Pin Routers: The Old-School Production Workhorses

[Bruce Johnson]

I had a "green monster" in my classroom at the college where I taught. It was under lock & key, and could not be used without direct supervision from a staff member qualified by the department chair, just like our shapers. All operators, including instructors who were qualified users, were required to run the machine with a "buddy" who could dial 9-1-1 and administer first aid until help arrived.

No one was ever allowed to hold a workpiece in their bare hands. In fact, we created fixtures that enabled users to keep their hands well away from the cutter at all times.

Plan for the worst that can happen, have a buddy double check all operations before the power is turned on, and never work alone.

Good luck!

Yep. As you'll see coming up, the fixtures I'll be building are going to have strong large handles spaced about 30" apart. You have to respect 10 horsepower. If something goes badly wrong, it can pull you off your feet, into the machine. I'm mostly going to be using mine at the slower speed, 10,000 rpm, and with a 1/2" dia bit. That reduces its ability to apply torque and throw things. I'm pretty scared of using it with larger diameter bits.

 

[Bruce Johnson]

Continuing on with the tooling set:

The AMB-2M Master Template is done. I spent some time carefully hand filing the cavities and cutouts, getting them smooth and true. I probably will be adding a few more reference features to it later. For example, when I make up the routing template for the pickguard, I'll probably drill the reference holes for the screw locations in the Master Template. And when I make up the routing pattern for the neck pocket, I may trace-rout it on the Master Template. It will remain the reference pattern to check everything against.

The next piece of the kit is a 19" x 24" rectangle of 3/4" Baltic Birch plywood. This becomes the frame of the pin router fixture. I blanked out two of them now, and will be cutting more later. I'll need one for each permanent fixture. I start by drawing a centerline on it and positioning the Master Template, then drill the two 1/8" reference holes down through the guide bushings. Next, I plug the Drill Guide into the reference holes, and drill the two 3/16" Template Pin holes.

The first job of this fixture will be to make up the final routing templates, the templates that go on the undersides of the permanent routing fixtures. I need two of them, mirror images of each other. Here's the MDF blank for the first one. I start by positioning the Master Template on it and drilling the reference holes. I pin the template in place by the reference holes and trace all of its perimeter and internal cutouts with a pencil.

Then plug on the drill guide and drill the two Template Pin holes.

I also made up this pair of handles. They are cut from 3/4" plywood, with plywood doublers, rounded off with a radiusing bit in a router. I've pressed in 1/4-20 T-nuts in the corners.

And here's how it all assembles: The part to be pin routed mounts on top of the plywood rectangle. The handles bolt onto the side edges...

And the template goes on the underside. That's where the pin rides around. In this case, I have the Master Template mounted underneath, and the MDF blank on top. I'll be using the pin router to copy the Master Template and make one of the Router Templates. That Router Template will then get mounted on the underside of its own plywood rectangle and become a permanent routing fixture. One of the set.

And here's what the whole assembly looks like, on the table of the Big Green Pin Router. It slides around on the table, with the pin riding in the template on the bottom side. I hold it and guide it by any of those six handles. They are long and low profile, to keep my hands widely spaced to resist the torque. And to keep my hands away from the cutter. And the guard completely surrounds the cutter anyway.

I think this will be a good safe, efficient fixture system. I'm about to start testing it!

 

[Beej]

Very, very cool. Nothing like a fun new toy that builds stuff!

 

[Bruce Johnson]

Well, I triple-checked everything, took a deep breath, and reached for the big ON button.....

Wow, it works! The Big Green Machine cuts away wood very quickly and accurately. I started routing the pockets in the MDF blank that will become the Routing Template for the inside of the backs of the AMB-2M model bodies.

A couple of things I learned:

• The fixture system seems to work very well. The weight of the fixture and those long handles make it easy to control and steer around the pin. I didn't feel any real torque or it trying to pull away from me. It was comfortable and safe to operate. And I could feel the template underneath sliding on the pin, and know that I was routing the whole chamber.
• I routed these chambers to 5/8" deep, mostly in 1/8" deep steps. I tried going 1/4" deep a couple of passes. It definitely had the power to go deeper, if I wanted to. But I found that deeper passes didn't really speed things up that much. With a deeper cut, I had to feed slower. The sequence of lifting the spindle with the pedal, clicking the depth stop wheel one notch, and tapping the pedal to lower the spindle was so quick and easy. Routing these chambers in 5 steps of 1/8" was easy.
• Note that there's no noticeable stepping lines down the side walls of the routed pockets. The fixture and the machine are tight and accurate.
• This thing consumes a lot of air when running. I had it plumbed to my main compressor, which has an 80 gallon tank. A couple of cycles of raising and lowering the spindle would drop the tank pressure enough to kick the compressor on. And, if the line pressure got below 100 psi, the spindle was real slow raising up. That got a little frightening one time when I hit the pedal and the spindle wouldn't raise up. The compressor was trying to catch up. I need to add some plumbing to mount a pressure gauge within easy sight range. So I always know if I have enough pressure to go, or need to pause for a moment.
• I hooked up my small dust collector to the port in the guard. It barely worked at all. The pockets filled up with MDF dust as I was routing. I couldn't really see that well what I was doing. But I could feel the pin sliding around the walls of the template underneath, so the dust buildup wasn't that much of a problem. But I need to re-think the dust collection and come up with something better.
• Overall, the Big Green Machine was comfortable to use. I wasn't wearing any ear protection, and it wasn't loud enough to be annoying.

Tomorrow I'll finish up routing this template, and then make its mirror-image twin.

 

[dwizum]

This thread continues to be an all time favorite for me.

The thing I can't get - and probably just because I've never run one of these myself - is how the operator develops a smooth sense of dropping the template onto the pin easily and smoothly for each pocket to be cut - since you can't see through the whole assembly to see the pin. When you're switching from one pocket to another, do you just sort of go by feel?

Also, do you route all pockets at a specific depth and then step the machine and do another pass in all of them? Or do you do one pocket at the time, stepping all the way down and then resetting prior to the next pocket?

Wondering these things because of all the little pockets in your design. The youtube vids I've watched of these being used in big production shops were all more or less just for routing an outline and maybe a pickup pocket or two, nothing as complex as your design!

 

[Bobo]

Continuing on with the tooling set:

The AMB-2M Master Template is done. I spent some time carefully hand filing the cavities and cutouts, getting them smooth and true. I probably will be adding a few more reference features to it later. For example, when I make up the routing template for the pickguard, I'll probably drill the reference holes for the screw locations in the Master Template. And when I make up the routing pattern for the neck pocket, I may trace-rout it on the Master Template. It will remain the reference pattern to check everything against.

View attachment 4240201

The next piece of the kit is a 19" x 24" rectangle of 3/4" Baltic Birch plywood. This becomes the frame of the pin router fixture. I blanked out two of them now, and will be cutting more later. I'll need one for each permanent fixture. I start by drawing a centerline on it and positioning the Master Template, then drill the two 1/8" reference holes down through the guide bushings. Next, I plug the Drill Guide into the reference holes, and drill the two 3/16" Template Pin holes.

View attachment 4240203

The first job of this fixture will be to make up the final routing templates, the templates that go on the undersides of the permanent routing fixtures. I need two of them, mirror images of each other. Here's the MDF blank for the first one. I start by positioning the Master Template on it and drilling the reference holes. I pin the template in place by the reference holes and trace all of its perimeter and internal cutouts with a pencil.

View attachment 4240204

Then plug on the drill guide and drill the two Template Pin holes.

View attachment 4240205

I also made up this pair of handles. They are cut from 3/4" plywood, with plywood doublers, rounded off with a radiusing bit in a router. I've pressed in 1/4-20 T-nuts in the corners.

View attachment 4240202

And here's how it all assembles: The part to be pin routed mounts on top of the plywood rectangle. The handles bolt onto the side edges...

View attachment 4240206

And the template goes on the underside. That's where the pin rides around. In this case, I have the Master Template mounted underneath, and the MDF blank on top. I'll be using the pin router to copy the Master Template and make one of the Router Templates. That Router Template will then get mounted on the underside of its own plywood rectangle and become a permanent routing fixture. One of the set.

View attachment 4240207

And here's what the whole assembly looks like, on the table of the Big Green Pin Router. It slides around on the table, with the pin riding in the template on the bottom side. I hold it and guide it by any of those six handles. They are long and low profile, to keep my hands widely spaced to resist the torque. And to keep my hands away from the cutter. And the guard completely surrounds the cutter anyway.

View attachment 4240208

I think this will be a good safe, efficient fixture system. I'm about to start testing it!

View attachment 4240209

awesome!

 

[Bruce Johnson]

This thread continues to be an all time favorite for me.

The thing I can't get - and probably just because I've never run one of these myself - is how the operator develops a smooth sense of dropping the template onto the pin easily and smoothly for each pocket to be cut - since you can't see through the whole assembly to see the pin. When you're switching from one pocket to another, do you just sort of go by feel?

Also, do you route all pockets at a specific depth and then step the machine and do another pass in all of them? Or do you do one pocket at the time, stepping all the way down and then resetting prior to the next pocket?

Wondering these things because of all the little pockets in your design. The youtube vids I've watched of these being used in big production shops were all more or less just for routing an outline and maybe a pickup pocket or two, nothing as complex as your design!

Hey dwizum;

Notice in the pictures that I have pencil lines drawn all over the top surface of the MDF board that I'm about to rout. As I'm prepping the board, I clamp the Master Template on it and drill the two 1/8" reference holes in it. Then I pin the Master Template down to the board by the two reference holes and use a pencil to draw all around the perimeter and inside all the chambers. This puts an accurate "drawing" on the top surface of the MDF of all the chambers. I'll probably do this same thing of drawing the lines on all the walnut blanks that become real bodies. It's a quick visual indication of where I'll be routing.

You can't see it, but under the front edge of the table is a small lever. Flipping it to the right lowers the pin down below the table surface. To the left brings the pin up about 1/2" above the surface. A very handy feature.

To locate the fixture on a chamber, I start with the pin retracted (and the spindle up and locked), and slide the fixture over until it looks like the cutter bit is over top of the pencil outline of the chamber. Flip the lever and the pin comes up into the chamber on the template on the bottom. If I'm off position, I'd feel the pin trying to lift up the fixture. It's actually very easy to find the next chamber in the template.

Another option I have is to make a top Mask Plate. Another rectangle of plywood which clamps down on top of the workpiece. It already has all the chambers cut through it, like the Master Template. The router bit lowers down through it to cut the workpiece. I've had some worries whether the walnut board may try to lift or bend up off the fixture from the vibration and cutting loads. So far I haven't seen any problem with that, but a Mask Plate would solve that by clamping the workpiece down. Also, I could write Sharpie notes on the Mask Plate to remind me what depth each chamber is supposed to be routed to.

In my testing so far, I've been routing these chambers in the MDF board 5/8" deep total, five 1/8" deep passes. I do all five passes in a chamber before moving to the next chamber. That aluminum rotary depth stop wheel really works well. It only takes about three seconds to change the depth between passes. One second to tap the heel of the pedal and raise the spindle up; one second to reach up and turn the depth stop wheel one click to the left; one second to tap the toe of the pedal and drop the spindle back down into the work.

As an example, look at the triangular pocket at the lower right. That's the control cavity. That took maybe 45 seconds total to rout out, all five steps. With some practice, I could probably do that chamber in under 30 seconds in five 1/8" passes. If I eventually get my courage up, I could do it in a single 5/8" deep pass in about 10 seconds.

That's what a pin router is really good at: routing complicated 2D patterns quickly and accurately. With good fixturing and some operator skill, it's as fast and accurate as smaller CNC routers.

 

[dwizum]

That's a great explanation. Raising/lowering the pin makes sense and I could see how the pencil outline makes it trivial to line things up. That sounds much more smooth than how I was picturing it mentally!

 

[Bruce Johnson]

Finishing up the routing templates, for the internal chambers of the AMB-2M body:

This is the matching pair of permanent routing templates that will be used to rout the walnut blanks that become the bass bodies. Here's the first one, after I routed in the perimeter of the body.

Tonight, I made its mirror-image twin. These are the Routing Templates, both cut on the pin router, with the pin following the Master Template that I showed above. The Master Template was pinned on the underside of the fixture by the two reference holes down the center. To make the reversed Routing Template, I just flipped the Master Template over on the underside of the fixture, and re-pinned it through the same two reference holes on the centerline. That's one of the reasons why the Master Template has all the chambers cut all the way through it; so it can be reversed.

When I routed the 2nd one, I got braver and did 1/4" deep passes. Three passes for each chamber; two at 1/4" and the final at 1/8". It worked well and saved more time. I'm getting more comfortable running the Big Green Machine.

The two Routing Templates are not cut all the way through. They are made from 3/4" thick MDF, and the internal chambers are routed 5/8" deep. The perimeter cut is only 1/2" deep, leaving 1/4" of material thickness at the bottom. This is for strength. I don't want the template to break if it bangs too hard against the pin.

Now each of these two Routing Templates will get attached to the underside of its own rectangle of plywood. They will become the two main Routing Fixtures for cutting the internal chambers of the AMB-2M body. One will cut the chambers into the inside of the top, and the other will cut the chambers into the inside of the back.

 

[aetheriac]

Finishing up the routing templates, for the internal chambers of the AMB-2M body:

This is the matching pair of permanent routing templates that will be used to rout the walnut blanks that become the bass bodies. Here's the first one, after I routed in the perimeter of the body.

View attachment 4241377

Tonight, I made its mirror-image twin. These are the Routing Templates, both cut on the pin router, with the pin following the Master Template that I showed above. The Master Template was pinned on the underside of the fixture by the two reference holes down the center. To make the reversed Routing Template, I just flipped the Master Template over on the underside of the fixture, and re-pinned it through the same two reference holes on the centerline. That's one of the reasons why the Master Template has all the chambers cut all the way through it; so it can be reversed.

When I routed the 2nd one, I got braver and did 1/4" deep passes. Three passes for each chamber; two at 1/4" and the final at 1/8". It worked well and saved more time. I'm getting more comfortable running the Big Green Machine.

View attachment 4241378

The two Routing Templates are not cut all the way through. They are made from 3/4" thick MDF, and the internal chambers are routed 5/8" deep. The perimeter cut is only 1/2" deep, leaving 1/4" of material thickness at the bottom. This is for strength. I don't want the template to break if it bangs too hard against the pin.

Now each of these two Routing Templates will get attached to the underside of its own rectangle of plywood. They will become the two main Routing Fixtures for cutting the internal chambers of the AMB-2M body. One will cut the chambers into the inside of the top, and the other will cut the chambers into the inside of the back.

Does that allow you to make leftie basses too? Or are there other considerations there?

 

[Bruce Johnson]

Does that allow you to make leftie basses too? Or are there other considerations there?

That's a good question, but I think I've got that worked out. All of the internal chambers are the same in the top and the back, except two are cut to different depths. So I should be able to use these two fixtures to make a lefty top and back set, as long as I remember to reverse the depth settings on those two chambers.

After the top and back are glued together, the body will go into another fixture to rout the neck pocket, pickup opening, and a few other things into the top from the top side. That fixture will need to be reversible to handle lefty bodies. That may be a little tricky to figure out. It may be easier to make a separate Left Hand fixture.

 

[Bruce Johnson]

A note about cutting the perimeter of the bodies:

On the two Routing Templates shown above, you'll notice that I've routed 1/2" wide grooves all around the body perimeter, with the pin following the outside of the Master Template.

In my previous process, I would use the Master Template to pencil-draw the body perimeter on the inside of the walnut top and back blanks. Then I would use the collar routers and templates to cut all the internal chambers. When that was all done, I would bandsaw around the pencil line to separate the top or back from the waste wood around the outside. Then I would glue the top and back together, with the perimeter rough bandsawn. And use the edge sander to smooth it out. That process worked okay, but I often had to spend some extra time smoothing lumps out of the perimeter shape. The external shape was bandsawn to a pencil line.

So, now I have the pin router, and I'm already going to have the walnut blank mounted accurately in the cool fixture....I decided that I may as well rout the perimeter shape to a pattern while I'm there. I added the groove around the perimeter to both of the Routing Templates.

Now, after I finish routing all the internal chambers, I'll go around the outside and cut perimeter shape accurately. I can't cut all the way through, separating the top, because the pins holding it to the fixture are out in the waste wood. But I can rout it down to +1/16" depth, leaving just 1/16" thick wood holding it together. Then a real quick zip through the bandsaw to separate it.

When I glue the top and back together, if I've made my templates accurately, the perimeters should line up exactly. And they should be smooth and free of lumps and dips. That's the purpose of all this tooling: Less labor hours to build it, and less time spent correcting things.

 

[Roxbororob]

Bruce your processes & tooling are great. I especially like the sled with handles and your comments about respect for the power of big green machine when using large cutters. Back in the day my first real job was shearing then routing printed circuit boards all day long on various pin routers. The shop had two exellon CNCs at the time but both were devoted to drilling (I eventually moved up to programmer/operator before moving on). If the boards were thin we would stack several on the jig to save time (the thick Sperry Univac power supply boards were mean). My finger were wrapped in tape and I took so many chunks out of them its a miracle that I still have them all! Good to see you are not working like we did in the dark ages.

Well, I just thought I'd pop in and tell you how much I enjoy reading your posts!

 

[Bruce Johnson]

Back to the Scroll Bass body tooling:

The next piece I needed to make up was a template to cut the big radiused recesses around the F-holes on the insides of the tops and backs. This has to be done with a big 1 1/4" dia cove bit. Currently, I do it by collar routing. I have a big Porter-Cable router dedicated just to that job, with a 1 1/2" collar on its base.

I thought about switching this operation over to the pin router. But I realized that it would be a big waste of time to have to shut down the pin router, change the bit, and set up the depth. Then have to switch it back to the regular 1/2" bit for the rest of the upcoming cuts.

So, I decided to stay with collar routing for this one operation. It works well, and I already have the router all set up, sitting on the shelf nearby. So, I made up a new routing template with a 1/8" offset, with the accurate two template pin holes on the corners. That way, I can rout out most of the chambers on the pin router, then shut it down. Carry the big fixture over to the nearby routing bench. Plug the new template right on top of it on the two pins, rout the undercuts with Porter-Cable router, and pop the template off. Take the fixture back over to the pin router, and carry on with the rest of the operations. The walnut part stays mounted on the fixture the whole time.

I had to make up this template pretty much by hand. Same basic process as the Master Template. A rectangle of MDF, drill the reference holes, pin down the drawing, transfer the outline of the routed cavities with carbon paper. I drew in the 1/8" offset with a pencil and ruler.

I cut out the openings by the same process as before; drilled a couple of big holes, rough sawed them out with the scroll saw, cleaned them up to the lines on the spindle sander. Done.

Next up: I'm liking this pin router process enough that I decided to go ahead and make up a full set of pin routing templates for the full-size AMB-2 model while I'm at it. This will actually be less work than the AMB-2M, because I already have all the collar-routing templates. I can use those aluminum adapter rings that I made up to copy them.

The first thing, of course, is a new Master Template. That's the starting point for all the others. I want to make a Master Template that has all the internal cutouts for the AMB-2, like I made for the AMB-2M. I start with a blank of MDF, draw the centerline, use the old Master Template to drill the reference holes, and roughly bandsaw out the perimeter outline.

Here it is, partway done. I don't have to drill the holes and use the scroll saw; I routed all the chambers with the pin router. The blank is pinned to the top side of the fixture.....

...And the old collar routing template is pinned to the underside.....

I followed around the collar routing template using the 1/4" Offset (1" OD x 1/2" ID) aluminum ring on the pin, to zero out the offset. Making the chambers in the new Master Template on top the exact size.

Next, I'm going to rout the perimeter using the old Master Template as the template.

This is what pin routers are best at: quickly copying patterns.

 

[saltymonkey]

I love this thread! Thanks for taking the time Bruce.

 

[Bruce Johnson]

I love this thread! Thanks for taking the time Bruce.

Hey Bill;

Yep, your AMB-2M will will be one of the first ones made with this tooling and the Big Green Machine. I'm sure I'll be documenting it.

 

[Bruce Johnson]

I should mention this type of fixtures and templates would also work well with an Inverted Pin Router, like those Onsruds that several of you have. Same construction of the plywood plate and the long flat handles. Just reverse it, putting the template on top and the workpiece (body blank) on the bottom. Use the pins to keep everything aligned.

 

[coy garcia]

Hey Bill;

Yep, your AMB-2M will will be one of the first ones made with this tooling and the Big Green Machine. I'm sure I'll be documenting it.

Will u be doing the ssb also with that machine?

 

[Bruce Johnson]

Will u be doing the ssb also with that machine?

Hey Coy;

Absolutely! Coming right up is the tooling set for the new Walnut SSB body. A few changes to the design. I'm getting comfortable with the Big Green Pin Router, and I plan to use it for making the bodies for all of my basses from now on.

On the neck side of the business, I'm about to start construction of a custom neck shaping machine. I can't predict when I'll get it operational but, if it works, it will take a big chunk of hours out of making my Scroll Bass necks. I don't know yet whether yours will get on that machine, or be shaped by hand, as I've been doing for all these years.

 

[Bruce Johnson]

It's been a busy several weeks here in the Secret Underground Lab, but I finally got some time last night to continue on with the pin router template sets.

Here's the new Master Template for the full size AMB-2 body. I made this template, routing it all with the pin router, using the old collar-routing templates mounted on the underside of the big sliding fixture. It didn't take long at all. So, this Master Template, as it is, is exactly the shape of all the AMB-2's that I've built up till now using the existing tooling.

But, using the pin router, I can enlarge some of the internal chambers and bring them closer to each other. With the collar-routing, the templates with offset oversize cutouts got in the way of each other. I'm going to make the changes now, enlarging the chambers in the new Master Template. I've got the changes drawn on there in pencil. Tonight I'll cut them out the old-fashioned way.

While I was working on the Master Template for the full-size AMB-2, I realized that I screwed up making the previous AMB-2M template set! Somehow, through the whole process, I completely forgot that I've changed the design of the AMB-2 pickup. The new pickup is split into two halves, and requires a different larger routed pocket. I made up the AMB-2M Master Template and the two Routing Templates to the old design! I'm going to need to rework them to enlarge the pickup pocket and reduce the chamber behind it.

Oh well, it's fairly easy to modify and repair these MDF templates. I cut and fit an MDF block and glued it into the Master Template.

And then glued similar blocks into the two Routing Templates.

I'll fix them tonight. I'll hand cut the new shapes into the Master Template, then use the pin router to make the Routing Templates match.

And then I'll go back in the computer and correct my CAD drawing.