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IndustryArena Forum > MetalWorking Machines > CNC "do-it-yourself" > How precise is this diy manual mill to cnc conversion?
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  1. #1

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    How precise is this diy manual mill to cnc conversion?

    https://www.drdflo.com/pages/Projects/CNC-Mill.html

    What's the best cnc conversion I can get that can cnc out precision parts really accurately?

    I'm new to cnc machines and manual mills so I would like to be able to learn as I go too.

    I want high quality metal parts

    How good is the project I linked? Are there better ones?

  2. #2
    Community Moderator Jim Dawson's Avatar
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    Re: How precise is this diy manual mill to cnc conversion?

    Define precision and accuracy in the context of your needs.
    Jim Dawson
    Sandy, Oregon, USA

  3. #3

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    Quote Originally Posted by Jim Dawson View Post
    Define precision and accuracy in the context of your needs.
    I was wanting it to do extreme tolerances for moving parts that will rub together.

  4. #4
    Community Moderator Jim Dawson's Avatar
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    Re: How precise is this diy manual mill to cnc conversion?

    Quote Originally Posted by Pullarius View Post
    I was wanting it to do extreme tolerances for moving parts that will rub together.
    That tells me nothing. Will the machine make a flat surface? Yes, depending on the skill of the user. Are you going to do NASA quality work on it, maybe not so much. Adequate for most applications? Probably.
    Jim Dawson
    Sandy, Oregon, USA

  5. #5

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    Quote Originally Posted by Jim Dawson View Post
    That tells me nothing. Will the machine make a flat surface? Yes, depending on the skill of the user. Are you going to do NASA quality work on it, maybe not so much. Adequate for most applications? Probably.

    I wasn't wanting NASA level just professional quality. I dont know enough about CNCs to know what I need to make what i want. I was wanting to make gun parts and idk if that's allowed on this forum or not. I can legally make gun parts for myself in my country and state.

    I was wanting to make top quality gun parts not cheap parts that malfunction and jam.

    I've shot guns my whole life just never made my own from individual parts or even put together a parts kit.

  6. #6
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    Re: How precise is this diy manual mill to cnc conversion?

    Hello.

    Some advise notes for what they could be worth.

    As Jim Dawson says you must first define the characteristics of the finished products you are planning to manufacture according to their final use and then select the proper machine to achieve that quality.

    In a company I worked for we manufactured from pins to airplanes. That gives you a broad selection of machines. For some parts in our airplane division accuracy had to be within 0.00001" and that was for crop dusting planes. For zippers and snap fasteners tolerance is normally kept within 0.0005".

    Another important factor to consider is the speed of the machine. That is how many pieces per hour you can afford to manufacture to keep your costs down an yet have the profitability that you want.

    Remember that as you increase accuracy speed is normally decreased. In that case you may need to switch from stepper driven systems to servo driven systems. Of course the price of these latter machines or retrofit kits is higher than that of the formers.

    To make my point please watch the following videos.

    https://www.youtube.com/watch?v=ErNjNtC60As

    https://www.youtube.com/watch?v=7MuOlVDJPg0

    Both machines manufacture the same products. The first one is driven by steppers. The second is driven by servos.

    By listening to the machines you can easily notice that the latter runs faster than the first. In fact nowadays it is running slightly faster than twice.

    In this particular configurations the price of the latter is nearly twice of the first. It would have cost some 20% less if the configuration had been exactly the same but in this latter system the owner required some additional function but in any case that gives you the idea.

    And it not only depends on what you want. If the owner of the first machine had wanted a servo system to increase its productivity it would simply would not have been possible due to the mechanical design of his machine. Using servos on it would result in a waste of resources as it was impossible to fully take advantage of them as the machine would not hold onto the extra stresses of high speed operation.

    So you see there are a number of factors you need to consider before buying a machine and then some. You will have to search for different machines that can produce what you now want but you have to take also a number of considerations like future upgrades, availability of spare parts, availability of service, etc.

    If possible try to get advice from professionals in your areas. Maybe you can pay a visit to actual workshops to take a look at what they do and what equipment they are using.

    It may also be possible that you get advice in this very forum from people like Jim as they are more related to the field. Or it might even be possible that some member is nearby you.

    One possible recommendation would be to take your time so that you select the best possible machine for your needs and your budget. Either being a hobby or a professional issue always think of it as an investment, not as an expense.

    One last advise thay may not apply to you but I always tell my customers when facing the acquisiton of used machinery. They have to think on why a particular machine is for sale. Was it that the owner renewed his equipment?

    It´s very common in the industry that when a machine starts to give problems and spare parts start to become scarce they decide to sell them while they can still sell them as machines. They also do that when their operating costs start rising above certain level.

    I sincerely hope this reflections help you take the best possible decision.

    Regards.

  7. #7
    Community Moderator Jim Dawson's Avatar
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    Re: How precise is this diy manual mill to cnc conversion?

    Then the answer is yes. A lot of firearm parts are made on machines just like that by hobby users. And yes, firearm discussions are allowed.
    Jim Dawson
    Sandy, Oregon, USA

  8. #8

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    Quote Originally Posted by BBMNet View Post
    Hello.

    Some advise notes for what they could be worth.

    As Jim Dawson says you must first define the characteristics of the finished products you are planning to manufacture according to their final use and then select the proper machine to achieve that quality.

    In a company I worked for we manufactured from pins to airplanes. That gives you a broad selection of machines. For some parts in our airplane division accuracy had to be within 0.00001" and that was for crop dusting planes. For zippers and snap fasteners tolerance is normally kept within 0.0005".

    Another important factor to consider is the speed of the machine. That is how many pieces per hour you can afford to manufacture to keep your costs down an yet have the profitability that you want.

    Remember that as you increase accuracy speed is normally decreased. In that case you may need to switch from stepper driven systems to servo driven systems. Of course the price of these latter machines or retrofit kits is higher than that of the formers.

    To make my point please watch the following videos.

    https://www.youtube.com/watch?v=ErNjNtC60As

    https://www.youtube.com/watch?v=7MuOlVDJPg0

    Both machines manufacture the same products. The first one is driven by steppers. The second is driven by servos.

    By listening to the machines you can easily notice that the latter runs faster than the first. In fact nowadays it is running slightly faster than twice.

    In this particular configurations the price of the latter is nearly twice of the first. It would have cost some 20% less if the configuration had been exactly the same but in this latter system the owner required some additional function but in any case that gives you the idea.

    And it not only depends on what you want. If the owner of the first machine had wanted a servo system to increase its productivity it would simply would not have been possible due to the mechanical design of his machine. Using servos on it would result in a waste of resources as it was impossible to fully take advantage of them as the machine would not hold onto the extra stresses of high speed operation.

    So you see there are a number of factors you need to consider before buying a machine and then some. You will have to search for different machines that can produce what you now want but you have to take also a number of considerations like future upgrades, availability of spare parts, availability of service, etc.

    If possible try to get advice from professionals in your areas. Maybe you can pay a visit to actual workshops to take a look at what they do and what equipment they are using.

    It may also be possible that you get advice in this very forum from people like Jim as they are more related to the field. Or it might even be possible that some member is nearby you.

    One possible recommendation would be to take your time so that you select the best possible machine for your needs and your budget. Either being a hobby or a professional issue always think of it as an investment, not as an expense.

    One last advise thay may not apply to you but I always tell my customers when facing the acquisiton of used machinery. They have to think on why a particular machine is for sale. Was it that the owner renewed his equipment?

    It´s very common in the industry that when a machine starts to give problems and spare parts start to become scarce they decide to sell them while they can still sell them as machines. They also do that when their operating costs start rising above certain level.

    I sincerely hope this reflections help you take the best possible decision.

    Regards.
    Thanks for the great reply I was planning on doing small scale so I dont think I need speed just accuracy and precision parts. I'm not sure I'm saying the correct terminology tho

  9. #9

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    Quote Originally Posted by Jim Dawson View Post
    Then the answer is yes. A lot of firearm parts are made on machines just like that by hobby users. And yes, firearm discussions are allowed.
    What quality of gun parts would a diy cnc machine make? And do you have a machine youd suggest for making the bulk of the exspensive parts like receivers and idk if a bolt is millable or not tho.

  10. #10
    Community Moderator Jim Dawson's Avatar
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    Re: How precise is this diy manual mill to cnc conversion?

    That machine would make all of the receiver, any mill work needed on the bolt, and anything else required. A lot of lowers are made on similar machines. Your not going to make barrels, or do any chambering on it of course.
    Jim Dawson
    Sandy, Oregon, USA

  11. #11

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    Quote Originally Posted by Jim Dawson View Post
    That machine would make all of the receiver, any mill work needed on the bolt, and anything else required. A lot of lowers are made on similar machines. Your not going to make barrels, or do any chambering on it of course.
    Thanks I'll look into that machine or others that are reliable I liked the oiler on it.

  12. #12
    Community Moderator Jim Dawson's Avatar
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    Re: How precise is this diy manual mill to cnc conversion?

    Quote Originally Posted by Pullarius View Post
    Thanks I'll look into that machine or others that are reliable I liked the oiler on it.
    Matt (PM) sells good machines with super support.
    Jim Dawson
    Sandy, Oregon, USA

  13. #13

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    Quote Originally Posted by Jim Dawson View Post
    Matt (PM) sells good machines with super support.
    Are you saying you sent a pm? I dont know how to set my settings on this website so I can see them.

    Does he have a website?

  14. #14
    Community Moderator Jim Dawson's Avatar
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    Re: How precise is this diy manual mill to cnc conversion?

    Quote Originally Posted by Pullarius View Post
    Are you saying you sent a pm? I dont know how to set my settings on this website so I can see them.

    Does he have a website?
    No, that machine you linked to is a PM25 (Precision Matthews), with an added CNC kit. Matt is the owner. https://www.precisionmatthews.com/shop/pm-25mv/
    Jim Dawson
    Sandy, Oregon, USA

  15. #15

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    Quote Originally Posted by Jim Dawson View Post
    No, that machine you linked to is a PM25 (Precision Matthews), with an added CNC kit. Matt is the owner. https://www.precisionmatthews.com/shop/pm-25mv/
    Which of his would you suggest for a beginner trying to get into gunsmithing? And what all attachments?

    Sorry to bombard you with questions I'm just not experienced with metal working.

  16. #16
    Community Moderator Jim Dawson's Avatar
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    Re: How precise is this diy manual mill to cnc conversion?

    Oh man, you ask hard questions The list is endless.

    You need:
    Tool bits; endmills, drill bits, center or spotting drills, countersinks.
    Tool holding; collets, drill chuck, maybe endmill holders
    Work Holding; vice, clamp kit
    Measuring instruments; mics 0 to 3'', digital caliper 6'', dial indicator 0.001'' reading, dial test indicator 0.0005'' reading, edge finder
    Other tools; files, deburring tool

    That should be enough to get you started.
    Jim Dawson
    Sandy, Oregon, USA

  17. #17
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    Re: How precise is this diy manual mill to cnc conversion?

    Hello.

    A note on retrofitting mechanical machines. Any type for that matter. Mills, lathes, quilters, drills. You name it. By mechanical I mean machines that have never had any control other than manually turned handles or cam drives.

    Since retrofitting usually requires that you substitute the standard transmissions with some high precision ballscrews or gears you can set your precision to whatever you want. Even if you don´t replace those transmissions and just motorize their handles you are the one who decides what precision you are going to give to your machine at issue.

    Note: the main reason to replace a transmission is the free play that standard transmissions have. That would introduce position errors distorting the geometries being machined.

    Please take a look at the posted pictures. the gear and screw shown have a ratio of 10/1. That is that the rolls driven by this speed reducer rotate at 1/10 the speed of the motor. Disregarding the microstepping switches on the drives and assuming a 200 steps per revolution motor the output shaft would require 2000 steps of the motor to complete one revolution. That is 10 full revolutions of the motor.

    If I wanted to have better precision I could replace those gear and screw by a pair having a 20/1 ratio. In that case 4000 motor steps would be required to complete one revolution on the output.

    As that action would reduce the speed to half I would also have to double the frecuency of pulses to the motor so that the RPMs are kept constant.

    All that is possible within certain limits as steppers lose torque as they are run faster. That´s why in some cases you switch to servos. They can be run faster without so much torque reduction.

    I hope that this comments clarify the fact that it is mainly the design of the retrofit system that sets the precision, not the machine. Just make sure your selected machine is rigid enough and doesn´t have to much free play in its rails and guides.

    Regards.

  18. #18

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    Re: How precise is this diy manual mill to cnc conversion?

    Wow that's a lot of needed parts to it. Will some machines come with that or is that all extra?

    So I guess after reading both your answers my next question is.

    Is it better to buy a cnc conversion kit as a beginner looking for a high quality cnc machine or is pure diy better?

  19. #19
    Community Moderator Jim Dawson's Avatar
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    Re: How precise is this diy manual mill to cnc conversion?

    I would look for a kit something like this. (Disclaimer: this is not a suggestion, but is only an example) https://procutcnc.com/product/pm25mv...onversion-kit/

    This particular kit does not include the motors, but those are readily available, as are the other electronics needed.

    Edit: I have no idea what BBMNet is posting pictures of, but it is not a CNC mill.
    Jim Dawson
    Sandy, Oregon, USA

  20. #20

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    Re: How precise is this diy manual mill to cnc conversion?

    Oh ok thanks I'll look into mills and then a cnc conversion kit for the one I want.

    I saw a pneumatic drill bit loader onto the mills is that an upgrade or something you can retrofit onto one that has the twist on I dont want to twist them all on and off every time I have to switch bits.

    And I'm guessing self loading drill bits are exspensive for diy so I probably wont go that route.

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