CR vs. Gas Pipe: I am not sure that the hardness is that different, in fact the gas pipe may be slightly harder. The important advantages of CR are:
-Better surface finish and dimentional tolerance . Gas pipe is actually made from a flat strip that is rolled into a pipe shape and welded, so there is quite a bit of dimensional variation in diameter. That said, the variation of gas pipe along the length is not too bad. You can get seamless pipe, at a higher price, but you need to go to a pipe supplier for that.
-Less deflection. Since it is solid, it will deflect less than a hollow. For 1" pipe, which is 1.315 OD and 1.097 ID, the deflection for CR is about half that of gas pipe. You can offset the defection problem by supporting the pipe or CR along the length.
The big advantage of gas pipe is that it is inexpensive. You can always change it to CR or drill rod at a later date. For my machine (using gas pipe for now), the problem is in the flexure of the structure.
Richard |