Sunday, May 8, 2016

Stanley No 12 blade holding screw

Brian Eve has bought himself a Stanley No 12, and the screw for holding the blade is bent.

He says that it still works, but it doesn't look too pretty. We have discussed the possibility of straightening out the thread, but in my experience those projects never work out really well.

So I offered that I could try to make a new screw for him on the lathe.
It greatly helps that the original is made out of brass, because turning stuff in brass is kind of like whittling away in balsa wood.

What doesn't help the project is that there seems to be comparatively little information on this particular screw regarding what type of thread it really is.
I compared Brians measurements with what information I could find, and I landed on a 5/16" 20 TPI (this time it is threads per inch, not teeth per inch as in a saw).

My next problem was that I have no idea if Stanley used the Whitworth system of 55 degrees threads, or if they used 60 degrees like metric standard thread.

A bit more searching on the Internet, and I decided that the American industries from a very early point liked the idea of having 60 degrees threads.

So armored with this information, I cranked up the lathe and made a screw.

Since I am in the middle of the North Sea, and the plane needing the screw is in Munich, I can't tell  if it was a success or not. We'll have to wait until I get home and can send the screw for actual testing.

But personally I think the screw looks nice, and I got to practice cutting threads on a lathe so that makes it a nice little project.

Stanley No 12 blade holding screw.


  1. That looks indeed very nice. Good work on the threads. I always have trouble with that part, mostly because I have not much experience and don't know what I am doing. Last time I made some threads for a wooden filister fence screws, I found that I had to advance the chisel both inwards and a little to the left on each succesive run to gradually reach the total depth. But your threads a re very small, do you cut them in one run?

    1. Hi Kees.
      Thanks for the nice comment.

      During my workshop training (1 year) in the beginning of the engineer education I did a lot more thread cutting, so I have been formally taught how to do it. But I haven't practiced it for a while.
      Your method of advancing in and to the left is correct.
      I think I made four or five passes to get to the correct depth, and then finally I took about three passe at the same depth, each time advancing to the left. This is to make the "hills and valleys" the same width.

      I think my most challenging thread job ever was a spindle with double trapezoidal thread meant for the brake system on an anchor winch. The length of the thread was around 100 cm, and the total length of the piece to be turned was 140 cm. Looking at a thread like that is hypnotizing.
      I think the pitch of each thread was 28 mm/revolution.


  2. Wow! It looks great! I wouldn't know where to start with a project like making this type of screw.

    1. Thanks.

      Well it is kind of like making a chicken pie - first you get a chicken..
      Jokes aside, I started setting the lathe up to be able to cut inch based threads, which meant altering the way the sprockets are connected on the end of the lathe.

      Then it is basically the same as a woodworking project, find some stock, roughly dimension it, get the dimensions to teh exact size and finish it :-)

  3. Stanley used a Whitworth Standard thread that was common in England around the 1850's.
    The pitch and angles are specific to Stanley.

    1. Hi Superdav

      Thanks for the information on the threads for the different parts.

      It would greatly help to have an actual plane to test the threads on, after all it only takes a little amount of material to make the screw bind in the thread. And the lathe we have here isn't exactly a Colchester or a MAS.


  4. Cap Iron screw : 5/16" 18tpi BSW (I believe this is the only standard BSW thread on benchplanes)
    Frog screws : 7/32" 20tpi Whitworth;
    Tote & Knob bolts : 7/32" 20tpi Whitworth;
    Tote Toe screw : 7/32" 20tpi Whitworth;
    Frog Adjusting Plate screw : 7/32" 24tpi Whitworth;
    Frog Adjusting screw : 1/4" 24tpi American/Unified;
    Brass Adjusting nut : 9/32" 24tpi American/Unified (left-hand thread);
    Lever Cap screw : 9/32" 24tpi American/Unified.