Opening up the ID of an aluminum tube

[WizardOfBoz]

I have a 12 inch piece of 1.75 x 1.625 alumining (6061-T6) tubing. It should be 1.638 (a little more than 41.6mm) ID. So I need 0.013 inch off the od, or about 0.0065 off the ID. The exact OD of the tube is not of super importance. I don't have a decent lathe to bore this. I don't have a reamer that would open the hole, nor do I anything that could hold such a beast. So I'm considering two shade tree mechanic/rub it with a rock approaches.
1) A 2" flap wheel 80 grit using my drill press. I only need about 3 inches to be enlarged. Several flap wheels, actually, and a lot of time.
2) A 41.5mm steel ball bearing and a small (1.5 ton) press. And probably some grease...
Comments? Better ideas?
Thanks,
Jim

 

[Garwood]

This is what a hone is for

 

[rons]

So I need 0.013 inch off the od, or about 0.0065 off the ID.

That would be .013 inch off the diameter of the ID, or 0.0065 off the radius of the ID.
Time for a homemade jig with a hand drill and a custom sanding drum.

 

[WizardOfBoz]

So, garwood, there are the spring loaded bar type hone. There is a flex hone. And there is a hone that is more adjustable .. Or, I can probably figure out someting with my (wood) lathe and a dowel.
Any suggestion on direction?
What grit would I use for hogging out 0.006 from the radius? And is this a 20 minute job or 8 hours of moving the hone back and forth? I can do either, I just want to plan.
Thanks for your help and patience.

 

[john.k]

A rigid (Sunnen type) brake cylinder hone would remove .012" from ally in maybe ten passes ,and a couple of adjusts......auto trans fluid is good for ally honing.

 

[L Vanice]

I will caution that my experience is that dry power "sanding" aluminum with aluminum oxide abrasive paper or cloth quickly leads to the metal getting hot and aluminum particles bonding to the alox grit and giving very bad results. I do not do enough aluminum work to advise a better approach.

Larry

 

[guythatbrews]

Make friends with a guy that has a lathe and knows how to use it. Bring him a 12 pack and the tube. Later get an uber and take the finished tube home.

 

[rimcanyon]

I've done a fair amount of brass musical instrument repair and fabrication of missing or damaged parts using dent balls, which aren't balls at all. They are typically oblong in shape (round in cross section), so the enlarging is more gradual than the curve of a ball. The balls are on a cable that gets pulled or pushed through the tubing with some lubricant, but there is no reason you could not push one through using a press, as long as the end of the tubing is square. The dent balls in the 1.625" range are part of a graduated set, differing in size by .0125", but they can be purchased individually. 1.6375" is one of the sizes available. They are highly polished. The brass tubing has to be annealed and kept annealed. I imagine you could do something similar with annealed aluminum.

N63B Larger Barrel Type Dent Balls(Half Sizes)

The larger sets listed below greatly increase your work range. The regular sets increase in .025 (.635mm) steps. The half size sets allow for much finer work if used with the regular sets. The combination cuts the size of range between balls to .0125 (.3175mm). These are pre-drilled to accept...

www.ferreestoolsinc.com

 

[john.k]

Any kind of abrasive on ally needs care .......if the ally is soft ,the abrasive may suddenly grab ,and rotate the work (especially if hand held) .....using any kind of grinding wheel on ally can be quite dangerous .........this especially so with angle grinders.

 

[boslab]

Good reason to get a lathe, useful things and fun.
Balling to size sounds plausible, a push ball on a press or jacked through, it’ll stretch as they say.
Mark

 

[WizardOfBoz]

Make friends with a guy that has a lathe and knows how to use it. Bring him a 12 pack and the tube. Later get an uber and take the finished tube home.

Is there anyone who likes beer anywhere near Kennett Square (or West Chester) PA?

 

[WizardOfBoz]

Good reason to get a lathe, useful things and fun.
Balling to size sounds plausible, a push ball on a press or jacked through, it’ll stretch as they say.
Mark

I have two, but neither are functional.

*Atlas
Monarch 10EE

 

[Garwood]

So, garwood, there are the spring loaded bar type hone. There is a flex hone. And there is a hone that is more adjustable .. Or, I can probably figure out someting with my (wood) lathe and a dowel.
Any suggestion on direction?
What grit would I use for hogging out 0.006 from the radius? And is this a 20 minute job or 8 hours of moving the hone back and forth? I can do either, I just want to plan.
Thanks for your help and patience.

Rigid hone. The other things are not good for much. Sunnen is the standard. Hand hones are made by Ammco, Lisle and others.

This is a 5 minute or less job. Honing is very fast in soft material. I would use 220 stones for a good finish. I would prefer to use a honing machine, not a hand hone for this. You need a good recirculating honing fluid system to get good results with aluminum.

Everyone should have a Sunnen hone or 3. If you don't have one, next time one pops up for $300 with a bunch of tooling buy it.

 

[WizardOfBoz]

I've done a fair amount of brass musical instrument repair and fabrication of missing or damaged parts using dent balls, which aren't balls at all. They are typically oblong in shape (round in cross section), so the enlarging is more gradual than the curve of a ball. The balls are on a cable that gets pulled or pushed through the tubing with some lubricant, but there is no reason you could not push one through using a press, as long as the end of the tubing is square. The dent balls in the 1.625" range are part of a graduated set, differing in size by .0125", but they can be purchased individually. 1.6375" is one of the sizes available. They are highly polished. The brass tubing has to be annealed and kept annealed. I imagine you could do something similar with annealed aluminum.

N63B Larger Barrel Type Dent Balls(Half Sizes)

The larger sets listed below greatly increase your work range. The regular sets increase in .025 (.635mm) steps. The half size sets allow for much finer work if used with the regular sets. The combination cuts the size of range between balls to .0125 (.3175mm). These are pre-drilled to accept...

www.ferreestoolsinc.com

rimcanyon, one of the reasons I like this forum is all the people that have done really cool things. Yes, it sounds like Ferree's dent barrels would work - but probably only in annealed aluminum. This stuff is solutionized and precipitation hardened (T6), so I may be consigned to a spring loaded hone. Or at least I need to get it within 0.001 or so before I try to push a swage through the thing.

I think that I'll be constrained to try either a self-made flap wheel with 40 grit wet or dry paper, using water as a lubricant. I'll report back.

 

[gbent]

I think I would make a hardwood boring bar. Make a pilot about 3" long that is a running slip fit, then make the rest the desired finish diameter. Drill a cross hole just before the diameter step for a tool bit. A set screw tapped into the wood would likely be sufficient hold the tool bit in place. You probably need a recessed area around the tool bit for chip clearance. You could drill a axial hole in the other end and insert a piece of 1/2 Dia. steel rod as a shank to turn with a cordless drill. Pin or jb weld in place.

You are removing .007. That could be done by hand with a scraper. A little power will make it better.

 

[boslab]

Haven’t I seen that guy who used to post trepanning bloody big nickel alloy bars into tubes several meters long doing a bore scrape using a tufnol lead plug with a cutter at the rear, can’t remember his name but trepanning nickel bar ought pull his videos up, he retired. I believe and sold his business to a big company, he was trepanning bits of challenger tank barrels on one video.
Mark