Depending on the accuracy you are trying to achive. There ae several options. If you are going for inexpensive you can just use std 1/2 - 10 treaded rod and nuts. If you want a bit more accuracy and more robust try 1/2 - 10 Acme rod. the nuts for those can be a bit pricey. An alterative to thoes are power nuts for trash compactors they are around 5-10 dollars each. Then you can get Thompson Rod very accurate and very pricey. Look at Mcmastercarr.com that will get you a good price range and you can order from them as well. I hope this helps