Question about a contact wheel durometer.

[Tom Lewis]

I have several contact wheels. Some are harder than others. My favorite is softer than the others, in other words when I push my thumb nail in to the contact wheel it is softer. This is my favorite wheel to use and I would like to get another one. I can get a smoother finish with this wheel than I can with the harder ones. How can I tell the durometer of my wheels?

 

[Stacy E. Apelt - Bladesmith]

For metal removal, harder is better. For handle work, softer. Probably the difference isn't really significant for most knifemakers.

 

[seanj]

You need a special tool to actually measure the Durometer of rubber. I used to work for a company that manufactured rubber liners for pumps and they had one. 70 Durometer is about as hard as you would want to go for Knifemaking. I believe, not sure though, that the majority of rubber wheels fall into that category. If I recall correctly the scale goes from 10 to 90. A 50 Durometer you could press a Finger nail into with some effort. Hope that helps some

However as Tracy mentioned it doesn't matter a lot for most Knifemaking.

 

[Contender Machine]

Here is a screen shot from McMaster-Carr that gives an idea of rubber hardness. I think Shore A is the most commonly used.

 

[seanj]

Here is a screen shot from McMaster-Carr that gives an idea of rubber hardness. I think Shore A is the most commonly used.

View attachment 2738009

Thanks for chiming in Contender. It looks like my own recollections are out of date. Good information

 

[Taz]

Most are 60-70 duro A for knifemakers. I picked up a 90 duro rubber 2" wide one on Big River and then an AmeriBrade 2.5" x 4" 90 duro for the surface grinder recently. The 90 Duro one is HARD! I haven't used it on handles at all yet to see how it does.

I believe you can find duro testers online fairly cheaply, but most are in the 60-70 range from knifemaking places. You may be able to find softer 50 duro ones online, too?

 

[Stacy E. Apelt - Bladesmith]

As Taz pointed out, the place it will matter is on a surface grinder. 90 Durometer wheels are what is needed to avoid a rippled surface effect.
Also, the wheel on an SG also needs to be perfectly round and concentric to the shaft. Any out of round will really show up in the finish of the metal.

 

[Tom Lewis]

Thanks to everyone for the information and help.

 

[GRapp]

How can I tell the durometer of my wheels?

The tool is actual the durometer. The numbers are value/reading. I've used them for years in my industry. Looks like amazon sells them as cheap as $30. The ones we use are $1500+, I'm sure you get what you pay for.

 

[Stacy E. Apelt - Bladesmith]

Yes, "durometer" is a term that refers to a reading on a Shore Durometer hardness tester. Same as "Rockwell" meaning a reading on a Rockwell hardness tester.

I have a 120-year-old antique one in the shop as a display.