Dressing contact wheel?

[Jared Dinwoodie]

Just wondering if anyone has dressed/trued up a damaged contact wheel and what technique they used. I have a 8” contact wheel with a substantial chunk taken out of it and was thinking about chucking it up in the lathe but am not sure if normal HSS tools would work with it being kind of soft. I know for my belt surface grinder I put a file onto the magnetic chuck and run it over it a few times and that dresses it nicely.

 

[navman]

I remember seeing a video of a guy using a lathe and HSS 4 flute endmill to true up a contact wheel that had a gouge in it. Looking now...

 

[navman]

Can't seem to find it. The video showed the contact wheel chucked up in a lathe (rotating) with a 4 flute HSS (not carbide) endmill being used to essentially peel off a thin layer of rubber.

Edit...found it...posted by Tim Galyean on Instagram.

 

[Jared Dinwoodie]

Can't seem to find it. The video showed the contact wheel chucked up in a lathe (rotating) with a 4 flute HSS (not carbide) endmill being used to essentially peel off a thin layer of rubber.

Edit...found it...posted by Tim Galyean on Instagram.

Found it! very cool thanks man!

 

[Stacy E. Apelt - Bladesmith]

Others have chucked the wheel in the lathe and used a hand held belt sander to reduce the wheel beyond the gouge.

Sunray offers wheel repair. https://www.sunray-inc.com/

 

[Ken H>]

Put the wheel in the freezer for a few hours so it's frozen and use a really sharp HSS lathe tool with a fairly aggressive angle

 

[REK Knives]

This is the most consistent way I've seen anyone do it

 

[12345678910]

Freeze the wheel.

Lathe, toolpost belt grind

 

[Contender Machine]

The durometer of the rubber plays a big part in how well it will turn. The harder it is the nicer it will machine typically. I’ve had good luck with a polished, very positive carbide insert (meant for turning aluminum) and spinning it very fast and feeding very slow. Grinding or sanding is the best for rubber if you can do it accurately enough.

 

[Fred.Rowe]

As Ken H stated above: [freeze] the rubber wheel first. whatever you cut it with.

 

[Nathan the Machinist]

I've tried everything and I've had very good results with a tool post grinder. I can't believe how well rubber grinds. All kinds of rubber too.

 

[Natlek]

This is useful to know about dressing contact wheel

Checking a contact wheel to indicate its roundness at operating speed is easy. Simply hold chalk or crayon lightly against the wheel face while it is running at operating speed. If a mark is indicated on the complete circumference of the wheel, it is then running true. If not, the contact wheel should be dressed or trued before being used on any application. To obtain the best results, this should be done at operating speed on the same machine in which the contact wheel will be used.

To dress a contact wheel, use a new piece of abrasive (preferably resin bond, 50-120 grit) wrapped or held on a flat board. The board should be long enough so that one end will stand on the floor, and the other end extends above the wheel (see illustration). Using light pressure, hold the abrasive covered section of the board flat against the contact wheel face. Light pressure is absolutely necessary to dress off the "high" spots. Heavy pressure will only follow the out-of-round condition, and will not dress the wheel into proper roundness.

To ensure proper dressing and truing of a contact wheel or to correct a poor dressing condition, the following recommendations should be adhered to:

1. Always use new abrasive. preferably resin bond silicon carbide in the 50-120 grit range. The aluminum oxide will work nearly as well.
2. Use light pressure only to dress out the "high" spots on any wheel. Then, hold the abrasive without any additional pressure to let the contact wheel "spark out" until no further grinding or dressing is noted.
3. Always dress or true, if possible, at operating speed.
4. Softer durometer contact wheels (60A Shore and softer) are always more critical and require greater consideration of the above three points regarding tracking when dressing. This is due to more resiliency and elasticity of the softer durometers, i.e., they deform more under light pressure.
5. A dressed contact wheel will always run smoother and give longer belt life than one that is not dressed, or a wheel that is out of balance.
6. For wheels harder than 60A durometer. proper dressing becomes critical as regards belt life. As little as .002" out-of-round in a 90A durometer wheel can reduce belt life by as much as 50-60%.

 

[Stacy E. Apelt - Bladesmith]

Good advice for dressing a direct drive contact wheel, like on a surface grinder or pedestal style belt grinder (Burr King), but most knifemaking grinders have a solid metal drive wheel with an arm mounted contact wheel turned by the belt. In that situation the above method can't be used.