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Pherdie
02-04-2010, 10:14 PM
I recently purchased a 7", 3/4 hp surface grinder for home shop use. Based on advice from this forum, I also purchased four additional wheel hubs in order to mount a selection of wheels. I have no experience or training in surface grinding. Grinding will be primarily on small, mild steel pieces, but may include HSS, aluminum (6061), grey cast iron and brass. I don't expect mirror finishes will be required.

Ignoring the fact the unit comes with one wheel, what four wheels would make up a versatile selection for my home shop use??

Fred

doctor demo
02-04-2010, 10:52 PM
What Grinder followed You home? I know You've been looking for one for a while.
All I have is white Norton wheels, general purpose. I've never ground alum. or brass, but I have ground rubber.
Post a pic or two Fred, You know the drill:D .

Steve

tdmidget
02-04-2010, 11:08 PM
For hardened steels, Norton 38A, 46 or 60 grit,h hardness
for mild steels Norton 32A, 46 or 60 grit, j hardness
for the nonferrous. Norton 86C 46 or 60 grit, j or k hardness
Maybe a Diamond wheel for tungsten carbide?
Better yet, Let Evan guide you. His wife is in the biz. Maybe SGs would be more versatile.

Ken_Shea
02-04-2010, 11:29 PM
Fred, hope you don't mind my butting in with a question.

Been wanting a SG for years, just bought one a week ago, not able to get it picked up as yet, anxious to get it here, up and running. A manual B&S No.2 6x18

My question, there is a like new diamond wheel on it but some one had gouged a perpendicular slot across the face about 1/8" wide with a fixture that was on it.

Is the wheel still usable or just cause for problems?

Carld
02-04-2010, 11:38 PM
Fred, I don't know what grinder you got but I think you will find that just changing the wheel and not the hub will be the best and fastest. First you don't have to balance the 7"" wheels used on the small surface grinders and second you will get tired of pulling the wheel mounting hubs off the spindle and it's completely unnecessary to do that.

In all the shops I worked that had the 6x12 surface grinders none of the balanced the wheels or removed the mounting hub unless something was wrong with the machine.

You don't balance your bench grinder wheels do you? Then why do you think you have to balance the 7" surface grinder wheels?

tdmidget
02-05-2010, 01:14 AM
Who said anything about balancing?

Machinist-Guide
02-05-2010, 01:14 AM
I agree with Carld. You don't to balence a 7" wheel just dress it.
A rule of thumb as far as your bond. Hard material use a soft wheel. Softer material use a hard wheel.

Evan
02-05-2010, 01:16 AM
If a wheel is out of balance it is defective. It does happen but not often with a brand name wheel. I happen to be checking one out right now that costs $1700 which the customer claims is out of balance. It isn't but I haven't done a close check yet for out of round. I will post a pic of it later.


You have several choices to make. Hard or soft, coarse or fine and what type of grit. Soft wheels cut faster and cooler but wear out faster and don't hold dimension as well. Hard wheels cut slower and hotter but hold dimension much longer. Incidentally, a soft wheel is made that way by including friable non-grit additives such as silica micro balloons or clay particles. These break down easily and release worn grit to expose fresh grit which makes the wheel cut fast.

Coarse or fine grit also has similar properties to soft/hard except for the resulting finish. Coarse cuts fast and cool and fine is slow and hot. A soft and coarse wheel will remove material at an amazing rate but the wheel won't last long. That isn't as important in industry if stock removal is more important than wheel cost. Time is money. The HSM is probably better off to buy a harder wheel that will last a long time. If you can't afford a selection of grits then a medium grit is the usual compromise, around 60 to 80 grit.

For the hard materials a CBN wheel for steels and a diamond wheel for carbides are indispensable. A good electroplate diamond wheel will last a long time as long as it isn't abused by grinding steel. CBN wheels will last even longer than diamond and have the advantage of holding dimension extremely well. They cost but good tools always do. Never grind carbide with CBN. It will glaze the wheel and then you have to dress it and waste a lot of expensive grit.

I use my milling machine as a surface grinder from time to time and I use aluminum oxide jockey wheels for mild steel. Those are cup wheels and they hold up well since they wear across the entire face. And yes, it is a major cleanup job after grinding something but at least the round rod ways are easy to replace if needed. Loosen two sets screws and pull the shaft out.

tdmidget
02-05-2010, 01:18 AM
Ken if there is significant thickness of the diamond layer below the scratch it could be saved . It could be ground down with a coarse vitrified wheel but wheel wear will be bad .

Ken_Shea
02-05-2010, 07:45 AM
Thanks TD, as I recall it was pretty deep, unfortunate, while diamond wheels are not as expensive as they used to be they are still not cheap, undoubtedly done by someone cranking the wheel while looking at the grinder. Maybe it's salvageable for some limited use. I have an old Belsaw carbide circular saw sharpener that has one on it that is used for sharping carbide cutters.

JoeLee
02-05-2010, 08:24 AM
I have an assortment of wheels in my shop. Ever since I bought a Triupmh ruby wheel in 60 grit I haven't used any of my other wheels. The ruby is by far the best I have ever used. They generate less heat and require much less dressing. The only thing is they aren't available in all the grits and hardness as the white wheels are.

JL.........

Evan
02-05-2010, 08:40 AM
The ruby grit wheel is a white aluminum oxide wheel dyed red. The colours are not important but the specific formulation of grit and friable materials is. You have found a wheel that is well suited to your use. Real rubys BTW are made of.... aluminum oxide.

JoeLee
02-05-2010, 09:28 AM
Thanks for the info Evan. I wasn't aware that the ruby wheel is actually a colored ALOX wheel. All I know is I can grind all day long and only have to dress a couple times. They almost seem non consumable.

JL..................

Pherdie
02-05-2010, 01:18 PM
Hey! How about a little more time for your keyboard challenged participants before you dump the reply editor???

Timeouts of the message editor have lost me three hard fought would be message postings in the past two weeks. My two fingers just don't type that fast and I'm too lazy to pre-type my message on another application and/or do frequent copy commands......

Fred

Edit: Posted in this thread by mistake and under duress (as proven by my message content!!!)

sidneyt
02-05-2010, 01:44 PM
I recently purchased a 7", 3/4 hp surface grinder for home shop use. Based on advice from this forum, I also purchased four additional wheel hubs in order to mount a selection of wheels. I have no experience or training in surface grinding. Grinding will be primarily on small, mild steel pieces, but may include HSS, aluminum (6061), grey cast iron and brass. I don't expect mirror finishes will be required.

Ignoring the fact the unit comes with one wheel, what four wheels would make up a versatile selection for my home shop use??

Fred
I am assuming you got the HF surface grinder like the one I purchased.

I also ordered extra hubs for my grinder and I did a little research on wheels. My first attempt grinding was to use the white ALOX 60K wheel that came with the grinder. It actually worked better than I expected. But, I thought I could do better. My first wheel purchase was two 32A wheels based on a brochure I found on Norton's site that suggested that a 60K or 80K wheel would be appropriate for grinding mild low carbon steel. My experience was that these were not ideal wheels for getting the best finish on this type of material. They were too hard and tended to chatter no matter what I did. I then tried white Alox wheels purchased from Enco, both 46j and 60i grade, that seem to do a better job on the 1018 and cast iron that I was attempting to grind. The fact is it is more difficult to grind low carbon steel. I had better luck grinding H13 and some unknown alloy steel.

Then I read the chapter in James Harvey's book Machine Tool Trade Secrets in which he suggests using a softer porous wheel even for materials like low carbon steel. I tried this 46J pink porous wheel from Enco:
http://www.use-enco.com/CGI/INSRIT?PARTPG=INLMKD&PMPXNO=26933385&PMAKA=SZ422-0187
This worked better. I have also tried a Camel AZ wheel (blue) with some success.

But, I can tell you this: it takes some practice to learn how to grind. It takes some experimenting with technique and with the proper selection of wheels.

As to balancing wheels, I note that a number of users say it is not really necessary...if you buy premium wheels. That may be the case, I have not been purchasing Norton SG $70 grinding wheels. There is one way to judge how much of a difference it makes to balance your wheels. Put a dial indicator on the top of the column so you can accurately measure not only the Z axis (I realize there has been some discussion on the issue recently as to which is the Z axis, I mean the up an down axis of the spindle), but also how much vibration there is with the wheel and hub mounted. My experience has been that without a wheel mounted on the grinder and using a .0001" DI I observe no movement in the DI needle. It runs very smoothly as expected. If I mount the wheel and run the grinder without dressing the wheel you can definitely see the DI needle wobbling. Dressing the wheel makes a difference. Balancing the wheel and dressing it together usually allows the grinder to run as smoothly as if there was no wheel and hub on the machine. Yes, the wheel does make a difference. I received one wheel from Enco that I just could not get to balance. It was just too far off. But, of the other six wheels I have received (USA and imported) all were improved by balancing them. It did not matter which hub the wheel was mounted on, all of them were off to some degree. Would it matter if the grinder weighed 1500lbs instead on 450lbs? Probably. How much does all of this make in the final grind? Well, I figure it certainly doesn't hurt to reduce any factor that causes vibration. There are a number of references I found concerning balancing. The best description is in the book:
The Grinding Wheel by Kenneth B. Lewis Chapter 12 on truing, dressing and balancing. I built the balancer that was described in the article in HSM last year with modificatons. Works well.

Pherdie
02-05-2010, 01:58 PM
Doctor Demo:
What Grinder followed You home? I know You've been looking for one for a while.

I purchased a Harbor Freight unit (two people applaud wildly, the remainder of the crowd issues a collective sigh of dissapointment). Frustration in finding a good used unit at a fair price (and a 20% off coupon!) helped to facilitate my choice. It appears adequate for my minimal home shop needs (the defense rests).

tdmidget: Exactly the type of information I was seeking, thanks.

Ken_Shea: No problem on adding to the thread. I learned something from your question.

Carld:
Fred, I don't know what grinder you got but I think you will find that just changing the wheel and not the hub will be the best and fastest. First you don't have to balance the 7"" wheels used on the small surface grinders and second you will get tired of pulling the wheel mounting hubs off the spindle and it's completely unnecessary to do that.

I bought the extra wheel hubs based on information in a previous HSM thread on HF surface grinders. I received the impression that leaving the hub assembly on the wheels and swapping wheel-hub assemblies on the spindle would be a better way to go. I understood there should be no balance requirement for the wheel itself, if properly manufactured. None the less, based on a copy of the grinder manual I got on-line (I have yet to see or receive a unit), it appears that the wheel hub assemblies have some sort of balancing arrangement incorporated into the wheel hub assembly. Oh well, if Iím incorrect in this spindle/hub issue, Iíll be the new King-O-HubsÖ.

Evan, Sindneyt, et al: Thanks for your additional input, much appreciated.

Question: 1/4" vs. 1/2"???

Evan
02-05-2010, 02:19 PM
This is what a $1700 grinding wheel looks like. It is a special profile grinding wheel. Claimed to be out of balance but at 850 rpm on my lathe I can stand a 25 cent piece on edge on the headstock and it will stay there. There is tape on the OD of the wheel so I could make a prelim measurement of the trueness and it is less than .001" out. This wheel normally runs at 3500 rpm so the next step to qualify it is to make a mandrel to mount it on and make an accurate measurement of the roundness.

With a wheel like this the hub is worth more than the electroplate diamond coating so they are sent back for recoating when they wear out. Methinks the customer has a worn spindle and it didn't sit just right when installed. It weighs 30 lbs so even a trace of imbalance will be very obvious.

http://ixian.ca/pics7/1700wheel1.jpg

sidneyt
02-05-2010, 02:24 PM
"I purchased a Harbor Freight unit..."

The HF grinder appears to be identical to the ones sold by Grizzly, Wholesale Tools, Enco, KBC and others.


"I bought the extra wheel hubs based on information in a previous HSM thread on HF surface grinders. I received the impression that leaving the hub assembly on the wheels and swapping wheel-hub assemblies on the spindle would be a better way to go. "

Yes, this is correct and you are better off having more than one hub.

" it appears that the wheel hub assemblies have some sort of balancing arrangement incorporated into the wheel hub assembly. "

Yes, this is correct

Carld
02-05-2010, 02:55 PM
I have the Central Machinery Co. surface grinder that is sold by HF, Grizzley, Wholesale Tools, Enco, KBC, and on and on. It does have a hub with little weights to balance the wheels. I put them in a box with the other stuff for the grinder and there they stay.

For about 17 years I worked in various job shops and they all had some brand of 6x12 surface grinders. No body balanced the wheels and they got changed according to the job requirements. Never did any of them show any balance problems. The larger wheels for bigger surface grinders and the huge wheels for the crankshaft grinder always got balanced.

I know I will not make those with strong opinions change their opinion so this is for the ones that are interested in the truth and the following is the truth.

IF THE WHEEL IS OUT OF BALANCE ON A 7" WHEEL FOR THE 6X12 SURFACE GRINDER RETURN IT OR THROW IT AWAY. It is trash and should not be used.

Evan has said this many times and his wife sells grinder wheels for a living so who should know better. There always seems to be some paranoia with home machinists about things that don't amount to a hill of beans but that is the nature of it.

As I said I have had the HF grinder that is made by Central Machinery for two years now and it does a great job WITHOUT BALANCING on the same hub everytime. I have about 15 wheels for spares to use on it and none of them fail to run true. Well, I did throw two of them away because they had side runout when I mounted them. I removed them, hit them with a hammer over the trash can and went on.

You do not need to change the hub or balance the wheel on a 7" surface grinder, period.

sidneyt
02-06-2010, 12:39 AM
You do not need to change the hub or balance the wheel on a 7" surface grinder, period.


"If you have a balanced/balancing hub for your wheels - use it, as that, as much as finer wheels, will give you a much better finish if set up and used correctly. Re-check the wheel balance periodically as wear and dressing will cause a progressive loss of balance."

Oldtiffie HSM Board posted 05-03-09

http://bbs.homeshopmachinist.net/showthread.php?t=12741&highlight=balancing+grinding

The article in Home Shop Machinist Magazine on building a balancer: Balance Your Wheel Once by Charles St Louis, May/June, '09 Part 1 and July/August, '09 Part 2

I built this balancer. It works great.

You can buy this balancer:
http://www.wmsopko.com/catalog.php3?pagelist=90-91
from Travers and other vendors

You many have missed my post above. There is a good description of balancing and truing a wheel in The Grinding Wheel by Kenneth B. Lewis Chapter 12 "Truing, dressing and balancing".

Even a 7" wheel can benefit from being balanced.

atty
02-06-2010, 12:57 AM
Thanks Syd. Your explanation of a DTI on the hub explains a lot. You have have answered a lot of head scratching on my Kent. Makes all the sense in the world.....hub balancing or not. If the DTI is wobbling, therein lies the problem. Dress the wheel, or toss it. I appreciate the info.

Evan
02-06-2010, 04:00 AM
Truing a grit wheel for a slight out of round condition isn't balancing, it's truing by dressing. Nothing wrong with that although it shouldn't be necessary on a good quality wheel. Where the problem appears is when a true running wheel still vibrates. That is a balance problem and with a grit wheel it indicates that there is a density variation in the wheel, assuming it has been mounted correctly.

Trying to balance a true running wheel is not recommended. It doesn't matter how it is done or how well it seems to work. A wheel that seems to be out of balance even though it runs true is dangerous to use. It has internal density variations that are probably a result of poor wormanship when the wheel hand was laying up the grit in the mold. Grit wheels are hand made and without sufficient care can be made improperly.

As proof of this I offer an example made by my wife during a factory training session. It was never intended to run but If I recall correctly did pass a spin test.

http://metalshopborealis.ca/pics/wheelsig.jpg

JCHannum
02-06-2010, 08:33 AM
What the OP is referring to as hubs are probably the adapters such as sold by Wm. Sopko. These are standard in any grinding shop and allow wheels to be removed and reinstalled without the need for heavy dressing or rebalancing.

Balancing is needed and done regularly, particularly on large wheels and to produce the best finish. Today's manufacturing produces wheels which are more uniform than previously available, but the need does arise. Sopko has adapters with balancing weights built in to provide for this requirement.

http://www.wmsopko.com/products.htm

In addition to the knife edge static balancers, some very sophisticated equipment is used for dynamic balancing of grinding wheels. This is one manufacturer;

http://www.ciro.com/Elasobal.htm

JoeLee
02-06-2010, 08:37 AM
Hey Evan,

If they can make wheels that are balanced why do almost all my wheels wobble a bit from side to side?? Why can't they make them flat as well??

JL..............

Peter N
02-06-2010, 08:44 AM
You really don't need to balance 7" wheels if you're getting them from a reputable source. We probably go through a couple of dozen per year for the 3 grinders in my partners Toolroom and haven't even got the balancer out in more than 10 years. As Evan said, dressing for out-of-round is a different thing altogether and usually 0.010"-0.015" off a new wheel takes care of this.

Incidentally we use Norton 95A wheels exclusively in the Toolroom now, except for grinding D2 where we'll use an SG wheel.

Peter

Toolguy
02-06-2010, 11:41 AM
If you are using coolant, turn off the coolant and let the wheel spin for a while before turning off the spindle. The wheel gets full of coolant while running. If the wheel is stopped with coolant in it, the coolant will pool at the bottom of the wheel, making it unbalanced when it dries out. If you think this may have happened to a particular wheel, you can take it off the adapter, soak it for a while, remount it and try again.

Carld
02-06-2010, 12:11 PM
I mostly have Norton wheels and I can change wheels and have no balance problems at all. I can also use the side of the wheel against a surface and have constant contact with no runout. None of the Nortons I have bought and used have had runout but that don't mean there aren't some bad ones, I just haven't gotten them.

The Chinese wheels I have do have some runout and if they don't vibrate I may true them and use them. If they vibrate I break them and throw them away.

Why do I break them instead of balancing them? Because the wheel has a heavy mass in one side of the wheel and when you balance it the mass is still there and there may be a stress point as well. Requardless of any stress a heavy mass on one side of a grinder wheel is always trying to escape and at some point it may explode.

Now I ask this, have you ever been near an exploding grinder wheel running at 3000+ rpm? Do a search on exploding grinder wheels and tell me you want to stand in front of and trust a wheel with an unbalanced mass in it.

A wheel that don't ring when taped or has an unbalanced mass you can feel when at speed is dangerous to use and should be destroyed.