North American Subsitutions

Is there a single document anywhere that gives the North American substitutions for the reprap mechanical parts? I understand that 5/16" threaded rod can be used for the studding so I assume that the same measurement will work for the barstock but what about the rest of the fasteners? Has anyone put together a full list of the non-metric options or do I just figure it out myself?

Good question. I'd like to know that one myself.

I think, though, that most of us Americans are just ordering the (more expensive) metric parts. No real reason to though. Except that nobody's figured it out and posted it yet.

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I'm building it with Baling Wire

I went through the trouble of spec'ing out all english parts. It cut the costs of the metal parts about in half.

There are some issues related to the bearings. When you get down into the numbered sizes of bolts they are no longer nice fractional dimensions, so finding a bearing with the right ID is tricky. Since the OD of the bearings would be slightly different, there might be trouble with the carriage - don't know for sure as I never thought this far.

Length of bolts is another issue. I planned on taking everything up to the next length and then trim down if needed.

The stopping point for me was the fact that all the parts would have to be changed. I initially thought I would just drill all holes slightly larger. Then I realized that this might reduce the structural integrity of the parts as inside the walls, the parts are sparely filled.

In order to get stucturally sound parts, I would have to modify the STL files and find a kind soul to print the modified STL files for me. Since that is such a long shot, I abandoned the idea. Once I have a working printer, I may revisit the idea due to the cost savings.

If you want the list of parts/sources that I considered, let me know.

Edited 1 time(s). Last edit at 03/06/2010 12:28PM by buzzard192.

Personally, I think almost all of the nuts/bolts need to be switched out for screws. Drywall screws as spec'd for the McWire would work great, and I think are available cheap worldwide? Since the diameter and length don't have to be exact, and the threads are self-cutting, I'd think any approximately correct wood screw would work.

But again, you'd need to modify the STL's and print modified parts, but in this case you'd need to make smaller holes.

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I'm building it with Baling Wire

problem with screws is that harder plastics (ABS?) will crack under the force that a self tapper exerts

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Wooden Mendel
Teacup Firmware

Triffid_Hunter Wrote:
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> problem with screws is that harder plastics (ABS?)
> will crack under the force that a self tapper
> exerts

Wear gloves, and heat the screw in a candle before screwing it in.

BeagleFury Wrote:
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> Triffid_Hunter Wrote:
> --------------------------------------------------
> -----
> > problem with screws is that harder plastics
> (ABS?)
> > will crack under the force that a self tapper
> > exerts
>
> Wear gloves, and heat the screw in a candle before
> screwing it in.

That would still be easier that the bolt/nut thing. Especially for those of us in the US.

But my experience with ABS plastic (none of it printed plastic, printed plastic may be (slightly) more brittle) would indicate that it's not really very brittle at all, and cracking wouldn't be a problem. Too small holes would be difficult to screw into, and too large ones would hold very well, but I suspect there is a very wide indeed of hole sizes that would work for ABS, HDPE, and other non-brittle plastics.

Other plastics, PLA and especially PMMA, are somewhat brittle. In those cases Triffid_Hunter is probably right, and there's no way to make something that you could screw into and get a decent hold without cracking/shattering your part.

I long to try it. I wish my extruder was working...

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I'm building it with Baling Wire

Self tapping screws in plastic are great for single use assemblies, but if you have to disassemble it ever, you're better off going with trapped nuts or threaded metal inserts. The plastic threads don't hold up over time. Lots of details on this subject in

Very few things on my reprap are assembled only once.

I just pay extra for metric hardware; it beats having to redesign everything.

Wade

I've always reversed the screw until it "clicks" down into the previously cut thread. This works fairly well, I've only occasionally had a problem with it even on plastic do-dads that I've taken apart dozens of times.

You are correct that they will eventually fail, but even then you can design it so the threads can be simply drilled out, and replace the screw with a nut/bolt. You get a low start up cost and easier part hunt in return for a slightly harder time modifying it down the road - and who knows how many of those screws will eventually be bolts? Maybe not so many.

You are correct, buying the metric hardware beats having to redesign everything. For me alone, there is no question of that. But I'm not the only one. Screws would be cheaper for everybody, and even a redesign into Standard measurements would be worthwhile considering how many people in the US will be making a mendel.

It's not something I have an interest in doing right now, as I have yet to print my first part on my McWire.

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I'm building it with Baling Wire

metric is standard everywhere except the US

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Wooden Mendel
Teacup Firmware

Note the capital, it's the name of the system of measurement. Not that you need to care, since obviously you're not in the US.

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I'm building it with Baling Wire