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  • gumby3344 7:21 pm on December 1, 2014 Permalink | Reply
    Tags: , , Machining, ,   

    Making a Paintball Gun From Scratch – Hey! It's a Gun! 

    With our last build resulting in a gun that could be muzzle loaded to fire single shots, Brian was confident that we could attain semi-auto firing over the course of the coming weekend. The main problems and parts that needed to be addressed to get to that point were correcting the cycling issues in the bolt, rigging a sort of makeshift trigger system to fire the gun, and feeding paintballs into the system.

    The issue that had to be solved first was the issue of cycling. After our second build, we found that the bolt was not being forced forward by the firing pressure when the control pressure was released. To fire the gun, we had to assist the bolt by pushing on the back of it with something. We expected that the primary cause of this problematic friction was the surface finish of our internal parts. This appeared to be an easy fix after some fine grit sanding on the lathe. Another way that we helped the movement of the bolt was by deepening the o-ring grooves to relieve a little pressure on the bolt.

    After these two fixes, the bolt started to cycle the way it was intended. In order to achieve semi-automatic dryfiring, we had to rig up a hose system to imitate our future trigger. This is roughly what we came up with…

    Gun air rig sketch semiauto

    In this setup, pressure is supplied by separate hoses. The firing pressure is constant as it will be on the final version, and an air gun is used to dump pressure from the control chamber in place of a solenoid-actuated valve. We did have a problem off the start because the trigger pressure input was pumping air too fast for the air gun to dump it. this was causing the chamber to remain at too high a pressure for the bolt to cycle. to fix this, we basically jammed a plug into the input hose to slow the rate at which air could flow through it just enough to allow the bolt to cycle. With this setup, we achieved semiautomatic fire without ammunition.


    At this point I am returning to this post after over a year of absence, so my recollection may be a bit fuzzy. I apologize for any inconvenience.


    In order to feed paintballs into the gun, we decided to create a basic hopper feed system by boring a large hole in the top of the gun. We then threaded the hole and created another piece that fit tightly onto the neck of a hopper and threaded into place on the gun.

    Since this was the first time we had to do anything on a different axis than the firing axis, it meant we got to use a new toy. Brian had recently bought a four jaw chuck that was useful for this type of operation. The mount for this job is pictured below. The hole was started using a wood bore bit, and the hole was widened using a boring bar.

    2013-07-20 11.05.21


    After making both parts, we attached a hopper and voila! It is amazing how much that hopper makes it look like a gun.

    2013-07-20 14.39.03

    We rigged up our makeshift trigger system (partially pictured above) and took it outside to try firing it a few times.

    Now that the firing mechanism is operational, we need to set up a trigger mechanism. The primary phase of this process will be the design of the solenoid valve. A concept is shown below.

    First: A cross-section of the valve                     Second: A full image of the valve hammer



    This valve will be actuated like a solenoid. There will be a copper wire winding around the left end of the valve body which will pull the hammer back when charged.

    In the rest state, pressure will be routed through the valve as such:

    Valve_clip_air_diagram_restWith the valve in its rest state, constant pressure is applied to both the control chamber and the firing chamber. Due to the pressure in the control chamber, the gun does not fire. Once the valve is actuated by an electric current through the solenoid, the air pressure will behave as such:

    Valve_clip_air_diagram_fireWith the control pressure now dumped, the present firing pressure will be able to fire the weapon. After firing, the source pressure will return the hammer to its original position as soon as the solenoid is deactivated, allowing the recharge of the control chamber.

    Hopefully with some refinements to this design, and a free weekend to build, Brian and I can get a real paintball gun together. We still have to deal with making the gun run on CO2, which brings in a whole host of regulation and expansion issues, but I think we are fairly close to a workable product.

    I am sorry to anyone who was affected by my delay in posting this write-up, and I hope you enjoy its contents.


    • pan 5:08 pm on December 16, 2014 Permalink | Reply

      • gumby3344 8:07 pm on December 16, 2014 Permalink | Reply

        Hey! Looks good! Using the end-final position of sigma and everything 😉 <-(Not actually smart, just looked at Wikipedia) I am curious about the sigma in place of the Tau in invention, however. I think yours pronounces better, but for the sake of readability and direct letter translation I think am going to stick with the Tau for now, unless you feel like convincing me otherwise (which you probably could). Definitely smart to replace the omega with a beta though, I was a sophomore in high school when I made that logo and I think I just used whatever Word put in for me 😉 Thanks for the interest in the site and the helpful comment!!

  • schoolie 6:05 pm on February 7, 2014 Permalink | Reply
    Tags: , Evanut, Machining, , ,   

    RF-45 Repair – Making a new Y-Axis Nut 

    The most recent success in my ongoing RF-45 mill repair project is the fabrication of a new Y-Axis lead nut. The stock nut was apparently lost somewhere along the way during the attempted CNC conversion that I’m partially reversing, so I had to come up with a replacement.

    My first thought at replacing the nut was to make a new one out of acetal plastic based on the method described at the Home Shop Machinist Forum. On second thought, I decided it would be much more practical to see if I could find a replacement part online. Like many of the chinese machine tools out there, this mill is one of many clones of an original design. In this case, the Rong-Fu 45 is the original, and my copy was produced by Penn Tools. Unfortunately, I was unable to find replacement parts through them, but Grizzly sells a similar mill along with replacement parts. I dug through the manual to find the part number, contacted Grizzly, and ordered the nut. Easy enough right?

    Unfortunately, the importer of my mill chose to use 8 TPI leadscrews, while the Grizzly version uses 10 TPI leadscrews, so the nut didn’t work. I returned it to Grizzly, and set off on my original plan of making the nut from scratch.

    I started by boring and splitting the acetal to fit the lead screw:

    (Read the rest of this post…)

  • schoolie 11:02 pm on November 6, 2013 Permalink | Reply
    Tags: Machine Repair, Machining, , ,   

    RF-45 Repair – Reinforcing the bed 

    The RF-45 mill I purchased on craigslist a few months ago had some issues… In an attempt to convert the mill to CNC using an extremely oversized ballscrew, a previous owner had milled a pocket out of the bottom of the bed, leaving the material below the bottom of the center T slot uncomfortably thin. With the goal of restoring some of the bed’s original stiffness, I’ve fit a steel plate into the pocket. This post documents the process of machining the plate to fit the bed.

    Here’s the bed as it stood before adding the plate:

    View of bottom of bed showing material removed, and thin wall condition at bottom of T slot

    (Read the rest of this post…)

  • schoolie 10:30 pm on July 31, 2013 Permalink | Reply
    Tags: , Machining,   

    Bringing home a new project – a Rong Fu 45 Mill 

    A few weeks ago, my Craigslist RSS feed returned a listing for a mill for $300 only a half hour from my house. It was an RF-45 clone that the seller described as a “project.” The RF-45 is a much more substantial mill than the X2 mini mill I currently have, so I was intrigued to say the least. After a bit of thought and contemplating if I had room in the garage, I decided to give it a shot and contact the seller to get some more info.

    It turned out that the previous owner had begun a CNC conversion on it, and in the process had milled a large pocket under the table in an attempt to fit a much too large ballscrew on the X axis. The mill was disassembled, but all the stock leadscrews and handwheels were included, except for the Y axis acme nut. The seller had intended to finish the CNC conversion that the previous owner had so poorly started, but never got around to it since he already had another CNC set up in his garage. Fortunately, he held on to all the parts necessary to run the mill manually. I’m not quite ready to jump into the world of DIY CNC just yet :-).

    All in all, it seemed like a pretty good deal, so I arranged to pick it up the next day. Now I had to figure out how to move it. 700 pounds of chinese cast iron doesn’t just jump in the back of a truck…

    (Read the rest of this post…)

  • gumby3344 4:05 pm on April 10, 2013 Permalink | Reply
    Tags: "I know what I am doing", , , Machining, , ,   

    Making a Paintball Gun From Scratch – Still building… 

    Following the first day of work, we had nearly completed both the bolt and the charge chamber, and had completed the boltstop. In this session we needed to finish up these parts and create the firing chamber.  Brian and I had high hopes going in to this session. He was confident that we would at least fire a shot by the time I had to head home. I was somewhat skeptical! Although we were interrupted by some thermite and Doctor Mario, we were able to achieve this goal.

    We did the usual shaping and machining to get the firing chamber roughed out and then got on to the fun stuff… threading. Three parts needed threads. The firing chamber and charge chamber had to thread together at the middle of the gun; and we had to thread the inside of the front end of the firing chamber in order to put one of our Spyder barrels into it. The charge/firing chamber threads would be somewhat simple, as they only have to match each other and require no standardized dimensions. The barrel, on the other hand, has its own thread type that we would have to match. Just to make things more fun, The threads were metric, (M22 x 1.5) and our thread turning gears were standard. Brian worked his magic and got something pretty close to the barrel (7/8 x 16) and we went with it.

    External Firing Chamber Threads

    2013-04-06 14.57.03

    Internal Barrel Threads

    2013-04-06 14.56.39

    Whole Firing Chamber

    2013-04-06 14.55.42

    And I have saved the internal threads from the charge chamber for last to present you with a conversation that took place just moments prior to the cutting of the first internal threads we had done.

    Joe and I: “Brian are you sure you want to do this without a practice run or anything?”

    Brian: “I know what I am doing.”

    2013-04-06 15.44.41

    He apparently wanted our threads to look like the mouth of the Kraken, but as long as he knew what he was doing, who were we to question him! 🙂

    The embedded video shows our first paintball break on target.

    Gun air rig sketch

    The graphic above shows the air system we had set up when we fired the gun. Constant pressure is supplied to the firing pressure input, where the pressurized air waits to be released and force the ball from the gun. The bolt is held back by air pressure from the trigger pressure input. Whenever the air gun valve is open, this pressure is supposed to be keeping the bolt to the rear and keeping the gun from firing. Whenever this pressure is released (the air gun is pulled away from the input) the firing pressure should cause the bolt to move forward and the gun should fire. This wasn’t happening for us due to what we speculate to be general surface finish and O-ring fitting issues. With some further work and refinement this should be fixable. We ended up poking the back end of the bolt with random stuff and that provided the motivation required to start the firing cycle.

  • gumby3344 11:03 pm on January 23, 2013 Permalink | Reply
    Tags: , , Machining, , ,   

    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

    2013-01-15 22.11.022013-01-15 22.11.11

    (Read the rest of this post…)

  • schoolie 12:09 pm on January 8, 2013 Permalink | Reply
    Tags: , , Machining, ,   

    Making a Paintball Gun from Scratch – Getting Started 

    Ben came over for the weekend a couple of months ago, and we were looking for a project to do in my fledgling machine shop. He’d never really used machine tools, and I hadn’t done any “real” machining in my home shop yet, so we were looking for an excuse to pick up some experience.  Ben’s in to paintball, so we decided to try to make a paintball gun.

    We tossed around making a Spyder clone since that’s what Ben’s taken apart the most, but decided not to because I wasn’t sure how we could make the stacked tube housing with the tools currently in my shop. Keeping things to a single centerline makes them a lot easier to make on a lathe!

    The next type of gun that came to mind was the Tippman style marker.  They work on basically the same principle as the Spyder, but are arranged in a straight line rather than two stacked tubes. However, neither of us had ever owned a Tippman, so we couldn’t just make up the design from memory. We did a bit of research and came across a great site in ZDSPB.com. With the info on that site, and a few crude hand sketches, we headed out to the shop to “get something done.”

    Ben running the Lathe

    (Read the rest of this post…)

  • schoolie 10:34 pm on September 26, 2012 Permalink | Reply
    Tags: , , , Machining, ,   

    PWM Board for MC-2100 Treadmill Motor Controller 

    Free treadmills from Craigslist are a great source of DC motors and motor controllers for machine tools.  A quick search will yield several examples of people repurposing these motors and drive for drill presses, lathes, and various other equipment.

    From what I’ve seen, the MC-60 type controller is by far the most common in low end treadmills (the type you typically can get for free).  Three out of the four treadmills that have passed through my garage have had the same MC-60 controller, and nearly identical permanent magnet DC motors.  This controller is relatively easily repuroposed as a machine tool drive, as the input is a simple voltage divider circuit driven by a potentiometer.  Just take the pot off the treadmill’s dash, mount it to your bench, and you’re up and running.

    The MC-2100 proved to be a bit more complicated.  My first clue was the all digital dash on the treadmill it came out of.  A quick google concluded that the MC-2100 required a 5v PWM signal with ~50ms period.  I found a good reference circuit on the All About Circuits forum (Link):

    This circuit has two stages.  The first is an astable 555 vibrator.  Tapping off the capacitor charge pin (Pin 6 on the 555) results in a sawtooth output, with the frequency set by R1, R2, and C.  This sawtooth is then fed into a LM393 voltage comparator to convert the sawtooth wave into a square wave.

    Here’s my final circuit sketch:

    And a quick first test video:

    In my opinion, it was worth the effort to figure out because the MC-2100 is a high frequency PWM controller, as opposed to the MC-60 which is an SCR based controller that operates at line frequency.  This results in a much quieter motor.  Also, based on a couple quick test cuts, the MC-2100 seems to have a higher current capacity.

    Check out the rest of the MC-2100 Project Here

    • James 2:17 am on October 22, 2012 Permalink | Reply

      I have the same treadmill motor controller with a motor that I’m planning on using on a metal lathe (I recently had to sell my old Atlas 618 and I’m planning to buy a smaller taig lathe and want to have the motor & controller resolved before I buy it). Your hand drawn schematic is a little difficult to read in some parts and I was wondering if you could provide a higher resolution image. I have some basic electronics experience and a few 555 timers laying around, though I certainly would not be able to engineer this circuit on my own. If you don’t mind too much, I may ask for some advice along the way as well if I run into any problems.

      • schoolie 8:44 am on October 22, 2012 Permalink | Reply

        I’m working on getting this design soldered onto protoboard, and making a few tweaks along the way. I’ll get a better schematic put up once I get everything checked out and verifed working. I wouldn’t mind answering a few questions along the way either.

        • James 1:35 pm on October 22, 2012 Permalink | Reply

          I’ll stay tuned. Thanks.

        • James 2:55 pm on October 25, 2012 Permalink | Reply

          I had a few old Arduino boards laying around. I relearned how to program them and came up with this simple code (pasted below for anyone looking to do this in the future) to run the motor off of a trim pot. It works perfectly. I had read that the controller likes a frequency of 51ms, mine likes 49 or 50ms, which is what I used for my code. I had also read that the maximum duty cycle is 85% on, which is why I scaled the pot value from 0 to 42.

          Necessary parts:
          1 – Potentiometer
          1 – Arduino Board (around $30)

          This code creates a PWM signal with 0-85% duty cycle and 50ms frequency on the MC 2100 treadmill motor controller

          int ledPin = 11; //this is the PWM signal out
          int pot = A0; //Potentiometer (connected from 5v+, A0, Grnd)
          int potValue = 0; //Tells Arduino there will be a # named potValue

          void setup()
          pinMode(ledPin, OUTPUT); //tells arduino pin 11 is output
          Serial.begin(9600); //arduino counts. only necessary if you want to pint (below)

          void loop() //the following cycle will repeat every 50ms
          potValue = analogRead(pot); //reads potentiometer value
          potValue = map(potValue,0,1023,0,42); //scales potValue to 0-42 (85% duty)
          digitalWrite(ledPin, HIGH); //turn duty on
          delay(potValue); //time duty is on
          digitalWrite(ledPin, LOW); //turn duty off
          delay(50 – potValue); //time duty is off (50 – on time)
          Serial.println(potValue); //not necessary. shows duty on computer
          The analog out pin (11, named ledPin) is connected to the blue wire, and the black wire is connected to the arduino’s ground. The arduino is powered by the red and black wires from the controller. I also found this wiring diagram of the controller:

  • schoolie 12:36 pm on September 17, 2012 Permalink | Reply
    Tags: , Machining, Miter Gear Repair   

    Repairing the cross-feed miter gear on an Atlas/Craftsman 12″ Lathe 

    I bought an old Atlas lathe on craigslist last year for $50. It was in need of a good cleaning and was missing a few parts, but all in all fairly sound. Joe made a replacement tailstock ram for it, and I’ve bought a new chuck and toolpost, and a few other bits. All in all it’s working pretty well after about six months of working on it off and on.

    One of the last features left to get working was the power cross feed. On this lathe, the cross feed is driven through a bevel gear set. The drive gear slides over the lead screw, and is supposed to be driven by a key that engages a slot in the lead screw. The bevel gears are ZAMAK castings, and the key appears to have worn away or broken years ago.

    Before Repair

    (Read the rest of this post…)

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