Pin Routers: The Old-School Production Workhorses

It's time to start a thread about pin routers. I personally have very little experience running them, but I now suddenly own two of them. A giant green monster, and a little tabletop model. Keith and I are going to start working with them, building the fixtures to use them for some of our production steps. It's going to be a learning experience, so I'm going to document it here.

Any of you who own a pin router, or have experience running one, are welcome to join in with your ideas and knowledge. Most Luthiers have heard of pin routers, but don't know much about them. I don't either, but I'm going to learn. I want to see what these machines can do.

Here's the big pin router. It's a monster. 3000 lbs; 7 1/2 horsepower. (Correction: 10.6 horsepower!! See below)





I acquired this machine from the estate of my buddy Mike Lipe, who died unexpectedly in December. I have a long history with this machine, maintaining it for Mike for many years. The whole story about it is on my thread Inside The Secret Underground Laboratory, Page 14, Post #268 and Post #272.

Inside The Secret Underground Laboratory

Over this weekend, I finally got the time to clean up and reorganize all the stuff around it, and to hook up the 3 phase power and air line to it. The Big Pin Router is now up and running and operational in my shop! It was glorious to hear that whine again, as I ran it this afternoon.

The other pin router is at the opposite end of the scale; a small bench-top Router Mate machine. This one also came from Mike's estate. He had it in his home shop, and used it for small trim operations. It's not heavy duty enough to be of much use making bodies or necks. I put it up for sale on CraigsList for a while, but got no nibbles.

Then one day Keith and I were talking about how messy it is routing pickguards, with our usual hand routers. So, we got the idea of keeping this machine, and making into a special machine, just for cutting pickguards. We both use pickguards on most of our models, and frequently need to make them. It would be cool to have a dedicated machine, ready to go any time.




As you can see, it's a simple little machine. A Porter-Cable router head that raises up and down pneumatically by the foot pedal. A simple cast iron C-frame. I set it on this old steel cabinet on casters as a mobile base. More on this machine later.

 

On the other thread, TB'er Teacher asked: What is a pin router, and how does it work? Here's a repost of my answer, with a little more detail:

Hi Teacher;

Pin routers have been around for a long time. I'm not sure when they first appeared, probably in the late 1800's, but they became the mainstay for woodworking in factories from the 1920's up through the 1990's, when CNC routers started replacing them. In those days, the pin router was the fastest way to make 2-D shaped wooden parts, with repetitive accuracy. Fender's factory had a hundred of them in the '60's. Up until recently, most of the operations shaping a guitar body or neck were done on a pin router.

A pin router is a 2-D pattern follower. The basic design is a large rigid C-frame and a flat table. On the upper side of the C-frame is the spindle, which holds the router bit and spins at 10,000 to 20,000 rpm. Think of it as a hand router mounted on the end of big sturdy arm. On the bigger machines, like this one, the spindle is driven by a belt drive, and the motor is mounted back in the frame somewhere. A belt drive that can transmit 7 1/2 hp to a spindle going 20,000 rpm is a scary thing! The belt itself is called a Panther Belt; it's about 2" wide and 1/16" thick, and costs $195. We've blown two of them over the years.

Inside the big green housing is a steel frame that holds the whole spindle assembly and bearings, the motor and the belt drive. That whole assembly weighs several hundred pounds, and it raises up and down about 3" by two synchronized pneumatic cylinders. With a foot pedal on the floor, you can make the the spindle raise up and down fairly quickly. At the down position, it's stopped against a rotating turret of adjustable stops. Working the pedal looks like it's just moving the spindle, but actually, the whole subframe inside is moving up and down.

Here it is with the top cover open, showing the whole internal assembly raised up and lowered down:





You can see the Panther belt is on the lower pair of pulleys, which runs the spindle at 20,000 rpm. On the upper pair, it runs 10,000 rpm.

That's the upper half of the machine. The lower half is a big flat cast iron table with a steel pin in the middle of it. The pin is accurately and rigidly in alignment with the router bit right above it. The pins are interchangeable, and normally, you use a pin that's the same diameter as the router bit that you are using for the job. There's a small lever under the front edge of the table which retracts the pin down below the table top surface, or pops it back up. The entire table is mounted on an elevating knee, like a milling machine. That's the big crank that you see under the front of the table. It raises and lowers the table precisely over a couple inch range, and locks. That's used for the fine adjustment of the cutting depth.

So, how does the whole machine work? Suppose you want to rout the control cavity in a bass body. Or, a hundred identical bass bodies stacked up on that pallet. You build a fixture, a big flat wooden thing that slides around on the table surface. On the top side of the fixture are cleats and lever clamps to lock the body down in an accurate position. On the underside of the fixture is a slab of 3/4" MDF with an actual size cutout of the control cavity shape. That template is accurately lined up with the clamps and cleats above, to get the control cavity in the right position on the body. The pin fits up inside that cutout on the underside of the fixture. As the router bit is cutting, you manually slide the whole fixture around on the table. The pin inside the cutout sets the limits of movement and creates the shape of the control cavity.

As the worker in the Fender factory, you start with the spindle raised up and the pin retracted down. Grab a body blank from the stack, set it into the top of the fixture, and lock it down with the clamps. Slide the fixture over underneath the spindle, and flip the lever to raise the pin up into the cavity on the underside of the fixture. Click the turret stop to the first depth position, and hit the switch to fire up the spindle. It whines up like an aircraft engine.

Hold securely onto the fixture, take a deep breath, and tap the foot pedal. The spindle drops down and the router bit ploughs down into the wood to the depth set by the turret stop. Do Not let go of the fixture! Slide the fixture around by hand, carving out the cavity, feeling the perimeter of it by the pin riding around the perimeter of the cutout on the underside. Streams of wood chips arcing up and away. When it's all cut away, release the foot pedal and the spindle raises up. That's the first pass. Click the turret stop to the second position and tap the pedal again. Go around again at the second depth. Repeat until you finish the last pass, at the final depth set by the turret stop. Release the pedal, the spindle goes up, flip the lever to drop the pin, slide the fixture off to the side. Unlock the body, set it on the stack, grab the next one.

That's what a pin router is for: Fast repetitive woodcutting in a production environment. If the fixture is made well, and the operator has decent training, parts cut on a pin router can be just as accurate as on a CNC machine. And almost as fast. Of course, a human operator has to run a pin router. The human is doing what the computer does on the CNC router; hitting the buttons and steering it around.

The key part of the speed is horsepower. This pin router has 2-4 times the horsepower of a hand-held router. It's capable of routing that control cavity in maybe 3 depth passes, instead of 6 or 8 that you'd need with a handheld router.

The little Router-Mate pin router basically works the same way, but without the massive frame and horsepower. The pin is fixed in the center of the table (removed in the pictures), and the router head moves up and down with the foot pedal. Operation is the same: the template rides around on the pin, and the cutter matches it.

 

By the way, I have a third pin router which was given to me for free by a Luthier who quit the business back around 2001. It was going to go to the scrap yard so, of course, I took it! I've had it all these years and haven't put the time into it to get it back together and running. At my Burbank shop, it was outside under a tarp. When I moved to Fillmore, I debated getting rid of it. But I found a spot for it. It's still sitting in pieces.

This is an Onsrud RO-117, a medium size overhead pin router. It weighs a mere 2000 lbs, and has only 3 horsepower.





It's an overhead pin router, like the big green one. The spindle with the cutter bit is on the top side of the big C-frame. The motor is in the back, driving the spindle by one of those Panther belts. Here, the front head that holds the spindle and bearings is removed from the front of the frame. It's all disassembled in a box nearby. The previous owner took it apart to change the bearings and couldn't get it back together again.



On this pin router, the spindle doesn't move up and down. The whole table moves up and down via a big pedal assembly down at the bottom. It's a complicated mechanism which raises the table up against an adjustable stop, while a smaller sub-pedal raises the pin in the center of the table. The pedal assembly is detached and tilted up here.



There's no pneumatics on this machine. Here's a picture from the web of one of these machines all put together. You can see the table-raising mechanism.



I'm not sure what I'm going to do with this machine, especially now that I have the big green one. One thought was to slow the spindle down and fit it with a Saf-T-Planer cutting head. Make it into a dedicated planing machine.

Another thought is to make up a 2-axis X-Y table for it, driven by leadscrews and servo motors, and a computer. Convert it into a simple 2-axis CNC router. It's already got the strong frame and powered spindle. That would certainly be a useful machine for the shop.

Onsrud is/was the biggest manufacturer of pin routers. They made many different models and sizes. Most of the guitar factories had Onsruds. They are still in business, these days mostly building big CNC routers. Of course.

Onsrud also builds Inverted Pin Routers. On this style of machine, the spindle and cutter are down in the table, and the pin is overhead on a much lighter C-frame arm. Pneumatic cylinders raise the spindle and lower the pin by a foot pedal.

The operation is pretty much the same, except the workpiece is on the bottom, facing down. The template is on the topside, where the pin follows. I've heard that the inverted configuration is a little better for small shops and one-off jobs. The overhead machines are better for heavy production.



These inverted pin routers are popular with small shops and home shops. A smaller, lighter, less expensive machine. Not as powerful or fast as the big overhead machines, but these will do a nice job on instrument bodies and necks.

 

I was just looking close at the nameplate of my big green machine. I was thinking it was 7 1/2 horsepower. It's actually 7.6 Kilowatts. Which is 10.6 horsepower! Yow! No wonder my shop lights flicker slightly when I power it up. I'm going to have to go back and re-check my wiring.

Can you imagine trying to hold on to the torque of a 10.6 horsepower router? That's why it weighs 3000 pounds. I'm sure that, with a heavy enough fixture, it could plow out a control cavity at full depth in one pass. Not me, I'm not going to try that.

I'm going to treat this machine with some serious respect. It's the most powerful machine in my shop.

 

Yes, that's a nice looking mid-sized pin router. A good size/weight/price for a home Luthier shop. Several other companies including Grizzly sell machines that are nearly identical.



For two years, Mike was sharing a shop with another Luthier who had one of these Grizzly machines. The big green machine was in storage in a shipping container at that time. Mike used this machine, and I helped him with technical issues with it a few times. Not real powerful, but it did the job and was sturdy and well built. And a practical size for our work. I remember thinking that I wouldn't mind having one.

This is about the same machine as your Delta, right?

 

Me? I haven't built any tooling or really used the big green monster yet! That's coming up, to be documented on this thread. I'm also going to start out by making up some guards for it, for safety and dust collection.