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I'm scratchbuilding and I'm at the point of cutting the mortise into the neck block orior to installing the neck block into the body. I've seen neck blocks where the mortise slot is routed the height of the tenon, and others where the mortise is routed the full height of the neck block, top to bottom. I can do this either way, but I see the full-height slot as easier to make. The height of the neck block is a bit over three inches, and I, if I'm going to slot to match the tenon, would cut the mortise 2.75 inches high, leaving roughly a quarter inch of material at the bottom.

So, is there a preferred method?

Thanks, folks.

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Peter Havriluk

What you do largely depends on the build method you're using and the tools you prefer to use. If you're pre-mortising the block prior to glue-up, the mortise is often cut on a table saw, which is why it goes straight through. However, you are left with an alignment problem (not insurmountable) in keeping everything in register when you glue up. If you cut the mortise after the guitar is boxed (and bound), which is arguably more accurate (and the way I do it), you only cut out what needs to be removed using a router mortising jig of which there are many different types. I prefer the type that holds the guitar upright whilst cutting the mortise on a table router. This avoids the assembly alignment issue and also means you immediately have a finished mortise, rather than having to clean away the side overhang from a pre-cut mortise. So what you do is largely governed by the tools you have and the build method you have adopted. There aren't really any structural or acoustical reasons for choosing one method over the other.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

For clarity, are you doing a bolt-on neck?

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

If you make it full height, can that not potentially lead to problems binding it, if the bottom is not filled in?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Thanks, folks, for taking the time to consider my questions and offer replies.

And yes, I was referring to a bolt-on M&T neck.

Colin, a valid question. My intent is to attach the top first, having done whatever needed doing to set a good neck angle, and then attend to the bottom. There's an opportunity to fill the air gap in the mortise while the body is upside down in the mold awaiting the back.

Trevor, I think I understand your analysis. You mentioned tooling driving the work, and that's what I considered. I think I can do a better job of aligning the neck block with a precut mortise than attempting to cut the mortise on the body with tools I don't yet have. I'd need to purchase/build a means to clamp the body securely so that I could cut the mortise with a jig and templates which I also would need to purchase. My present projects are using two necks that I'd purchased a while ago that have tenons I chose to retain; future necks will be fastened flush to the front of the body. In both the present use of M&T necks and future use of flush-mounted necks, I'm intending to support the fingerboard with a tongue of sorts vaguely resembling what you do.

To attach necks, I settled on a bolt-on process whose hardware I purchased from 'Luthier's Cool Tools', as much for their instructions and descriptions of their process as their hardware and custom millwork. I am planning on cutting the mortises in the neck blocks on a table router and I was interested in seeing if I was heading into stormy seas by running the neck blocks through the router from top to bottom. I think I'll be able to start out with mortises at right angles to the top of the guitar. I've spoken with the vendor and using a mortise/tenon neck in conjunction with the rest of his process does not raise alarms as long as I've accounted for the tenons' penetrating the neck blocks.

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Peter Havriluk

I do bolt-on necks and I route the mortise on my table router against the fence. I route in multiple passes increase the depth of the bit in small increments until the mortise is final depth. I do not rout all the way through the bottom of the block in the interest of maintaining block strength Don't know if that's important, but it's what I do.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Thanks!

Sounds just like the process I anticipated. I won't cut all the way along the height so long as I set the end stop right...

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Peter Havriluk

I have pre-routed the mortise on a router table, cut it on a table saw and plugged the bottom with a piece of Mahohgany, and eventually went to routing it after the box was closed which I like best.

Table saw and plugging the lower end of the mortise was quick and easy and made binding easier. You really have be compulsive about neck block alignment at glue up but I was able to do it consistently.

If using a bolt on I saw no problem making the mortise 1/32 or so wide with 3/8 bolt holes (for 1/4” bolts) and that little bit of lateral wiggle room made alignment a bit more forgiving.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

This is how I approach it too. Vertical alignment of the pre-routed mortise hasn't been a problem, but I rout the mortise 1/16" wider than the tenon and use 1/4" bolt holes and #10 bolts to allow for, as you say, wiggle room for alignment since there's no need for the tenon to have a tight fit to the mortise.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

"there's no need for the tenon to have a tight fit to the mortise."

I am really happy to see someone say that. I have built 8 and quickly come to the conclusion that the mortice fit is not important. I also believe that the tenon length is not important and that 1/4" is fine - I make it a little longer for more meat with the bolt.

This has been a seriously rewarding conversation for me...thanks, everybody!

And the deed is done. Had to clamp scrap MDF to the router table to create a channel for the neck blocks to drive through. Router's own fence wouldn't go back far enough to get the router bit centered. The most basic table imaginable, bought it 30+ years ago from Sears. First block took an hour and a half to set up and center the neck block over the router bit. The second one took ten minutes. That's why there's two of them. I've found that making two of anything takes lots less time than making one and returning later to do the second. Of anything.

But done. Next up, trimming the neck tenons. Onward.

Now I know why folks use a dado blade and a table saw to cut the mortise channels.

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Peter Havriluk

I'm a little late on this one but, this is how I do it.

I cut the mortises, both for the neck tendon and the truss rod access channel, on a table saw after I have glued on the top piece, then I glue on the bottom piece. This block just needs final sanding and a couple holes drilled for the neck bolts.

I use a CF rod in the truss rod channel to align the block during glue up.

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Joe Beaver
Maker of Sawdust

Looks right familiar...

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Peter Havriluk

Peter,
You mentioned that making more than one 'part' at a time speeds things up. I couldn't agree more.

I just finished making up the 'parts' i'll need this year. It included 6 neck and heel blocks, five laminated neck blanks and enough carbon fiber reinforced braces for five guitars. It's a pain doing all of that at once but it is much faster than doing them on a guitar by guitar bases.

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Joe Beaver
Maker of Sawdust

I use the lazy mans method.
I dado out a ~2’ piece in one shot and then slice off what I need for the block. It only takes 6 or 7 passes on the table saw with a .120 kerf blade.and if you flip the piece each pass, only 3 fence adjustments are needed and the mortise is dead center. I can do this quicker than setting up the dado blade.
Fill in the bottom with a 3/4” cube, layout the bolt holes, relieve the truss rod slot on the drill press. Done and 5 or 6 more blocks roughed out.

B

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My memory is so good, sometimes I remember things that never happened.