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Table saw mfgr. need to mirror polish cast-iron tables

2004

We are a new company making table saws designed to detect when a person accidentally contacts the spinning blade. We detect that contact and stop the blade within 3-5 milliseconds, which typically results in a small scratch instead of a serious injury to the person using the saw.

Our table saws include a cast iron table made from FC-25 that measures 30"x24". After casting, we machine the surface and grind it flat. It is important that the table remain flat. We measure flatness by placing a straight edge diagonally across the table and measuring any gaps between the straight edge and the table surface. There should be no gaps larger than 0.010".

We want the surface of the table to have a mirror finish, i.e., a finish with a roughness average of 1 to 1.5 microinch, but our manufacturer has not been able to achieve that finish. We are now trying to learn how to achieve that finish. Does anyone have any specific recommendations how to achieve that finish on a cast-iron table?

David Fanning
table saw manufacturer - Wilsonville, Oregon

I do not think that it possible to get that kind of finish on cast iron. You might be able to prep, strike and heavy plate with copper, grind flatten, polish and plate with chrome of electroless nickel to achieve what you are trying to do.

James Watts
- Navarre, Florida
2004

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Probably, the only way to achieve the flatness and polished finish that you are looking for is via a lapping machine. My biggest question is the material. Why bother going to all this trouble when you are very susceptible to oxidation and contamination problems. If you do this, I think you may require some kind of protective plating.

AF Kenton
retired business owner - Hatboro, Pennsylvania
2004

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Why not instead of going through all the time and money of trying to finish cast iron just buy #8 mirror finish sheets and have them formed to fit your table. Here's some words of advice if you ever are in the same predicament but with a stainless steel table. First grind the table down to a four hundred grit with a 5 inch grinder with a soft back, then hand buff with first black then white and finally blue rouge and it'll come out looking like a perfect mirror

Brandt Hinton
- Elk River, Minnesota
2004

Hello, as a woodworker the most important thing in a table saw is that it is flat, quickly and accurately adjustable. The mirror finish is not a real consideration, nor would it influence my decision to purchase. Sincerely, Bob.

Robert Romstead
- Albuquerque, New Mexico
2007

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2007

Did you ever get an answer to your question? I was wondering the same thing when I ran across this in search engine.

Thanks,
Robert

William (Robert) Laurents
- Sterlington, Louisiana

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I saw three answers to David's question, Robert, which all echoed the sentiment of the manufacturer: that trying to machine cast iron to a mirror finish could not be done and it would immediately rust anyway. The answers seemed to be to electroplate it or clad it with stainless steel. If that isn't quite answering your question, maybe you could tweak your phrasing so I understand it better. Thanks.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007

I don't think they ever figured it out. good finish, but not mirror.

Richard Price
- Monroe, North Carolina
2007