Neck Block Problem

[musicman2000]

In the picture is my neck block as shown from the top of the guitar. I just removed the clamps. Do you see the problem? The neck block overhangs on the right rim by 1/32", but overhangs on the left rim by only 1/64". I thought maybe I glued the neck block on crooked, but look closer. There is no slant in the compensation. It turns out the right rim is sunken by an additional 1/64". The block is straight on the bottom and top, but the rims are not even on the top.

I'm a little frustrated - Martin supplied me with laminate rims that are not straight. How do I fix this? I was thinking maybe I could sand everything flush when I go to add the 25-foot radius into the top, thus evening out both rims. What do you think?

Tom

[tippie53]

You are not in any problem you can adjust the tenon . Next time think of what is more critical , Since the top is where every thing locates, you make sure the top is flush and make the changes on the back.
The top is the critical location not the back.
You can make adjustments to the top when you get ready to set the top.

Minor issue and won't hurt anything. Your top is most likley .125 thick so you have .025 to thin without hurting anything.

[phavriluk]

Get hold of Bill Cory's two books on building kit acoustic guitars.

If you haven't yet purchased these books, then I think you would be very well served to stop work, get hold of then, they're advertised on this forum, and read up on his take on building Martin kit guitars. I found them to be a treasure trove of information, and it might help understanding when the train goes off the tracks a bit.

[musicman2000]

Yes, I am following BC's books. I have both.

[tippie53]

The one thing I can't stress enough is that Glue is a lubricant when wet. I often use tape to help position critical things when gluing. The small amount you are off isn't a killer but if you want to pull the block and reglue , you can do that.

[B. Howard]

[quote="tippie53"]The one thing I can't stress enough is that Glue is a lubricant when wet. [quote]

Yep, things can get slippery. Another trick I use is to spread the glue and let it sit for a few minutes. It will tack up and be less slippery when you clamp up. Just don't let it sit too long or it won't hold.

[Darryl Young]

Ideally, the top is flat when you glue the sides to the neck block. Another important geometry point is that the mortise in the neck block is vertical so the neck mounts square to the top.

Often the top/bottom of the neck block isn't square with the sides. The sides of the neck block should be parallel with the mortise but it's worth checking. So I usually square the top/bottom of the neck block to the sides of the neck block before gluing it in so all sides of the neck block can be used as a reference. Remove the minimal amount of material to get it square (don't want to make the neck block too short).

Not sure if this is a mortise and tenon neck or a dovetail.....but if the neck block isn't rotated so that the neck is square with the top, you'll be ok. Remember that you likely be sanding an angle into the top from the top of the soundhole up so you will be sanding this portion flat/square anyhow.......so if the mortise is 90 deg to the top, don't worry.

If the neck mortise isn't square/vertical or if this just bothers you.......heat the area with an iron and remove the neck block. Clean up the left over glue and give it another try. It won't take as long as you might guess........and this likely won't be the last thing you rework <smile>. We've all been there.......I'm re-working finish right now <egad>