Thread: Increasing inside diameter of brass tube

Hi all,

I’m making a portable coffee machine out of brass tubing and need to increase the inside diameter of one of my tubes from 63.35 mm to 63.55mm. I don’t have a lathe and I’m not sure how I should go about this. I should add that I only need to do this for the first 20mm of a 40mm long tube.

Any help is appreciated and I may have more questions as I progress so please excuse my complete lack of knowledge when it comes to metal working.
Cheers

Rob

Originally Posted by rrjtedge

Hi all,

I’m making a portable coffee machine out of brass tubing and need to increase the inside diameter of one of my tubes from 63.35 mm to 63.55mm. I don’t have a lathe and I’m not sure how I should go about this. I should add that I only need to do this for the first 20mm of a 40mm long tube.

Any help is appreciated and I may have more questions as I progress so please excuse my complete lack of knowledge when it comes to metal working.
Cheers

Rob

If you find a (ball bearing) ball of 63.55mm diameter, you could press that 20mm deep into your tube, then punch it out again. Chris

Originally Posted by cba_melbourne

If you find a (ball bearing) ball of 63.55mm diameter, you could press that 20mm deep into your tube, then punch it out again. Chris

Thanks for the suggestions, but I forgot to mention that the wall is 3.25mm thick - will a ball bearing still move that wall?

I can't see how it could be done very easily( or accurately ) without a lathe.( may be wrong....lol )

Pressing a mandrel into it would require a lathe to make the mandrel first.....same problem.

A car exhaust business could expand it but it is such a small amount, they wouldn't have the control precision to do a good job and they would probably end up splitting it.

Maybe someone here with a lathe, who is local can help.

Is there a small machine shop close that would be able to do it for you? a TAFE machine shop?

Sorry, I can't be of more help.



Steve

Any expansion method means it should be annealed beforehand.
That means heating is several times to read heat and holding it at red heat for a couple of minutes and then letting it cool slowly in air.

With a 3.25 mm wall thickness I would just get that 0.2 mm bored out on a lathe.

A question we should ask is what is this piece doing, is it under pressure, liquid or gas, how tight does the fitting need to be?

If high accuracy or pressure sealing is not needed, another possibility is - have you already cut the 40 mm length?
If not cut a 60 mm length and then use a wooden arbor with emery cloth and work it back and forth and around and this should eventually take of the 0.2 mm. This will create rounded internal edge which can be removed by cutting 10 mm off each end.

Thanks for all the suggestions! The piece will be slipped over another tube (63.5mm OD) and brazed in place. It wont be under pressure and precision is not really required for the brazing - I just need a gap for the braze filler to flow through. Using the arbor and emery cloth may be the easiest option and if it fails I will find someone with a lathe.

Thanks

Originally Posted by cba_melbourne

If you find a (ball bearing) ball of 63.55mm diameter, you could press that 20mm deep into your tube, then punch it out again. Chris

Where exactly would one find a 63.55mm ball bearing and how much would it cost?

G'day Rob.

Which part of Melbourne are you in? That would be a 5 minute job here. I'm north, factory in Thomastown. Work Saturdays if that helps.

Regards Phil.