This could be the ultimate router planing jig. Should be very light to use. Thoughts?
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Router Planing Fixtures
- Thread starter Bruce Johnson
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This could be the ultimate router planing jig. Should be very light to use. Thoughts?
Certainly that should be super smooth, and looks pretty easy to build. Could get pricey if you wanted to build a large one. Those rails can get expensive (used them on my CNC build).
It's a refinement of the "table leveling" jig available from Amazon (HERE) that's already been mentioned.
These types of fixtures have a number of disadvantages for the small home shop.
1. They require a large amount of shop space.
2. They require a LARGE dead flat table (seldom mentioned in the "easy" part of these videos)
3. They are EXPENSIVE to build
4. They require a lot of modification to use for anything other than a specific specialized task
5. Lots of parts that aren't fastened down means small bits of debris can severely effect any accuracy they claim
6. The "easy" part won't look so easy once there's a bit of dust accumulated in those bearings.
7. There's a lot of set up time involved in this process. Time is a valuable commodity in our everyday lives as we get a bit older (and hopefully wiser...)
This is another of the "magic bullet" attempts to solve a problem by throwing money at it. Bruce's setup is much more cost-effective if you want to build a router sled planing fixture that is task-specific.
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Of course for luthiery I would not make an acre sized router sled. I don't see how a router planing sled is nothing but a task specific tool no matter what it is made of. I would for sure mount the rails on the table. Cost is sure a lot more than few strips of mdf.
Here's an update on one of my classic Router Planing Fixtures!
This summer and fall I'm going all through my process of building the necks for my Scroll Basses. Improvements on existing fixtures, some all new fixtures, and a few new special machines. I'm building up a Scroll Bass factory here. Investing time and money in tooling, to allow me to build my basses steadily in less labor hours.
Here's a simple operation: Blocks of wood that will become the halves of the headstocks need to be trimmed down to 1.050-1.060" thickness, with good flat gluing surfaces. This is a job for a Router Planing Fixture!
The wood blocks are either walnut or maple, 1 1/4" thick, and they are already ripped to 3 1/8" wide and cut off to 18" long. Waiting on a cart are a batch of 18 of them.
I decided to use my classic "universal" router planer fixture for this job. It's been in heavy use for about 24 years, but it's still going strong. I'm planning to build a new replacement for it that's about 8" longer. Same basic design, with a few mechanical improvements. But for right now, the old one will do.
That's it in the background. In the middle is a new custom insert frame that I made for it. In the front is the first walnut block that I cut with the fixture, using it to calibrate the fixture.
The insert frame is two parallel rails of 3/4" MDF They hold the block up at the right height in the fixture, raised up just enough above the inner rails of the fixture to rout off the excess thickness; about 0.200".
The insert frame's rails are spaced a little less than 3 1/8" apart, to fit the width of the headstock blocks. The two insert frame rails are held together with MDF blocks on the ends. Those end blocks are slightly tapered vertically. The bottom is a full 3 1/8" wide, but the right side leans in a bit, so the top is about 3 1/16" wide. This is so the fixture will clamp on the headstock block when the knobs are tightened.
The end block on this end was originally taller than the thickness of the headstock block.
The block on the other end is shorter than the rails, but it also tapers slightly from bottom to top.
And here's the insert frame set in place inside the router planing fixture. The purpose is a quick repeatable setup, for making this particular part. Set it in there, and the fixture is ready to clamp the headstock block in the right position, ready to cut.
When I cut the first board in there, I took light passes, measuring carefully, bringing it right down to the correct thickness. And, I was also trimming off the top of that end block to be flush with the surface of the walnut headstock block.
That end block sticking up now becomes the setup gauge. Whenever I set the insert frame into this fixture, I adjust the router down to just touch the top of the end block, and the depth of the router is set to cut the headstock block to the right thickness.
And here's the rig in operation: My standard PC 691 router with the wide flat base and a 3/4" dia planer bit.
I'm ready to router plane a stack of headstock blocks. The tools of production!
This summer and fall I'm going all through my process of building the necks for my Scroll Basses. Improvements on existing fixtures, some all new fixtures, and a few new special machines. I'm building up a Scroll Bass factory here. Investing time and money in tooling, to allow me to build my basses steadily in less labor hours.
Here's a simple operation: Blocks of wood that will become the halves of the headstocks need to be trimmed down to 1.050-1.060" thickness, with good flat gluing surfaces. This is a job for a Router Planing Fixture!
The wood blocks are either walnut or maple, 1 1/4" thick, and they are already ripped to 3 1/8" wide and cut off to 18" long. Waiting on a cart are a batch of 18 of them.
I decided to use my classic "universal" router planer fixture for this job. It's been in heavy use for about 24 years, but it's still going strong. I'm planning to build a new replacement for it that's about 8" longer. Same basic design, with a few mechanical improvements. But for right now, the old one will do.
That's it in the background. In the middle is a new custom insert frame that I made for it. In the front is the first walnut block that I cut with the fixture, using it to calibrate the fixture.
The insert frame is two parallel rails of 3/4" MDF They hold the block up at the right height in the fixture, raised up just enough above the inner rails of the fixture to rout off the excess thickness; about 0.200".
The insert frame's rails are spaced a little less than 3 1/8" apart, to fit the width of the headstock blocks. The two insert frame rails are held together with MDF blocks on the ends. Those end blocks are slightly tapered vertically. The bottom is a full 3 1/8" wide, but the right side leans in a bit, so the top is about 3 1/16" wide. This is so the fixture will clamp on the headstock block when the knobs are tightened.
The end block on this end was originally taller than the thickness of the headstock block.
The block on the other end is shorter than the rails, but it also tapers slightly from bottom to top.
And here's the insert frame set in place inside the router planing fixture. The purpose is a quick repeatable setup, for making this particular part. Set it in there, and the fixture is ready to clamp the headstock block in the right position, ready to cut.
When I cut the first board in there, I took light passes, measuring carefully, bringing it right down to the correct thickness. And, I was also trimming off the top of that end block to be flush with the surface of the walnut headstock block.
That end block sticking up now becomes the setup gauge. Whenever I set the insert frame into this fixture, I adjust the router down to just touch the top of the end block, and the depth of the router is set to cut the headstock block to the right thickness.
And here's the rig in operation: My standard PC 691 router with the wide flat base and a 3/4" dia planer bit.
I'm ready to router plane a stack of headstock blocks. The tools of production!
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I router planed that whole cart load of headstock blocks last night. Both sides of each block, right to 1.050"-1.060" thickness, 18 blocks. I clocked 4.4 minutes each, including cleanup time.
Here's the piles of walnut and maple chips collected in the routing bench.....
Here's the piles of walnut and maple chips collected in the routing bench.....
Yet another custom special router planing fixture! Because there so many that still need to be built. And I need them. I don't have enough. I can't stop.
This is a simple production router planing fixture. It's made to do one job only in the production process of building my AMB-2 Scroll Basses. A simple flat bevel cut on the headstock block halves. That one operation, quickly and accurately. On a whole tray full of parts, or a single one when needed.
A simple classic design router planing fixture. Two parallel rails of 3/4" MDF that the router base slides on. A center piece that's tilted at the correct angle, at a depth below the rails. The headstock blocks already have a pair of 1/8" dowel pin holes on their back side, to locate them in fixtures. You saw me cut them to shape over on the Pin Routers thread. So this fixture has two pairs of steel dowel pins to mount the left or right headstock block halves. The blocks just plug onto the pins and stay on there by friction.
The cross bar at the back allows it to be clamped down securely to the routing bench. That's a smear of Johnson's Paste Wax on the top of the rails. The shallow Forstner bit holes going under the edges of the parts make it easy to use a little pry bar to pop the part up off the pins.
I made the fixture long enough on the back end that I can park the router there, even leaving it running while I change parts.
The center strip also functions as the built-in setup gauge. I fitted it in there a little high. Then routed the first part carefully, working it down to the correct depth. Then I ran the router across the top of the center strip, trimming it to the same height. Now, whenever I set up to use this fixture, I place the router on the rails, lower the bit until it touches the center strip, and zero the depth ring on the router.
I routed that first test block in four depth passes, going side to side. Now that I'm working down through the stack of blocks, I'm routing them in three passes, in a circular motion CW, climb cutting. Trying to minimize chipping on the outer edge. This is a final surface on the instrument.
Again, this is an example of a production fixture. I expect to be doing this operation hundreds of times over the coming years. The fixture will get labeled and take a place in the shelves. I'll normally pull it out and set it up once a year to do maybe 24 sets in one batch. But it's simple enough to set up to do one set if I need to.
This is a simple production router planing fixture. It's made to do one job only in the production process of building my AMB-2 Scroll Basses. A simple flat bevel cut on the headstock block halves. That one operation, quickly and accurately. On a whole tray full of parts, or a single one when needed.
A simple classic design router planing fixture. Two parallel rails of 3/4" MDF that the router base slides on. A center piece that's tilted at the correct angle, at a depth below the rails. The headstock blocks already have a pair of 1/8" dowel pin holes on their back side, to locate them in fixtures. You saw me cut them to shape over on the Pin Routers thread. So this fixture has two pairs of steel dowel pins to mount the left or right headstock block halves. The blocks just plug onto the pins and stay on there by friction.
The cross bar at the back allows it to be clamped down securely to the routing bench. That's a smear of Johnson's Paste Wax on the top of the rails. The shallow Forstner bit holes going under the edges of the parts make it easy to use a little pry bar to pop the part up off the pins.
I made the fixture long enough on the back end that I can park the router there, even leaving it running while I change parts.
The center strip also functions as the built-in setup gauge. I fitted it in there a little high. Then routed the first part carefully, working it down to the correct depth. Then I ran the router across the top of the center strip, trimming it to the same height. Now, whenever I set up to use this fixture, I place the router on the rails, lower the bit until it touches the center strip, and zero the depth ring on the router.
I routed that first test block in four depth passes, going side to side. Now that I'm working down through the stack of blocks, I'm routing them in three passes, in a circular motion CW, climb cutting. Trying to minimize chipping on the outer edge. This is a final surface on the instrument.
Again, this is an example of a production fixture. I expect to be doing this operation hundreds of times over the coming years. The fixture will get labeled and take a place in the shelves. I'll normally pull it out and set it up once a year to do maybe 24 sets in one batch. But it's simple enough to set up to do one set if I need to.
The next phase is to create the Bruce Johnson Router Fixture index so you can quickly locate the designed tool from amongst so many useful pieces. I am imagining a point when your wall will be a bit intimidating otherwise...
we will measure the cleverness and efficiency of router jigs by the ‘Bruce Johnson Router Index,’ or simply ‘The Bruce Index’
for reference, a plain plywood jig with two rails and a free floating router sled has a Bruce index of 2.5
I've got the parts, and will build one much like it, soonish.
I’m waiting for the hardback edition of the Bruce Johnson Router Fixture Compendium, personally. It’ll look sharp on a coffee table or in the shop!
Most of my fixtures could be measured in NanoBruces (nB).
@Bruce Johnson
Is the neck shaping router rig on the schedule for any time soon? I know there's a bunch out there, but I'm very excited to see your take on it. So much so that I want to put off my next build so I can see your rig first and build my own to do the next neck.
Any chance of maybe divulging a few ideas before you build it? Like a movie trailer? Is it something that will copy an existing neck shape, or more of a traditional style sled with a neck rotisserie?
Is the neck shaping router rig on the schedule for any time soon? I know there's a bunch out there, but I'm very excited to see your take on it. So much so that I want to put off my next build so I can see your rig first and build my own to do the next neck.
Any chance of maybe divulging a few ideas before you build it? Like a movie trailer? Is it something that will copy an existing neck shape, or more of a traditional style sled with a neck rotisserie?
Yeah, I definitely need a Warehouse Management System of some kind. I literally have hundreds of templates, fixtures, and special tools stored away here, built over 30 years. Most of them are somewhat organized on shelves and in cabinets. And I usually label them pretty well. But I will occasionally find one, where I can't remember what it's for or what it does. I do recycle obsolete templates and fixtures to some degree, reusing the hardware and MDF parts...to make new fixtures!
By the way, I've continued to add to my shop space here in the Secret Underground Lab. My main working shop area is now about 3500 sq ft, plus 800 sq ft of clean warehouse space, plus 1500 sq ft of space that I sub-rent to other tenants. My old shop in Burbank was only 1800 sq ft total. More space for cool machines and storing fixtures!
Yes, I am just about to start building the long-rumored Neck Shaping Machine. I want to have it up and running this fall. I need it to shape production Scroll Bass necks.
Through this spring, I spent some more time reworking the design of it. In particular, I was originally going to make some major parts of it from aluminum, fabricated and machined. But I decided to build it almost all from wood, MDF and plywood, with minimal machined metal parts. I'm doing this deliberately so that folks here on Luthiers' Corner can make their own versions, with basic woodworking tools. I think this machine will be a practical and useful thing for a small hobbyist Luthier shop. I'm going to offer the design out to the Luthier community for free to copy as you please. If it works well, I may build replicas for customers if there is interest. Hey, maybe I could sell them through Stew-Mac!
A quick overview of the machine:
Picture two built-up plywood cradles, each about 4' long and 4" deep. The two cradles are side by side, horizontal axis, in bearings at both ends. They roll through 180 degrees; 90 degrees in either direction from the center position. A cable and pulley system connects them together, so they roll accurately, synchronized. A crank at the end allows you to roll them in finer than 1 degree increments, both exactly the same.
Mounted in the left cradle is a Master neck. Hand carved to exactly the dimensions and contour that you want. Or it could be a commercial neck that you want to copy. In the right cradle is the Workpiece neck, the one to be shaped into an exact replica of the Master neck.
Between the two cradles, and to the outside of the right one, are aluminum tube rails. They are mounted on pivoting boards, so that they can shift side to side about 3" in either direction.
A carriage slides down the two rails, riding just above the two cradles. The rails keep the carriage parallel to the cradles, but you can move the carriage freely side to side and down the length of the cradles, with the handles on the carriage.
On the right side of the carriage, over the right cradle, is a router. A standard PC 790, fixed base. It has a 1/2" dia x 2" long standard bit hanging straight down. On the left side of the carriage is a 1/2" dia x 2" aluminum pin, which rolls in bearings, also hanging straight down. The distance between the pin and the router bit is exactly the same as the spacing between the cradles.
The aluminum pin hangs down to the side of the Master neck, and rolls along the side of it, as you push the carriage over. The router bit cuts along the side of the Workpiece neck, cutting with the side of the bit, not the end of the bit. That's important.
That's the operation: With the cradles stationary, you slide the cradle down the rails, rolling the pin along the side of the Master while the bit cuts down the side of the Workpiece. Slide the carriage back, rotate the two cradles a degree or two, next pass down the length. Repeat in small increments of rotation, working from 90 degrees to zero, the center. At the center, tilt the carriage up, and shift it over so the bit is on the other side of the neck. Do the passes down the other side, in small increments of rotation.
The cool thing about this arrangement is that putting the side of a cylindrical cutter against the side of the convex shape of the neck, will make a very accurate shaped surface. The ridges between facets will be tiny. As compared to a standard 3-axis CNC machine, which cuts the shape with the tip of a rounded cutter, leaving small rounded grooves.
With my machine, if you work slowly in 2 degree increments, the finish of the neck should be accurate and nearly perfect, requiring almost no filing or sanding. And, it will do the complete 3-D transitions to the heel and headstock as part of it.
I estimate that it will shape one of my Scroll Bass necks in about 15-20 minutes. It will save me 2-3 hours over my current hand-shaping process.
That's the conceptual design outline of my Neck Shaping Machine, that I've been talking about for years. I hope to have it in operation in the next few months.
I'll start a separate thread about its construction and development.
You gotta find a better name than "Neck Shaping Machine". Something like "BruceNeck-9000" or "Insta-Neckerator-9000". 
Good deal, Bruce.
It sounds a bit conceptually like the pantograph carvers that are used to duplicate gun stocks, with the exception of using the side cutting process. That's something I haven't seen in a duplicator before.
The gun stock duplicators link the two spindles with sprockets and a small gauge chain thaat is similar to a bike chain to keep them in perfect synchronization.
It sounds a bit conceptually like the pantograph carvers that are used to duplicate gun stocks, with the exception of using the side cutting process. That's something I haven't seen in a duplicator before.
The gun stock duplicators link the two spindles with sprockets and a small gauge chain thaat is similar to a bike chain to keep them in perfect synchronization.
