Help! I need some expert advice!

[losgetlost]

I am having a 24 x 36 x 12 machine being built that I will be using to cut electric guitar bodies and necks. It is being built with nema 34 670oz. stepper motors, 20mm linear rail on all axes, and the cutter will be a hitachi m12vc (midsized router). The builder is suggesting that I go with 3/8" 16 tpi lead screws. I am wondering if this is the best lead screw to use? Is the 3/8" too flimsy for this size machine? What would be my best bet as far as lead screw? Thanks in advance for any input.

Also would like to say that this place is great and I have already learned quite a bit from other posts!

[dertsap]

sounds like he wants to use ready rod
your motors will twist the screw into a pretzel , i have stainless screws , the one end was turned down to 3/8" . the x axis with a 1145 oz motor eventually twisted and broke the 3/8 dia , that was only a 1.5" length that was 3/8 on the 3/4" screw.
over the distance you have, you will destroy those screws in no time
if you going to use a cheaper type of leadscrew i would suggest using a 3/4-6 acme which is my preference diameter or a lot of guys are using 1/2-10 4 start acme

[losgetlost]

Thanks for the reply. That was my hunch. I'm not sure why he's suggesting an underated lead screw - the rest of the machine is beefy. What is my best option for a lead screw? If it means spending a little more that's fine. I don't want to skimp on a vital component.

[dertsap]

sounds like your building such nice hardware into it , have you concidered ballscrews , they are pricey but would work bautifully with the type of gear your using , and really if your going to be doing long runs and making money from it then it would be a small price to pay for the piece of mind

[losgetlost]

The builder actually offered ballscrews as an option. If I were to go that route than what would be an appropriate type of ballscrew for the size of my machine?

[dertsap]

it would depend up on the resolution you want to have , and the rest will be determined by the number of steps your motors and drivers will put out , theres two ways to go , high resolution lower speed , higher speed and lower resolution ,
for eg. the screws i use are 3/4 10 start screws (not ballscrews) ,they are
2"/ revolution so i get .001 resolution/step ,which is good enough for what i need my machine to do , but with that comes the speed , i keep my machine set at a conservative 500ipm and i dont need to wait on slow rapids and retracts , its all dependant on what you feel is good enough , the thing to take into concideration is what you will be cutting , do you need .0001 resolution for wood ?

[losgetlost]

So many choices....... My head hurts. I'm thinking that I will stick with lead screws. It looks like I just need some more "meat" so 3/4" looks like the way to go. So perhaps 3/4" 10 tpi. But how many start? You mentioned that you are using "3/4 10 start". Do you mean 3/4" 10 tpi? How many start?

[dertsap]

Originally Posted by losgetlost So many choices....... My head hurts. I'm thinking that I will stick with lead screws. It looks like I just need some more "meat" so 3/4" looks like the way to go. So perhaps 3/4" 10 tpi. But how many start? You mentioned that you are using "3/4 10 start". Do you mean 3/4" 10 tpi? How many start?

mine are 10 start , 2 inches travel per revolution , i got them from ebay so i have no clue of who sells them

on my sons machine we used 3/4-6tpi single start acme from fastenal which work pretty good

[ger21]

Go with 1/2-10 5 start acme. Most users here find that it gives the best performance for the price.

[Micky15044]

Originally Posted by ger21 Go with 1/2-10 5 start acme. Most users here find that it gives the best performance for the price.

I bought the 12-10 5 start and my machine is roughly 5' X 3'.

[losgetlost]

Spoke with my builder this morning. I'm going with 5/8" ballscrews. He pointed to the fact that if I ever want to machine any of the hardware for my guitars (ie. guitar bridges) that the extra precision that the ballscrews give would be ideal. Thank you everybody for your input.

[gerryv]

With a 12" Z axis aren't you concerned about losing a great deal of accuracy? There are some huge moments of force there to contend with. Even industrial machines seldom venture into that territory.