I have the picture of the jig. As mentioned before some extra holes can be seen in the plate and the reason is that I used a piece of scrap aluminum. The rectangular slot on the left is for the first setup and the one on the right with the shape of the hammer spur is for the second setup. The swirls that seem in 3D are just optical illusions caused by the machining pattern because the floor of the cavity is perfectly smooth and flat except for 2 small bosses.
The following picture shows the brass stock placed in the jig for the first setup. The clamps are fairly large compared with the bar to be machined.
Here the first setup is finished.
The part is flipped around for the second setup. Since there was material removed between the head and the main bar during the first sequence of operations, the head might want to curl up. This is the reason another clamp was added at the top.
The second setup is finished. It might be difficult to see but only 2 small tabs are still connecting the hammer to the main bar.
In the close-up, the view of the two tabs is clear.
They are easily broken to remove the hammer from the stock. There is only a bit of deburring to do to remove the sharp edges and to file down the two small stubs. Basically, except for the built-in pins, this hammer should be identical to the one which is in my pistol. Again this part is untested because I didn’t want to unnecessarily reopen my 451 since it is working fine.
To give you an idea of the time involved in the preparation of the CNC milled part, let’s say that from my hammer model (already existing) it took me about 2 days to be ready to machine.
This includes finding the stock for my jig and my hammer, then thinking about the machining strategy, deciding which tools I will use and establishing the toolpaths (for the jig and both hammer setups).
For the machining itself, it took me another 3 hours to output the G-Code, transfer it to the memory of the CNC mill then I had to load the tools in the carousel and adjust the Z offset. At this point, the jig was machined, the stock installed for the first setup and finally flipped for the final setup. This was for the first hammer.
The subsequent ones will probably takes a bit over half an hour to machine but will still require some finishing touch by hand such as deburring and removing the tabs.
I am not sure of ongoing CNC machining rate as we are not involved in commercial production but I suppose that $100/hour is probably realistic. A bar of brass of 1/2″ x 1″ x 12″ is about $40 (maybe $50 or more after shipping is included) and I think probably 5 could be made in that length so it would be about $8-$10 for the material for 1 hammer.
Adding the machining time, basically it would be around $60-$70 for one hammer if nothing else is calculated, but all the program development time (15 hours with the model already existing) has to be amortized somewhere. It quickly becomes prohibitive, so this is the reason why I think that being able to make ourselves a single copy, using relatively basic equipment, is the way to go.
If you have a Crosman 451 with a broken hammer, you cannot make it worse. Consequently you have nothing to lose in trying my method. The possibility to be able to enjoy shooting your 451 for years to come will easily offset the day you have spent in your garage making your own hammer.
It will still cost you a little bit but if you could find some small scrap 1/4″ and 1/8″ plates it shouldn’t be too bad. On top of that you will need a few spring pins and you are on the way to restore your treasure.