Leaving no stone unturned.
After enjoying some time shooting my Crosman 451 equipped with my custom hammer, I was still a bit dissatisfied.
Not with the airgun (since it is working perfectly with the parts I made) but with failing to achieve my initial goal. The idea was to provide other owners of a Crosman 451 (who may already have a broken hammer or would like to take preventive measures to avoid a breakage) with the information necessary to make a replacement hammer with a minimum of equipment.
In all the previous iterations in my research for a working geometry, I had to use some equipment that was not my own.
In the first case, it was the metal band saw of a friend and in versions 2 and 3, it was a specialised piece of equipment (waterjet cutter) from work.
In these two installments I am planning to cover both extremes. I will make two other hammers. One will be done according with my initial parameters but the other will be at the other end of the spectrum and will be made on a CNC mill.
My simplest approach will only require a drill press, a metal hand saw and a few metal files. A Dremel tool could be a useful addition if available.
For this test I decided to opt for brass instead of steel. It is a fairly hard metal (at least a good deal harder than aluminum), it is also heavy but it is fairly easy to shape and machine.
Based on my working hammer, I created a new computer model for my chain drilling template then I printed both versions on a piece of paper. The first step is to glue the paper to the brass stock with double faced tape.
This should be a single day project. It took me about two hours to centerdrill and drill my quarter inch brass plate. Unless you have a very good punch, centre drilling cannot be avoided. I rarely do a lot of drilling in metal by hand as I have access to a CNC mill and I had forgotten that brass is a little tricky. The bit has a tendency to grab when it starts and also when it breaks through. A wood backing can help as well as holding the piece in a drilling vise. It is possible to do the job without both items since I did it, but you will need to be extra careful.
After the drilling operation is completed, the paper template can be discarded and the hammer must be separated from the main plate. It would be easier if a Dremel tool with a cutting disk is available otherwise a hand saw with a metal blade will do the trick (at a slower pace).
The next step is a critical one as the other paper template (shape of the hammer) must be cut with an X-acto knife to be positioned correctly over the separated piece of brass and glued with double faced tape.
Again, if a Dremel tool with a grinding stone is available, it will make life easier but a few good files will do the job.
The critical contour areas are at the bottom around the teeth, all the other spots are pretty much forgiving. It took me about 2 hours and a half for the shaping. The result is not too bad but the hammer is a bit skinnier than it should be. To remove all the drill marks I had to file down a bit more that I expected.
If I had to redo it again, I would either offset the chain drill guide or if I used the same template I would simply use a smaller drill on the same center point. This will leave a bit more meat and the drilling marks could be filed off while stopping on the guide line.
This is the same approach as my previous ones where there is a main core and two thinner plates to thicken the head. For my exercise, I didn’t make them but I guess it would be another couple of hours.
I should also warn you that I didn’t disassemble my pistol to test this version in it. There is no reason why it should not work. I think the best strategy would be to leave some material in the teeth region and make the adjustment by testing the interface with the other components once your pistol is opened.
Next time: making a CAM version of the 451 hammer.