The Acoustic Guitar Forum

Go Back   The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > Build and Repair

Reply
 
Thread Tools
  #1  
Old 01-08-2020, 07:47 PM
Mking Mking is offline
Charter Member
 
Join Date: Aug 2010
Location: Norfolk VA
Posts: 631
Default Checking the neck angle on a archtop

I know for a flat top you put a straight edge on the fret board and see where it lands in relation to the top of the bridge to check neck angle. How do you do it for an arch top guitar?
Reply With Quote
  #2  
Old 01-08-2020, 09:27 PM
charles Tauber charles Tauber is offline
Registered User
 
Join Date: Feb 2011
Posts: 7,142
Default

Actually, neck angle is responsible for achieving a target vertical distance from the surface of the top to the bottom of the strings measured at the bridge. That distance is related to the torque (moment) the strings exert on the top/bridge. For Martin style guitars, that target is 1/2. The neck angle is correct when the string action is at the desired height above the frets and the 1/2 target is achieved. The bridge thickness is then what is left after the desired saddle projection - about 1/8 - is subtracted from the 1/2 target. That leaves a nominal bridge thickness of 3/8. Martin uses several bridge thicknesses to maintain the saddle projection with varying neck angles (ie tolerance on 1/2 target).

For classical guitars the target vertical height is 10 or 11 mm, which necessitates a different neck angle than steel string guitars - the nut is higher than the plane of the top, rather than the nut lower than the plane of the top.

For arch top guitars, the target vertical height is often a little more than 1. (The 1 value is a target for laying a straight edge on the frets and measuring vertical height at the bridge.)

Last edited by charles Tauber; 01-08-2020 at 09:40 PM.
Reply With Quote
  #3  
Old 01-09-2020, 07:58 AM
Mking Mking is offline
Charter Member
 
Join Date: Aug 2010
Location: Norfolk VA
Posts: 631
Default

Quote:
Originally Posted by charles Tauber View Post
Actually, neck angle is responsible for achieving a target vertical distance from the surface of the top to the bottom of the strings measured at the bridge. That distance is related to the torque (moment) the strings exert on the top/bridge. For Martin style guitars, that target is 1/2. The neck angle is correct when the string action is at the desired height above the frets and the 1/2 target is achieved. The bridge thickness is then what is left after the desired saddle projection - about 1/8 - is subtracted from the 1/2 target. That leaves a nominal bridge thickness of 3/8. Martin uses several bridge thicknesses to maintain the saddle projection with varying neck angles (ie tolerance on 1/2 target).

For classical guitars the target vertical height is 10 or 11 mm, which necessitates a different neck angle than steel string guitars - the nut is higher than the plane of the top, rather than the nut lower than the plane of the top.

For arch top guitars, the target vertical height is often a little more than 1. (The 1 value is a target for laying a straight edge on the frets and measuring vertical height at the bridge.)
So you mean on Martin type guitars the distance from the guitar's top to the bottom of the strings should measure a half inch? On an archtop the distance between the bottom of the straight edge to the top at the bridge should be a little more than an inch?

Thank you.
Reply With Quote
  #4  
Old 01-09-2020, 08:36 AM
charles Tauber charles Tauber is offline
Registered User
 
Join Date: Feb 2011
Posts: 7,142
Default

Quote:
Originally Posted by Mking View Post
So you mean on Martin type guitars the distance from the guitar's top to the bottom of the strings should measure a half inch? On an archtop the distance between the bottom of the straight edge to the top at the bridge should be a little more than an inch?

Thank you.
Those are common design targets, though not universal. For example, on the steel string guitars that I make I use less than 1/2” as the design target: I do use 1” for my arch tops.

Any individual instrument, particularly as it ages, might or might not be at the designed target. That an instrument is not precisely at its design target does not necessarily mean that a neck reset is needed. The need for a neck reset can be determined on a case by case basis. For steel string guitars, a typical indicator that an instrument might be in need of a neck reset is that the string height (action) on a property set up guitar is too high while there is too little saddle projection from the top of the bridge. One factor in the determination is bridge thickness.

What are the symptoms you are experiencing that lead you to question the neck angle of an arch top?

Last edited by charles Tauber; 01-09-2020 at 09:11 AM.
Reply With Quote
  #5  
Old 01-09-2020, 09:50 AM
Mking Mking is offline
Charter Member
 
Join Date: Aug 2010
Location: Norfolk VA
Posts: 631
Default

Quote:
Originally Posted by charles Tauber View Post
Those are common design targets, though not universal. For example, on the steel string guitars that I make I use less than 1/2 as the design target: I do use 1 for my arch tops.

Any individual instrument, particularly as it ages, might or might not be at the designed target. That an instrument is not precisely at its design target does not necessarily mean that a neck reset is needed. The need for a neck reset can be determined on a case by case basis. For steel string guitars, a typical indicator that an instrument might be in need of a neck reset is that the string height (action) on a property set up guitar is too high while there is too little saddle projection from the top of the bridge. One factor in the determination is bridge thickness.

What are the symptoms you are experiencing that lead you to question the neck angle of an arch top?
Charles, I don't have a problem. The reason for my question is that I bought a 1935 Kalamazoo KG-21 and I will take delivery of it tomorrow. The seller (GC in Fort Wayne) says the action and intonation are fine with no issues. I have never owned an archtop and wondered how I would determine the neck angle on this guitar. These guitars reportedly don't have a metal rod in the neck (not that this would pertain to the neck angle???). Thank you.
Michael
Reply With Quote
  #6  
Old 01-09-2020, 10:00 AM
John Arnold John Arnold is offline
Registered User
 
Join Date: Jan 2009
Posts: 3,050
Default

Those Kalamazoos don't have an elevated fingerboard, so the neck angle measurement may not be quite as high. I see those with bridges in the 7/8" range, and they seem to work just fine.
Reply With Quote
  #7  
Old 01-09-2020, 10:08 AM
charles Tauber charles Tauber is offline
Registered User
 
Join Date: Feb 2011
Posts: 7,142
Default

For those following the discussion: The Kalamazoo fingerboard is glued directly to the top, similar to "flat top" guitars, rather than have the fingerboard elevated above it, as is common for arch tops.



Elavated fingerboard:

Reply With Quote
  #8  
Old 01-09-2020, 12:33 PM
MC5C MC5C is offline
Registered User
 
Join Date: Mar 2016
Location: Tatamagouche Nova Scotia
Posts: 926
Default

I seem to end up with neck angles of around 4.5 degrees, using the Benedetto method of floating fretboard, etc. Sometimes a little less. You can easily measure neck angle by putting a protractor on the side of the body, and measuring the angle at the bottom of the fretboard. I target a 1" height above the body for a measuring stick placed on the fretboard (with frets installed), and try to finesse the neck set to accomplish that. That gives me 1 1/8" bridge height with a 1/16" action at the 12th fret. I have no idea how this would relate to a Kalamazoo, though.
__________________
Brian Evans
1935 Dobro model 25 resonator
1943 Paramount (made by Kay) mandolin
1946 Epiphone Zephyr electric archtop
1957 Hofner Senator archtop
1962 Gibson Melody Maker electric
1963 National Dynamic lap steel
1996 Landola jumbo
1998 Godin Artisan TC electric
1998 Epiphone SG electric
2010 GoldTone PBR-CA resonator
2015 Evans electric archtop
2016 Evans archtop
Reply With Quote
  #9  
Old 01-09-2020, 12:59 PM
charles Tauber charles Tauber is offline
Registered User
 
Join Date: Feb 2011
Posts: 7,142
Default

Quote:
Originally Posted by Mking View Post
I have never owned an archtop and wondered how I would determine the neck angle on this guitar. These guitars reportedly don't have a metal rod in the neck (not that this would pertain to the neck angle???). Thank you.
Michael
As you state, the amount of bow in the neck is irrelevant to the neck angle. It influences playability, but is a separate variable.

One thing you can look for is whether or not the top is deformed - pressed inwards - in the area around the fingerboard. That can indicate the neck angle changing. You can also look to see that there is no gap at the heel, indicating movement of the neck in the joint - not likely, but possible. Otherwise, if the guitar plays and sounds fine, and there is sufficient bridge height/break angle, I wouldn't worry about the neck angle.
Reply With Quote
  #10  
Old 01-09-2020, 08:25 PM
Mking Mking is offline
Charter Member
 
Join Date: Aug 2010
Location: Norfolk VA
Posts: 631
Default

Quote:
Originally Posted by charles Tauber View Post
As you state, the amount of bow in the neck is irrelevant to the neck angle. It influences playability, but is a separate variable.

One thing you can look for is whether or not the top is deformed - pressed inwards - in the area around the fingerboard. That can indicate the neck angle changing. You can also look to see that there is no gap at the heel, indicating movement of the neck in the joint - not likely, but possible. Otherwise, if the guitar plays and sounds fine, and there is sufficient bridge height/break angle, I wouldn't worry about the neck angle.
Thank you Charles! You've been a big help and I learned a lot! Take care.
Reply With Quote
Reply

  The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > Build and Repair

Thread Tools



All times are GMT -6. The time now is 01:06 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Copyright ©2000 - 2020, The Acoustic Guitar Forum
vB Ad Management by =RedTyger=