Granite Surface Plate: Drilling & Cleaning

Quote:

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Originally Posted by wbarocsi

I bolted my BB post on a 1" surface ground steel plate, and use clamps to hold the plate onto the granite. It was originally going to be temporary
until I drilled the plate, but it has worked so well, that I doubt I'll change it.

Wade Barocsi
CycleDesignUSA.com

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you got a picture of this to share?

Hi Nick,
Here's a photo of my post. This set-up with 3 clamps works fine, and is more versatile for non-bike work because the table isn't drilled.

I hope the photo shows up... nope hmmm.
I'll try again later.

Wade Barocsi

Quote:

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Originally Posted by John Winston

I want to install a BB post on my new to me surface plate (Mojave 36x48x6). (anyone got an extra post?)

Should I through drill or drill for inserts? Best method/tooling for a success?
What should I avoid?
John

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Here is how I did it.

Clamped drill press to surface plate, set it to its slowest speed.

Made a water dam around the target area.

Wedged a 4x4 wood block hard against the underside of the granite to prevent blow out and chipping when the bit came through. You can't see it but the stand has a horizontal steel member about 5" below the underside of the plate. It was convenient and easy to use wood wedges to firmly snug a block against the plate.

Used 5/8" Bosch carbide bits, the longer ones to give me more room to work. Used two.

Drilled for about 5 seconds, retracted bit while adding water down the hole, advanced without cutting engagement, retracted with more water, a few repititions, flushing like this to keep the bit from ever getting warm, then started the cycle again. Constantly flushed with plenty of water, and if the water is warm then I think the carbide is too hot and starts to dull quickly. My goal was to keep it far from hot and I failed a few times which I think is why I had to get a second bit to go the last inch.

Light feed pressure until the bore hole was established, medium thereafter. Go easy and thoughtfully about this and you can feel the optimum pressure for best rate of advance.

Don't get in a hurry, it can take a while. My advance rate was about 1" per 45 min, something like that.

Perfect hole, no chipping or blowout on the underside. It was worth all of the drill press setup and takedown.

Attachment 68875

Attachment 68876

Just please remember, we who ride bikes do love our builders. Mario Confente died from trying to lift a granite surface plate on his own.

There are always safer ways, including borrowed fork lifts, pallet jacks, auto engine hoists, and so on.