Fixture for machining ends of thin-wall aluminum tubing...

I just finished my new fixture for machining the ends of 2" dia thin-wall (0.049") aluminum tubing so that the ends are perpendicular to the OD.


The fixture is made from a piece of 2" stainless steel pipe. A plate is welded into one end so the fixture can be held tightly against the lathe chuck with a threaded rod through the spindle. The chuck jaws are tightened only enough to center the fixture.

The plastic inserts were bored with the fixture mounted and marked so it could always be installed in the same position. This eliminates the effect of the error in the chuck.


The piece of aluminum tubing is rough-cut to length on the bandsaw, the ends are smoothed, and it's inserted into the fixture. The two setscrews are tightened just enough to keep the tubing from spinning as I take light cuts to square up the outer end. After removing any burrs, the tubing is flipped for doing the other end. Measuring from the end of the fixture to the end of the tube, and adding the depth of the fixture gives me the exact length of the tube.

Getting the ends perpendicular to the OD is important, since any error is multiplied by three when the tube is installed between the 6" diameter endplates.


The previous method of holding the tubes didn't always produce square and parallel ends, since it didn't elininate the chuck error, and it picked up on the ID of the tube, which wasn't always concentric to the OD. There was no way to true up the assembled drums since the outer edges are pretty thin.

I hate drums that don't run true. This new fixture will cure the problem nicely.

Roger

Very Nice! How are the 6" end plates attached to the tube on the finished part?

There are several screws running from each end into a "nut ring" in the middle of the tube. Here's all the parts before assembly.


Note: The picture shows an old drum which has the endplates fiting into the ID of the tube. The new drums will have the endplates fit over the OD of the tube.

Roger

How about slitting the fixture part of the length of the tubing inside it and welding 2 ears on each side of the slit. One ear has a tapped hole the other clear for a 3/8 socket head capscrew. One twist of the clamp screw squesses the tubing and holds it straight in the fixture so you can finish the end. A stop inside can be made to make sure the length is always the same.

What are the reels used for?... Tuna ?

Roger, looking quite nice as usual.

If I may be so bold as to make a suggestion, you may want to scribe to replace the sharpie marker...while I admire the effort to mark that out, I have experienced sharpie to "wash away" under cutting oils, greasy hands, and the like...when you least expect it

Roger,

I've heard of winch drums crushing under the compression of multiple layers of tightly wound cable. Obviously you find 0.049 thickness is sufficient, but just guessing, I'd have used thicker tube. I suppose your "nut ring" provides additional strength.
Comments?

- Mike -

Gary,
Slitting the fixture would certainly work, but I'm concerned the pipe might deform if it was cut. The bushings are bored to have a tight slip fit with the tubing I have right now. It takes very little torque on the setscrews to keep it from spinning. I'll probably replace the bushings when I get a new supply of tubing. It doesn't take very long to bore them.

There's a shoulder/stop on the inside bushing. You can see it in the first picture. The tubing is seated against the shoulder for machining the second end.

The drums are used on winches I build for launching radio-controlled sailplanes. They are powered with a variety of modified automobile starter motors. They look like this:


Mike,
The nut-ring does provide some support for the tubing. It's a slip-fit with the tube ID. I've never had a tube failure, even on the drums I've built without the nut-ring.

Most of my winches are "sport winches", and they probably won't go over 150 pounds of line tension. Some of my drums with the nut-rings have been installed on six-volt Ford starters running on twelve volts. Those winches will produce a lot more tension, and I've had no reports of failures.

Roger

I want to do thin wall milling of aluminium sheet of thickness 1mm. but it became bend every time. please suggest me about some fixture arrangment so that i can mill it

ANUSHKA said:

I want to do thin wall milling of aluminium sheet of thickness 1mm. but it became bend every time. please suggest me about some fixture arrangment so that i can mill it

Click to expand...

The general solution for nearly ANY material that is in too thin a section to stand up to the stresses of working it is to provide some form of removable support. Look around, and you may find examples that let you address your specific challenge.

If not, PM community would need the specific details of the item you are trying to make, also from what form and starting point, and on what equipment.

Stating only "aluminium sheet of thickness 1mm" is too vague by half to get any sort of start on a solution. Find more options. Or share more information.

No soft jaws available?

Three jaw scroll chucks are a liability!

CalG said:

No soft jaws available?

Click to expand...

Yup, that would have been my approach--much simpler...

CalG said:

No soft jaws available?

Three jaw scroll chucks are a liability!

Click to expand...

3-J scroll chucks are never MY problem, period.

But ANUSHKA?

For all we know - so -far - he may be working with flattening a place to attach fuel fittings to curvy motorbike gas tanks - no lathe involved. He did say "mill", not turn.

"Winchman", last person to post before the thread missed the last bus to the crematorium most-recently logged-in over six years ago.