Is there a way to prevent the spacer coming off when swapping grinding wheels?

[flyvert]

As per the subject, is there some neat trick I can apply to prevent the spacer to come off when I swap between grinding wheels?

[John Hancock Sr]

Not really. It does tend to stick to the wheel when you take it off.

[RickKrung]

Yeah, annoying. When I remember to, which is often not, I move the wheel out enough to reach in and touch the spacer to separate it from the wheel and then finish removing the wheel.

[John Hancock Sr]

Yeah, annoying. When I remember to, which is often not, I move the wheel out enough to reach in and touch the spacer to separate it from the wheel and then finish removing the wheel.

Same.

[BPalv]

Same as above... forget to every now and again... still annoying.

[MARC LAVINA]

Same problem here

[Ken S]

I have been closely following this forum since 2009. This posting is the first I have noticed on this issue in that time. The spacer has not changed. The shaft was changed to stainless steel many years ago., as was the conversion to the EZYlock.

Anyone who has experienced a frozen EXYlock (which includes me) would consider a sliding spacer as a minor nuisance. Noticing occasional frozen EZYlock posts over the years, I sent an email to support requesting advice. Support really went the extra mile. They ran tests and discovered that they could get the EZYlock to fail, IF there was no grease on the face of the spacer facing away from the grinding wheel. Putting a thin coating of grease on this face eliminated the failure. Problem solved.

How big of a problem is a sliding spacer? For the majority of Tormek's fifty years, there was only the SG wheel. Even today, with several wheels available, many users still choose to use only the SG, which remains the most versatile wheel. The wheels could be redesigned to incorporate built in spacers. That might solve the problem, but would increase the cost per wheel. How many users would be willing to pay the extra cost?

Ken

[RichColvin]

I believe there is a solution if you have a metal lathe. 

I asked Claude (an AI),

Capillary adhesion is experienced between the grindstone and the washer on a Tormek grinder. If the washer had most of the surface dished out (as if it were a bowl), would this surface adhesion become almost negligible?

The response was,

Yes, and quite significantly — for two separate reasons tied to the two mechanisms:

Capillary suction (Laplace pressure)
This force is roughly proportional to the contact area where the thin film exists. Dish out the center and that area shrinks to just the outer rim, so the suction force drops proportionally to how much area you've removed.

Stefan (viscous squeeze-film) adhesion
This is the bigger effect for a fast pull-apart, and it's the one that benefits most dramatically. The Stefan equation says resistance scales with the fourth power of the radial distance water has to travel to escape:

F ∝ R⁴ / h³

That R⁴ term exists because water at the center of a flat disk has to travel the full radius outward to escape when the plates squeeze together — a long, slow path. If you dish out the center, that water is sitting in an open reservoir with nowhere to build pressure — it's not trapped. Only the water in the thin rim band actually gets squeezed, and it only has to travel the width of that rim (not the full radius) to escape. Since the effective flow-path length drops so much, and the force depends on that length to the 4th power, the reduction is dramatic — often far more than proportional to the area removed.



Net effect: You wouldn't make it perfectly zero — there's still a wetted rim doing some work — but you'd cut both the suction and (especially) the "stuck fast" viscous resistance dramatically. This is essentially why things like vacuum-cup release valves, dimpled/grooved plates, and relief channels are common tricks for beating stiction — you're shortening the escape path for the trapped film rather than trying to eliminate the film itself.


You could test this premise using a 3d printed part. 

[Ken S]

Well done, Rich! This should solve the problem, with the added bonus of being very cost effective. Just one modified spacer should suffice.

I like the 3D printed idea. The original pattern would print quickly and work even with smaller printers. Plus, the pattern could be easily modified to make spacers of different thicknesses. (I am thinking of adapting Norton 3X wheels with one inch thickness and one inch bore.) While everything is set up, I would suggest making up a few spares. They would be useful and inexpensive gifts for Tormek friends.

An alternative plan would be to modify a Tormek spacer. I purchased a couple as spare parts for projects several years ago, although the original spacer would also work. Dishing out a spacer would be an easy project for a home shop machinist of local machine shop.

Again, good thinking, Rich!

Ken

[RichColvin]

I designed and printed a part using ABS.  It seems to work quite well, though it may also be due to the bore for the 3D-printed part being a little tight on the spindle shaft.

The original one is depicted to the left, and the 3D-printed on on the right.

If you want to print one for yourself, it is available on the Sharpening Handbook:  https://sharpeninghandbook.info/Jigs-GrindstoneWasher.html.

[tgbto]

Rick, it's a nice idea. My first thought was "let's print it with a Igus filament", although buying a roll just for one washer may slightly impair the financial equation

Quick question : Aren't your concerned with the plastic washer wearing down with time ?

[RichColvin]

Rick, it's a nice idea. My first thought was "let's print it with a Igus filament", although buying a roll just for one washer may slightly impair the financial equation

Quick question : Aren't your concerned with the plastic washer wearing down with time ?

When I looked at the stainless steel washer on the machine, it did not show significant wear.  So that is good. 

Regardless, I am not concerned as I can print another in less than an hour.  

I am not familiar with Igus filament, so I cannot comment on that.  I used ABS to print the ones I am using, but PETG may be a better choice if you are concerned about it wearing down too soon.

Of course, you could take your current one to a machinist friend and get it modified. 

[tgbto]

I agree with the PETG suggestion. There are even some not-so-expensive low-friction ones.

I was not really afraid of having to print additional ones (I usually print a couple anyway, just in case). I was rather thinking of tiny plastic particles getting inside the bearings...

[RickKrung]

.snip...
Quick question : Aren't your concerned with the plastic washer wearing down with time ?

When I looked at the stainless steel washer on the machine, it did not show significant wear.  So that is good.
...snip..
Of course, you could take your current one to a machinist friend and get it modified.

Stainless is a lot tougher than plastic.  I see "wear" indicated by the shiny ring that abuts the rubber bushing in the case. It isn't wearing down the stainless, just polishing it, but that could change for plastic, especially if not kept greased. But as Rich says, easy to print another. 

Taking a washer to a machine shop sounds nice, but it would be costly enough I think one should re-evaluate the whole situation.  Cutting a shallow concavity in that washer is not as easy as it is to say.  Easy if CNC is an option, but the time to set it up could be prohibitive for a one-off.

This seems like a solution looking for a problem.  Just put your finger on the washer as you slide the wheels off.