The Smyth book sewing machine is an extraordinary device

For over five years I have been working to restore a 1935 Smyth book sewing machine. You can read several posts on that topic here, mostly related to the mechanics of getting the machine running after a long dormancy, and subsequent electrical and electronic improvements to get the machine turning again.

The machine is part of the collection in the Shakespeare Press Museum at California Polytechnic State University in San Luis Obispo, California.

I had declared in one of those posts that I had succeeded in getting the machine to work again. This was not entirely correct. I had the machine making single rows of chain stitches using its needles only. It was not making the cross-threads inside each signature, nor the chain stitches that run parallel to the primary stitches. At the time I was unconcerned that it wasn’t behaving perfectly. At least it was behaving.

My unconcern was rooted in the fact that there was no demand for Smyth-sewn book blocks in our department. No one was hankering for this service. This despite the fact that Cal Poly teaches a class called Book Design Technology where students learn how to sew and bind books, and they study machine sewing and binding in the process.

The instructor of that class, Prof. Donna Templeton, asked me late last year to demonstrate the machine for her students. I did so, but I was frustrated by not being able to demonstrate it working perfectly.

Dr. Templeton asked me, in January of this year, if I could get the machine working in time for the students in our TAGA chapter to use for their annual technical journal production. I said yes. (TAGA is the Technical Association of the Graphic Arts.)

Then I began the process of troubleshooting the 90-year-old machine to solve the stitching problems.

I have the instruction/parts book that came with the machine. I read it from cover to cover. I attempted to adjust the variable settings on the machine, and I tried numerous times to get the parallel stitches to work. It didn’t respond.

Then I dug in. I knew the machine inside and out, having disassembled and reassembled most of it, after it arrived in the museum. I understood in principle how the sewing process works, and I had visited a bindery in Los Angeles County to see their machine, one identical to ours, running. I took photos and videos, and I had an hour of training on the machine so I could operate it.

Back in the museum I sat, frustrated, in front of it, feeding folded signatures into the machine, and having it poke holes and stitch single rows of thread through the spines of those signatures. The signatures were not sewn firmly together, nor would they stay together after they were sewn.

I tried to understand the thread tension adjustments, thinking that I could make successful book blocks by tightening the tension. That didn’t work. I read the troubleshooting guide in the original manual to no avail. It was just not working correctly.

Eventually I removed all the needles and crochet hooks from the machine, and figured out how to remove the punches (see the illustrations for more on these components). I scrubbed all the parts and surfaces with solvent. With these parts now sparking clean, I started over, putting new needles and crochet hooks into their blocks. I put the original punches back also, being careful to place them opposite each needle or crochet hook (this is essential). Once I had them all lined up, I tried again to sew book signatures. The machine refused my efforts, continuing to make rows of straight chain stitches and no more.

So I stared at the machine. And stared, assuming that I would eventually see what was wrong.

At one point I disassembled the saddle mechanism again so that I could analyze the operation of the needles, hooks and punches. Inside the saddle is a component called the Loop Hook Bar. It carries eight loop hooks across against the back of the needles. The purpose is to snag the thread from each needle and carry it over to the right, then hang that thread on one of eight adjacent crochet hooks.

I turned the machine by hand, observing the Loop Hooks as they moved from left to right. I noticed that they were not hooking the threads at all. They were arriving too late; they moved to the right, then retreated back to the left, leaving the threads on their respective needles. I couldn’t figure it out.

The Smyth machine is cam-operated. The machine has a common driveshaft that runs through the center of the machine, and on that shaft are nine cams, each about 14 inches in diameter. Some of those cams have patterns cut into their faces; some have patterns cut into their rims. Some have both. One of those cams causes the needle bar to descend into the spine of a signature, then to pull the needle bar back up, lifting all of the needles and their threads back out. Another drives the Loop Hooks left and right.

My observation was that the Loop Hook Bar was out of time with the other parts of the machine. It was arriving late and retreating early. I crawled on the floor with my brightest flashlight and examined the operation of the cam that operates that bar. It was the only one that made sense. I loosened its setscrews with a socket wrench, and attempted to rotate it relative to the other cams. It wouldn’t budge.

While down on the floor I noticed that all of the cams on the machine are keyed to a common key-way that runs along the main driveshaft. Each cam has a setscrew that is tightened into the key-way. In theory, if each cam is aligned with the key-way, the machine cannot be out of sync.

The machine was confounding. It refused to work; it refused to be in time, and thus it would never sew the parallel lines of stitches that make Smyth-sewn books so sturdy.

I made another trip to Los Angeles to visit a book bindery where there is a working Smyth machine. This one is younger than ours. It’s a Model 15 (ours is a Model 12). It was probably manufactured in the 1950s. Its serial number is in the thousands. Ours is in the hundreds. I was allowed to take plates off and look at the workings of this machine; I stitched a couple of book blocks. I took photos and videos, and I brought samples home that I had made on that machine.

I readjusted our machine and studied its behavior. It was just crazy. It did everything out of time, with the punches coming up after the needles retreated.

Pressure: I am working on a deadline here. The students’ books must be sewn in the next week. The machine must work in time for this project to be completed. I was on hooks and needles trying to solve the problem (the traditional phrase was pins and needles, but this is close enough).

I stared at it, and studied its behavior again and again. I was stumped.

At one point I was inching the machine through its steps, and the Loop Hooks missed again. I backed the machine up to see it more closely. I turned the handwheel forward and backward. And when I turned it backward a second time I realized that the timing was correct when I turned it backward!

Was our machine running backward?

I inched it backward a few times and observed that it worked correctly when in reverse. This was entirely my fault. I assumed that the machine (and its handwheel) turned clockwise when running. I wired the motor to turn clockwise. And I have been running it clockwise for several years now, and it has not been sewing books correctly exactly that long.

I had never observed the rotational direction of either of the two working machines I visited. Both of them in fact operate with the drive wheel turning counter-clockwise! Since I had never seen a Smyth machine run prior to installing the new motor, I assumed that it would turn clockwise. Why would it not?

So (or sew…) this morning I rewired the motor to turn counter-clockwise. That took just minutes (three-phase motors can be made to run in reverse by switching any two of the three power wires). I started it up, and it now turns counter-clockwise.

I carefully checked the position of all the needles, crochet hooks and punches, tightened everything and cleaned all the handling surfaces. Then I turned it on and fed a signature into the machine. The punches come up through the spine; the needles and crochet hooks then come down through the holes made by the punches. The Loop Hook Bar slides from left to right, catching all of the threads (all but one in my case) and pulls them over to the crochet hooks. Then the Loop Hook Bar returns to the left, and the needles and crochet hooks retreat upward and out of the signature, carrying the thread with them.

It works! For the first time in our possession of the machine, it works!

I stitched a handful of signatures, checked the tensions, and made a few more book blocks. My second-from-the-left Loop Hook needed to be adjusted. I did this by loosening the screw that holds it in place, and I stuck a tiny piece of tympan paper behind the top half of that hook, and tightened it again. That moved the hook 0.003 inch closer to the needle, allowing it to snag the thread successfully. And, with this small adjustment, I made the machine work. All six threads are being captured, all are being lifted and twisted, and all are being chain-stitched to the next signature. It’s very satisfying!

Addendum March 11, 2025: The TAGA students did have their books sewn on time! We gathered all the signatures, prepared the Smyth machine by setting the width of the books and the depth of the delivery table, and we started sewing.

Almost immediately, we had a strange mis-feed, where the front half of a signature folded up and over the previous signature, and we broke three crochet hooks. Ouch! We also bent a needle. I replaced all of these and we started again. Soon, we were sewing signatures again, and it was running quite well. We had a total run of 50 books, and we made it through the first 35 before we had to quit for the day. We will begin anew tomorrow, and we’ll finish the project.

We are applying a thin coat of bookbinder’s glue (PVA) to the spines immediately after we take them out of the machine. We found that this helps to prevent the unraveling of the chain stitches that can happen with this kind of sewing. (The Smyth machine we have included a built-in paster, which I removed; since we are not a full production shop, I didn’t want to have to deal with paste on the machine, and the clean-up after a run.) I kept all the parts in case I ever need to replace it.

I will post more after we finish the project.