Grinding rubber

I have made myself a rubber edged idler wheel for a record turntable. The actual rubber grippy part is a 65mm diameter O ring of 5mm section, this afternoon I stuck with araldite this onto a grooved aluminium pulley.

I am 'hoping' that tomorrow when it's dry I can mount it between centre's and using my toolpost mounted die grinder I can true up and shape the rubber O ring!

I have trued up a new wheel for the job and it feels quite keen, as though it will cut.

Any useful tips or experiences which might come in handy?

Alan

I used to grind rubber to earn a living the wheels were very course and very soft, but I am going back 40 plus years.

Recently I needed to grind some silicone rubber tube to make exhaust seals for one of my tuned pipe racing engines the only emery paper that would work was 40 grit.

Thanks, the wheel I have prepared is about 60 grit I might have a coarser one to try. I was thinking of putting it in the freezer but as there is not a lot of mass I reckon it would warm up quickly.

I feel my problem might be melting the surface so will have to experiment slowly!

Alan

If the O-ring is a good quality, with no ring of flash around the od, it may well work properly without further attention. And if it lets you down, then you can try grinding.

cheers, Tim

I wonder if a squirt of that plumbers freezing spray would harden the rudder and make it easier to grind? If not, a freshly dressed grinding wheel is sharper.

Edited By old mart on 12/04/2020 20:54:28

Edited By old mart on 12/04/2020 20:54:53

Thanks once again, it is a good O ring, no flash but I need to reduce its diameter by taking a couple of mm off to enable it to rotate in it's frame support and to give it a true running surface.

It's complicated by the addition of a soft silicone rubber assembly which is used for damping vibration transfer. Good thought with the freezer spray, especially as I have a couple!

Alan

Don't see why not. Rubber print rolls (big un's from printing machines are were regularly trued by toolpost grinding. I've seen 7 foot long x12 inches diameter rubber rolls receive such treatment in the past on a big Swift lathe. The workshop used to set it up at the beginning of the shift and leave it to itself until packing up time.

Seriously though as Tim says it should work without grinding. A freind of mine has a frreind in Holland who repairs ancient tape recorders and the like and the O ring trick works well. I'm sure he never bothered with araldite but you have to be careful to get your diameters correct.

regards Martin

I grind cork and rubber with a Dremel on my lathe. I use the hand extension and made a simple clamp to hold it .I use the sanding drums, 120 grit or 80 grit for a fine finish, and the 40 or 60 grit for the roughing. I use a vacuum cleaner hose very close to the set up , mainly to suck away any rubber off the sanding drum, to reduce it from being blocked. This turned out to be quite important and keeps it all cool as well. The fine grades, need to be very sharp, and for my set up, they do not take a lot of volume of material . The course grade will take away a very large volume of material. I did make some 38mm drums that screwed onto the handpiece, and used the pre adhesive commercial sanding belt material. It worked very well. I quickly learnt why they have a spliced joint arrangement. Contact adhesive worked very well for using carborundum wet/dry paper. The carborundum paper in eiether the sanding drums, or on my 38mm drums, worked the best of the various paper types available. For smaller holes in urathane, I use the cheap open structure mounted points. The white ones were best, but the pink ones also worked quite well, Use the coursest grit available. The course desic diamond wheels also work, but will block or clog quite easily. Using just some water with a small amount of dish wash water to break down it's water tension worked quite well. Small holes being around 3mm to 12mm ID.

Hope this helps some people out..

Neil

I read about someone filling their workshop with disgusting gritty black swarf from working on traction engine tyres (LIttle Samson?)

Hopefully your o-ring is small enough not to be a big problem...

Neil

Interesting that you use white mounted points as it is a white that I have dressed in preparation! Diameter not that critical (it's only an intermediate wheel) as long as it fits it's mounting frame I am more interested in replicating the original tyre shape and ensuring it runs true.

Alan

Well I got my dressed white point wheel going on the slowly rotating idler assembly, absolutely useless, didn't remove anything worthwhile.

Had a dig around and found a carbide burr the I bought at Ally Pally, unbelievably coarse and sharp but it worked a treat! Finishing off with some fresh 120 wet/dry paper used dry.

Alan

You need to dress the mounted point with a sharp diamond, not a dressing stick. Looks like I did not mention that important part. Sorry. You can easily see if the wheel is dressed sharply or not,by just putting a scrap piece of the material to be ground, against the wheel, or mounted point.

Neil

Ah, that's obviously where it went wrong, I used (what I have) a diamond impregnated dresser which looks like miniscule diamonds set in a mild steel rod.

Have used this for dressing wheels over the years and appears to work - but not for this application!

Alan