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Neck / Tail block radius jig
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Author:  bcombs510 [ Sun Dec 17, 2017 5:43 pm ]
Post subject:  Neck / Tail block radius jig
Hello,

I recently picked up a router table (merry Christmas to me!).... and was thinking about how I could incorporate it into the building workflow. I thought about tasks that I don’t like to do or don’t like the results I get. One that comes to mind is putting the radius on the neck and tail block. I’ve been using a chamfer bit for a while to 45 the corners of the blocks so I’m going to have the router out anyway, might as well put the radius on them too.

I first searched around online and on the OLF to see if a jig had already been posted. I saw the question asked a few times on the OLF, but most responses were to use a hand plane or a sandpaper caul. What I had been doing was taking a little off with a plane and then using stickit in the body mold and lapping the block until it fit. It worked ok, but I like the idea of a nice clean face getting glued to the sides.

In the responses here I saw where T. Kennedy had made a sled that held the block and used the robosander to put on the radius. I used that idea to build this one for the planer.


First, I cut the radius for the butt and neck end of the guitar on the edge of two boards that will be come the base of the sled. The pattern bit will ride along the base to cut the radius.

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I made a small L shaped backstop that is adjustable so that I can mount the block in just a tiny bit proud. The rails on the side keep the backstop square. I put hold downs on top and also double stick taped the block to the backstop. You can see in one of the pics the pattern bit. It’s a 2.5” cutting length so that it can cover more than half the block height on a dred. A different bit will be needed for smaller body guitars or for ukes.

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Here is a pic after the first pass:

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Flip the block and take a second pass:
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The fit is good on the tail block. Like most, I use a caul on the upper half to clamp the sides and use the mold itself on the lower half:

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I made a second “base” for the neck block radius. Note the extra block needed for the hold downs because of the height. The setup is the same:

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Pros
1) It’s accurate and repeatable
2) A nice clean cut

Cons
1) That bit is straight up scary
2) Flexing the jig is possible which can affect the cut (note the 45 degree reinforcements added later to be safe).

Thoughts? If you have the hardware it seems like an improvement over the sanding caul method. If your doing multiple builds I think it’s faster even with the router setup needed.

If you think of any improvements, or just want to tell me I’m just asking to lose digits, let me know.

Brad



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Author:  Glen H [ Sun Dec 17, 2017 6:04 pm ]
Post subject:  Re: Neck / Tail block radius jig
Very slick! There isn’t much tool wise in my shop that draws more of my concern than router bits (the skin on my right ring finger can attest). Be very careful.
Author:  Colin North [ Sun Dec 17, 2017 6:21 pm ]
Post subject:  Re: Neck / Tail block radius jig
Nice one Brad!
Author:  J De Rocher [ Sun Dec 17, 2017 6:24 pm ]
Post subject:  Re: Neck / Tail block radius jig
That's a slick design and I bet it gives good reproducible results. It looks scary to me, but that's me with router tables.

The routine uses for my router table are to rout the truss rod slot and to taper the fretboard. I also use it when making body molds.

I use my belt sander which is positioned vertically to radius the neck and tail block. I don't use a jig, just sand to the lines drawn on each end and check for trueness with a straight edge. I find that to be reasonably fast and no stress.
Author:  david farmer [ Sun Dec 17, 2017 9:38 pm ]
Post subject:  Re: Neck / Tail block radius jig
Brad, your already part way to the method below.
The part of the cut that is "up hill" with a straight bit on your set up must be dicey. It's is really the job of a shaper, or at least a bit with some shear. One that pulls the work towards the table.

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Author:  bcombs510 [ Sun Dec 17, 2017 10:08 pm ]
Post subject:  Re: Neck / Tail block radius jig
david farmer wrote:
Brad, your already part way to the method below.
The part of the cut that is "up hill" with a straight bit on your set up must be dicey. It's is really the job of a shaper, or at least a bit with some shear. One that pulls the work towards the table.


Thanks, Dave. I wonder about the up hill part as well. The only reason it worked OK was because it was a dred so the radius is next to nothing to begin with. Coming in on something with a tighter radius like a parlor or a Uke it would be much worse.

The sander idea is interesting. I don’t have a disc sander that it tall enough to try.

By shear bit, you mean this correct? https://www.amazon.com/gp/aw/d/B009WSDW ... SY340_QL65

Brad





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Author:  david farmer [ Sun Dec 17, 2017 11:20 pm ]
Post subject:  Re: Neck / Tail block radius jig
hmm.... with a quick look I don't see any long pattern bits with up shear. Spiral bits are less grabby against the grain. The one you linked to will tend to push the work up off the table. Not good. You may be stuck with a straight long bit.
The keys to avoiding excitement are:
1. removing the smallest possible amount of material.
2. always moving the work forward never back (climb cutting).
3. making sure the block can't/doesn't shift one iota in the jig under cutting force.
if the block shifts, at all the next thing you'll be doing is trying to figure out what happened. :(

One more thing that really helps a cut like that is more mass in the jig. a large MDF base instead of a small piece of pine will cut down
on chatter/ kickback considerably.

This baby makes a cute purring sound as it slices through endgrain. :mrgreen:

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Author:  Terence Kennedy [ Sun Dec 17, 2017 11:35 pm ]
Post subject:  Re: Neck / Tail block radius jig
My jig which I copied from one in Charles Fox’s shop is designed for the 6” belt sander(or disk sander like David) and also uses a raised buttress on the table to guide the template.

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Using a bit that long, especially with a 1/4” shaft makes me a little nervous. I could certainly visualize it catching the work with resultant disaster.

David that is a very manly cutting tool! I profile my necks exactly the same way but with a Robosander.
Author:  david farmer [ Sun Dec 17, 2017 11:49 pm ]
Post subject:  Re: Neck / Tail block radius jig
Terence Kennedy wrote:
My jig which I copied from one in Charles Fox’s shop is designed for the 6” belt sander(or disk sander like David) and also uses a raised buttress on the table to guide the template.

Image

Using a bit that long, especially with a 1/4” shaft makes me a little nervous. I could certainly visualize it catching the work with resultant disaster.

David that is a very manly cutting tool! I profile my necks exactly the same way but with a Robosander.
1/4" shank? !!!
I don't think I'd do that.

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Author:  bcombs510 [ Sun Dec 17, 2017 11:50 pm ]
Post subject:  Re: Neck / Tail block radius jig
That’s the pic I saw in the previous thread. Thanks, Terence.

The bit I’m using is a 1/2” shank, but it for sure is a ton of whizzing metal above the table!

I’ll have to think about it a bit more. Maybe build a larger base like Dave mentions.

I had the block just barely proud of the edge of the sled so wasn’t taking off much material at all.

I felt in control of the situation, but I do worry about the amount of material that would be coming off of a tighter radius like a Uke or small body guitar. I could take a bit off on the sander first but that somewhat defeats the purpose. :)

Appreciate all the feedback and ideas!

Brad


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Author:  bcombs510 [ Sun Dec 17, 2017 11:54 pm ]
Post subject:  Re: Neck / Tail block radius jig
david farmer wrote:
1/4" shank? !!!
I don't think I'd do that.

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The bit I was using is 1/2” shank, 2 1/2” cutting length. It’s indeed hard to find a pattern bit with a cutting length longer than two inches.


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Author:  doncaparker [ Mon Dec 18, 2017 4:41 am ]
Post subject:  Re: Neck / Tail block radius jig
In addition to fear of injury regarding the routing operation in question, I can see some room for error coming from the need to flip the workpiece and make another pass. If there are any alignment issues, the surface might not be completely flat in the top to back plane.

I favor the use of a 12" disc sander with the curb and a jig that rides the curb, as shown in some of the photos above. You can get the whole block in one pass, with no fear of router mishaps.
Author:  bcombs510 [ Mon Dec 18, 2017 6:46 am ]
Post subject:  Re: Neck / Tail block radius jig
doncaparker wrote:
In addition to fear of injury regarding the routing operation in question, I can see some room for error coming from the need to flip the workpiece and make another pass. If there are any alignment issues, the surface might not be completely flat in the top to back plane.


I wonder about this as well. The original idea I had for the jig was a plate with the radius on both top and bottom and you flip the jig, not the block.

I didn’t have any issues with the test cut but I see your point.

Thanks!
Brad


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Author:  klooker [ Mon Dec 18, 2017 9:25 am ]
Post subject:  Re: Neck / Tail block radius jig
These are a less expensive alternative to spiral helix bits.

https://www.amazon.com/CMT-806-690-11B- ... VTSK6WA49Y
Author:  david farmer [ Mon Dec 18, 2017 10:33 am ]
Post subject:  Re: Neck / Tail block radius jig
IMO, loothing without a good 6x48 and disc set up is swimming up stream. It's also the best way to make blocks quickly. Put a thicknessing set-up on the belt part for nuts and saddles and you'll wonder how you did without it. It's the closest machine to my bench and gets turned on 3x as much as any other.

If it helps:
Feel free to use this post for family lobbying.

Brad needs a combo sander for x-mas!
Author:  bcombs510 [ Mon Dec 18, 2017 10:39 am ]
Post subject:  Re: Neck / Tail block radius jig
david farmer wrote:
Brad needs a combo sander for x-mas!


Ain't that the truth! bliss
Author:  Terence Kennedy [ Mon Dec 18, 2017 11:02 am ]
Post subject:  Re: Neck / Tail block radius jig
Sorry about missing the shank size, looked smaller in the picture.
Author:  Clay S. [ Mon Dec 18, 2017 11:55 am ]
Post subject:  Re: Neck / Tail block radius jig
Hi Brad,
That looks like a pretty good set up. With the 1/2 inch shank bit and the light passes you are doing I don't think you will have any problems.
A couple of things you could do;
Add a fiducial mark on the top of the jig and top and bottom of the work piece to align the center.
For tighter radius blocks requiring deeper cuts you could set up the jig to first make a partial cut and then by adding shims behind the block (to move it out further) make additional light passes.
Author:  bcombs510 [ Mon Dec 18, 2017 12:30 pm ]
Post subject:  Re: Neck / Tail block radius jig
Thanks, Clay. The backstop is adjustable so no need for shims. There is a complication though, if trimming a little at a time and slowly exposing more of the block, I’ll have to have a way to know how far to expose the block when it’s flipped for the second pass. I could put a mark to help line it up each time. Not sure. :)

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Author:  Bryan Bear [ Mon Dec 18, 2017 12:52 pm ]
Post subject:  Re: Neck / Tail block radius jig
You could set up a bottom guide for your bandsaw like the one shown above allowing you to use the same jig to trim as close as is practical on the bandsaw, then take the jig directly over to the router table to remove the saw marks and clean it up to the line.

It still seems a bit scary to me though.
Author:  doncaparker [ Mon Dec 18, 2017 2:36 pm ]
Post subject:  Re: Neck / Tail block radius jig
Here's an idea that scares me a lot less. I still like using a disc sander (as I said above), but if you want to use the router, here is a way that gives me fewer willies:

1. Do everything exactly the way you are doing it now, except use a much shorter router bit (like 1" max). This includes doing one end of the block, then flipping, then doing the other end.

2. This will leave you with both ends profiled the way you want, but an uncut middle. Just hand plane down the middle to match the two ends.

It is more hand work, but you are less likely to injure those hands this way.
Author:  bcombs510 [ Mon Dec 18, 2017 4:39 pm ]
Post subject:  Re: Neck / Tail block radius jig
Just to be clear, the purpose of this exercise was to find purpose for the router!! :D

Although I did make a jig to put the radius and chamfer on braces using the design in the Gore book.

Let’s see if I can talk myself into using a sander for this operation.


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Author:  Clay S. [ Mon Dec 18, 2017 7:10 pm ]
Post subject:  Re: Neck / Tail block radius jig
"I could put a mark to help line it up each time. Not sure. :)"

Having made the jig adjustable as you did, a few lines at the back on the base could show you where to set it for the next pass.
I have used large routers and bits (some 4 inches across) handheld for a number of years. As with any tool they demand respect, but when properly set up aren't particularly dangerous.
My worst injury when working as a cabinetmaker was from a sander. My finger was sucked into a belt sander and the end was ground off. I got too comfortable with the tool and had the switch locked on when changing the positions of my hands.
Disc sanders, belt sanders, band saws, and routers can all hurt you if you aren't careful.
The jig you made looks well conceived and should allow you to keep your hands well away from the cutter. The 1/2 inch shank of the bit is unlikely to snap with the light cuts you will be doing. As long as it is properly secured in the router (always allow a little bit of space between the bottom of the bit and the bottom of the collet) I think you will be fine.
Yesterday I profiled an end block for a travel guitar I am building. It was about 6 inches long and 4 inches tall. I used a band saw and a 6 X 80 belt sander. I think for the next one I will make a router jig similar to yours. I think it will be quicker and safer.
Author:  jeffhigh [ Tue Dec 19, 2017 1:14 am ]
Post subject:  Re: Neck / Tail block radius jig
I use a 12" disc sander too.
It's a long lower and upper board, drilled at 1" centres for a pivot
I just fix the block on with a screw since I always use a cross grain veneer to the inner face.
once I have worked out the best radius by trial (working from numerially large down) I write the number on the mould for that guitar
Author:  jeffhigh [ Tue Dec 19, 2017 1:14 am ]
Post subject:  Re: Neck / Tail block radius jig
I use a 12" disc sander too.
It's a long lower and upper board, drilled at 1" centres for a pivot
I just fix the block on with a screw since I always use a cross grain veneer to the inner face.
once I have worked out the best radius by trial (working from numerially large down) I write the number on the mould for that guitar
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