Making a Paintball Gun from Scratch – The Build

Once Brian had gotten his design work fairly completed, we knew it was time to dive in and start our construction. I got a free weekend and headed up to Brian’s for a long day of trial, and hopefully not too much error!

We decided to start work on the smallest and most simple part to sort of “get our gears turning” on the lathe. 😉 This part was the bolt stop, as shown in the picture below and depicted in yellow in the previously posted CAD screenshots. We somehow proceeded to pull it off without a hitch and moved on to some more “interesting” parts.

Bolt Stop

Next came the bolt itself, and it brought its fair share of difficulties. The three possibly challenging sections of this part were as follows: 1.) The scarily skinny back end, 2.) The grooves for air travel, and 3.) The drilled holes in the front end. In order to keep The very small back end safe from breakage and deflection, we decided to provide some extra support by operating with the part between centers. In order to do this, a small hole is drilled with a center drill and a pointed center pin is greased and inserted, this pin keeps the end of the part from “deflecting” -being pushed away from the tool by the pressure from the tool.  In addition to the added support, cutting a part between centers also makes most actions much more repeatable. Repeatability isn’t really an issue for us, as we will be happy to get one to work! A quick sketch of the setup for cutting between centers is below.

Between Centers Sketch

Problems…

Problems 1 and 2 shown in the top and bottom pictures, (respectively).

Problems…

And I think you can find problem 3.

Issue 1 was contained by placing the part between centers, and #3 proved to be less problematic than anticipated,  so these proved to be easily overcome with teamwork, but when left to my own devices, #2 went a little haywire! Although I will tell you it was Brian’s Chinese mill doing all the wandering, it might not have been helped by my haste to finish the grooves. They wandered around a bit and four of them were 50 thousandths longer than intended, but with a couple tweaks to the design we were able to compensate fairly well.

Up next was one of the largest and most technically demanding parts, the charge chamber. At first, the dimensions seem fairly easy and the lathe work rather simple, but all of the cutting has to take place inside of the metal. This cutting proved to be quite similar to building a ship inside of a bottle. For these cuts, we were going to need some special tools…

Cutting Tools

The primary tools used for digging into the metal in this way were the boring bars, (every tool shown except those in the left tool holder.) One handy trick that Brian picked up online for making these was to grind up an Allen wrench instead of the usual steel blocks. the Allen wrenches’ “L” shape allows for the cutting tip to reach outward more than with the normal bars. In addition to these tools, there was also the necessity for grooving tools, both internal (top tool on left holder) and external (bottom). These tools allowed us to make O-ring grooves on the inside and outside of the metal.

Sadly, as it happened, we ended the day with some minor touches on our manufactured parts and the entire firing chamber left as activities for a future day.