Making a Wooden Pitman Rod

 

Most of the old treadles used a wood pitman rod as the driver between the treadle platform and the drive wheel. After 75 to 100 years of use and 25 to 50 years of no care, they are often dried out and fragile, and break. Making a replacement pitman rod is a relatively easy wood working project.

Basically, all the pitman rod is is a wooden stick with two holes in it, connecting two moving parts. It's great if you have the original piece. Then you can measure the distance between the end holes and you know exactly how long your pitman rod should be. I happened to have a rather odd size treadle... a Singer industrial base that has been fitted with a home size drive wheel. This meant that no original pitman would fit it, so I had to determine a length before I could make one. This would be your situation if you don't have the original. This determination is pretty easy. Observe some treadles. Most have a nearly level treadle platform when the back of the platform is at the bottom of the cycle. Level the platform and put something under it to hold it. Now turn the drive wheel until the crank is at the bottom. Measure the distance from the center of the shaft or fastening on the treadle platform to the center of the crank... that's the distance you want between the holes in your new pitman rod. This will become clearer as you read through the instructions.

Note that the rod I am replacing here is already a non-original, which I made some years ago, in oak. I decided to replace it for the purposes of this project. Let's take a look at how I went about it.

1.

Here is an original pitman rod, broken. Because of the delicacy and age of the wood in the broken area, it is not readily fixed. Making a new one is a better bet.

2. If the pitman is still attached, you will have to remove it. At the lower end, this will usually involve removing a tapered pin, or a cotter pin. At the upper end, you will have to remove the adjustment pieces from the pitman rod, or break it off. It won't be possible to slide it off of the crank.

 

3.

Here you see the bottom fastening. In this picture, you are looking at a rod I made some years ago, so it is already a replacement. Note: the machine is upside down! You can see the shaft that comes through the rod, then a washer. The pin that you see sticking out from the bottom of the shaft is, if present, usually tapered. Do NOT try to drive it out from above! It is best driven with a small size nail set, or an old drill bit that has been dulled... some kind of harder steel. I show a nail here, which was not successful... it simply bent.

4.

The size of the replacement stick is basically 1/2" thick, by between 3/4" and 7/8" wide. Splitting the difference at 13/16" is geat if your table saw is accurate. You can go to a craftsman wood store and buy a small board 1/2" thick... I did. You can see the unused portion in the upper right of the picture below. Or you can plane one to thickness. The 1/2" dimension is fairly critical. You want a hard wood. I used maple this time around. The one I'm replacing was made of oak. Walnut would also be good. Don't use pine or softwood.

Here you see the new rod cut out... in this installation I determined that the correct distance between the holes should be 13". I marked those centers when the piece was first cut and was longer. Then I measured 1 1/4" from each hole center... that made my length... 15 1/2". I then bored a 1/2" hole at the two marked centers. I did the cutting on a table saw, and gave the piece a quick sanding with a belt sander.

  1. A word about drilling and bits. The best bit to use for projects where you want accuracy, smooth sides and no breakout is a Fortsnter bit. Few people have them around unless they are wood workers. A flat spade bit will work, as will simply drilling out the hole in gradual sizes with standard drills. The important thing is that the drill be in good condition... sharp and clean, and that the job be done well. Don't use a high speed hand drill. You'll burn the wood and ruin the drill. Use a drill press if at all possible, a slow variable speed drill if not, and if the latter, be very careful to get the hole perpendicular to the rod.

To the right is a picture of some bits: Forstner, flat spade, and graduated standard bits at 1/8", 1//4", 3/8" and 1/2".

6.

7.

Here is a close up of a Forstner bit... for those who have not met one previously. These are not cheap. A good 1/2" one costs about $12.

8.

In this picture you can see the drilling of a hole. in the new rod. I wanted to show the use of a piece of sacrificial wood under the rod. Whenever drilling wood, use a scrap to provide for the drill runout. This will save splintering and rough edges on the work piece.

 

9.

This is the crank end of the new rod. We have the 1/2" hole at the end, and down 6" from it, a 1/4" hole. (Note: the 6" was probably excessive... 4" would undoubtedly have been adequate). I have drawn a line down the center from the 1/4" hole all the way out to the end of the rod. This line will be sawn open, using a band saw with a relatively fine blade.

10.

Here the slot has been cut as described in block 9. I have placed it in a vice and am using a strip of sandpaper to sand the edges. Once the slot is cut, you will be able to open up the end of the piece to fit it to the crank. The hole at the bottom end of the slot allows the wood grain to adjust so the piece doesn't split.

11.

Here you see how the slot works... the end of the new rod is being slipped into place on the crank.

Before fitting the rod onto the machine, coat the inside of the 1/2" holes liberally with Singer motor lubricant or other grease.

12.

The new pitman rod in place. You can see what I meant about the length of the slot probably being overkill.

13.

The slot is much too sloppy to use as is... it must be held closed. You could do this with two small wood screws, or even two bolts with double lock nuts on them. One screw or bolt would be above the crank near the end of the rod, and one down maybe 1" to 1 1/2" from the crank. I chose to simply use plastic electricians tape, as being less damaging to the wood. The wood is going to wear, and occasionally you are going to have to adjust this tension. I have used the tape in the past and never had a problem from doing so.

14.

This is a close up of the bottom end, where the rod fastens to the treadle platform. Approved technique for making a rod calls for a slot treatment here the same as at the crank end, but with a shorter slot... say 2" to 3". Again, you would drill the smaller hole at the end of the slot. For no good reason other than to try something different, I did not do this. I just drilled the 1/2" hole and slid it onto the shaft. It is possible that later, with wear, I will have to cut a slot, but I figured this would be interesting to watch. Note the large washer between the rod and the cotter pin, which has been used to replace the original tapered pin, which is a pain in the posterior to get in and out. This washer is vital if you don't want the cotter pin to chew up the wood.

15.

The finished job. Check the tension... The tape should not be so tight that the treadle will not run on freely and fall to the bottom of its cycle from its own weight (see treadle rebuilding and adjusting instructions in The Sewing Machine Shop). If you have a problem with getting it too tight, try putting a very thin shim in the end of the slot to keep it from closing up too tight. Even though you greased the crank and bottom shaft, a few drops of oil there, and at all the bearing points of the treadle is now in order.

  1. Well, I hope this was more or less clear to you. Really, it amounts to getting the old pitman off, making a stick the correct length with correct size holes, and using the slotting technique to make it possible to fit the stick to the crank and to adjust the tension. You fit this new rod, adjust the tension, and treadle on!

 

Dick Wightman