The best screw wins

screwsOnce again I’ll start by saying sorry for the long holiday in the blog. The job searching is slow going and working full time in the shop doesn’t leave as much time at the end of the day for collecting my thoughts. On the upside, I’ve enjoyed some projects like adding cruise control and a spline lube to my K75 motorcycle.

BMWThis has been one of the colder winters I can remember here in the northeast but I welcome the warmer weather as I write this. Spring is a time for renewal, doubly so as the coffers are getting low. I look forward to finding some new treasures and the adventures that go along with them.

I did make it out to the midwest tool show, Cabin Fever, in January, and this year it truly was cabin fever as many of the members traveling from Ohio and the midwest were having their own winter wonderland. The weather is always an issue for this show but it did cooperate with cold temps while the snow held off till later in the day.

toolshowA good selection of tools was available and I was lucky enough to pick up a nice Atkins 400 and few Disston workhorses. In addition to the show I got the chance to catch up with friends. Mike had just picked up a really rare and early Disston backsaw that needed some handle attention.  I don’t often get a picture of me with others so I made sure to get one with the boys, Mike and David.

Mike asked for a quick turn on the repair for an up and coming show so the picture I have isn’t the greatest, but I was really happy with the final repair, as was Mike.

I’ve talked a little about this in the past but I wanted to revisit the one part of vintage saws that’s often overlooked – the screws. Most of us just divide them into two categories pre- or post- split nuts. That’s fine for conversational talk but when you get a little more technical, the time right around the end of the split nut, and what we currently find on saws, based off the Glover patent and later, commonly called a Chicago screw by some, was very active. Hand saws were being produced in high numbers and all the makers were looking for a better way to hold the handles to the plate.

The years preceding the split nut, say. . . mid-1870’s and pre-Glover mid-1880s, produced, in my opinion, the best looking and split the line between collectable and users among the best. Handles were often still quite detailed with hand shaped horns and wheat carving.  In my sale descriptions, I’ll call them “pre- or post- Glover patent.” From time to time I get questions as to what’s that about or in reference to, hence this post; so read on.

There are a number of good sources for patent dates and information, but to simplify things I’ll be using DATAMP or the Directory of American Tool and Machinery Patents. I’ll do my best not to plagiarize the hell out of them, but just understand that this is not new research or ideas that I’m taking credit for.

They have a number of good lists of patents and info. A complete list of the 9 saw patents can be found here but I’m just going to touch on a few of the more notable.

munger

The Munger Patent: Iff you look at the top of the bolt (male side) you can often see the ring where it attaches to the shaft. The shaft of the screws also tend to be very thin in comparison to the others. I tend to find them on Peace and Wheeler Madden and Clemson saws.

David T.Munger Dec. 21, 1869 Waterbury, CT
This was issued after the Washborne’s patent (what’s commonly known as split nuts). Construction differs in the use of a perforated disk that’s secured to the shank around the edge of the head and looks similar to the later Glover style screws at first glance. Looking closer you’ll note the threaded shafts are thinner, and looking at the screw top you’ll see the round center of shaft where it was connected. This patent is marked on several manufacturers; I mostly find them on Peace, Richardson, and WMC.

disston

Disston Patent Saw Screws: These can be tricky to tell when on the saw but once removed note the casting marks. Also note the square section on the bolt (male side) where it attaches to the head.

Henry Disston Aug. 29, 1876 Philadelphia, PA
The heads of the saw screw and nut are slightly domed and their outer edges beveled so that they flare outward toward the face. Additionally, the screw is received by a threaded socket in the tubular shape (female side of the saw screw). The tubular projection (female) may or may not be long enough to engage the saw blade. Disston expressed a preference for those which are long enough to engage the blade. The overall purpose of this patent is to allow the handle and the saw nuts and screws to be finished and polished prior to assembly. Remember that split nuts would have been sanded with the handle and installed before finishing the wood. The beveled underside of the edges formed their own seats in slightly undersized shallow holes in the handle. This allowed the saw screws to be subsequently tightened without altering appearances.

Saw nuts based on this patent were cast, unlike the Munger patent of 1869, which makes them more expensive to produce. Additionally, the shafts were relatively thin, so were prone to twisting off. In time, they would be superseded by Glover’s patent (375350).

So taking these two patents into consideration you can see the groundwork for the final design of the modern saw screw, aka Glover patent screw we all know. The Glover patent screw is an improved Munger design, just making the male side of the screw out of a single piece of metal like the Disston patent, but turning it from a single piece, as well increasing size and a few other improvements.

glover

The Glover Patent: The de facto standard chances are if the saw was made after 1890 you’re looking at a Glover saw screw. They do change in size a little bit over the years but over all they are beefier. Note the ridge on the lower section of bolt (male side) the ridges were used to hold it when threading and also helped prevent them from spinning.

Charles Glover Dec. 27, 1887 Hartford, CT
The final chapter: The primary focus of this patent is the two-part construction of the saw medallion (“label screw”). In a sense, it can be seen as an improvement on Munger’s patent (U.S.P.N 98180), which had no provision for preventing the shaft from twisting independently of the head if the swaged joint failed. This improvement was found in the Disston patent. The large surface of Glover’s medallion, in conjunction with the squared shoulder where it is seated into the handle, allowed it to resist turning.

The medallion (figures 2, 3 & 4) and the saw screw (figure 5) shown in Glover’s patent drawings both feature the internally threaded construction patented by Henry Disston in1876 181648. This form displaces the through screw and “split nut” arrangement which had been the norm. Glover’s saw screw differs from Disston’s by being formed in a die rather than being cast and having longitudinal ribs on the shaft rather than a square section to resist turning. Also, though not specified in the patent, the shafts of Glover’s saw nuts were of stouter construction. Glover’s form eventually superseded Disston’s.

Saw medallions with the Glover patent date have been found on saws from a wide variety of manufacturers and would eventually wind up in the hands of Disston after he dissolved the National Saw Company.

So with this in mind, the next time you’re out at the flea market searching for lost treasures, take a second glance at the brass nuts on some of the smaller makers, like the WMC, Peace, and Richardson Brothers, and I’m sure you’ll find some pre-Glover gems.

Cheers
Joe Federici
Jobber of fine handsaws

2 thoughts on “The best screw wins

  1. Thanks for the article! I have an 80’s No. 12 that was missing a bolt with a makeshift screw in it’s place. The nut is pre-Glover and fortunately not stripped out from the screw. Thanks to your article I was able to locate a replacement bolt that I’d previously removed from a “frankenstein” thumbhole D-8 that had parts spanning eras. It is a perfect match structurally and aesthetically. If I come across any more down the road, I may just send them to you. That’s what I was going to do with this one until I realized it fit my prize saw.

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