[Fuzzy Wuzzy]

Hey everyone! I am new to this forum so I'm not sure if I'm posting this in the correct place. Anyway I'm currently trying to build a cnc as part of a class project and since I live in Egypt there are only a limited number of stores (that I know of) that sell lead screws or ball screws. I found a store selling ball screws but they were two expensive and the diameter was too big anyway (16 mm) for the stepper motor I chose. I need a 1/4 in diameter lead screw. So my question is: can I make my own lead screws. And if so: how? Will it work or do I need to get Acme ones? Can I just follow the engineering drawing of an Acme screw and get it done at a local workshop or will there be complications involved. And if so, how about the nut? Can I make it too?
Thanks in advance!

[alan_3301]

My first machine, a hot wire foam cutter, had 1/4 - 20 threaded rod as leadscrews. They flex and whip, and are painfully slow, I think around 12 ipm max.
But if it is a class project, and not to be used for anything other than demonstration, that is what I would get. I'm sure it'd be the cheapest.

As far as a nut, just use a piece of plastic, and tap it for the thread size of the screw you will use.

[Fuzzy Wuzzy]

My first machine, a hot wire foam cutter, had 1/4 - 20 threaded rod as leadscrews. They flex and whip, and are painfully slow, I think around 12 ipm max.
But if it is a class project, and not to be used for anything other than demonstration, that is what I would get. I'm sure it'd be the cheapest.

As far as a nut, just use a piece of plastic, and tap it for the thread size of the screw you will use.

than you v. much. I'm sorry but I'm not sure I understand what do you mean by "tap it for the thread size"? what do you mean by "tap"? thanks again!

[awerby]

Attempting to make your own leadscrews would be a last resort, if there were really no other alternatives - if you were marooned on a desert island it might be worth considering. The accuracy of your machine is dependent on the accuracy of your screws, so this isn't the place to fake it. You don't need ball screws; a good acme screw (with flattened rather than sharp threads) is much better than a piece of hardware store all-thread, and not very expensive, even if you have to import it. The diameter of the screw doesn't have to match the diameter of your motor shaft either; 16mm is not too fat at all, and 1/4" is too thin for most purposes, as Alan learned with his first project. Attach them to your motors with flexible couplings - the Oldham style is cheapest - so you won't break your motor shafts with a little misalignment.

Tapping is how you make threads on the inside of your nut; it requires a tool called a tap that cuts the thread as you screw it into the correctly-sized hole. If you're using acme leadscrews, then you'll need an acme tap - or you can buy the correct nut when you're buying the screw.

[Fuzzy Wuzzy]

sorry I forgot to explain that my motor torque is 9 kgf.cm which I don't think would be enough for a 16mm diameter ball screw (the load of the screw itself would be too big for the motor I think...?)

[awerby]

Ball screws actually require less torque to turn than other types of screws; that's their main advantage. But ball screws with good precision tend to be quite expensive. Look for an acme screw that's 10-12mm in diameter; that should work well without whipping and bending, and it shouldn't cost too much.