You young whippersnappers probably won't get this but all the seniors will. I ordered plastic test tubes to be used as blade holders. I liked the idea of caps. I have never knocked my blade holder but it can happen. I had a block with holes from another project but put in the tubes to see how badly it would work. The tubes are .640 diameter. The 5/8 bit is .625 just a bit to small. I will purchase a 17mm Forstner bit. There is no point to this post only to try and increase traffic on the site. Everyone wants pictures.