Truss Rod Pocket Depth

[cal3g]

I have a bit of a problem which hopefully someone from the Cafe Builders message board can help me with.
I need to know the recommended depth for the truss rod pocket.
Recently I thought I had finished the neck, veneer overlay, great, peg holes fit the tuners great, then wham, I turn it over and during the night or day a crack appeared right below the peghead on the back of the neck. After examination I found that the Truss Rod Pocket must have been too deep and by shaping the neck to the proper size exposed part of the pocket, and under very little strain cracked the back. So down the tubes about three days worth of work went.
To avoid this from happening again please let me know what you suggest. I am using Simiroff's Ultimate Construction Guide.

Thanks in Advance
Garry

[fidlmaker]

Sorry to hear about the unpleasant surprise.

If you are using a 3/16" diameter truss rod with the Gibson style 5/16" hex nut, your truss rod slot should have been 7/16" deep. If your peghead angle and thickness is consistent with the drawing, the pocket should be .470" to .500" deep relative to the surface of the neck (without the fingerboard), with the bottom of the pocket parallel to the same said surface. Sorry about the inch dimensions (old school machinist). I use a 1/2" diameter ball end milling cutter to make the pocket and finish up the flat washer seating surface with a round-ended chisel. These dimensions give you a clean shot at the adjusting nut with a standard nut driver.

[Rob Grant]

cal3q wrote:
"So down the tubes about three days worth of work went."

Might be better to start over again, but is it possible to cut the affected area back slightly and laminate a strip of some nice hardwood, re-shape and call it "decorative." I've been know to turn a couple of stuff ups into a regular work of art.<G> Heck, it might actually improve the strength!

[Jim Hilburn]

Here's a trick I picked up from the Bennedetto video set. It's a 1/2" counterbore with a 5" long 3/16" pilot. The pilot follows the slot and all you need is a depth of cut mark. This makes a pocket just the right size for the standard adjusting wrench.
I made some real gapers before getting this rig.

[sunburst]

I like to use a 1/4" nut so that my pocket doesn't have to be as deep.
Also, by using a slightly longer rod, and moving the pocket farther from the nut, you can leave more wood (and strength) below the pocket.

Jim. That looks like the "spot face reemer" we used at the shop where I used to work.

[ShaneJ]

Jim, where do you get one of those? I've poured through a stack of tool catalogs lately, and I don't remember noticing a doohicky like that.

[Chris Baird]

Jim, Where did you get that? I want one but haven't found em. I have a way of cutting the slot with a 1/2" round bit but it still requires a bit of handwork.

[sunburst]

MSC.
If you click on the page numbers you should get PDF pictures.
Link (http://www1.mscdirect.com/CGI/NNLMK3?PMK0NO=381938&PMPROD=152)

[sunburst]

Actually, those don't look like the best to use for truss rod pockets.
I know I've seen them in the 4736 page catalog, but it might take a while to find them again.

These (http://www1.mscdirect.com/CGI/NNLMK3?PMK0NO=380162&PMPROD=304) look better.

[Darryl Wolfe]

Sunburst..I agree on 1/4 hex nuts. Do you recall the thread spec on the orig Gibsons...I need to make/buy some orig style nuts. (don't believe Stew-Mac on their expensive little "Gibson" truss rod nuts)

[sunburst]

10 32.
Unless it's one of the real old ones with 8 32 threads.

I use "stand off" nuts from MSC. They look a lot like the originals, but without the bevel, or chamfer, or whatever it's called.

[Jim Hilburn]

I did a web search and found it at an aircraft tool co. I don't seem to have any of the catalogs anymore but MSC should have it.
It has a 1/8" pilot hole,so a machinist friend turned a piece of 3/16" down to fit it. I also have to use it with a bit extention so the chuck doesn't hit the peghead.
Now, I've been using the two-way rods and haven't used this for a few years, but I've made the decision to go back to the traditional rod. I think the 2-ways work well for guitar but I've found they aren't nearly as effective as they should be for mandolins.

[Darryl Wolfe]

Sunburst..I see nothing in 1/4 hex with 8 or 10-32..everything is 3/8

[sunburst]

Darryl, these are the ones I use.
link (http://www1.mscdirect.com/CGI/NNSRIT?PMAKA=67731489)

[Darryl Wolfe]

thanks..I'll get a supply

[Jim Hilburn]

That's what us electricians call a rod coupler.