emt conduit, galvanized pipe or black pipe?

[JohnG]

I'm looking for piping to use as my rails. After looking at home depot, I found 3 possible choices. They are emt conduit, galvanized pipe & black piping.

I'm just not sure which would be the best. I'm kindof thinking the black pipe is not the way since I noticed some surface rust on a few of the pipes. While the galvanized pipe conduit had a nice surface, it was no were near as smooth as the emt conduit.

I do have to take the y axis length into consideration, since those pipes need to be about 5 feet in length. But it's a moving table and not a moving gantry, so not much weight will be applied to it.

Any recommendations?

[Al_The_Man]

Not emt but Electrical RIGID (threadable).
Al.

[JohnG]

If I recall, the Electrical RIGID piping was similar to the galvanized piping when it comes to surface texture. Though I'm not sure if it's stronger. But it was more money if I'm not mistaken. I think it was something like $35 for 10 feet of it. Were the galvanized piping was half that.

[ger21]

I used EMT on my router. It's not finished yet, but it is mostly asembled. Just pushing it around by hand, I've noticed that the galvaized coating quickly wears off, and the bearings are wearing flats on the tubes. I think that the flats will gradually stop wearing as they get wider. Just a little info for you.

[wizard]

Originally Posted by JohnG I'm looking for piping to use as my rails. After looking at home depot, I found 3 possible choices. They are emt conduit, galvanized pipe & black piping.

I'd suggest agianst galvanized pipe. That leaves EMT and black pipel

Generally I find EMT to be of good quality as far as dimensions and straightness goes. Black pipe is a bit looser in that respect. EMT is thin walled tubing where as Black pipe can be had in a number of schedules, schedule 40 being common in home centers. In enay event schedule 40 is significantly heavier than EMT.

As I see it EMT woud only be suitable for the absolute lightest duty possible. It will not be anywhere near as strong as the piple plus it deforms easily. That easy manner in which it can deform might have been alluded to in another posting. The big positive is that EMT is easy to work with.

Iron pipe on the other hand is much stronger though I have a hard time believign that it is a straight and uniform as EMT. Also nice is that if you want a bit more stiffness you can go to a heavier schedule say 80,120 or what ever the number is as you get thicker. The outside diameter remains the same. Pipe requires a bit more effort to work with, tha is a bit of a negative.

One thng that you can consider using is Hydraulic tubing. This is often available in stainless if you are concerned about rust. The nice thing about hydraulic tubing is that it is designed to be used with comprssion fittings and such. Thus the OD dimensions are kept a little more uniform. The wall is much heavier than EMT so that helps a bit.

I'm just not sure which would be the best. I'm kindof thinking the black pipe is not the way since I noticed some surface rust on a few of the pipes. While the galvanized pipe conduit had a nice surface, it was no were near as smooth as the emt conduit.

I'd have to say that black pipe is the way to go if this is arouter for wood procucts. Galvanized pipe has a thick plating of Zinc which will wear off and get nto place you don't want it to. Plus until the wear stabilizes around the bearings you will have to adjust the bearing tension often.

I do have to take the y axis length into consideration, since those pipes need to be about 5 feet in length. But it's a moving table and not a moving gantry, so not much weight will be applied to it.

Potentially you have more weight being applied to it. It depends on usage of course, with a moving gantry the wieght never changes. The good thing about a moving table is that you should be able to add center supports to the table pipe. This can have a signifcant impact on stiffness.

Any recommendations?

Stainless Steel pipe! Yeah I know it is expensive, but you did ask for recommendations. As it is if you are working on wood or other materials without coolants, I'd suggest going with the black pipe. Spray a little Break Free on them from time to time.

Thanks
dave

[JohnG]

Thanks for your recommendations. I think I will go with the black piping considering how wear affects the coating on the other pipes. I would like stainless steel but I can't find any locally in my area. And I'm sure buying online would cost a fortune to ship.