I'm getting ready to start on a Solsylva Belt Drive table. I'm making my metal order up now. I'm going to be ordering most of the metal from Metalsdepot.com.

I noticed that they sell a variety of round tube and round bar. Depending on what type you order, the tolerances are as low as .001" for their expensive stuff to a tolerance of .002"-.008" for their cheaper stuff.

What are the tolerances for gas pipe? Would it be worth it to buy the round tube or bar from this place?

Thanks

Karl

Do you mean tube or pipe. Bar usually refers to solid stock. I believe the difference between tube and pipe is that one is specified using ID and the other OD (I cannot remember which is which).

What is the tolorance referrng to - wall thickness or diameter. As long as the tolorances are what you need for your build you should be fine.

Have you looked at stock and pricing at you local steel yard. I've usually found they have better pricing than the online stores.

I'm new myself to CNC and this forum. I don't follow this thing with using gas pipe. Usually gas pipe is black or galvanized steel pipe - is that what people are using for the designs.

The tolerances are for the diameter. I'm just wondering what the tolerances for the black pipe are.

http://tinyurl.com/6olgwh

According to Wikipedia:
"In North America and the UK, pressure piping is usually specified by Nominal Pipe Size (NPS) and schedule (SCH). Pipe sizes are documented by a number of standards, including API 5L, ANSI/ASME B36.10M (Table 1) in the US, and BS 1600 and BS 1387 in the United Kingdom. Typically the pipe wall thickness is the controlled variable, and the Inside Diameter (I.D.) is allowed to vary. The pipe wall thickness has a variance of approximately 12.5 percent."

For pipe fabrication/weldments, the nominal OD is used, as it's "good eneough".

regards

http://www.cnczone.com/forums/search.php?searchid=2474014
there's a few builders using black pipe, search "black pipe" if the link above doesn't work

Is there something specifically about black gas pipe that makes it attractive for use in a CNC machine (over say regular steel pipe). I know from using black pipe in gas applications they tend to corrode easily. Maybe a better choice would be gavanized pipe - it is less likely to corrode.

Galvanized may not corrode, but the Cadmium and other constituent ingredients in the coating will kill you (death on the installment plan) when you weld them. Sch#40 pipe will take a long time to corrode through. Cut, burn and prime/paint will do the job....

regards

That's a good point - having not looked at any plans I did not realize there was welding of these pipes involved. Having said that galvanized steel is welded - normally you need to wear a approved respirator to prevent metal fume fever and scrape off as much of the zinc coating as possible.

There's not any welding of the pipes in the plans.