Thread: Bench grinder vibration

Originally Posted by BaronJ

Hi Weekend.Warrior,

Most small 500-750 Watt bench grinders will happily run a 100 mm abrasive belt. Problems arise when you want to do more than the motor is capable of. I have a commercial 100 mm belt grinder and it only has a 350 watt motor, as long as you don't put too much pressure on the belt, it does fine.

I also have a home brew finger sander that uses a 13 mm wide belt that I built using a 100 watt 3000 rpm pump motor. Now that one just rips metal off if you press too hard.

The bottom line is how much metal do you want to remove and how fast !

Good to hear that 1hp is plenty, makes me wonder why the guys on the belt grinder page go so much higher. I imagine that coarser belts require a bit more oomf to maintain speed under load?
The more I think about how the bench grinder performs, the more I am leaning towards a conversion to belt. I'd better check out the belt supply situation before committing to a size. Australia is notorious for limited supply and choice.

[QUOTE=BobL;1960479][QUOTE=ptrott;1960465]Both wheels have been replaced at different times with supposedly good quality ones, and it did improve the issue, but didn't cure it.
It is mounted on a stand made of very thick walled square tube as the vertical, with a steel wheel rim as the base.

How does it run if you take it off the base? Just on a bench.


Ah, . . . . one of the benefits of a 3P powered grinder on a VFD.

I haven't ever run it on a bench, but it should run anywhere without vibration, but it never has.
You don't need to sell me on 3ph VFD Bob, it is the ducks nuts as far as I am concerned.
My lathe is a pleasure to use now thanks to your suggesting the swap, but my Abbott & Ashby grinder has only 1ph motor, and repurposing it is preferable to selling it for a pittance. It cost me an arm and a leg 30 plus years ago, and it hasn't seen a lot of use. I would be lucky to get 70 bucks for it now.

[QUOTE=ptrott;1960499][QUOTE=BobL;1960479]

Originally Posted by ptrott

Both wheels have been replaced at different times with supposedly good quality ones, and it did improve the issue, but didn't cure it.
It is mounted on a stand made of very thick walled square tube as the vertical, with a steel wheel rim as the base.


I haven't ever run it on a bench, but it should run anywhere without vibration, but it never has.
You don't need to sell me on 3ph VFD Bob, it is the ducks nuts as far as I am concerned.
My lathe is a pleasure to use now thanks to your suggesting the swap, but my Abbott & Ashby grinder has only 1ph motor, and repurposing it is preferable to selling it for a pittance. It cost me an arm and a leg 30 plus years ago, and it hasn't seen a lot of use. I would be lucky to get 70 bucks for it now.

Does it vibrate with no wheels or attachments on it?

Regardless what you do, I'd kind of like to know what the issue was. So I can recognize it if/when I see it next time.

Sent from my SM-G950U using Tapatalk

[QUOTE=Weekend.Warrior;1960509][QUOTE=ptrott;1960499]

Originally Posted by BobL

Does it vibrate with no wheels or attachments on it?

Regardless what you do, I'd kind of like to know what the issue was. So I can recognize it if/when I see it next time.

Sent from my SM-G950U using Tapatalk

After spending some time on it today, I am of the opinion that it is a crappy designed machine.
It has plain shafts, with a tiny shoulder/register of about 1/8" on the inner ends, against which pressed metal bell washers about 75mm diam. rest.
That tiny shoulder is responsible for all the power transmission to the wheels, and for aligning the wheels, which have loose fitting plastic bushes in their centres.
The same sort of belled washers go on the outside of the wheels and a nut on the shaft end to clamp the wheels between the washers.
After spending a lot of time on one wheel centralising it, and still having the vibration, I noticed that there was a wobble in the wheel, so I removed the belled washers and trued them in the lathe, but the wheel still wobbled.
A bit of measuring revealed that the wheel itself did not have dead flat and parallel sides, so no way of getting it to run true without stuffing about with shims etc.
Other grinders I have seen have substantial sized areas to locate the inner side of the wheels, so in with a chance.
It would be more work than it is worth to get it to what I want, so it is going to be a belt grinder sooner rather than later.

One way to reduce wheel wobble is to use pairs of wobble washers like these.

WobbleWashers.JPG

The wheel is fitted, with a pair of wobble washers either side, semi tight and checked for run out .
Tapped lightly on the side with a wooden mallet until the wheel runs true.
More details here
https://www.woodworkforums.com/f155/.../2#post2146795

Originally Posted by BobL

One way to reduce wheel wobble is to use pairs of wobble washers like these.

WobbleWashers.JPG

The wheel is fitted, with a pair of wobble washers either side, semi tight and checked for run out .
Tapped lightly on the side with a wooden mallet until the wheel runs true.
More details here
https://www.woodworkforums.com/f155/.../2#post2146795

Interesting read Bob, and glad you got a good result.
I don't have the necessaries to make those washers, and I don't know that they would work in with the mount/drive setup used on my grinder.

IMG_20191220_091657.jpgIMG_20191220_091548.jpg

From what I have read (quite a lot) about the belt grinders, it would likely get a lot more use than the wheels ever did, not just because it would be a nice smooth machine, but the ability to change belts for a different grit, and a flat grind at a perfect 90deg would be a bonus. It is a struggle to think of anything I would miss about the wheels.

Originally Posted by ptrott

Interesting read Bob, and glad you got a good result.
I don't have the necessaries to make those washers,

Sorry I forgot you can't angle your compound.

[QUOTE]and I don't know that they would work in with the mount/drive setup used on my grinder.
That's about all I have on my (GMF) ginders

IMG_20191220_091657.jpgIMG_20191220_091548.jpg

From what I have read (quite a lot) about the belt grinders, it would likely get a lot more use than the wheels ever did, not just because it would be a nice smooth machine, but the ability to change belts for a different grit, and a flat grind at a perfect 90deg would be a bonus. It is a struggle to think of anything I would miss about the wheels.

I use my bench grinder based belt sander a lot and is the most common use of one of my bench grinders. When I got my mill I thought I would not used the belt sander as much but the sander is just too quick and easy even if significantly more "agricultural". The next most common use of my grinders would be the Scotchbrite wheel and then the wire whee and the thin kerf cut off wheel. Actual grinding using a wheel eg sharpening would come in as leas common.

Yesterday I made this Table Saw motor suspension/adapter plate for a member on the woodies forum.
The original was mad of some crap alloy and had snapped across the middle
This one is made out of scrap 6mm and 10 mm thick mild steel plate welded together.

TSadapterplate.JPG

I basically rough cut the 4 pieces out using my thin kerf cutting saw and used a 40 grit belt to hog it roughly into shape and then an 80 and 120 belt to finish and then welded it all together.

I could have milled all the edges nice and square etc but that would have taken too long and besides it's not like its for a precision application.
The only thing that really had to be reasonable accurate were the positions of the 2 x 10 mm and 2 x 16 mm holes which was more of a marking out issue.

"" I use my bench grinder based belt sander a lot and is the most common use of one of my bench grinders. When I got my mill I thought I would not used the belt sander as much but the sander is just too quick and easy even if significantly more "agricultural". The next most common use of my grinders would be the Scotchbrite wheel and then the wire whee and the thin kerf cut off wheel. Actual grinding using a wheel eg sharpening would come in as leas common. ""

Pretty much along the lines of my thoughts, so I am over the bench grinder, time to turn it into something a lot more useful

Nice job on the saw bracket Bob

Hi Phil, Guys,

A thought pops into mind ! I had a new wheel and it came with some plastic hubs that you put on the grinder shaft and they fitted into the wheel centre, badly ! I turned up some new ones from a bit of Nylon bar. They fit much better and support the wheel true.

It could be that the hubs that you have got fit so badly that it allows the wheel to twist and not run true. That would cause vibration.

Phil,
While this is maybe moot if you are going to convert to a belt grinder, but the wheel washers as depicted are only stamped, wheel wobble can be reduced by placing washer wheel side down on a piece of emery paper on a reasonably flat surface and give it a couple of laps to get an even surface, place the washer face in on a 3 jaw chuck with jaws reversed so as to give it a reasonable surface to sit on and skim true the face that goes against the shoulder on the shaft. Do all washers the same, when remounting some rotational jiggling of the washers will probably still be required to get the best position, when done mark all and the shaft position so they can go back the same way when changing wheels. Has worked on several grinders I've refurbished, fiddly but worth it. Also a good blotter between wheel and washer helps. Good luck with it. Alan.

Originally Posted by BaronJ

Hi Phil, Guys,
A thought pops into mind ! I had a new wheel and it came with some plastic hubs that you put on the grinder shaft and they fitted into the wheel centre, badly ! I turned up some new ones from a bit of Nylon bar. They fit much better and support the wheel true. It could be that the hubs that you have got fit so badly that it allows the wheel to twist and not run true. That would cause vibration.

That could be a contributing factor for sure, but I am going down the belt road with it.
It will be so much more useful

Originally Posted by C-47

Phil,
While this is maybe moot if you are going to convert to a belt grinder, but the wheel washers as depicted are only stamped, wheel wobble can be reduced by placing washer wheel side down on a piece of emery paper on a reasonably flat surface and give it a couple of laps to get an even surface, place the washer face in on a 3 jaw chuck with jaws reversed so as to give it a reasonable surface to sit on and skim true the face that goes against the shoulder on the shaft. Do all washers the same, when remounting some rotational jiggling of the washers will probably still be required to get the best position, when done mark all and the shaft position so they can go back the same way when changing wheels. Has worked on several grinders I've refurbished, fiddly but worth it. Also a good blotter between wheel and washer helps. Good luck with it. Alan.

Alan, that is just about word for word what I did a couple of days ago, and got no better result than before. That was basically what sealed the deal to go with a belt.
I put as any hours into trying to fix it as it would take to build a belt grinder attachment,...well nearly anyway

Originally Posted by ptrott

Alan, that is just about word for word what I did a couple of days ago, and got no better result than before. That was basically what sealed the deal to go with a belt.
I put as any hours into trying to fix it as it would take to build a belt grinder attachment,...well nearly anyway

Phil, it seems like you have done most of the usual checks. You said one of the wheels is dished, so, try marking a clock face on it, I.E. 1,2,3 etc. Put a short bit of 6mm rod in a vice, get it perfectly level and place the wheel on it at 12 o'clock. See if it sits there without movement, then try each hour in succession. If it turns at any point you could have a variable density wheel. If so, bin it and get a new one, I have found 4 or 5 in my lifetime.
As for the belt, best decision you will make and you will be surprised how much you will use when you have one. I bought a Multitool attachment a long time ago and I got the 1200mm version as I like it's extra length. ( Doesn't everyone say that extra length is better?)
They are made for the RHS of the grinders, but I wanted it on the LHS. I had a good look at how it's made and from memory I had to grind a little bit out to clear a mounting bolt, did that and never looked back.
BTW, I had a constant problem of the belts coming apart at the tape join when deburring sheet metal, so I buy 2 in advance bend them open on the tape join and squeeze in a bead of good quality wood glue. Wait about 5 minutes and then flatten the belt, add some small weights either side of the join and let it dry out for a few days. The excess dissappears with use. I have never had a belt let go since doing this, and I don't miss being rapped on the knuckles by a broken belt.
Rgds,
Crocy.