Parting brass bushings

J

Jkassis

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This may be a no-brainer to most of you, but I'm a bit baffled by this one. In my business, I have to cut down brass bushings (on a lathe) to accurate lengths and would like to have some suggestions on how to do this consistently without having to measure and mark each bushing and try to hit the mark accurately each time with the parting tool. Maybe some kind of a stop system to get the bushing and cutter into position so all I have to do is insert the bushing into a chuck stop, and bring the parting tool to its stop, and part it. For example, I have a 2" long brass bushing and I have to make two bushings at .750" each. Currently I use a dial caliper set to .750" and scribe two lines (one from each end) to make my marks for parting. I chuck up the bushing so that both lines are showing with a little extra hanging out of the chuck, cut the bushing that is furthest out first, then cut the remaining small piece from the bushing that is still in the chuck. Then I have to slowly trim each bushing to the correct size, bit by bit until the proper dimension is achieved. I have to stop the lathe many times to make sure I don't cut too much off. Then I have to radius the end of the bushing to eliminate burrs.

Is there some kind of stop made for a chuck that would set the bushing to a certain depth every time so that I could lock my cross feed to a certain position and just part the bushing accurately every time? I have a few different diameters of bushings that I have to do this to.

There must be an easier way...:thinking:
 
If you accurately know the width of the parting tool, take a very light skim cut at the face, then using either your DRO or a travel indicator, dial off the desired length plus the width of the tool. That should get you within a couple of thousandths.
Another approach is to use a set of soft jaws bored with a shoulder to stop against and hit the finished length every time. Within a thousandth or so easily.
 
Is there some way to hold these bushings on a surface grinder, if available?


-= Matt =-
 
Start by cutting a disk of metal or even plastic thick enough to hold the bushing out as far as you've been setting it up. Drill three holes in the disk big enough to clear the jaws of the chuck. (Maybe a couple of holes you can cut between to make three slots if that works better.) Position the holes/slots so that the jaws can tighten on your bushing with the disk in place on the chuck. That will set your depth consistently.

The next step is to make or buy a carriage stop to fit your lathe bed. With this locked in place, it is easy to move the carriage to the same place every time. You will still have your compound to make fine adjustments.

One last bit of tooling - grind a radius into the corner of a piece of HSS for chamfering the bushings after they are cut to length.

The whole setup will be most efficient if you do a bunch of bushings in one session. Slip the disk on the chuck and put the first bushing in and clamp it. Measure and position your cutoff tool. Cut off the first one, but have the end in the chuck set to 0.750", not the outside piece. Take the first one out and put in the longer piece that got cut off. Cut it to length without moving the carriage. Repeat with all of your bushings.

Next, set up your chamfering tool and dress all of the bushings. Again, the chuck disk will let you get all of the pieces the same length.
 
Don't know the size of your chuck or lathe, but another quickie way is to stick a piece of tool steel between the jaws against the chuck face and slip the bushing back against it lightly, then chuck the piece and remove the tool steel. It should hold pretty close. Just be sure to remove it before applying power. This assumes that the bushing is long enough to extend past the jaws with the tool steel (or whatever spacer you use) behind it.
 
My first choice would be to use 5C collet and a collet stop. Second choice Make some soft jaws for your chuck and bore them to the depth you are using now. Third choice make a spider for the chuck.
 
Great ideas everyone. Thanks! I think I will try the soft jaw idea first, as I have different diameter bushings to machine and I would like to have a set of soft jaws for my lathe anyway.
 
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I would use a 5C collet with a stop.

Another method, if you don't have collets is to use the parting tool as a work stop. Hold the stock against the parting tool, clamp it with the chuck and move over the length of your bushing plus the thickness of the parting tool. You can either use a dial indicator on the carriage or a hard stop and a spacer of the required length.

Tom
 
All good suggestions made here already. I dont ever have alot of these to do at once, but the simplest meathod for me is touching the end of the bushing with the blade and using an indicator offest the tool the desired length plus the width of the blade. If your using a good 3-jaw or collet chuck this can be done quickly ans easily.
 
There is really no one right answer. If you are simply parting a bunch of bushings from a tube, it can be as easy as chucking a bit of rod in a drill chuck on the tailstock and using that as a stop. Pull the tube out to the stop and part. Repeat...

If that isn't practical because you have to do multiple operations you could make a little L-shaped template that you can use to quickly set the parting tool position. Set the small leg of the L against the stock and bring the left edge of the parting tool to touch. Lock the carriage and part. If you are making a lot of parts, this is a lot faster than fussing around with a dial indicator but for very short runs, the dial indicator might be a better bet.

I don't know what you are using for a tool post, but with a QCTP you could make a little bracket that sits on the unused dovetail and holds a depth stop. Lock in your parting too, slip the bracket over the dovetail, and bring the guide to bear against the bushing.

bob
 
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