Inside Or Outside First?

[cvairwerks]

Got to think ahead on making some things that have tight tolerences and thin materials. I've got an aircraft restoration project that is going to require somewhere around a thousand bushings ranging from 1/4" to 1" od, and id's from 3/16" up to 1/2". Lengths will vary from 3/16" to 6".... Wish I had a big swiss machine in the shop to do them.

 

[2volts]

Got to think ahead on making some things that have tight tolerences and thin materials. I've got an aircraft restoration project that is going to require somewhere around a thousand bushings ranging from 1/4" to 1" od, and id's from 3/16" up to 1/2". Lengths will vary from 3/16" to 6".... Wish I had a big swiss machine in the shop to do them.

That will be quite a planning exercise to balance making good use of raw materials, optimising machining time and to have the right parts ready for when you need them. Achieving tolerances will probably be the easy part of it all. Bearing in my mind I have no directly relevant experience in planning something like this I would make up a spreadsheet of parts and sort it by OD then ID and lengths then try to work out a bill of materials that will minimise machining to OD, then work out a machining schedule based on common ODs and IDs...
Anyway, my brain is starting to spin now the more I think about it. There's a lot more variables to think about than first comes to mind. I'll quit commenting while I'm ahead. But I'll probably keep thinking on it!

pete

 

[cvairwerks]

With CNC capability and especially with a sub spindle, you now have to factor in cost to change material size vs just running one or two sizes and having lots of waste. I've had to crunch the numbers before at work on a job like this. Was it cheaper to hog a box our of 6" plate offcuts or shear up the sheetmetal and angles needed and rivet it together. In our case, hogging it out of plate was about 15% of the cost of riveting up the box.

In my case, I will probably make all of the bushings at once, as they have to be hard anodized too. Platers pretty much charge by the pound and have a minimum too.