Hi
Thanks Nick and SCC
We also need a blast nozzle and blower
This took a bit of studying to figure out how it works and how to make it so I'll give a little more detail.
Starting with a bit of phospher bronze bar, face and machine a 1/8" deep pocket and part off and finish to 7/16" as per the plan
Looking at the part it just didn't look right
. After some more studying of the plans it finally dawned on me that there is an error on the drawing. Good old Martin errors has struck again
The dimension showing the total height of 11/16" is wrong. It should be 13/16".
Start again and make the part the correct size
Using the same bar make the cap
Silver solder the two parts together
This makes an internal circular chamber
To cut the internal taper and tapping size hole for the 1/2" x 32 tpi I made a cutter. Starting with some silver steel turn the taper, the tap size and the 3/16" spigot to 1/8" long
Transfer to the mill and machine away exactly half the diameter
Heat to cherry red and quench in clean water. I didn't bother to temper it.
The part is mounted in the lathe and drilled through 3/16" followed by the custom made cutter
The cutter is advanced slowly until the 3/16" spigot just protrudes and is flush with the face of the part
Followed by the 1/2" x 32 tap
Now comes the 4 little jets. And they are small. Too small for my eyes
I have one of these little CO baby lathes. Too be honest they are in my opinion not that good for general work but where they do score points is the 3800 rpm they are capable of. So I dragged it out and donned some magnifying glasses.
The jets are made from some 5/32" brass hex. Turn down and thread. I have used M3. Drill the larger hole. Cut off and make another 3.
Chuck a bit of scrap brass, face and drill and tap M3. Each jet can be screwed in and with a hand ground cutter turned to profile.
With the tiniest of drills, which I could barely see, drill the jets
The body must be drilled and tapped M3 at an angle of 2°. I have a rotary table that tilts
Back in the mill to drill and tap 1/4" x 40 and silver solder in a bit of threaded brass that is centre drilled to form the cone
A few shots of the finished part
Cheers
Rich