How would you make that.

I saw one of these in action at Southwell ploughing match a couple of years ago:

formatting link
Awesome!

Reply to
Dave Osborne
Loading thread data ...

If the pins really need to be an integral part of the disc for strength reasons then I'd do all the turning, mill away the rough between each pin just leaving enough material and then finally form them into round pins with a trepanning tool which you can make out of scrap fairly easily. I have made similar things for machining out valve spring seats on cylinder heads. Basically a boring tool but with the cutting edge facing inwards.

Doesn't need to be much more complex than a bit of square bar held horizontally in the mill off a mandrel and drilled at one end to take something like a 1/4" round HSS boring bar with a grubscrew to lock it in place. You can create size adjustment potential easily enough just by drilling for the boring tool somewhat off the vertical so the further down it sticks the smaller the cutting diameter. You can then set it to size against a dial gauge after taking a trial cut on some scrap.

It helps to grind a flat for the grubscrew on the boring tool so it always keeps exactly the same orientation. That means the relationship between depth (amount sticking down) and cutting diameter stays constant every time so if you do the trig at a known angle you can actually set the cutting diameter with a dial gauge on the top of the tool to indicate the depth. Just slacken the grubscrew a tad and tap the tool a bit further down to reduce the cutting size.

Sine of the angle is what you want so for a 10 degree angle every 10 thou further down on the tool gives you 1.7 thou reduction on radius. You get very accurate adjustment on diameter that way due to the multiplication factor. You just need to get the starting position of the hole for the tool in about the right position for your target size.

To be honest it doesn't seem as if your application requires a very specific size for the pins as long as they are smaller than the bores in the mating disc so anything close to 1/4" diameter should do the job.

Reply to
Dave Baker

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.