Gerhard Gerber Posted February 8 Share Posted February 8 (edited) Been breaking my head trying to figure this out, if I have this contact wheel dressed to get rid of that tear, will the size of the hollow grind still be the same? Secondly if there is any advice for the machinist that will try and fix this, it would be much appreciated Edited February 8 by Gerhard Gerber Link to comment Share on other sites More sharing options...
timgunn Posted February 8 Share Posted February 8 I "think" the radius will reduce and the depth of a hollow grind will increase slightly, as a result of reducing the diameter of the wheel. Essentially you'll just be reducing the wheel diameter. No experience of contact wheels, and it was a long time ago, but when I've machined "rubber" on a lathe, really sharp tooling and machining the rubber straight out of the freezer worked better than I expected. 1 Link to comment Share on other sites More sharing options...
Gerhard Gerber Posted February 8 Author Share Posted February 8 I don't know why this messes with my head so much, but thinking the opposite makes it clear, a big enough wheel will give you an almost flat grind. I'll have to modify the little sanding block I matched to the wheel then. Thanks Tim, never would've thought of that! Was going to ask the machinist to use a new tool tip, now I find out if he has a fridge in the shop! Link to comment Share on other sites More sharing options...
Dick Sexstone Posted February 8 Share Posted February 8 How did that damage happen? I have used flapper wheel to sand rubber but it leaves a very ruff surface ….. freezing the rubber is an excellent idea…… Link to comment Share on other sites More sharing options...
Brian Dougherty Posted February 8 Share Posted February 8 We've machined rubber at work after putting in our environmental chamber set to -78C. It machines like metal until it warms up. I've never tried it at the warmer home freezer temps. I'd be a little worried about the glue that holds the rubber on the wheel. It may come loose if you get it too cold. 1 -Brian Link to comment Share on other sites More sharing options...
Gerhard Gerber Posted February 9 Author Share Posted February 9 19 hours ago, Dick Sexstone said: How did that damage happen? I have used flapper wheel to sand rubber but it leaves a very ruff surface ….. freezing the rubber is an excellent idea…… That is the million dollar question, I had a Trizact belt on, machine was going very slowly while I was doing a final touch-up, light pressure. Suddenly felt something wrong and immediately assumed the belt had failed, only to discover that...... I was in shock, wanted to finish the blade so I cut off the flap that tore loose. Why I didn't think of super glueing it in place I have no idea, still would've needed to be fixed but would be much more usable in the mean time. Basically, I would love to know how/why/what I did wrong. Link to comment Share on other sites More sharing options...
Gazz Posted February 10 Share Posted February 10 I think rubber can machined abrasively - like with a tool post grinder in a lathe. I might be tempted to use an angle grinder if I could spin the wheel. Kind of like dressing a grinding wheel. Link to comment Share on other sites More sharing options...
Gerhard Gerber Posted February 10 Author Share Posted February 10 Well, thanks to all, but it seems I'm justified in waiting for the new machine before trying any fixes. I get what you're saying @Gazz, but I would think it's critical the wheel ends up true and flat, difficult if not using a precision tool (I guess). Actually meant to ask for ideas here on a DIY fix, I had dreams of building a jig at the back of the work rest and using a sharp chisel to "machine" down the wheel. Problem being the belt drives the wheel, and I imagine if you start taking material off the one side it will affect tracking, belts and chisel flying, wheel fubar...... I know there are smarter and more experienced people here, but with my skills it just sounds like a bad idea......just like my neigbour's instance I should just plug it with WondaFix Link to comment Share on other sites More sharing options...
Brian Dougherty Posted February 10 Share Posted February 10 10 hours ago, Gerhard Gerber said: ....just like my neigbour's instance I should just plug it with WondaFix To be honest, if it were mine I'd probably try to patch it with some 2-part urethane. I'd wrap a band clamp around the wheel with a piece of card stock around the gap to create an even/fair former for the patch. If you find something of a similar density it will stay balanced, and if you can get the transition smooth, it would still be usable. Until the patch flew out in your face... Of course, I am on the same continent as Suncoat Wheels, so getting a new wheel if my high risk plan flopped would be a bit easier for me. I'd be a little less cavalier in your neck of the woods. -Brian Link to comment Share on other sites More sharing options...
Pieter-Paul Derks Posted February 10 Share Posted February 10 I crowned the contact wheel of my grinder with a farriers rasp before, it was a bit scary to attack a 200 euro wheel with a rusty rasp, but it even improved how smooth it runs If you can spin the wheel somehow on its own bearing it is an easy fix, maybe with patching the hole a bit like Brian above me suggests 1 http://mefecit.nl/ Link to comment Share on other sites More sharing options...
Joshua States Posted February 13 Share Posted February 13 On 2/9/2023 at 2:10 AM, Gerhard Gerber said: I would love to know how/why/what I did wrong. It looks to me like you were trying to polish right down to the edge and rolled it just a bit too far. The edge dug in and by the time your reflexes reacted, you had taken a bite out of the wheel. If you are going to try and use Trizac belts to polish down to the edge, you have to grind them edge down so the belt runs off the edge instead of against it. 1 “So I'm lightin' out for the territory, ahead of the scared and the weak and the mean spirited, because Aunt Sally is fixin’ to adopt me and civilize me, and I can't stand it. I've been there before.” The only bad experience is the one from which you learn nothing. Josh http://www.dosgatosdesignsllc.com/#! https://www.youtube.com/channel/UCdJMFMqnbLYqv965xd64vYg J.States Bladesmith | Facebook https://www.facebook.com/dos.gatos.71 https://www.etsy.com/shop/JStatesBladesmith Link to comment Share on other sites More sharing options...
Gerhard Gerber Posted February 13 Author Share Posted February 13 On 2/10/2023 at 10:06 PM, Pieter-Paul Derks said: I crowned the contact wheel of my grinder with a farriers rasp before, it was a bit scary to attack a 200 euro wheel with a rusty rasp, but it even improved how smooth it runs If you can spin the wheel somehow on its own bearing it is an easy fix, maybe with patching the hole a bit like Brian above me suggests As far as that is concerned my imagination never got further than the jaws of a lathe. Never thought about a file........ Link to comment Share on other sites More sharing options...
LeeO Posted February 18 Share Posted February 18 (edited) as already mentioned, before taking off, i'd be tempted to try putting on and shaving back to suit, or fill and sleeve, Belzona 2311 (SR Elastomer) - Emergency Repair Elastomer as an example, but anything local, any tyre specialists out your way,they usually have alot of knowledge on this stuff or forklift engineers etc, can always take off after trying etc, good luck, Edited February 18 by LeeO 1 Link to comment Share on other sites More sharing options...
Gerhard Gerber Posted February 24 Author Share Posted February 24 I contacted the machinist yesterday, he phoned this morning. First time I used his services I was working half day, every time I dared go to his shop he would literally talk the day away, I'd escape when he closes shop to go pick up his wife. Phone call went about the same, BUT........ He worked with a Swiss machinist that did his apprenticeship at a printer where they used rubber coated wheels, this guy showed him how to make a tool that successfully machines rubber. I will send my dad who is also 70+ and talks just as much to drop off the wheel, should be epic! 4 Link to comment Share on other sites More sharing options...
Gerhard Gerber Posted March 3 Author Share Posted March 3 (edited) Got same day service but I'm a bit anxious, machinist informed me he had to take quite a bit off and there's only a thin layer left, will try to collect this afternoon. He does talk more than my dad, apparently he carried on talking while my dad walked away I was a bit peeved when he phoned, he proceeded to tell me all the design and material selection for the platten wheels he made for me 2/3 years ago, then I reminded him he'd built them........ He's making spacers to connect the bearing inners free of charge. Edited March 6 by Gerhard Gerber 1 Link to comment Share on other sites More sharing options...
Gerhard Gerber Posted March 7 Author Share Posted March 7 Very little tread left on the wheel and there is still a small hollow left, damage was deeper than it looked. Link to comment Share on other sites More sharing options...
Bob Ouellette Posted March 11 Share Posted March 11 If you're worried about the diameter of the wheel or the amount of rubber left, you could probably add layers of rubber and have it machined down to the original diameter. I'd use a strip of material half as thick as what you need per side. Apply it with plenty of the appropriate adhesive and lay the strip so that the tail end won't catch as you grind. Similar to the way you'd put Teflon tape on pipe threads. After the adhesive cures, your machinist should be able to true it up. Bob O "When I raise my flashing sword, and my hand takes hold on judgment, I will take vengeance upon mine enemies, and I will repay those who haze me. Oh, Lord, raise me to Thy right hand and count me among Thy saints." My Website Link to comment Share on other sites More sharing options...
Gerhard Gerber Posted March 14 Author Share Posted March 14 The machinist told me there's another business close by that rebuilds rubber mounts for vehicles, they should be able to help when the remaining padding fails. Fortunately I still have the wheel on the new grinder with plenty life in it, still not running though..... 1 Link to comment Share on other sites More sharing options...
Gazz Posted March 20 Share Posted March 20 Try looking for polyurethane bandsaw tires or maybe even tubing. I found 10" polyurethane tires and 6" rubber tires but didn't spend much time searching stuff. I don't know the diameter of your wheel but do remember looking for similar stuff years ago for my grinder. Link to comment Share on other sites More sharing options...
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