drilling a convex hole

[Custom carving]

is there a way to drill a convex hole for a marble to fit into nicely? I have a friend that wanted to know if I could build her this board game and Had no clue how to drill a hole for the marble to fit in

[adze_cnc]

A marble is convex. The hole you want is concave. If you have ball-end router bit that has a similar diameter to the marble you could use that either with a drilling toolpath or a pocket toolpath if the ball-end diameter is less than the marble diameter.

Questions about cutting holes for marbles to seat into come up quite often. Typing “marble hole” (without the quote marks) into the search box above should find something.

[Tex_Lawrence]

is there a way to drill a convex hole for a marble to fit into nicely? ...

Around here we call that game "Wahoo". I've made several versions of it in different sizes, but one thing that is the same between all of them is the marble holes.

I started out with a 3/8" ball bit, but the other thing in common with all of them (including the old ones) is that the marbles are really easy to dislodge from their spot. (We even had players that would consistently and "accidentally" jostle the board to their advantage. )

I started making the marble holes with a down cut flat end mill of the appropriate diameter and depth. Figured it out where the sides of the hole contacted the marble at the same time as the bottom. Its different with different marbles.

The holes have an edge (instead of a ramp) that keeps the marbles in place. The marbles are much more stable in these flat-bottom holes, and the holes are much quicker to make with a spiral ramped inside profile cut. I'd have to look, but I think I used a 0.250" diameter down cut bit.

[Custom carving]

A marble is convex. The hole you want is concave. If you have ball-end router bit that has a similar diameter to the marble you could use that either with a drilling toolpath or a pocket toolpath if the ball-end diameter is less than the marble diameter.

Questions about cutting holes for marbles to seat into come up quite often. Typing “marble hole” (without the quote marks) into the search box above should find something.

thanks for correcting me I couldn't decide which it was and some times I'm just bass ackwards

[RickW3DS]

I did a test run for marble holes using a 1/2" core box bit and a 0.563" vector. One pass using a profile tool path, 0.17" deep and one pass with a drilling toolpath to remove the little bump at the bottom of the hole, 0.2" deep. The marbles seem to fit fairly tight but as Tex pointed out, I still need to do a jostle test before I run the entire job six times.

[neilgill]

You could also use a V Carve Bit on a vector, you select the depth with a Profile path, that way the marble runs in the grove and is less likely to jump out, also making a v hole that holds it snuggly.

Neil

[FabLab Wageningen]

One word of warning:

Marbles do not have 100% exactly the same sizes. I have once designed and lasered a lamp with marbles, but to my endless frustration some holes were too small and some holes were too large.

This is the final result. I had to make all holes too small to start with, and I had to file each hole out for the individual marble to fit in. My marble supplier had warned me in advance, to be honest.

Marcel.