How tight of tolerance to ask for?

I'm looking for a machine shop to cut my threaded rods. I keep getting asked what the tolerance is. Can someone explain what tolerance should be?

McMaster provides tolerances for all the rods they sell. Perhaps you could look up a similar rod to get an idea.

[www.fastenal.com]

This link may be useful in determining what you are looking for. Why do you want a machine shop to cut your threads? You may save a lot of money just ordering from McMaster or other reprap suppliers with exactly what you need. Unless you are doing a custom ball screw, I'd definitely avoid having custom machined threaded rod, and even then, you really should weigh your options unless money is no object for you.

However, your tolerance will likely be best explained using the class system as described in the link. If it's a length of thread tolerance then you need to determine how close to a specific length it needs to be. Example, you need 300MM length and you are holding it between 325-350MM apart in your x-ends, then you may say 350 +0.00MM/-25.00MM. Because it cannot exceed 350MM in length or it wont fit, and it cannot be less than 325MM in length or it wont hold properly or fall out.

Remember, the tighter the tolerances, the more money you are going to pay.

Edited 2 time(s). Last edit at 02/22/2013 08:20PM by Bobbitay.

I think he is asking the tolerance on the length. +/- 2mm should be easy for them to achieve (I.e. not add any extra cost) and amply accurate for a reprap.

I don't have a shop cut them anymore. too many ruff ends and not threading bolts on ends properly, in otherwords too hard for nuts to be placed on the ends . I would recommend using bolt cutters, and with a die and a drill follow thru the die and recut the threads thru to the ends after the threaded rods have been cut, and sand grinded.

if you have a hardware store cut them for you max out of pocket is 25 cents a cut, but you will still want to sand them down, and cut them again with a die.

I just cut mine with bolt cutters, and sanded the ends to be round with a disk sander so nuts went on nicely. You can always thread a regular nut on, cut with a hacksaw, and unthread it to repair the thread. The length tolerance is really unfussy - you could get +-5mm and probably have no problems.

Measure twice cut once