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Stone vs Carbide burrs

Practical Engine Building

Discussion and questions related to the course Practical Engine Building


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Ever since I've got my rotary tool, I've been exclusively using stone burrs for any grinding work since they were what originaly came with the tool and I have been replacing them stone burrs again once they have been worn out.

In all the demonstration within the course, carbide burrs were used. Given I have always been using stone burrs, I feel more comfortable using them. Will there be any negative effect if I use a stone burr instead of carbide?

Thank you!

I wouldn't say there is any negative effect other than it can take longer to remove material with a stone than a coarse carbide cutter. On the upside the surface finish is generally smoother so you're less likely to leave any stress raisers. The stone will also wear out faster than a carbide cutter.

Just had a go at balancing the pistons over the weekend and realized stone grinding bit is really not the best tool for removing material from a piston. It's MUCH slower compared to a carbide burr and is also susceptible clogging while working on soft material like aluminium. With only a diamond bit on hand, that's what I continued to use after clogging up a stone grinding bit. The diamond bit was slightly better than the stone bit but still took forever and I spent over half a day while only successfully balancing two pistons removing just 2 grams of material in total.

Went to the shop and purchased a few carbide bits on the next day and the difference was night and day!! It did not take long before I have successfully removed another gram of material from the final piston and complete my balancing.

The stone bit did work great on ferrous metal though and had no trouble taking weight off the big end of the connecting rods. I simply clamped my rotary tool on a vice and glide the edge of the big end over the stone much like how you glide the big end over the linisher in the video with little trouble.

I am still stuck on the small end though, and will most likely end up buying a linisher to do the job.

Even with the carbide burrs you can find that the fine ones become clogged with aluminium material. I recommend quite a coarse burr to prevent this or alternatively you can spray the burr regularly with a cutting lubricant which helps too.