbide stick so I'm only grinding with a small band at the perimeter of the wheel that I then dress with the diamond. Less of the wheel is in contact with the work and less heat is generated, much like a cup wheel would. Like M'buck mentioned, grinding with the side of the wheel in a SG can be a touchy affair with much opportunity for thermal expansion, burning, and the ever present "oops" factor. New to grinding or an unfamiliar machine should exercise extreme caution and several dry/trial runs before making sparks.

When possible I also like to plan an "escape" if I anticipate over-heat (D-2 or long section), burning (loaded wheel), checking dimensions, etc. More than once I've reached for the cross feed, while watching the grind, only to accidentaly bump the feed in the wrong direction. I'll position the cross feed handle at 9 o'clock (when grinding with front of wheel/ back side of work) so a downward motion that disengages the wheel is more likely to happen. Using parallels against the back stop helps attain this. When the shower of sparks gets bigger or the sound changes, disengaging the grind is a better option than just finishing the pass. Excess heat being generated and the resulting thermal expansion is rapid and may make the difference between a salvageable piece and scrapped work. In an emergency situation your focus will likely be on the wheel/work, not on the cross feed wheel orientation. That's not the time for your hand to bump the feed in the wrong direction.

B to T grinding wheels hardness
One might remember ...

*Wheels are Butter to Tungsten. So saying soft to hard.
(Good one for my surface grinder book.)
RE: a clever mnemonic you use to remember this?


Grit size ihs how many you can set in a 1" square grid mesh screen (with the wires)

Concentration is 100% is when the grits are as tight/close packed as they can be.


The common advice is use a softer wheel for harder work. That is correct but only works to a certain part hardness. Some steel, like some CPM steels can be so hard that going softer doesn’t not work. The bonding lets lose before the wheel grits can penatrate the part material.
Often a friable white aluminum oxide, very hard, and very open wheel will work on a grinder that has enough Horse power to keep RPM.

Regarding nomenclature, my wife came up with SAFT. Don't know if you were sentient in 1971, but many of those of us who were will remember the radio theme song from the movie "Shaft", so SAFT is easy to remember. And, of course, it's close to soft, and it has the A in it. Ergo A is soft, therefore Z is hard.

I had been getting more and more frustrated trying to get a decent finish. Yesterday I balanced the wheels and wrapped a sheet of paper around the wheel adapter spindle before installing the wheel (to keep it located radially). I carefully dressed the wheel and then did a grind on my test part. YUK! Worst finish yet, by far!

I went to bed thinking "It's spindle bearings. That's why they sold it to you, dummy!"

Today, calm and in my right mind, I decided to do a rough test to see if the wheel was unbalanced. I put a glass of water on top of my wheel guard and let it come to rest with the spindle on and wheel mounted. The water sad dead flat. OK, I can't be that far off.

Then, in order:

inked up the periphery of the wheel
dressed doing 3-2-1 (.003" then .002" then .001") no ink left
broke the leading edge with a dressing stone
knocked off the "hangers" with a piece of wood
took a cut between 1.5 and 2 thou, horizontal speed on 24, crossfeed .016"
then took a cut 0.3-0.4, horizontal speed on 12 crossfeed .050"
then did a sparkout pass, horizontal speed on 12 crossfeed .050"
finish MUCH better

My operating theory is that I hadn't been dressing enough off the wheel to get it really trued up.

The wheel is a 46H aluminum oxide, vitrified bond, somewhat open matrix, made by Radiac.

This is on a KO Lee 718 grinder from just about when that movie Shaft came out.

If you have any suggestions as how to further improve the finish, please post them. I know this is a very commonly discussed topic. I did spend about 3 hours reading previous posts on the subject.

metalmagpie

Sounds like you did right stuff.
About the only thing is to be sure that your diamond has a bit of a facet. A round top diamond crushes the wheel and can even make it chatter a little when dressing. Often the diamond sets at 10 to 30* angle so when the diamond flattens a little you can give it a little turn and get a bit of a facet.

(15 to 20* angle is my choice)

Dressing the wheel with a sharp edge on the diamond makes a big difference. Even a diamond begins to resemble a ball bearing after prolonged use, magnified inspection of the tip determems when it's time to rotate the diamond. As for how many dressing passes are required, that's hard to say. Each wheel will be off axis a different amount. Use of a very thin shim, while knocking off "hangers" can sometimes reveal the vibration of a wheel not quite dressed all the way. There's another technique for quickly determining if the wheel has been fully dressed but it's a dangerous technique (finger) used by some seasoned grinder hands and I DO NOT recommend anybody new to grinding attempt this.

The finger method has been done by seasoned grinder hands since before the cows came home..but in the direction of the wheel so the wheel does not go the way to flip your finger back.

So nowadays I agree with AD
QT AD: {and I DO NOT recommend anybody new to grinding attempt this.}

You don't want to tell the super your finger is broke because you tried to feel a running grinder wheel.

michiganbuck said:

The finger method has been done by seasoned grinder hands sonce before the cows came home..but in the direction of the wheel so the wheel does not go the way to flip your finger back.

.

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Thought I was the only one that used this method, gotten lots of looks from others for doing it but it works better/faster than anything else I've used. Thanks Buck.

IMO, the finger method is from the past and should be left there.

Small 612 grinders are a special case. They aren't terribly heavy, rigid or powerful. If you go wider than 1/2", there's a good chance balance will be horrible unless you carefully balance it and you may not have the power to take advantage of the wider wheel anyway. Watch out for the SG wheels. Great wheels, but probably not for small grinders. This was talked about in a recent thread and a real eye-opener for me. They need pressure to work right. The manufacturers don't tell you that because they want to sell more wheels.

I've been bitten by the not-enough-off problem. If you grind a piece of soft steel with some oil, stop the wheel and look at it. It should be slightly grey all the way 'round. If you see lighter spots, the wheel isn't dressed far enough.

Speaking of soft steel, which is what I grind a lot of, you don't gain much by going to a finer wheel. A 46 grit white AlOx wheel with a coarse dress will do as well as a finer wheel. That's a profilometer talking, not just me. A very fine dress is almost never your friend unless you like loading and burning. You should also feel nothing in the hand-wheel as the grinder spins up. If you feel any vibration at all, at any speed, the wheel should be balanced. My somewhat nutcase take on the matter- Grinding Wheel Balancing

Agree we should teach and practice no finger feeling a wheel. And keep hands and fingers well away from any running grinding wheel. Park the work far enough away so there is no pinch zones between hands, work and wheel …perhaps 8”+ clear or shut it down.

Every accident makes OSHA and employers want to out law manual machines or add expensine devices..so every bit of extra caution is in our favor.

michiganbuck said:

Agree we should teach and practice no finger feeling a wheel. And keep hands and fingers well away from any running grinding wheel. Park the work far enough away so there is no pinch zones between hands, work and wheel …perhaps 8”+ clear or shut it down.

Every accident makes OSHA and employers want to out law manual machines or add expensine devices..so every bit of extra caution is in our favor.

Click to expand...

Been there, done that unfortunately. Luckily escaped with a small cut to my knuckle that only needed 3 stitches. Guy I worked with was not so lucky. Went to wipe the magnet off, and ZIP, half a pinky finger now.

Back on topic, we used to have a chart hanging in the grinding room from Norton that had all the nomenclature and what it meant. Maybe contact them and see if you can get one?