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Dec 13, 2019 - 5:38:19 AM
354 posts since 9/21/2018

Do to certain equipment deficiencies in my workshop, I've been toiling over how to effectively and accurately accomplish cutting the radius on my heel cut. I would think were I building an open back this might be a little easier to overcome, but with three different contact points to deal with it's tricky.

So I set my mind to work, and came up with a non-power tool option. Attached is a pic of the design as rendered in Solidworks. I'm working on assembly of the 3D printed version currently. It basically uses a pivoting, 11" surface with adhesive backed sandpaper attached. The image below shows the spacer attached to reach the bottom most contact area, the upper contact area is sanded by removing the spacer, and there is a thin sanding jig for the radius around the hoop at the top. The device attaches to a 1x2, and the pivoting portion can slide vertically about an inch and a half. The neck clamps to the 1x2, with a wedge in between to set the angle properly.

I prototyped it with wood, and it worked pretty well for the first surface, the bottom contact point will require the stability of the printed machine to make it work.

I like making stuff, especially stuff that leads to saw dust.


Dec 13, 2019 - 6:40:55 AM
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rudy

USA

14868 posts since 3/27/2004

Regardless of how you make your jig, do NOT cut the heel radius to match the diameter of your rim.  This will often result in a neck that doesn't lock solidly to the rim and therefore your instrument won't have stable tuning. 

The heel radius needs to be slightly smaller so the sides of the heel contact the rim solidly.

Dec 13, 2019 - 6:56:02 AM
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Fathand

Canada

11535 posts since 2/7/2008

3D printing and computerized design software may be a bit overkill for occasional use. My Heel jig is a scrap piece of 2x6. The bolt on the left goes into the T slot on my milling machine cross feed table (could be adapted to a drill press). The neck is held down down by the U shaped blocks and deck screws, heel angle is adjusted by a wedge under the neck. I install a 3" sanding drum or suitable router bit into the chuck and advance the table to the desired radius (Rudy is correct that slightly smaller works well). I then pivot the table on the bolt and probably make a few passes until I reach the desired radius. The neck can be flipped for cutting out the tension hoop notch.

I would probably build something fancier for a production shop but this works for the dozen banjos I have built.

BTW, there are only 2 contact points on a 1 pc flange heel. The finger board does not really contact the tension hoop.


Dec 13, 2019 - 6:57:18 AM

354 posts since 9/21/2018

quote:
Originally posted by rudy

Regardless of how you make your jig, do NOT cut the heel radius to match the diameter of your rim.  This will often result in a neck that doesn't lock solidly to the rim and therefore your instrument won't have stable tuning. 

The heel radius needs to be slightly smaller so the sides of the heel contact the rim solidly.


Thanks, Rudy. I'll double check that it is before use and reprint as needed. That makes complete sense. 

Dec 13, 2019 - 6:59:14 AM
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Helix

USA

12140 posts since 8/30/2006
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Let me help here, moose.

My mentor is older than me, he's not on the hangout.

He made one of these sanding jigs, and I have used it to "dress" the heels of new necks.
Your jig looks very much like his. I suggest using a 50 grit belt sander belt. I make my own for my 2" sanding drum.

For those of us using a table saw to do the heels, the 10" saw blade which uses a 5" RADIUS is perfect for this because the heel "forms" to fit the rim, rather than flopping around. A builder on the hangout said he had an 11" saw blade made just for this, but my opinion is they are just over over building and advertising their own lack of understanding.

Any heel can use a little "dressing" afterward, examine with a straightedge to make sure you aren't off center.

My mentor's jig was set permanently at 3 degrees. Hope this helps clarify for you. Good work on the jig, you used your noggin.

Dec 13, 2019 - 7:03:08 AM

6586 posts since 8/28/2013

quote:
Originally posted by Moose_Roberts

Do to certain equipment deficiencies in my workshop, I've been toiling over how to effectively and accurately accomplish cutting the radius on my heel cut. I would think were I building an open back this might be a little easier to overcome, but with three different contact points to deal with it's tricky.

So I set my mind to work, and came up with a non-power tool option. Attached is a pic of the design as rendered in Solidworks. I'm working on assembly of the 3D printed version currently. It basically uses a pivoting, 11" surface with adhesive backed sandpaper attached. The image below shows the spacer attached to reach the bottom most contact area, the upper contact area is sanded by removing the spacer, and there is a thin sanding jig for the radius around the hoop at the top. The device attaches to a 1x2, and the pivoting portion can slide vertically about an inch and a half. The neck clamps to the 1x2, with a wedge in between to set the angle properly.

I prototyped it with wood, and it worked pretty well for the first surface, the bottom contact point will require the stability of the printed machine to make it work.

I like making stuff, especially stuff that leads to saw dust.


Why not simply eliminate the spacer and just use a wider sanding surface that reaches both the top and bottom of the rim all at once? 

Dec 13, 2019 - 7:08:11 AM

354 posts since 9/21/2018

quote:
Originally posted by Fathand

3D printing and computerized design software may be a bit overkill for occasional use. My Heel jig is a scrap piece of 2x6. The bolt on the left goes into the T slot on my milling machine cross feed table (could be adapted to a drill press). The neck is held down down by the U shaped blocks and deck screws, heel angle is adjusted by a wedge under the neck. I install a 3" sanding drum or suitable router bit into the chuck and advance the table to the desired radius (Rudy is correct that slightly smaller works well). I then pivot the table on the bolt and probably make a few passes until I reach the desired radius. The neck can be flipped for cutting out the tension hoop notch.

I would probably build something fancier for a production shop but this works for the dozen banjos I have built.

BTW, there are only 2 contact points on a 1 pc flange heel. The finger board does not really contact the tension hoop.

I like it, Rick. A drill press is next on my list for shop tools. Shop Fox makes one that has an oscillation setting that would kill two birds with one stone for that purchase. 

I teach an intro engineering class at a middle school so Solidworks and 3D printing are always going on here. I like to work through projects like this to a printed part as an example for my students on creating solutions to probelms they encounter, it's a fantastic teaching tool (and it's fun). 

 

The three contact points was a misstatement. It's three spots that need sanded. 

Dec 13, 2019 - 7:13:14 AM
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354 posts since 9/21/2018

quote:
Originally posted by G Edward Porgie
quote:
Originally posted by Moose_Roberts

...


Why not simply eliminate the spacer and just use a wider sanding surface that reaches both the top and bottom of the rim all at once? 


Those two points aren't co-planer. The bottom of the neck sticks out slightly further than the "center". If it is wide enough to reach the bottom, it won't contact the top. 


Dec 13, 2019 - 8:27 AM

6586 posts since 8/28/2013

quote:
Originally posted by Moose_Roberts
quote:
Originally posted by G Edward Porgie
quote:
Originally posted by Moose_Roberts

...


Why not simply eliminate the spacer and just use a wider sanding surface that reaches both the top and bottom of the rim all at once? 


Those two points aren't co-planer. The bottom of the neck sticks out slightly further than the "center". If it is wide enough to reach the bottom, it won't contact the top. 

 


I wasn't aware of the fact that your tool was made for sanding that type of neck. I was assuming a straight neck heel, which I shouldn't have.

That said, I do hope you realize that the two different aspects of this neck design calls for a  slightly different radius on the top curve than that of the bottom. You should have two different pivoting surfaces, one  for each portion of the neck.

Dec 13, 2019 - 9:00:44 AM

354 posts since 9/21/2018

quote:
Originally posted by G Edward Porgie
quote:
Originally posted by Moose_Roberts
quote:
Originally posted by G Edward Porgie
quote:
Originally posted by Moose_Roberts

...


 


 


I wasn't aware of the fact that your tool was made for sanding that type of neck. I was assuming a straight neck heel, which I shouldn't have.

That said, I do hope you realize that the two different aspects of this neck design calls for a  slightly different radius on the top curve than that of the bottom. You should have two different pivoting surfaces, one  for each portion of the neck.


Rudy pointed this out above, and it probably lends to the popularity of using a 10" table saw for this cut, that a slightly smaller radius provides for better "lock-up" against the rim. Otherwise, the difference between that cross section of the two different radii on there are probably at or less than 1/64". I did think about that as I was working through the design. 

Dec 14, 2019 - 2:39:29 AM
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Helix

USA

12140 posts since 8/30/2006
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I've seen people make a sanding drum at 11" with the bluegrass flange built in at 10-3/4", then they put this drum in their drill press and use their sliding jig to sand those heels. Not me,man, I don't like the odds.

The analogy of Luke Skywalker's artificial hand with those rods moving back and forth before the robot closes the access panel: that's what the heel of a banjo neck does, it forms to the rim. One can hardly tell the difference between a 5" and a 5.5" radius.
This even works with a 12" banjo rim, the 5" radius is totally accurate and solid. I have no warranty issues with this method.

Your jig is the perfect use of 3D printing. As the military is soon to be printing bone, I'm going to have new teeth printed, seems logical.

Dec 16, 2019 - 5:36:55 AM

354 posts since 9/21/2018

quote:
Originally posted by Helix

I've seen people make a sanding drum at 11" with the bluegrass flange built in at 10-3/4", then they put this drum in their drill press and use their sliding jig to sand those heels. Not me,man, I don't like the odds.

The analogy of Luke Skywalker's artificial hand with those rods moving back and forth before the robot closes the access panel: that's what the heel of a banjo neck does, it forms to the rim. One can hardly tell the difference between a 5" and a 5.5" radius.
This even works with a 12" banjo rim, the 5" radius is totally accurate and solid. I have no warranty issues with this method.

Your jig is the perfect use of 3D printing. As the military is soon to be printing bone, I'm going to have new teeth printed, seems logical.


Thanks! Printed teeth? That sounds amazing. I'm going to have to do some research on that to share with my students. This technology has been around since the 60's. and has really only taken major strides in advancement since becoming popular in the consumer market in the last 10 or so years. 

Dec 16, 2019 - 5:49:23 AM
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354 posts since 9/21/2018

Update: Pics of the jig (ignore how messy my garage/ work-space is, my wife already told me...). The wedge for the neck angle was printed to get the exact angle for the drop based on the bridge height.




 

Dec 16, 2019 - 6:12:11 AM
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Fathand

Canada

11535 posts since 2/7/2008

Looks pretty cool.

Dec 16, 2019 - 6:13:18 AM
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conic

UK

617 posts since 2/15/2014

Interesting topic , thats a nice messy garage, just how i like it.

Could a 10" solid 2" thick plywood disc be used horizontally with sandpaper on the edge and mounted on a motor then offer up the heel on a jig like a sawbench sled

Dec 16, 2019 - 6:18:10 AM

354 posts since 9/21/2018

quote:
Originally posted by conic

Interesting topic , thats a nice messy garage, just how i like it.

Could a 10" solid 2" thick plywood disc be used horizontally with sandpaper on the edge and mounted on a motor then offer up the heel on a jig like a sawbench sled


Probably, though there are always risks involved with motorized mass. There are tons of jigs to be seen via google search. 

Dec 17, 2019 - 4:45:32 AM
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Players Union Member

Helix

USA

12140 posts since 8/30/2006
Online Now

Moose_Roberts, your printed jig looks very similar to my mentor's wooden one, they work the same.

They are printing ears and noses, yes the military is working on bone. Teeth are like city states, they are special bone, they should have names.

This has been proven here on the hangout a couple of times:  hand-operated devices can be as accurate as machines, and a lot less noisy, less dust. 

Keep up this good work, very clean.

Edited by - Helix on 12/17/2019 04:47:57

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