Drilling out the top

[chilos]

HI, I'm just working on my first carved top instrument, using the MacDonald book. I've done the outside, and am pretty happy with that, and I've just rigged up a dowel jig so I can drill the top out to the appropriate depth on my pillar drill. So far so good, but on the test pieces I've done, the dowel makes small but discernible dints in what would be the top of the mando. Anybody have any tips for avoiding this?

[mikeyb2]

I'm no expert, as I've just finished my 3rd carved top mandolin, but I had this problem on my first build, so I used a larger dowel around 20mm and made a very gentle dome on the top. A little extra care with the drill press too, and everything went well after that. Good luck. Mike.

[sunburst]

I put a little leather pad on mine.
Also, I do the gauge hole drilling with the outside of the top sanded to 80 grit. After re-sanding with 80, sanding with 120, wetting to raise the grain, and re-sanding with 120 any little dimples are gone. (Further sanding happens after the instrument is ready to prep for finish.)

[luthier88]

1-fresh, sharp drill
2-You can swell out the dents with a warm, damp sponge, just don't get things too wet.
3-As John said, a leather pad on the post
4-don't go too fast, don't press too hard

[chilos]

Thanks for the advice, guys. Leather pad and a wider dowel seems the way to go. Don't want to have to sand anything out as the arch is already at 15.3mm, so not much wiggle room for losing material off the top.

[chilos]

Ok, slightly different approach. Let's see how this pans out.

[sunburst]

I sometimes build with arches as low as 14mm when the wood is very stiff and dense. You'll be fine with a little sanding if needed.

[chilos]

Thanks, that's reassuring. It is a nice stuff piece of Sitka. All went ok in the end. Just need a tiny bit of refinement inside and final pre-finish sanding outside, so all looking good.

[chilos]

'Stiff', not stuff. Though I guess it's quite nice stuff, too.

[HoGo]

I would check sharpness of the drill bit. STandard twist drill bit requires some pressure to cut. I also use smaller bit (4.5mm) for pre-drilling and sharpen it to more accute angle for wood (both the tip angle and the cutting edges). The smaller holes interfere less with chisel work than large holes.