Acme rod question

[THend]

Greetings,

I built, many years ago now, a 4 axis machine for cutting foam. The x axis 1/2 x 10 acme rod is not straight, and thus has a wobble. I made my own floating nuts so to say, but I have long wondered what the pros or well, those in the know, do about this anomaly?

Is the wobble normal? I don't know if I am describing this properly or not. Imagine 36 inches of acme rod supported on each end, and well there is a sag so to speak. However, it has been there from day one as far as I can remember.

I'd like to get some delrin nuts or the like, and get away from the floating syndrome I have had all these years. I am going to be doing a rebuild and this is one item that has bothered me because it does induce some backlash error.

Thanks in advance.

th

[ger21]

It's probably bent, if the "sag" rotates with the screw. You can try to straighten it, but it might be easier to just replace it. 1/2-10 acme is cheap. As long as the new one isn't bent.

[joecnc2006]

It can also be that things are not totally lined up, if its easy to remove then pull a stringline through the machine to see if everything it straight, if it is then it is a bent leadscrew like ger21 said. if not then look and see what makes it out of alignment.

Joe

[THend]

Well, it is bent, has been from day one. I guess that is the best description. Any idea how to straighten it, other than merely rolling it back and forth on a table and tweaking as required?

Thanks

[DSL PWR]

The tweaking method may work, but you will probably end up with a rod that has several "S" curves in it. Buy a new one...

[THend]

Ok, yes this is an old thread, but I am finally getting around to buying new Acme 1/2 - 10 rods. I bought the last ones from McMaster Carr.

I have recently bought linear slides and am ready to upgrade the rig.

Which material that they list would most likely be straight and work the best? Keep in mind, the machine is not "fast", but for me to use the delrin nuts sold by DumpsterCNC the rods need to be straight.

Thanks in advance for the help.