Poor finish

DieRepairman · Sep 23, 2009

My company has recently purchased a Brown and Sharp micromaster 1224 automatic surface grinder.

I have leveled the machine, and everything seems to be functioning properly, yet I cannot get a good finish on the tool steels I am grinding (Mostly D2).

The previous owner (Now currently out of business) did a good job of keeping records for this machine. He had the spindle completely rebuilt back in 2002.

Before I call someone in to look at the machine, is there anything I can check and possibly adjust myself?

Ox · Sep 23, 2009

Doo you know what grit wheel that you have on it?

Have you "dressed" the wheel with a diamond mag'd down to the table? (Ass opposed to the handheld units for the bench grinder eh?)

(Sorry if I'm talking down to you. I don't know where your starting from.

)

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Think Snow Eh!
Ox

Kevco · Sep 23, 2009

First thing to do is rule out the wheel. If a wheel get contaminated with a heavier liquid on one side it can throw it out of balance. It is junk then. We go through a lot of wheels in a year and noticed we get way too many NEW Norton wheels that are bad when new. So bad, you can't even get them balanced with double side dressing. Norton takes them back and resells them by injecting them with some kind of liquid on one side. If you have a wheel that has a pop can size white looking ring on one side you got one!

Most of the time even then they still leave a poor finish. If you can use a "known" good wheel you can at least rule that out. Either try your wheel there or use a known good wheel from another machine. When the wheel thing first started happening 8 years ago guys at our placed tried replacing spindles till we found out it was the wheels.

Another thing to try is start the machine with NO wheel on and see if you can feel a vibration. Bearings can go bad anytime. Is the finish bad evenly or???

Mark H · Sep 23, 2009

Size of the wheel. (A small diameter wheel won't get the optimum SFPM to achieve a good finish.)

Wheel balance.

Correct bond and grit.

An old boss of mine decided that name brand bearings were too expensive. He went and got what I believe were bearings for a trailer to put in our Boyar-Schulz. There was considerable chatter on the finish. Of course he blamed the fellow rebuilding the machine.

Put your hand on the wheel guard. There should be no feeling that the machine is on, assuming a correctly balanced wheel. You may have to dress the sides of the wheel to correct vibration.

If the hydraulic cylinder isn't adjusted correctly, that can affect table travel. The table could float, or slop around.

More info on what the poor finish looks like could help. Hardened D2 isn't the friendliest material to grind.

Mark H

Bob E · Sep 23, 2009

(I'm a slow typer, so some of this is has already been addressed)

Expand on the bad finish:

Chatter?
Burning?
Dimensional?

Some things that directly affect finish:

Rotate or change dressing diamond.
Use a faster dressing speed
Wheel grit/hardness
Check wheel balance
Was the grinder recently "cleaned" with an air hose? Grit gets in the table rollers and cause terrible chatter marks.

One thing I saw once after transporting a used grinder, the rollers under the crossfeed carriage became dislodged and needed reset in the cage. This showed itself as a .003" taper across the workpiece and irregular finish.

Lots of other variables here as well.
Can you post a pic or scan of the finish?

DieRepairman · Sep 23, 2009

It is definately a chattered finish.
The wheel I am useing is a Norton 32A46-IVBE
12x2x5 (No Recess)
I have dressed the wheels sides and dressed with the diamond on the chuck

I dont know how else to balance a wheel

I do not see any white bonding, but that is interesting and I will look from now on at all the norton wheels I purchase.

I will definatly look into the other suggestions you guys have made, thanks for the info.

precisionworks · Sep 23, 2009

start the machine with NO wheel on and see if you can feel a vibration.

Then mount the wheel to see if there's any vibration. Some wheels, even after side dressing & face dressing will vibrate.

I dont know how else to balance a wheel

You may need to use a Sopko balancing hub. First do a static balance (off the machine) to get the weights close. Then install the wheel and make tiny changes to the balance weights until all vibration is gone.

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Barry Milton

Ox · Sep 23, 2009

"Crush" paper on boths ides of the wheel? Is it tight enough?

Not shutting off between dress and cut? If you shut it down it may not start back exactly the same.

Not fluent in the grinding wheel number. I use a baseline of a 46J (I think) on my Harig FWIW.

Does it start out bad? Or git that way quickly?

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stannp368 · Sep 23, 2009

D-2 (high carbon-high chrome) is difficult to grind as it wears the wheel down quickly. I noticed in past years that wavy finishes were caused mainly by grinding wheel not being clampeed tight enough. Also dressing the wheel, turning off the machine then restarting which can throw it off balance or the spindle itself. You indicate the spindle was rebuilt in 2002. Even a .0001 play can cause ocean waves on your work as it is revolving 5000 fpm

Lost in LA · Sep 23, 2009

Nothing counts until you balance the wheel. That machine has a wheel flange with balance weights and you should have a balance arbor and a balance.

Dressing the sides and the OD of the wheel is a good first step. Now remove the wheel with the wheel flange in place--do not loosen it. Balance the wheel and put it back on the machine and see what happens

Lost

Arnie3 · Sep 24, 2009

Lost in LA has it right, only thing I would add is dress the wheel again after balancing.

Also agree with Kevco about the new Norton wheels being way out of balance. I have had small cup wheels that were so bad they went back to Norton!!!

DieRepairman · Sep 25, 2009

I really appreciate everyones input on this.
I have a question.

I have the weights on the wheel flange, but I have nothing off the grinder to balance the wheel with.
I have looked in a few catalogs and have found wheel balancing kits, but they seem to be for standard 7-8 inch wheels.
Does anyone know where I can find a wheel balancing kit for the 12" wheels?

By the way, if I purchase the small wheel balancer, how would you balance the small wheels without the weights?
(Really showing how naive I am now) :confused:

WILLEO6709 · Sep 25, 2009

first things first.... tenth reading dial indicator, mag base on the wheelhead, run the table both with handwheel and hydraulics, can you see the indicator twitch/ move? If yes, it can be an magnet that needs reground or a way issue. the way issue can be as simple as an inoperative lube orifice or as complex as rescraping. If the indicator is smooth, remove the wheel and put the indicator on the flange. Same drill, can you see it moving? Can you push the spindle and see deflection? Balancing stands for larger wheels are available. Sometimes called static balancing ways, try ebay. Wheels can have a great effect. the wrong wheel can give the effect you describe as well. My all purpose wheel is a radiac 8BP series. I like radiac's h800 open structure.

Lost in LA · Sep 26, 2009

Die man:
You are going to need an arbor for the wheel flange. Do you have one? Might be hard to find.

You need a good size balance stand. The cheapest ones have 2 rails and a bubble level. They work OK. Search ebay or call a machinery dealer. Usually the rails are beat up but you may be able to refinish. I made my own with two 1 inch thick bars ground top and bottom and placed on a level granite plate.

Smaller wheels about 7 inches dia X 1/2 usually do not need balancing. The wheel hubs usually do not have provisions for balance weights. If you can balance a small wheel it will improve the finish a bit.

cash · Sep 26, 2009

Here is what I would do-Unless you have somebody local with a IRD machine, this is what you use to get your wheel arbor in balance, just take all the weights off of your flange.

Put your wheel on, true it up by dressing and see what happens.

If when you are truing your wheel and as it goes over your diamond, with some coolant on it listen and see how it sounds. If the wheel sings real nice across your diamond then I would say you do not have a balance issue but a wheel that is too hard issue.

We have several smaller okamoto type grinders that use 14" wheels. We never balance them before putting on and do not have issues. We have several mattison grinders that use 20' wheels. We never balance them and never have issues.

Hardened D-2 58-60 rc is everyday work for us. To really be able to gring this effieiently try a ceramic wheel in the G-H hardness and 60 grit. This may solve your problems. Most machine tool mfg.'s go for 6500 sfpm starting out with a new wheel. This may be fine for mild steel but not for tool steel. We have V.F.D.'s on all of our spindles and 4400 sfpm is really what works best, give or take.

Oftem we will see our parts that have been reground by some other shop and you can see chatter over the entire part. they are just using too hard of a wheel.

MIKE DELMO · Sep 26, 2009

Grinding d2 is the worst matl u can grind if u r grinding die sections then the best wheel u can use is a norton 38a white
80 j wheel. If u are doing a lot of grinding then my choice
would b a borazon wheel it works great talk to ur wheel people
about choice.

tdmidget · Sep 26, 2009

Listen to cash.

Peter Neill · Sep 27, 2009

Standard Al Ox wheels don't work well for grinding D2, the grains blunt and then rub on the work instead of cutting.
You should be using a blue SG (seeded gel) ceramic wheel for this, and Cash has given you good advice. The grains in the SG wheel tend to 'micro fracture' and produce a constantly sharp cutting edge, whereas the Al Ox wheels tend to crush a bit and become blunt on D2.

I think you'll be amazed at the difference when you try it, but be warned that SG wheels are a much higher cost.

Peter

Edit: Forgot to mention that they also cut a lot cooler too.

easymike29 · Sep 27, 2009

Aluminum oxide and SG wheels both have their place in a tool room environment. Each have advantages and disadvantages. Volumes could be written on their merits. As a general rule, SG wheels perform best on harder materials such as D2 or CPM-10V especially when removing lots of stock but fall short when trying to pick off that last tenth and maintain a relatively fine finish on an intricate contour.
A VFD and a good selection of both kind of wheels is key to covering all the bases.

Gene

cash · Sep 28, 2009

The 12x2x5 wheel is a bit odd and norton only stocks this in 32A. May I suggest going to a 12x1 1/2x 5, this gets you way more options. You can then go with SG or the new Quantum.

The only modification you may have to make is shorter bolts on your hub. With the narrower wheel you machine will require less h.p.

Poor finish

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