mendel w/ 3/8- 16tpi threaded rod?

I have a large quantity of 3/8- 16tpi threaded rod w/ a major diameter of about 0.355 inches.

0.355 inches = 9.01700 millimeters

I've got the standard mendel parts on the way. Does anyone foresee any issues with drilling out the parts to just over 9 mm and using my rod? I have not ordered washers and nuts yet.

The only issue I can think of is the bearings for the z-axis. You can't fit a 608 bearing on the 9 mm rod. You will either have to order the correct size bearings, or use 8 mm or 5/16" threaded rod for those two rods. Another issue is the steps/mm for the z-axis will be different, but you can calculate that and change it in the firmware.

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Darwin clone, Gen 2 electronics, Arduino Duemilanove w/ AtMega328, 5D Firmware, Pinchwheel extruder
[www.codeerrors.com]

Depending on how the parts have been printed, drilling the holes out may leave the holes without walls or with very thin walls.

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[www.hydraraptor.blogspot.com]

mccoyn Wrote:
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> The only issue I can think of is the bearings for
> the z-axis.

Thanks, and good point. I may just use the metric rod for the z-axis.

nophead Wrote:
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> Depending on how the parts have been printed,
> drilling the holes out may leave the holes without
> walls or with very thin walls.

Yea, that was what I was worried about. I'm thinking of replacing the "triangles" and all the threaded rod that connects the two "triangles" with my threaded rod, appropriate washers, and nuts that fit.

It's obvious I'd save a significant chunk of change based on pricing here in the USA, but I'd be reaming out parts where I had no replacement for. If it didn't work I'd have a pile of wasted cash.

The 3/8- 16tpi threaded rod is widely used here in the USA to hang stuff like suspended ceilings, sprinkler heads in parking garages, and HVAC assemblies in warehouses. It's cheaper than metric, but I got mine free out of a construction dumpster (a/k/a "skip shopping") I have enough for maybe 4 Mendels

The imperial equivalent of 8mm is 5/16 which is close enough to make no difference. I don't know about the US, but in the UK threaded rod is much cheaper than the plastic parts, so I wouldn't risk 3/8. You would have to drill out all the vertexes and the 4 big z-brackets and two y-brackets and somehow enlarge the U shaped holes in the y-bar clamps.

If you were printing the parts yourself then you could perhaps find parametric versions of all the parts in openScad on Thingiverse and make all the holes 9mm. Certainly there is a parametric version of the vertexes with feet.

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[www.hydraraptor.blogspot.com]