Blocks

[Stop36]

I am building a Martin OM from a Martin kit. My rim at the tail is 4" and the tail block is only 3 15/16" . My rim at the neck is 3 1/4" and the neck block is 3 1/2".
I have read Bill Cory repeatedly and I am at a loss since he says never cut down the neck block and that the tail block should be 1/16" taller than the rim.
How should I proceed?
Thank you,
Marc

[Diane Kauffmds]

Hi.

You'll radius the top and bottom of each side. Some people do things differently, but I only radius from the waist down on the top of the sides, leaving everything above the soundhole flat and even. I do this because my transverse brace is flat. Basically, all that's radiused on the top of acoustic guitars is a very gentle radius from the soundhole down. However, backs are radiused all around, with a much more pronounced curve.

Generally cut my tail blocks 3/32 - 1/8" taller than the tail, so that they're taller on both sides. I cut my neck blocks ~ 1/16" taller than the sides, but when I glue the neck block in, I glue the block even with where the sides come together, on the top. That leaves the neck block taller for back radiusing by 1/16".

Some people like to radius the entire top; if you're going to do this, you'll have to radius your transverse brace too. But, radiusing 1/8" off of a block is quite a task. If it was me, I'd take that down.

As far as your tail block, I'd glue it in so that you only have ~ 1/32" difference on each side. Actually 1/32" isn't much. Just radiusing will bring your sides down fast, then continue to radius until done.

I hope this makes sense. John Hall has a great video on radiusing, on YouTube. I'll see if I can find it and I'll post the link for you

[John Reid]

Here’s a couple of John Hall's rim prep videos:

https://www.youtube.com/watch?v=LrgRKKsxL-M

https://www.youtube.com/watch?v=pz6xzVR ... 4&index=25

[BlindBo]

Hey Stop36. I see this is your first post. Welcome. When talking about the neck and end block heights, don’t forget that you’ll be adding approx 0.200” to the height when you glue to top and back on. I trim my tail block flat, about 1/16” taller than the finish height I’m shooting for (Incl. the top and back thickness) and let the radius dishes bring it down to my target. But, I also don’t get too hung up on making the height precisely the designers spec.
I spend more time on the neck block. I try to cut it to height with a 1.5 degree angle on the top and a 5 degree on the back. This is fairly close to what the radius dishes will yield. My goal is to minimize the amount of sanding needed on the neck block. As Diane said, removing significant thickness from there can wear your arms out!
Good luck on your build and post as many questions s you need to.

[Kevin Sjostrand]

I do it just like Blindbo. Almost to a tee. And I've not had any issues.

[BlindBo]

Stop 36, I left out one item that I think is critical. In my early days of building kits, most of the time, the neck tenons didn’t align with the neck block mortises. The result would be that the fret board surface (top of the neck surface) would end up way above the surface of the guitar top. This creates all sorts of problems for a new builder. Once I started learning about setting the neck plane I realized what a problem this is. So, now when trimming the neck block I focus on the top surface and temporarily install the neck into the neck block. I make sure I trim the top of the neck block so that the neck (fretboard bottom) will align reasonably close to the final elevation of the guitar top. This saves a lot of adjusting later. This hopefully makes the final neck fit easier. And, if you miscalculate or cut it wrong, there is always the ability to adjust the neck elevation with shims or more sanding.
Since the neck block is already close to the final height, I again let the radius dishes do their jobs and adjust the neck heel distance once the neck is set and the bindings are installed.
Hope this isn’t too confusing. And, I’m pretty sure the. More experienced builders here know an easier way to accomplish the same results.

[phavriluk]

I've found judicious (and measured) use of a low-angle ('cos I have one) block plane can save a whole bunch of sanding tine. Profiling isn't ordained to be a sandpaper-only purgatory.

[Stop36]

Thank you. This is helpful
Stop36

[Diane Kauffmds]

I've found judicious (and measured) use of a low-angle ('cos I have one) block plane can save a whole bunch of sanding tine. Profiling isn't ordained to be a sandpaper-only purgatory.

Absolutely! I always start with a low angle plane. It saves time, muscle fatigue, and my sanity.

[BlindBo]

Me too. My homemade side templets can get a little wonkie sometimes like the set I just bent a few days ago. Ended up leaving way too much meat on the bone. I use John Halls method of leveling once before installing the kerfing. After initial chalking and some disk sanding, I’ll knock down the high points till they start to match the low spots. Rechalk and repeat until all the blocks and rim show no chalk. This has reduced my “Bus Driving” job to part time. 👍
Once the kerfing is in just ever so proud, it doesn’t take long to finish the job on the second dish sanding.