A Brief History of my screw making efforts

The following post gives an overview of the development of the wooden screw making methods I’ve developed. Along with the tools and methods and how they evolved I will provide a more personal story line for those who are interested.

Above are the first taps and dies that were made using the 1977 Fine Woodworking article. In this approach a tap is first made which is in turn used to make the die.

I have always been fascinated by mechanical things and was immediately drawn to this FWW article. I didn’t actually attempt making the tools until the early to mid 1980s when I was living in Madison, Wisconsin. My spouse, Pati Scobey, (www.patiscobey.com) was in grad school at UW-Madison studying under Warrington Colescott and Walter Hamady. Book Arts were a major part of her studies which encouraged me to pursue paper mould making and making bookbinding tools. We rented a small house next door to Ace Hardware on ‘Willy’ Street which was very convenient for an aspiring inventor.

The screws made with this tool were not very satisfactory. I was looking for a dependable way to make high quality wooden screws so that I could produce book presses for sale. At least half of the screws were unusable with badly chipped threads. I put my screw making ambitions on hold for a few years and concentrated on making paper moulds.

Around 1996 I was asked to teach a workshop at Paper and Book Intensive. By this time we were living and working in Michigan. (I had already taught a workshop in paper mould making for PBI in 1991.) As I recall I received a phone call from Pam Spitzmueller inviting me to teach and it was she who suggested the subject of making finishing presses for bookbinding. Soon after that I received a call from Tom Conroy (who I had never met) who generously offered a lot of very good advice about what makes a good bookbinding press. He also mailed me copies of his extensive notes and drawings and a copy of an article by Derek Beck which I found particularly helpful. (Derek Beck, New Bookbinder, Issue 1, 1981) What seems amazing in retrospect is that I agreed to teach this class without actually having any workable tools and methods to make wooden screws! I was 41 years old; evidently still young and foolish enough to give it a try. It worked out OK though.

This contraption was my next attempt at making good wooden screws built with the idea of using it for the upcoming class. It is a sort of hand powered machinist’s lathe complete with a lead screw. By changing the chain sprockets it was (theoretically) able to produce threads of several different pitches, including two, three and four threads per inch. Friction (a lot of it!) was a major problem as was excessive ‘play’ in the lead screw propelled tool post. However I was able to make 3 wooden master screws (in the foreground) which became essential parts in the next attempt. As it turned out these wooden master screws were used to make hundreds of screws before they also became obsolete.

Another view of the lathe and the master screws produced on it.

This is the first tool that could actually produce very nice wooden threads. This is one of two ‘threading frames’ that I took with me to Penland in North Carolina to teach the PBI class. As you can see the master screw is made of wood. I had discovered the method of making a two part cutter by this time (very exciting!) and the method used here is basically identical to what I still use. Since then it has been a process of refining things to make the same process easier and more reliable.

The 4TPI threading apparatus shown along with the original taps for 4TPI and 3TPI threads. There was also a larger tap for tapping a 1-3/8″ diameter hole for a small lying press. And there was another 3TPI threading frame that could make both 1-1/4″ 3TPI threads and 1/5/8″ 3 TPI screws. I still use all of these pitches and sizes. We used the same router lathe that is pictured in previous posts. The process was very successful; we made a lot of presses. But it was slow; the threading was driven by hand with the knobbed crossbar and the router lathe was hand cranked.

Now back at home in Michigan I knew that I could make good wooden threads but I wanted to speed things up a bit. The next idea was to drive the tap and die with a bit brace. With the die the bit brace was mounted in a wooden rack that traveled along on ball bearing drawer glides (not pictured). The tap could be driven by hand with the cross handle or with the bit brace by means of the bolt head on top. This turned out to be a brief transitional phase as it soon led to the next step (below).

The next advance was making this ‘universal’ threading frame. It was designed so that dies and master screws could be switched out to produce any pitch wooden screw. As you can see the original parts of the first threading frame have been ‘cannibalized’ to make this tool which functioned quite a bit better than the one before.

I made a lot of wooden screws using this set-up. The original wooden dies were capable of making great threads but wear from use was a constant concern. As the parts of the die wore down the adjustment of the thread had to be closely monitored so the thread would be well formed.

For the wooden master threads to work well they had to be firmly fitted to their nuts without any play which would have caused a badly cut thread. This made for quite a bit of friction. I can’t remember when I thought of switching to steel master threads but it was a wonderful solution. The friction decreased a lot making the screw blank much easier to drive. And there was no significant play to worry about. They aren’t cheap but their use transformed the threading apparatus into a very efficient hand powered production tool.

Steel master screws with matching brass nuts.

I kept the wooden master threads lubricated with beeswax which built up at the margins. You can see the paper shim added to reduce ‘side-play’ which if excessive causes the thread be ruined.

The ‘half nut’ which was tightened against the master screw (loosened here).

Inside the ‘nut’. Wear was always a concern.

The last step was to re-think the design of the dies. The original dies controlled the thread depth by adjusting the position of the cutter in relation to the ‘hole’ (slot) n the die that the blank passed through. These were simpler to make but more complicated in use (than the later design). The screw needed to be held firmly against the back of the slot by the pressure bar on the left. The depth of cut was controlled by the ‘eye bolt’ at the bottom right. Each time the eye bolt was adjusted the other wing nut needed to be re-tightened. And for reasons too complicated to relate here the pressure bar needed to be constantly re-tightened too. (The pressure bar surface and die surfaces wore unevenly due to the multiple passes of the screw being formed as the thread became progressively sharper. I hadn’t started using very hard HSS wear bars.)

Another view of the die.

Parts removed to show the structure of the original die.

The pressure bar on the left (here slightly opened) would press on the surface of the screw blank to keep it against the back of the slot. The cutter mount (on the right) would be adjusted IN RELATION TO THE BODY OF THE DIE (compare with below).

The new style die pictured here turned these concepts ‘on their heads’. In it the cutter is mounted in a shutter that is adjusted IN RELATION TO THE SURFACE OF THE SCREW BLANK. An adjustment disc (see other posts) has a dual function of both controlling the depth of cut while at the same time pressing against the screw blank to hold it in the slot.

The culmination of years of incremental progress. Here is my current threading frame including the die pictured above and steel master screw.

The last step of all in ‘perfecting’ this method of wooden screw making was the master screw driven tap. It also makes for a much more efficient method than what came before in producing the internal threads. It is very dependable and low maintenance.

Summary

The process for making wooden screws that I’ve presented in the previous dozen or so posts is the culmination of many earlier efforts, including many mistakes and a few dead ends not covered here. Only this last method using a combination of ‘off the shelf’ steel master screws and fittings along with custom made dies really achieves a workable method of production for a small ‘cottage industry’ making wooden book presses or other similar tools. I’m getting a little weary of making big batches of things and more interested in having fun advancing the craft. I hope that someone else might build on what I’ve learned.

One thought on “A Brief History of my screw making efforts

  1. Tim,
    Excellent; you have set in motion a never ending story. Your brief history comes close to describing the industrial revolution. I wonder if the next post will be ” A Brief History of Book Repair Press Design”. I was able to covert the post to a PDF page layout and now I am visualizing a revisualization print-out of book making. This is a story for the ages.
    Gary

    Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: