Core Bit Search/Experiment Update

Not being satisfied with having to purchase every kind of dot and hating making them with a sander I decided to try to track down some core bits. I found these on ebay. They were cheap, less than $10 for the set, they aren't high quality but can handle shell easily. I bought the set not knowing what size the cores would be. To my delight the 8mm core bit produced a 5.5mm core or in my case dot. That is exactly the size I wanted. A 5mm dot is too small for a position marker and the 6mm dot too large for my liking, 5.5mm is perfect for me. I also hate throwing away lots of abalone dots because they just don't have that shine we look for. The 5mm core bit produced a 2.74mm core which I like for a bold side position marker. The 4mm core bit produced a 2mm core. The 9mm Core bit produced a 6.8mm core, too large for my liking. Care had to be taken making the smaller dots and it would be better to do these in a tray of water. As always carefully control your dust or better yet drill in a tray of water for your lung protection.




http://cgi.ebay.com/5-pcs-8mm-Diamo...ultDomain_0&hash=item4154233a70#ht_3577wt_792
Here is an ebay auction for 5, 8mm core bits for $6.99 plus 3.95 shipping. I'm sure the guy would make you a set of the 8mm, 5mm, and 4mm for pretty cheap. Those are the ones I believe are useful.

Further update...Drilling in a tray of water is the way to go. No water leaves the tray at medium drill press speed, No dust, Core bits are made for wet drilling so will last 10 times a long.

Sounds interesting. I've been looking for a core bit to cut 5mm dots from wood. 5.5mm is probably close enough for my purposes. One question: where did you find a 5.5mm drill bit for cutting the recesses into which the dots are inlaid?

You couldn't cut wood with these bits. They are diamond bits, made for cutting stone, glass, tile and the like.

7/32 is very close to 5.5mm.

5.5mm brad point bits can be found online. The 5.5mm comes in the Wood River bradpont drill bit set from Woodcraft.

I bought a set a couple of years ago to do some shell that I couldn't get in the size I wanted. They do cut shell, but don't leave as clean an edge as the commercial dots I buy

I remembered this guy who wrote this to make Abalone dots..and it works... the Ancient Egyptians used a similar device to carve out holes in stone.
mgdesignsDecember 4th, 2009, 09:13 PM
Make a core drill with a piece of appropriately sized copper tubing, and then pound it onto a hard steel plate covered with 1000 grit diamond dust from any good lapidary supply house online. Voila - a diamond sintered core drill that'll cut thru anything, cheaply, and with a little bit of mineral oil as a lubricant and coolant, will last forever - or until you burn it up, and have to re-sinter the diamond dust. Been there - done that.

Looks like a good idea.....but I can just imagine how many hours I'd spend looking for shell dots that fell off the drill press onto my messy floor :wallbash:

ksquine said:

Looks like a good idea.....but I can just imagine how many hours I'd spend looking for shell dots that fell off the drill press onto my messy floor :wallbash:

Click to expand...

They end up inside the tube ..you have to poke them out ..it's a core drill.