How to machine motorcycle swing arm?

The lathe is also a great idea. Clamp it to the cross slide with hold downs and spacers to get the height right.
Robert
 
All great info and appreciate the responses - thank you.

I don't want to file it as it's a visible part of the swing arm and want it to look nice.

I had thought about clamping it to the cross slide on my PM-1236 lathe but everything I had read about this type of machining was never particularly positive - but maybe that's just from a purist's point of view. Anyone had good success with performing similar machining on a lathe?
 
Well here is my take on this. First I want to make sure we are on the same page and you need the clearance in the swingarm in order for the axle to be adjusted for the chain adjustment is what I am thinking. Use machinist jacks or something and clamp down to them being indicated for the machining. Don t plunge your cuts and use a small endmill and mill on your sides. It s only roughly .100" each side you can creep up to it and there is alot of material in the cutting force direction but the trick is to use a small cutter and keep the forces minimal. You may still have to creep up to it but a good finish I feel can still be achieved on a final pass. Hss is better here!
Since it s clearance take your measurements of location flip over and repeat. Your concern is finish and function. Don t sweat it too much but still be on the ball.
 
mcarroll_nz said:
I had thought about clamping it to the cross slide on my PM-1236 lathe but everything I had read about this type of machining was never particularly positive - but maybe that's just from a purist's point of view. Anyone had good success with performing similar machining on a lathe?
Click to expand...
Use the "Search" function to look up user "savarin." He's documented several projects, mainly telescopes of various kinds, and he's done some absolutely magnificent milling work on a 9x20 lathe.
 
That slot you see is a piece of oval shaped tube welded in place and by the time you mill it out 5mm there will not be a lot of wall left. What equipment do you have? The oval shape extrusion is a standard shape available in different sizes, have you checked what the next size up is and if it is close,(Metric or Imperial),to what you need? You may have to make a custom piece and I'd be sorting that out first. Alumiweld is a low-temp brazing rod that would excellent for this job.
Re-tramming the head is not a big deal and as you are going to have to do it sometime just accept it as something you have to do on some jobs.
If you have a drill press it would be easier to drill out and blend with a die grinder.
I strongly suggest you get an insert that fits your new axle before doing anything else though.
 
It's tubing, correct? Clamp it up horizontally and use a key cutter to widen the slots, then blend with a file.
 
I appreciate everyone's input but in the end I chickened out. I dropped it off today to a machinist guy I know who has a mill that swings horizontally and extends so he can clamp the end he's machining directly to the bed.

I still have plenty more machining to do for this swing arm, creating the pivot shaft inserts and aligners and components for the axle locator inserts. But if I mess any of this up then it's easy enough to start again machining a new part.

Thanks again.
 
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