Bench Grinding Wheel Selection

[chris mabbott]

With the vast variety of bench grinding wheels available, in various compositions, colors and sizes, I was wondering what kind of setup do you use on your bench grinders for general use, I.e. forming gravers, making tools, performing repairs etc
And in what grit size do you have in your configuration.

I picked up a fairly inexpensive small bench grinder, brushless motor type, on which came the normal crappy wheels, so I’m trying to figure out what replacement wheels to buy that will serve most of my needs in watch repair, silicon carbide, aluminum oxide, diamond grit, in green, white, beige or spring yellow.
Most of the use will be for gravers, carbide, and maybe a little stainless now and then, the harder materials..

[david pierce]

Chris,
For grinding tungston carbide the only wheel I ever had any luck with was diamond. In theory the green silicon carbide is supposed to be able to grind tungston carbide but I found it to be useless. The only use I ever found for it was dressing aluminum oxide bench grinding wheels. I suppose it could be used for dressing a sharpening stone or a slip but I had no luck with it grinding metal. For surface grinders and tool and cutter grinders I always dressed the (white aluminum oxide) wheels with a diamond point. My choice of a grinding wheel on a bench grinder for grinding tool steel is white aluminum oxide. It will run put less heat into the part than the gray aluminum oxide. That is why it is used for grinding tools, cutters, and parts in general that can be ruined by too much heat. The gray aluminum oxide wheels are generally used for more general work such as grinding off welds, lawnmower blades, grinding off rust etc. The danger in grinding is always overheating the part so use the most coarse wheel that will get the job done. A finer grit wheel leaves a nicer finish but heats the part more.
david

[chris mabbott]

Thanks David, I will go with your recommendation of the white AluOx.

This is one time that I must admit to there being too much selection and too much product boasting by the various manufacturers/sellers, confusing.

[demewill]

I was faced with the same decision a couple of years ago and got lucky as a local woodworking store was clearing out their stock of aluminum oxide wheels. I think they were switching from one manufacturer to another. The wheels I bought are a fairly friable grade. They cut great, but as they are soft, they need more frequent dressing, a small price to pay for not burning up expensive tools. I use these for carbon steel and HSS with good results on both. I don’t sharpen any carbide tools at all. In fact I only use carbide for tablesaw blades in the wood shop. I have had mixed results with carbide on my metal lathes. My lathes are lightweight and I can’t push them hard enough to get the advantage of carbide. HSS does a better job for me as it takes a keener edge. The only time I ” had” to use a carbide tool on the lathe was machining cast iron. I was taking a light cut and work hardened the piece and had to resort to carbide tooling to get past the work hardened “skin”.

Take a look at the norton 3X. I have seen some good press for them as in this article: http://www.toolsforworkingwood.com/store/item/NO-WHEEL3X.XX/Norton_3X_Super-Cool_Grinding_Wheels

You may find woodworking suppliers a good source as I did. There are a lot more amateurs in woodworking than in watchmaking. The tools we sharpen are not all that different than used in the wood shop.

Dan

P.S. how many 18S and 16S pocket watches do you have?

[david pierce]

Dan,
Cast iron can be machined with steel. It requires a slow rpm, a heavy feed and a compressed air blast. Do not use any oil or coolant with cast iron. The iron or carbon in the iron acts as a abrasive and eats up your tools; especially drill bits. The air blast is to blow the abrasive iron powder away from the cutter.
david

[demewill]

Slow speed and heavy feed is not what the Taig lathe was designed for. Maybe if I had one of those Myford super 7’s you are saving, I could have dropped into back gear and delighted in the 16 microInch finish.
Dan

[david pierce]

I believe Paul is the one who has the Myfords. They look like really nice machines in the pictures but I have never seen or used one. Lathes the size of the Taig and smaller were definately not designed for the machining of castings.
david

[chris mabbott]

David I’m going to put on a parrot costume and come and sit on your shoulder because I seem to be parroting you, but you have to dress as a pirate with an eye patch and wooden leg 😆

But yes, machining of this type is a bit too heavy for our little friends. Our machinist would use kerosene/water mix, I think it was 60/40, for any cast material as regular cutting lubricants are not suitable, for some reason kerosene is, just have to watch your heat and subsequently your eyebrows or POOF.
Really though, Kerosene has a low flash point when diluted so you’re ok.

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