Counter sinking bolts BO/BO fretboard extension

[lamanoditrento]

Hi,

Yesterday, installed t-nuts and bolted the fretboard extension, which left like a milestone I was pretty happy about.

However as the head block plate is 45mm deep, you can easily see the bolt head through the sound hole, which I am unhappy about. I have used M5 bolts/t-nuts but after 2 washers they are clear as day through the SH. Anyway, I don't have an appropriate reverse countersink bit and the 5mm hole will likely be an issue for finding something commercially available.

Does anyone have any ideas about how I might countersink them?

[simso]

I like the way you have done that.

It could be onsold as a commercial bolt on kit.

Why not turn the bolt location into a feature, turn some round wood up to go around the bolts and glue them to the neck block, emphasize it to make people go, Mmm.

Steve

[Trevor Gore]

Some people use a re-purposed standard spade bit. Just re-grind the shoulders to the same style of cutting edge as is normally on the bottom. It can be done with a small grinder (Dremel or die grinder), or even with just a file. The shafts are typically ~6mm diameter (or a little less) so with the hex part cut off they work well for M6 hardware. They should work OK for M5 too, giving a bit of wiggle room for the fasteners. The hole needs to be a reasonably close approximation to the shaft diameter to avoid a lot of chatter. People normally cut off the old (bottom) cutting edge.

Otherwise Google "reverse spot face" or "reverse counterbore" or look for one of those counterbore cutters that are held on with a grub screw so you can mount it in reverse (like in the book).

[dotbot]

A recent thread on this very subject at Ukulele Underground:

http://forum.ukuleleunderground.com/sho ... -neck-bolt

[lamanoditrento]

Thanks Steve, but I'm just following the instructions that Trevor & Gerard lay down in there book. I don't mind the idea of some wooden bolt heads, maybe on the next one.

Thanks Trevor & dobot. I will give making a bit out of a spade bit or bolt.

[Trevor Gore]

This tool from Stew-Mac:

http://www.stewmac.com/Luthier_Tools/To ... utter.html

would do the job. Expensive, but maybe worth it if you also do head-end adjustable truss rods.

[lamanoditrento]

So I ended up widening the holes in the neck block to 6mm and them making a bit by filing to shape and sharpening with a diamond stick. Worked a treat! Thanks everyone. A few photos and a before and after:

[Ken Lewis]

A connector bolt like this one shouldn't require any counter bore. The low profile keeps it out of site.
Hardened and plenty strong.

connector.jpg (35.65 KiB) Viewed 15834 times

[ArmstrongLutherie]

Hi Ken, do you know if they're available in M5 and if so where can be bought. These are normally M6 which is too big for this particular application.

[Ken Lewis]

I use m6 or, 1/4" even, for this exact application with no problem. You're right, the m5 version probably won't be
found in your neighborhood hardware store but a quick Google search turned up several vendors. A search from
your neck of the woods might turn up something more applicable to you but here's one online site.

https://www.fastenright.com/general-fix ... pe-e1/ff06

I haven't bought from them, don't know if they ship your way but m5's are available.
Regards, Ken

[Trevor Gore]

If you use this type of fastener, be sure to get the hardened ones. Most of the furniture grade ones aren't and the hex socket will round out if used a few times with a ball end hex wrench. This was the reason we moved to the M6 socket head cap screws, which have a larger socket and are normally hardened, but will hold up even if they aren't.

[blackalex1952]

There's more than one way to skin a cat!- Ross

[kiwigeo]

There's more than one way to skin a cat!- Ross

Ross, I tried those round headed bolts and found that with the frequent working of the bolt during neck fitting the socket edges started getting quite worn. I went back to the bolts that Trevor specifies with the thicker head walls. I also find the heads of these bolts easier to turn with my fingers.

[Jonny]

^^^^^^^^
Can we see this bolt you speak of Martin?