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IndustryArena Forum > Hobby Projects > Gunsmithing > CNC Rifling and drilling
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  1. #1
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    Jul 2014
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    3

    CNC Rifling and drilling

    Hello,
    I am building a CNC gun barrel drilling, reaming, and rifling machine based on the Bill Webb design and I need some help. I am a machinist so I have the CNC part down but I have never delved into the realm of hobby CNC before and there is so much info out there that I have no Idea where to start. I have read a few books on hobby CNC and I know I need motors, I need a driver, I need software, but that’s about it. Here is what I know I need and maybe we can go from there.


    1. The drilling portion of the machine is a very slow feed process that utilizes a, carriage with a tool holder and gun drill, that is moved in a linear fashion by a leadscrew. Basically it is the same thing as a regular metal lathe.
    2. The reaming portion is the same as the drilling but it is done at a higher feed rate.


    Question: Is a leadscrew the best option for CNC or would a ballscrew be better?
    Question: Can a servo handle these types of operations?


    1. The machine spindle rotates during drilling and reaming operations just like a lathe. The spindle will have to be rotated to upwards of 2000 RPM for drilling and much, much lower for reaming. The spindle is usually locked in position for rifling.


    Question: Can a servo handle these three things?


    1. During rifling operations, the carriage is disengaged from the leadscrew via a half nut so the carriage can rapid traverse on the x axis. The carriage is hooked to a motor bike chain and sprocket and moved via a hand crank. Since the cutting tool is only removing about .001” per pass this works but gets old very quick. I would like to attach a servo to the sprocket and have it control the x axis movements for rifling.


    Question: If a servo can be used, can I bypass the entire sprocket idea and use the servo that controls the x axis movements for drilling and reaming? Can a servo move that fast with a 20 lb. tooling plate attached to it? If so leadscrew or ballscrew? Which would be better.


    1. During rifling operations the spindle has to be manually indexed to the next position for cutting. Basically you must pull the cutter through the barrel until it exits one the opposite side and then send the cutter back through the barrel along the same groove to it’s x axis start point. Next you must unplug the spindle stop and rotate the spindle to the next index point, lock the spindle in place, and repeat cycle. This must be done for every cut. If you have a 6 groove barrel the process must be repeated six times. Then you must manually raise the cutter height another .001 and go another six times. Rifling can be cut to different depths but you get the idea. This can take hours.


    Question: Can a servo be used to index the spindle after a set of six cuts is performed, or eight cuts, or 4 cuts, etc…?
    Question: As I understand it a servo is rigid when it is not under power and will not free rotate. Is this correct?
    Question: If a servo can be used can it be the same servo that is used to rotate the spindle during drilling and reaming?
    Question: After the desired number of groves have been cut, can a small servo be used to turn the rifling head knob to increase the depth of cut for the next 6 passes? I have seen a machine like this where the rifling head plugs into a slot at the end of every pass and dwells for a bit while the spindle indexes. I believe one person used a male square shaft, that plugged into a female square hole on the rifling head and turned it a bit to change the depth.
    I can furnish anyone that is serious about helping me with drawings and images and I am also available through email and talking on the phone. I apologize in advance if I am going about asking the questions and listing what I know all wrong but like I said I am new to CNC builds. Any help will be thoroughly

  2. #2
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    Oct 2014
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    22

    Re: CNC Rifling and drilling

    fredd,

    sounds like you need "Rifling Machines and Methods" by Cliff Labounty Rifling Machines And Methods | Rifle Boring

    I have Bill Webbs disc etc but am likely to order Cliff's book shortly as he has information on building CNC rifling machines.


    There is also another book on www.steelhelixrifles.com about drilling and reaming barrels that may be of interest.

    "Barrels and Actions" by Hoffmann is also worth a look.

    I have not read Labounty's book nor the Steelhelix book.

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