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Cecil McKenzie
05-07-2012, 10:52 AM
I am using one of the better diamond core bits to drill holes for pendant lamps. It has slowed down in performance. HIS recommended drilling into a brick to renew the surface. I was wondering how much do I drill on a brick to properly resurface the core drill ? Minutes or inches or is there someway to tell if you have drilled enough?

I am using a water feed apparatus and using a piece of rubber tire around the lamp part to create a puddle on top of the piece. RPMs are at about 1100. Would a faster speed be better?

Pete VanderLaan
05-07-2012, 10:58 AM
Do it for about five to ten seconds. It will help for a short period of time since it pulls some silicates off of the diamonds, but it doesn't really work very well at all. A new bit is in your future.

Kenny Pieper
05-07-2012, 12:27 PM
Use a hard brick or a silicon carbide piece like an old wheel. Just drill very shallow. You don't want to remove the diamonds up the side you want to expose new ones on the tip.

Cecil McKenzie
05-07-2012, 12:47 PM
Thanks for the tips,gentlemen. The shallow grind sounds very logical.

Pete VanderLaan
05-07-2012, 01:19 PM
still keep it really wet!

Joe Deanda
05-13-2012, 08:58 PM
1100 rpm sounds really fast to me. May cause the surface of the bit to get hot even though its under water.

Henry Halem
05-16-2012, 01:16 PM
Here are the recommended drill speeds as found on pg. 319 of Glass Notes:

1/4 inch-2000 rpm, 1/2 inch- 950 rpm, 1 inch- 700 rpm, 2 inch- 525 rpm, 3 inch- 450 rpm, 4 inch- 400 rpm

Pg. 318, 319 has excellent information on diamond drilling. And I quote a bit of that info: The exact speed of the drill will depend also on the type of drill used, how the coolant is applied, the material being drilled, whether one is starting or finishing a hole, and the experience of the operator.

Cecil McKenzie
05-16-2012, 09:53 PM
Thanks for the suggestions. I was drilling at the lowest setting but after talking to a sales person at HIS I bumped it up to the next level. Actually I don't know exactly what the rpm's are because the drill press I am using is ancient and doesn't have a chart to tell what the speeds are. I have a newer drill press that has a chart but I haven't checked to see if the pulleys are the same diameters. I finished my small batch of lights and will probably go back to the lower speed.

I'm thinking of slicing some firebrick up and drilling through them to make circular fusing molds while I sharpen my diamond bits.

Pete VanderLaan
05-17-2012, 03:16 AM
I wouldn't get all that worked up about it. It's not going to work all that well.