Rotring 600 Polycarbonate Cap

Rotring 600 with polycarbonate lid

For a late birthday present, I got a Rotring 600 0.5mm mechanical pencil. It’s a great pencil, but the tip does not retract, making it very un-pocket-friendly. I set out to make a lid for it, and after exploring wood, acetal, UHMW, and teflon, I opted to go with polycarbonate (partly because I found it for cheaper than the others). First, I measured it with a dial caliper, and then selected drill bits and depths from there.

Rotring 600 Grip
Measurements of the Rotring 600 Grip

After building a proof-of-concept model with a wood dowel, I used my Grizzly 7×12 lathe with center drills and four regular bits (smallest/deepest first) to build one with 7/16″ polycarbonate rod. I cracked the first attempt, broke off a drill bit in the second, and while the third is not perfect, it works. Apparently, polycarbonate turns to powder when overheated — not good, but good to know.

Rotring 600 0.5mm Polycarbonate Lid Measurements

Thanks to the slight taper on the grip, the cap as built fits snugly, keeping the tip out of harm’s way. Now the pencil is pocket friendly, can be carried or stored with the lead out, and as long as I don’t drop it on the tip while using it (granted, this is when it is most likely to be dropped), I should be good to go! As an added bonus, the cap is apparently compatible with the Alvin Draft/Matic series; I bought an 0.3mm pencil ( No. DM03 ) as a more-affordable complement to the Rotring, and its grip has similar dimensions.

Finished Rotring 600 0.5mm Polycarbonate Cap

UberKlamp for King Kutter Food Processor

Disclosure:  I’m posting this after-the-fact on January 8th, 2011.

A neighbor presented me with this problem.  Her mom had come up with a perfectly worthy kludge to table-mount a very nice hand-crank food processor.  However, the kludged mount had failed, and I had the opportunity to either fix it or come up with something better.  I should add that I was always looking for any projects that would give me an excuse to use my Harbor Freight Tools Mini-Mill (44991).

King Kutter with original kludged table mount clamp

I opted to start over from scratch.  The clamp/mount would need to accommodate a range of table top thicknesses, give enough height to allow room for a bowl, provide a strong mount without marring the table top, and be able to take some abuse.

The original mount used a hex piece to mount to the triangular base of the cutter body.  I opted to mill three flats at a taper, onto a piece of 3/4″ round aluminum stock, with a 3/8″ hole drilled through it; this turned out to be two pieces, since I felt like the height was too low with just the one.  For the clamp itself, I used 1/2″ x 2″ 6061 aluminum bar stock.  The vertical piece was drilled and tapped, to accommodate four 1/4-20×1-1/2 stainless steel button head hex socket screws I had around.  The top horizontal piece was milled to accept the head of a long 3/8″ bolt used to attach the round pieces on the top, with a lock nut at the very top.  The bottom piece was drilled and tapped for a 3/8-16 thread, and I used an i-bolt to act as the clamp spindle.

Design and parts almost ready to go

For the clamp pad, I originally used a 3/8″ stainless cap I found at Home Depot, but I didn’t like it – it was loose and unstable, and not up to the standard of the rest.

Substandard clamp pad

If I had a lathe at this point, it would have been easier to make a nice clamp pad from a small piece of 3/4″ aluminum.  It was challenging to get an exact center on the mill, and I originally planned to connect the pad via a short #4-40 flat-head screw, screwed into the end of the i-bolt.  This would have worked, but the tap broke off in the i-bolt, and I went with plan B, which was a screw in the side of the pad, just long enough to keep it on while the pad rotated freely.  This involved grinding off a couple of the i-bolt’s threads just wide enough for a #4-40 screw.  All this was done so the pad wouldn’t come off when the clamp was unmounted and rattling around in a drawer.

Some felt was attached to the bottom of the top piece, and it was ready!

Finished clamp
Finished clamp attached to cutter

Not long after this, it was strenuously field tested and pronounced done!  I was a little sad to part with it, but it found a good home.