Letter to RPM conversion chart

[JPG]

Well Done ED.

[charlese]

Reible is correct in his story! I had forgotten. RPMs come in very handy to know when using Forstner bits. Should have mentioned that above.

[Ed in Tampa]

I guess as I reading Ed fictional story I was saying in my mind what letter he should be on.
I know the low high and sawing RPM . So if something says slow incrank her down if the say something around saw speed 3000 I set it in the saw range and if they say fast I crank her up.

The only thing I look at RPM for mostly is to insure i don't exceed manufactures recommended speed. I know slow is around 750 saw is around 3000 and top speed is around 5000.

Works for me.

I think you probably would have broken the glass anyhow. Never was able to drill glass on the shopsmith always had to use an electric hand drill and lots of mineral oil. Even then risky. Glass shop is less than two miles away they will usually do it as I wait.

[ERLover]

I worked in High School at a local window company and cut many pieces of glass, and later in life for 20 years installing ceramic tile, cutting and drilling it. All you need is a small chip under neath either when putting pressure on it from the other side and bang, broken. That little chip just acts like a Fulcrum on a material that has no lateral strength unless fully supported evenly.
Yes oil and the right speed is essential, and the more costly bits. I had Granite coated hole saws for making holes in porcelain tile.