Dicing with Delrin - A Repair Job.

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Pete W.:
Hi there, Pete,

Thank you for your post. Yes, it would have been nice to have a mill - I think I did mention earlier in the thread that a neighbour had offered to let me use his mill. However, since I couldn't complete the project in one session, I declined the offer - I don't think it's reasonable to 'time-share' a mill!

These parts are quite small, the through bore is approximately 5/8" diameter and the remaining wall is quite thin so holding the part would be challenging, even in a mill. When I get to the profiling stage of the job I'm intending to try a method recently shown by Dale Derry in one of his YouTube videos - it doesn't require a rotary table.

After I posted my previous post I remembered that I'd left out one operation. The Delrin sheet from which the dominos are cut is about 65 thou too thick so I turned the domino around on the boring fixture and relieved the back surface around the bore by that amount. In anticipation of doing that, I'd taken particular care to position the two fixing holes symmetrically about the centre-line of the domino. There was a misalignment error of maybe 15 thou but I don't think it'll show once the part is profiled.

awemawson:
Coming along nicely Pete :thumbup:

What are you plans for the 'mill less profiling' ? I'm imagining it mounted on a spigot turned to fit the bore, and fixed on the cross slide using the lathe as a mill :scratch:

Do you have a small rotary table to mount it on, on the cross slide?

Pete W.:
Hi there, Andrew,

Thank you for your post.

You're partially right. I plan to trim off as much of the excess material as I dare using a junior hacksaw. Then the blank (it'll be the wrong shape to be called a 'domino' by that stage) gets mounted, as you say, on a spigot, secured by an inverted cup washer or clamp-plate and cap-head screw. I think I showed the spigot in an earlier post. The spigot will be mounted on a horizontal plate gripped in the vice on the vertical slide.

The first stage of alignment is to position the carriage so the cutter is the right distance from the centre of the bore of the blank. The carriage gets locked in this position for the remainder of the process. I'm thinking of using an end-mill in my Clarkson AutoLok chuck in the lathe mandrel. Alternatively I might use a small side & face cutter if it will reach the work-piece. I can't use a between centres mandrel because the vertical slide gets in the way.

Then the blank is aligned so the straight flank (still concealed within the blank!!) is in-line with the cutter. Traverse the cross-slide to make the cut, hoping that the clamp-plate is tight enough to stop the cutter from sucking the blank round on the spigot and into the teeth! Re-align and repeat for the other flank.

Then, machine the circular part of the profile as an infinite number of infinitely small flats ('infinite' means as many as my patience will allow!!). I'll set the cross-slide to set the centre of the bore of the blank on to the lathe axis and lock it, then release the clamp-plate and turn the blank in azimuth a little bit between cuts and re-clamp. Delrin seems to cut better than it files.

Have I confused you? If not, say so and I'll try again! :lol: :ddb: :lol: :ddb: :lol: :ddb:

Pete W.:
Hi there, again, Andrew,

Here's a link to the YouTube video that gave me the inspiration for my proposed profiling method:

seadog:
Not a bad way of doing it, for metal. I had some hinge parts to make for a neighbour's gazebo, quite intricate, but still, made in Delrin. There was a radius called for, so I set up a cutter in my lathe and arranged a pivot, at the correct radius from the chosen end mill, and then just rotated the part by hand against the cutter. Obviously you're back milling so it's not snatched into the cutter. In you case you've a larger radius to cope with but, with a little imagination I think it may be the easiest way to go.

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