Truing end of aluminum rounds.

Forestgnome · Feb 9, 2012

I'ld like advice on a task. Starting with a 3" aluminum round, slicing off 1" long pieces. I then want to true the ends perpendicular to the axis of the round, hopefully on the lathe. I suspect I would have difficulty getting such short pieces in axial alignment in the chuck, especially since both ends would be of unknown perpendicularity (is that a word?). Any suggestions would be appreciated.

bcstractor · Feb 9, 2012

Not sure I get this? Typically aluminum "rounds" aren't that round. So turn the round, face the front then it will be perpendicular to the axis because that is what the lathe did. Cut off just over the length you need and put the machined face against the chuck to finish off the other face.

Am I missing something here?

TDegenhart · Feb 9, 2012

Assuming your cutoff saw is square and you have chuck with replaceable top jaws, I would cut the blanks with allowance, true up a set of soft jaws, face one side turn it over and finish the other side. The reason for the soft jaws is the most hard jaws are deep enough that you may not be able to seat the blanks against the back of the jaw.

Tom

VertigoGlass · Feb 9, 2012

TDegenhart said:
Assuming your cutoff saw is square and you have chuck with replaceable top jaws, I would cut the blanks with allowance, true up a set of soft jaws, face one side turn it over and finish the other side. The reason for the soft jaws is the most hard jaws are deep enough that you may not be able to seat the blanks against the back of the jaw.

Tom

I had to do a procedure like this once a while back and this is the way my boss showed me something similar. skim cut the outter to true it round face it, cut off on a saw repeat till the all the pieces are done then use a square block to space the piece out of the jaws this will square the trued up faced side to the chuck. tighten the chuck down and remove the block then face the saw cut portion. I have see a tool a guy made once with a piece of tubing that had three pieces of flat strap welded onto it like legs this was then milled flat and used like the block mentioned above but it stays in the lathe the whole time. put the spider in then the material and the chuck is tightened up and the material tapped square into the chuck locking the spider in.

TDegenhart · Feb 9, 2012

VertigoGlass said:
I had to do a procedure like this once a while back and this is the way my boss showed me something similar. skim cut the outter to true it round face it, cut off on a saw repeat till the all the pieces are done then use a square block to space the piece out of the jaws this will square the trued up faced side to the chuck. tighten the chuck down and remove the block then face the saw cut portion. I have see a tool a guy made once with a piece of tubing that had three pieces of flat strap welded onto it like legs this was then milled flat and used like the block mentioned above but it stays in the lathe the whole time. put the spider in then the material and the chuck is tightened up and the material tapped square into the chuck locking the spider in.

I've done this on occasion, the loose blocks. The trouble is I need four hands to hold everything in place. The other issue is using the blocks introduces an additional source of error.

Tom

Mike C. · Feb 9, 2012

Part in the lathe. Both sides square. Alternately, don't completely part, but slot say, 1/4" deep... then saw the center of the slot. You can use the face of the grooves to indicate in and then face off the end.

magicmaker · Feb 10, 2012

I do a similar process quite often. I use pot chucks rather than regular three jaw chucks. The metal is cut slightly over length and the resulting slug placed into a deep pot chuck (5C collet) but not seated against the bottom. A facing cut is done, the slug flipped (seated this time) over and the second side faced. I have built up quite a collection of the larger pot chucks of varying depths and diameters. If the roundness needs improving, I can turn down the slug side when doing the first face. The resulting slug is then mounted in a second stepped pot chuck for final facing and truing. This is fast and easy when doing a run of them. If you use a Kalamazoo 5C collet holder, the collet will not be drawn into the headstock and setting thickness is super easy/repeatable. That is a 3" diameter slug in the photo.
Jim

Metal Slave · Feb 10, 2012

Another vote for soft jaws. Running a small job now using that method. I would sure hate to be indicating faces all day long.

Limy Sami · Feb 10, 2012

First Qs - How many?................... what sort of tolerances?

The answers will have an effect on how much you put in to the job.

US-Okuma · Feb 10, 2012

Like magicmaker said use a 3" collet. I would take a long length of bar stock, turn the od to size, part the lengths a 1/4"+ depth like someone else mentioned, cut them in bandsaw. Turn the first face flip and seat then turn the last face square and to size. If you don't have means of using collets enco always has those chuck spiders on sale.

Forestgnome · Feb 10, 2012

Not enough pieces to warrent investment in a 3" collet, and I don't have a chuck with replaceable jaws. I believe the partial cutoff before hitting the bandsaw is the answer I'm looking for. The collet ideas are great though. I've been wanting to add the oversized and emergency collets to my collection. Thanks everyone.

toolmaker35 · Feb 10, 2012

Mike C. said:
Part in the lathe. Both sides square. Alternately, don't completely part, but slot say, 1/4" deep... then saw the center of the slot. You can use the face of the grooves to indicate in and then face off the end.

I've grooved many a rounds before to get an indicating surface before high-tailing off to the saw. Works like a champ for small batches.

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