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Jun 13, 2024 - 5:04:08 AM
7 posts since 6/30/2020

I was wondering if anyone knows how Gibson made heel cuts and adjusted heel fits in the prewar era? I've seen that these days it's often done with a router attached to a rotating surface. I was wondering how this was done back then and how good the resulting fit was compared to today.

Thanks!

Jun 13, 2024 - 11:27:46 AM
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banjoez

USA

2807 posts since 7/18/2007

Very crudely compared to today's methods. Exactly how I can only guess. Some I've seen look hand chiseled. I'm sure someone with more knowledge will chime in.

Edited by - banjoez on 06/13/2024 11:34:01

Jun 14, 2024 - 5:48:35 AM
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3062 posts since 2/12/2005

The tenor neck for my 1926 tb3 has a nice looking heelcut. There are horizontal marks that seem like a shaper was used.

Here is the interesting part. The shiny compression marks are to the outside only. This makes a lot of sense for stability. With a little bit of clearance at the lag bolts, The clamping forces are to the outside.

In other words, It's my firm opinion that they used a diameter for the cutter that is different than the diameter of the rim. For example, a 10 15/16" cutter would shift those compression points outward.

I thought about going to Jim Mill's shop and examining numerous tenor necks to see if they all had the same marks and compression style. Maybe somebody could tell us If my theory is correct.

Jun 14, 2024 - 6:58:44 AM
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RB3

USA

2048 posts since 4/12/2004

I think they would have procured a custom profile cutter for a shaper. A clamping/pivoting fixture would have been added to the shaper to allow the neck to be swept on an arc, past the profile cutter to create the radiused heel profile in a single operation. If there were different heel profiles, they would have a separate profile cutter for each heel profile.

Jun 15, 2024 - 6:49:33 AM
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3062 posts since 2/12/2005

quote:
Originally posted by RB3

A clamping/pivoting fixture would have been added to the shaper to allow the neck to be swept on an arc, past the profile cutter to create the radiused heel profile in a single operation. If there were different heel profiles, they would have a separate profile cutter for each heel profile.


Yes. That is likely. The "sweep" mechanism would be adjustable for different pot sizes. So the same small cutter would make a 8" piccolo, a 11" standard, 12" bass banjo etc.  I still think there was a slight undersize to move those contact pads out.  Of course it might depend on the guy working on that particular day to adjust the machine.

Edited by - randybartlett on 06/15/2024 06:52:09

Jun 15, 2024 - 8:49:21 AM
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RB3

USA

2048 posts since 4/12/2004

Randy Bartlett,

Having the radius of the heel be slightly less than the radius of the rim makes sense to me. It assures that the contact points between the heel and the rim are at the edges of the sides of the heel. That means that those contact points are as far apart as possible, which should result in the most stable connection between the neck and the rim.

With respect to manufacturing, dimensional tolerances must be taken into account in design. There are tolerances associated with the radii of both the heel and the rim. It appears that Gibson dealt with those tolerances by making the heel radius slightly less than the rim radius.

Could this be the secret to the pre-war sound?

Jun 15, 2024 - 9:15:59 PM

3062 posts since 2/12/2005

quote:
Originally posted by RB3

Could this be the secret to the pre-war sound?


Only one of many small details that can be important.

(By the way, I appreciate your tab for Columbus Stockade Blues. I really dig into that initial walkdown.)

Jun 16, 2024 - 6:01:30 AM

RB3

USA

2048 posts since 4/12/2004

Randy,

I wasn't aware that the tab for Columbus Stockade was in the BHO archive. I added that as a Tabrite file to another banjo forum years ago. Someone converted it from Tabrite to Tabledit and added it to the BHO archive. Unfortunately, in the conversion from Tabrite to Tabledit, the hammer-ons and pull-offs don't translate quite right when you play the Midi with Tabledit.

Edited by - RB3 on 06/16/2024 06:02:43

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