View Full Version : Al. pipe Tolerances

01-10-2009, 11:47 AM
I have a question about the use of an Al. pipe.

If I put a suitable bearing, (not gonna say what kind !), inside of a 5" OD x 2" thick Al. disc. make 2 of these, put a good 2" tgp shaft in the bearings, how "well" will it fit inside the Al. pipe ? I know there isn't a true 5" ID pipe, but just for example. The tolerances given that I can find are +0.00" and -.020" for the ID. I want the shaft to fit inside the pipe and still be on center after I bolt it in place. How is that going to be possible if the pipe is .020" "off" ?
Obviously, I plan on putting a gearbox, motors etc. in the pipe attached to the shaft too, but I think the concept is there...

Do I need to send the pipe to someone with a big ass lathe to open the ID so that it is all the same from end to end ? I was considering like a 24" long piece.

I can make an "assembly" that slides all of the pieces inside the pipe lined up beforehand, but that is extra work..

Maybe the wall will flex enough when I bolt the discs from the outside ? Not messing up the alignment ?

Thoughts ?


01-10-2009, 02:59 PM
To get it all the same I.D. the full 24" I think you would need to line bore it. Gary P. Hansen

01-10-2009, 03:55 PM

Yeah, that is what I was afraid I would have to do.
Any idea what that costs ?


01-10-2009, 04:57 PM
Could you line bore two 12" sections and screw them together to make a 2 foot section? Gary P. Hansen

01-10-2009, 05:37 PM
I was thinking of doing 3 segments and putting a larger piece over the seams. That would work ok I think. Do the ID and OD where the bearings, gearhead and the motor go so that it is accurate. Where the shaft goes is the ony part that has any weight on it. The other two have no weight or pressure really.


01-10-2009, 05:40 PM
You might not need to bore the pipe if you could make those bearing holders to fit. Pipe sizes, even though this aluminum, are nominal. And they can and do vary.

I would order the 5 inch inside diameter pipe first and then make the holders to fit.

But this might bring up the question of what difference there might be in Schedule 40 pipe and another product called holobar.

01-10-2009, 08:29 PM
Just counter bore each end for the bearings to fit and run with it. Are bore the pipe to fit the aluminun disk the bearings are in.