My current project involves, among other things, drilling 30, 2.5 mm diameter holes about 2 cm deep in maple or European beech in relatively precise locations. These will subsequently be threaded (by hand) and have machine screws inserted into them after hardening the threads with CA glue.
Is there a reasonable way to do this with my Shapoko 5 pro with a spindle? The lowest spindle speed seems pretty fast for a brad point drill, which is what I’d use on a drill press or mill (if only I had one!)
Should I just mark the hole positions on the CNC and then drill them on a drill press?
I have to make several of them, so am OK with buying tooling.
I use solid carbide bits from Drillman1 on Ebay to drill my cribbage board holes. I use 0.1250" and 0.0781" bits for the boards I make. They make extremely clean holes.
Here is the 2.5mm (0.0984") bit you would want, if you decide to go this route.
Edit: I guess it depends on what “precise” means. It means different things to wood workers compared to metal workers. For wood, I feel these short carbide PC board drills perform fantastically. I have not however had the money to buy a hole gauge to measure the drilled holes in wood right after drilling and then later after the wood has had time to swell from moisture due to the hole wall now being exposed.
Edit 2: I run them at 12K-15K RPM and peck drill their diameter (.0.125" bit gets 0.100 to 0.125" peck steps) depending on how easy the wood chips clear the hole.
Drilling them on a drill press will not be precise. Even if you have laser cross hairs some of them will be off. Drilling on a CNC is somewhat problematic but will more precise than any hand method. The only solution if you want to drill on a drill press would be to make an indexing jig. The time to design and build a jig you might just as well do it on the CNC. Regular drill bits are run around 500-700 RPM. A spindle will not drill that slowly. As @WillAdams and @MadHatter suggested a router bit designed for drilling would be best. However that depends on how often you plan to do this. If it is a repeat job then getting a specialist bit would be effective but if this is a one of then just use a cnc end mill and slow down and feed slowly. It is 6 of one and half a dozen of another. To compensate for rpm slow the feed rate down.
I also highly recommend the tools from drillman1
They’re so cheap that it almost makes sense to grab a few to try even if you’ve got an appropriate Endmill already…breaking a single nice small single flute Endmill would cost me ~15x the price of a decent sized order from drillman1
The thing I would be most concerned about with high speeds and small holes in wood is burning. Not so much because I’m worried about a fire (one should be prepared for that regardless) but because it might mess with the thread forming technique you mentioned.
A layer of carbon dust doesn’t seem great for super glue penetration
And just to add, it sounds like precision isn’t at the level that you have to care about hole roundness or sizing all that much. That said, if you need a 2.5mm hole, maybe get a slightly undersized tool and let runout in the drilling operation bring your hole to size.
A beautiful attribute of the pcb tooling is that it comes in 0.1mm increments for virtually no change in cost. Super convenient.
Thank you, some great suggestions here. I guess my main concern was clearing the chips as the hole got deeper-- I’m used to going back and forth multiple times when using an ordinary drill to clear the flutes on the drill. Wasn’t sure if there was an equivalent action one could or should program into the CNC.
I only need woodworkers accuracy, not machinist accuracy. Using a fence to keep one dimension constant and hitting a pencil cross point with a brad point drill has been fine thus far.
I tried something similar a few years ago. My conclusion was that running a little hot on RPMs isn’t a big deal as long as you don’t stop moving. Peck drilling isn’t a bad idea either.
