Hey everyone! I'm on the hunt for some help finding a drill bit. I've been scouring the internet, but I haven't had any luck. I need to drill several smooth-edged, flat-bottomed holes that are 21mm wide and 100mm deep. While I have a 21mm forstner bit, I'm limited by the shank length and can only reach about 70mm—60mm on the drill press and a bit more with a hand drill, awkwardly positioned in the edge of the chuck. I tried using a longer auger bit, but it leaves an indent at the end of the hole and messes up the interior too much. What I'm really looking for is either a long shank forstner or a Japanese F type bit that's 21mm in size. I'm based in the UK. Any help would be greatly appreciated!
4 Answers
Have you tried using an extension on the bit? That can sometimes help with reaching deeper holes without needing a special bit.
I feel your pain! I’ve dealt with the same issues since the variance in shank shapes and sizes is ridiculously frustrating sometimes.
You could consider something like this: [Japanese Drill Bits](https://workshopheaven.com/star-m-japanese-601-precision-drill-bits-singles/?sku=394391&gad_source=1&gad_campaignid=18133554652&gbraid=0AAAAAD-iXFkkSKw59V7kNx_Ta0aY3k1V1&gclid=CjwKCAjwk7DFBhBAEiwAeYbJsSqiFvrB2lOWFgeRm7fH7OXgM_-fiyT4xYcbxEWFbkXdY1RSG1YU4hoCTgsQAvD_BwE). You could drill to about 95mm and then grind the tip to finish off the hole. It's a bit pricey, though!
Could you share more about what you need these holes for? There might be different methods you haven't thought of yet. For instance, using a 1/2" x 6" end mill could help. You could drill the majority of the hole with your forstner and finish with the end mill using a router template.
I'm trying to create deep holes in wood for plant propagators, and sometimes I need a flat base for the visual test tube part. That's why those clean finishes are important to me.
I thought about that, but it’s tough to find a good quality 21mm forstner. I’ve bought so many subpar ones! I saw some that look decent, but extensions for them seem impossible to locate.