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im using Robert O'Briens neck angle jig. this is my first guitar and i have the jig set for a 3.5mm gap at the saddle like he recommends in his video. for some reason after i routered the body and neck i only have a 2mm gap. the neck isnt flush with the top yet. It still is sticking up about 3/16" so i have room for adjustment. i already tried to adjust the angle on the jig a little more and rerouted the tendon, that didnt seem to help at all. will 2mm be fine? ive seen other people say anywere from 1/16 to 1/8 is fine. if not what should i do to get it right?

FWIW, I use the same jig but not Robbie's measurements and I set gap for a minimum of 2mm and max of 2.5 mm. I build mostly Martin and Gibson style guitars. The issue I see is when you drop the neck will there be any gap left? If you only have a 2mm (.078") to start when you drop it 3/16" (.1875) your plan is gone. Or am I reading you post wrong?

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"I've been had again"
Tim Benware
Creedmoor, NC

Yeah I should have been more clear with my wording. I had a 2mm difference from the neck to the saddle location.I messed with it a little and now I have the neck sticking up 1mm from flush and I have 3.5 gap at the saddle so I have a 2.5mm slope. My joint is all really tight and looks good to. So should I file the tenon a little so it sits flush with the top and call that good?

ACE - Angle, Centerline, then Elevation. So now that you have the angle right, check your centerline to see if it is on center or you have to swing it left or right and once you are satisfied with that lower the neck into the mortise. I go until it is about a credit card thickness proud and press it the remainder of the way.

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"I've been had again"
Tim Benware
Creedmoor, NC

I ended up with 2 mm slope. 7mm at the highest point of the fretboard and a little over 9mm at the saddle location. What will I have to do differently than Robbie. Since he does 3.5

Maybe I'm not understanding this correctly.
If you do neck plane projection at 3.5 mm at the saddle position, that gives you 10.5 mm at the saddle with 7mm fretboard thickness (including frets).
10.5 mm + 0.2 mm (relief?) + 4 mm (2 x average action over strings at 12th) = 15.7 mm string height at the saddle, (and also add 0.?? mm soundboard pull-up)
I don't think Robbie's aiming for that.- ?
2 mm sounds about maximum to me, i.e. 2 + 7 + 0.2 + 4 = 13.2 mm string height at saddle.

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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.

Is the area of the body where the neck mounts curved or dead flat? Is the heel tapered or straight?

I don't believe a Woolson-style jig will produce an accurate neck angle unless the neck mounting area of the body is dead flat (which seems to me to produce a body shape that is very unattractive) or the heel is untapered.

You can see why this is so with a simple demonstration using a large sauce pan and a scrap of dimensional lumber like a 2 x 4 cutoff. If the cutoff is held against the side of the pan as a neck might mount to a body, the distance between the edges of the block and the side of the pan are constant. If the block of scrap is then tapered to approximate a tapered heel and the experiment is repeated, the distance between the edges of the block and the pan vary...the wider the block of scrap is at the edge, the greater the distance to the side of the pan...and it is this variation that is not accounted for with a Woolson-style neck jig. The greater the taper of the heel and the smaller the radius of curvature in the neck area, the greater the amount of reduction in neck back angle will be once the neck is fitted.

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We have become a civilization that elevates idiots, prostitutes, and clowns. Am I still to defend it? Yes, for its principles. Yes, for what it was. Yes, for what it still may be.

-Mark Helprin, The Oceans and the Stars: A Sea Story, A War Story, A Love Story (A Novel)

Thickness of the bridge. For example, if you ended up 2.5 mm your bridge would be .5mm thicker and if it ended at 1.5mm it would be .5mm thinner. Make sense? I make my own bridges so when I get to that point I take the measurements thickness the bridge accordingly. My bridges end up between approximately .315" and .375" thick.

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"I've been had again"
Tim Benware
Creedmoor, NC

Guitar building gets a little easier once this reality is understood -- much time can be spent making adjustments to end up with a finite dimension at the bridge plane pass over point. To Tim's point -- while the factories (including Martin) don't make a custom bridge for each guitar they do in fact have a range of various thickness bridges and use one that best matches the guitar in process. Also, tweaks can be made adjusting the saddle height as well.

For the sake of play-abilty having the finger board and string plane on correct and matching trajectories, in my view is paramount.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Why so much variation in bridge height if the goal of adjusting the geometry is to get a specific string height at the bridge and a set height of exposed saddle?

_________________
We have become a civilization that elevates idiots, prostitutes, and clowns. Am I still to defend it? Yes, for its principles. Yes, for what it was. Yes, for what it still may be.

-Mark Helprin, The Oceans and the Stars: A Sea Story, A War Story, A Love Story (A Novel)

Ok so right now I'm sitting with 2mm slope that's without the frets on. 7mm fretboard 9mm at the saddle. So what thickness would you guys recommend I make my bridge.

Once I get to that point I build the guitar. The bridge is the LAST thing I glue up. I shape the bridge, check the plane and thickness my bridge so that a straight edge that extends along the top of the frets gives 1/16" clearance over the bridge (my acceptable range is from 1/32 -3/32 over the bridge). I rough out my bridge thickness just under .400"

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"I've been had again"
Tim Benware
Creedmoor, NC

I guess it depends on your building preference. If you want to reach the target number by varying the height of your bridge or flossing the heel to change the angle.

After my tour through the Martin Factory and talking to the techs setting the action I realized real quick it was easier to adjust the bridge thickness. Martin has BINS filled with bridges of different thicknesses. They pick one that closest fits the thickness to match the plane. Even under factory controlled conditions there is variation. Wood stiffness etc. varies the final domed height even if everything else seems to have followed the exact same manufacturing process.

_________________
"I've been had again"
Tim Benware
Creedmoor, NC

I build differently, don't use this jig etc.....
But at this stage an easy way to check your neck angle is with a straight edged piece of dressed timber cut to 3mm longer than scale length.
Glue a block on at the nut end which is the fretboard thickness at the centre plus fret height and one at the body joint location which is fretboard thickness plus fret height plus desired string clearance.
Glue a slip of veneer (0.6mm) under the bridge end as an allowance for relief.

Position this on the neck from the nut and you can directly read off the string height at the bridge location, and make adjustments to end up at the top of your desired range.( to allow for settling in and body distortion etc)