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Richard Brown - Posted - 03/17/2013: 16:28:48
I promised a while ago that I would post some pictures of my heel sanding jig which I made a few years ago. I still make the initial cuts on the table saw as I have shown before because it also cuts for the tension hoop. I use this jig to refine the cut for a near perfect fit on 8", 10" and 11" rims, any radius could be accomplished by the addition of more holes. The three size rims are indexed by the three 1/4" holes and pivot on a 1/4" brass pin, the distance is set from the center of the pin to the outside of the sanding drum.
The banjo neck in the pictures is one I am working on now, it has an 8" rim and 17" scale length.
Richard Brown brownbanjos.com
Richard Brown - Posted - 03/18/2013: 09:31:08
Todd and Ken,
The cut to allow for the tension hoop is done on the table saw by passing the neck standing on end across the blade sideways against an adjustable fence, the same as the initial heel cut but stopped by a block positioned for the desired depth of cut. Both cuts must be accomplished by making several light passes as a saw blade is not designed to cut from the side. Also keep in mind the axis of the blade as it rises dose not maintain the same center, the fence must be adjusted to assure that both cuts will be centered on the heel at the final depth of cut.
I have tried to explain this operation quite a few times in the past but it seems as though everyone has a hard time wrapping their heads around the concept. It is quite simple and does a nice neat job once you understand the few mechanics involved. Maybe I'll do a video some day if I get the time?
The second picture shows the neck being held by a sled which I no longer use, now I just hold the neck by hand and pass it along the fence.
rudy - Posted - 03/18/2013: 11:23:40
quote:
Originally posted by Richard Brown
The cut to allow for the tension hoop is done on the table saw by passing the neck standing on end across the blade sideways against an adjustable fence, the same as the initial heel cut but stopped by a block positioned for the desired depth of cut. Both cuts must be accomplished by making several light passes as a saw blade is not designed to cut from the side. Also keep in mind the axis of the blade as it rises dose not maintain the same center, the fence must be adjusted to assure that both cuts will be centered on the heel at the final depth of cut.
Richard, Sometimes unorthodox methods are just fine to press a machine into service to create something in a way that was not originally intended. If I need radius blocks to profile fret boards I create them by following a pattern created on the end of a hardwood block. A quick pass with a curved cabinet scraper removes any small raised portions of the desired shape.
Richard Brown - Posted - 03/18/2013: 11:38:53
quote:
Originally posted by rudy
quote:
Originally posted by Richard Brown
The cut to allow for the tension hoop is done on the table saw by passing the neck standing on end across the blade sideways against an adjustable fence, the same as the initial heel cut but stopped by a block positioned for the desired depth of cut. Both cuts must be accomplished by making several light passes as a saw blade is not designed to cut from the side. Also keep in mind the axis of the blade as it rises dose not maintain the same center, the fence must be adjusted to assure that both cuts will be centered on the heel at the final depth of cut.
Richard, Sometimes unorthodox methods are just fine to press a machine into service to create something in a way that was not originally intended. If I need radius blocks to profile fret boards I create them by following a pattern created on the end of a hardwood block. A quick pass with a curved cabinet scraper removes any small raised portions of the desired shape.
Randy, Yes that's the same idea, I used to do a lot of restoration work on antiques and often reproduced moldings using a table saw. A cove can be cut by setting a fence at an angle to the blade, you could do that and accomplish any radius you like with a little tweaking, the cut is also somewhat easier as you are not only cutting from the side of the blade.
Ken LeVan - Posted - 03/18/2013: 14:41:05
Richard, Thanks!
I understand it now, and it makes a lot of sense - it's like the way you can cut a cove molding on a table saw by running the stock at a diagonal, except you are running it straight on, and the 10" saw blade cut gives you a nice relief - very clever!.
I like the way you can do the heel cut and tension hoop cut independently from one another. I can't do that with my system.
I use a more complicated sanding jig with 2 diameters, one which cuts the heel, the other which cuts the tension-hoop relief. It's made from stacked plywood with sandpaper glued to it, and they are linked together:
This makes a nice cut, but it's specific to my pots, and works on Vega pots, too - I can't really disassociate the rim from the tension hoop:
Ken
Richard Brown - Posted - 03/18/2013: 15:04:54
This is a very simple jig which is used to adjust the fit of the neck to the tension hoop. Normally this is done as part of the final assembly after the head and tension hoop have been have been attached to the finished rim in their proper location. Tension hoops are usually somewhat out of round and I do this adjustment to get even spacing ( about the thickness of a piece of paper) between the neck and tension hoop. The profile is scribed to the fingerboard using an old credit card as a spacer and a white pencil.
the neck is clamped to the underside of the jig and sanded to the line at a slow speed on the drill press. usually it takes several attempts of sanding, marking and sanding again to get it perfect,
The heel cap can be sanded by clamping the neck to the top of the jig with the heel facing the other way, though I now do this with the heel sanding jig shown at the beginning of this topic.
rudy - Posted - 03/18/2013: 17:44:52
I do tension band notches by marking the tension band clearance in the same way, then matching the desired cut to a carbide tipped router bit in a rotary hobby tool jig as shown. I take a light initial cut then drop the cutter down to make successive cuts 1/16" for each pass. It's quick and accurate. I do like the totally visual approach of your jig, I'm just not sure I could be steady enough to not wander off the desired result. (Yes, the first set up step is draping the drill press plug over the end of the jig...)
Richard Brown - Posted - 03/20/2013: 15:35:52
Here are a few simple tools I made some time ago for final fitting of the tension hoop to the neck. Strips are cut from a sanding belt, inserted into the slot (cut on the band saw) and held at the other end by the thumb in the depression on the handle.
I have three sizes for 8" 10" and 11" rims.
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