Thread: Low speed grinders advice please.

Originally Posted by Sturdee

Did ask about getting different wheels for the Axminster, and was told that only replacement wheels sold by C/T fitted the machine.


Peter.

Hi Peter, It's good to know this problem has filtered through to the staff, I wonder if they are offering that advice without prompting though. For the sake of completeness, in case an owner of the Axminster grinder stumbles on this thread with stated problem, it is easy enough to buy a 31.75mm bore x 25mm wide x 8" (mixed metaphor?) stone, available in a suitable variety of grits and fit that to the machine with a 5/8" washer either side.

Wow, its been a long time since I logged on.

I have just been reading this post about slow speed grinders. I have just been involved in the setting up/modifying one of these Axminster grinders. The solution (other than not buying one) is to machine off the built in bushing incorporated in the inner flange. Then purchase whatever wheels you want, then machine up a bushing to suit from Delrin plastic.

The problem is the shaft on the grinder is metric and most wheels have imperial bores. The bushings I made had a 0.706" bore and 1.000" outer diameter. If you don't have access to a metal lathe, this may be a costly exercise.

Glen.

As best I understand it the wheel is held by the pressure on the washers and some slop in the bushes on the shaft shouldn't be an issue. I understand that this is not the prob. referred to here but the suggestion to source a similar external washer and use it on the inside would solve it if I'm correct.

Ern - you are correct, again.....

Credit where it's due: the 'hold' on the wheel was mentioned by DJs Timber a while ago when I was publicly cussing the business of trying to get some shim strip between sloppy nylon bushes.

Once everything is tightened up, its always a good idea to dress the wheel to true it up (especially on a new grinder just out of the box.......)

Yeah, almost always necessary.

Don't forget the tap test before mounting either. (Not referring to the missus here either )

And dressing regularly (oh dear, no, I won't venture further).

I'm going to have a play with a star wheel dresser to try to preserve the coarseness of my wheel. Appreciate that there are conflicting opinions about this but it's clear that a diamond T-bar dresser smooths a coarse grit wheel; the old carborundum stick when used aggressively does better but tends to put the face out of true.

Hi Ern,

Your concerns about getting the bushing right are warranted. It is true that the flanges do clamp the wheel in place and keep the set up "true". However the bushing ensures the wheel is located correctly prior to clamping it in position.

If the bushing is the wrong size or poorly manufactured, you cannot get the wheel located correctly and it will not run concentric or square to the shaft. Yes you may be able to dress the wheel and make the circumference run "true" but it will not run concentric and may result in vibrations during operation.

The machine I repaired, had bushings which had been re-sized to suit the shaft of the grinder, however they were a 'bit' out. The wheels could not set up correctly and all the dressing in the world could not get them to run 'True'.
The machine had a vibration that could be heard and felt through the work shop.

As I said originally, two new accurately machined bushings allowed the wheels to spin concentric and square to the shaft. After dressing the wheels, the machine run smoothly and quietly.

Cheers,

Glen.

Another problem with current grinders is the washers they use today are basically pressed metal into a shape and dont have a lot of strengh.

So if someone gets a bit over excited and tries to clamp the wheel too much this can distort the flanges and the wheel gets that waving motion .

As greg indicates no amount of dressing the circumfrence will get rid of the vibration that it now causes.

I have an old GMF grinder that has cast flanges and this grinder never vibrates and the wheels do not have any wobble no matter what we put on there.

Here are some photos to explain the problem with the Axminster grinder flanges since the story seems to be getting confused.

Photo1
This is the flange arrangement as it arrives on the grinder. One side has a standard flange the other has an integral bush. The shaft of the grinder is a bee's peepee over 5/8"(maybe metric) , the OD of the "bush" is 32mm.
Attachment 172518

Photo2
This shows the bush flange mounted on a replacement wheel that is 25mm wide. You can see that the bush is short enough that it will accept a wheel down to 25mm wide WITHOUT MODIFICATION. The closest standard and common arbour size to the 32mm OD 'bush' is 31.75mm. It is a very simple matter of wiping the bore of the replacement wheel with wet and dry until it is a snug fit on the bush. You do not need to modify the bush or turn a new bush.
Attachment 172519

Photo3
A photo of the 25mm wheel mounted on the shaft. This is where the real problem lies. As you can see, the thread on the shaft is not tapped in far enough to allow the nut to reach the flange when using a 25mm wide wheel. The narrowest wheel that can be accepted without some work-around is 30mm (not standard). The grinder comes with 32mm wide wheels originally (also not standard).
Attachment 172520

Photo4
By simply obtaining a good quality 5/8" washer and reaming it very slightly, you have a low cost spacer which sits on the grinder-side of the wheel and packs the wheel out to where the nut is able to tighten down on it.
Attachment 172522

Photo 5
Happy days, it fits. For the price of a 5/8" washer you have now opened up a greater range of wheels to your Axminster slow speed grinder.
Attachment 172521
The problem does not require machining off the bush, the problem lies with the shaft thread being insufficiently tapped to accommodate 25mm wheels. If you machine off the bush, you will not have solved this problem and will then have to fabricate another bush. A 5 cent washer is all you need. There is also no problem with wheel slop if you leave the integral bush on there. You can wipe the 31.75mm bore out to a perfect fit. As I stated, the integral bush will accept wheels down to 25mm wide without modification.

Hi Mic,

Thanks for the photos, yes thats exactly what we had. Your repair is very clever and as long as you got the wheel to run true, then you have achieved the end result.

I did forget the issue with the thread not being long enough. I had to machine up a 1/4" thick spacers.

The biggest problem I see is POOR DESIGN. Unless you buy true top quality industrial machinery, then the tools/machines we purchase for home workshops and hobbies will be made to a price, and quality control may be questionable even when we think we are buying "good quality".

This slow speed grinder is poorly designed, when you consider the limited number of accessories that can purchased for it, and the fact that it requires so much thought, discussion and attention to make it suitable for most applications.

I would suggest that people steer completely away from it, and maybe the importers might get a company to machine an "adapter" to allow a greater range of wheels to be fitted.

Glen.

Originally Posted by Glen Bridger

I would suggest that people steer completely away from it, and maybe the importers might get a company to machine an "adapter" to allow a greater range of wheels to be fitted.

Glen.

I agree. If you don't have one, don't buy it.

So Mic how much is some manufacturer going to charge for a reamed out 5 cent 5/8' washer .......I like your way of thinking ...

The difference between Chinese-made and Taiwanese-made woodworking gear increasingly seems to be that the former often requires modification/fixing/replacing parts by the purchaser to work properly, while the latter generally at least fulfill their intended purpose out of the box.

Certainly true for the grinder(s) and disc sander I've purchased from Carbatec.

Yer pays yer money and yer takes yer pick.....