Interesting. I'm usually pretty fearless about grinding my own tooling, so I'd be more inclined to try to make a gang slitter that would fin an entire cylinder in one go.
But then, I said "fearless", not "smart", and first I have to get it working the dumb slow way.
That would put so much load on the workpiece and the tool that it probably would tear the whole setup apart. Multi-feature form tools, which were used a lot in production years ago, usually require serious engineering of the setup and tuning of the tool to make it work.
This may well be the way Cox made the originals, but if they did, you can be sure they had that setup worked out by trial and error and with special fixturing. It's not for onesies.
That's not dumb. That's the job-shop approach.
I looked up some of my old MAP books and found another reference to making a filler disk to go between adjacent grooves in engine cylinders. That may be where I saw the idea originally, but I think it was in some tips I saw when I was at _American Machinist_ 30 years ago.
-- Ed Huntress
This may be considered by some as silly, but have you considered mounting something like a Dremal with a saw blade on your cross-slide and using the saw to slice out the fin areas while you turn the lathe chuck VERY slowly, by hand even? That should relieve any problems with digging in and will allow you much more control over the whole process. Just a thought.
Jim
SNIP---------------->
Actually, what will work better - I've done it to make very fine features in ebony, is to use one of those high speed carving tools - mine is 200,000 rpm - it's like a cheapened dental drill - put a straight sided bur in it, set the lathe to turn medium slowly and then slowly advance the tool (running, of course) into the work to the desired depth. I cut some fins in ebony that were about .020 thick with this method - it puts almost no load on the material. you could use a ball ended burr if you wanted a rounded bottom to your grove - get the burrs free from your dentist - that's what I do.
My bad, I assumed aluminum
================ After you have checked to make sure the gibbs/bearings/etc. are tight, check
We use carbide gang groovers in a few of our lathes at work. On a good day if the programmer gets too agressive the spindle amp faults. On a bad day the poly belts slip and burn up first. What a mess having plastic stuck to a poly vee style pulley. :(
Wes
Yuck! Imagine what it's like with a little hobby lathe.
My uncle, who taught shop, had an exceptional student who made a whole set of form tools to turn chessmen, in a single plunge-cut each. They ran in a
10" South Bend. He'd make one set of brass and another of aluminum.It was such a job, getting the clearances and reliefs right so they would cut in that little lathe, that it took him almost a whole term in school to get them to run right. And they had a very nice optical profile grinder to do the job.
-- Ed Huntress
Tim:
Fins? Fins?, did somebody say fins?
wow- I want that thing they made for the demo - that is a very cool little object
** Posted fromJust amazing, Bob. I was thinkin', so what's the globe on the end, and this guy's just babbling about fins, those are a couple of disks, and then.. we get to see fins
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