Metric to US standard conversion help

I finally received my printed parts for the Prusa in the mail. Excitement has me frantically running around town to get all the necessary vitamins. One problem though, no one in St. Louis, Missouri [United States] sells the metric nuts, bolts, etc. that I need in bulk! I can only get like 3 washers at a time. All the machine shops are closed because it is Sunday so i cant order any; besides I don't feel like waiting for another order to come in. So I need your help.

What are the things I need to look out for when switching all my measurements to standard? All my printed parts, I'm assuming were intended for metric measurements, So I don't want to ruin any of the parts, or have anything out of alignment. Is there some forum or list that outlines all the best standard replacements for the vitamins?

Edited 2 time(s). Last edit at 11/13/2011 12:23PM by kyleeamonahern.

Hey kyleeamonahern,

Awesome congratulations on your parts! Your in luck, it doesn't really matter what type of fasteners you buy as long as they hold your stuff together, it fits, and it doesn't get in the way of anything moving. My current printer is a Frankenstein's Monster of sorts, meaning that my Z threaded rod is SAE and my smooth rods are metric, mixed in with SAE and Metric fasteners here and there. All you have to do to make the SAE threaded Z rod work is just change it in the software for your controller. The x and y work the same way too. You can have different sized pulleys on each you just have to change the software. All you have to do is calibrate and change one value.

The only thing I would watch out for is that the standard #6 nut is WAY bigger than the M3. The #6 machine bolt and nut are the "equivalent" to the M3 but check out the photo below. This makes of the captive nut designs for M3 completely incompatible with SAE, that is assuming your printed parts are for metric fasteners. I know that there is an "undersized" #6 nut, but i'm not 100% on how it compares to the standard M3 but I do know it's a lot closer.




Stay calm out there.

Ben

you could get them from Canada since they use the metric system the same as the rest of the world

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Experimenting in 3D in New Zealand

A list of most of the conversions can be found in the Notes section of [reprap.org] with quantities of each specified in [reprap.org]

---Rant begins----
Slight correction to the previous post: according to the CIA factbook (via wikipedia [en.wikipedia.org]) aside from the US it is only *almost* the rest of the world that uses metric: Burma (Myanmar) and Liberia are bucking the trend as well at the moment plus the US military has been using metric for a long time :-)

So, outside of the US: "standard" length measurements means metric and ironically what you want is more widely known as "imperial units" (http://en.wikipedia.org/wiki/Imperial_units) taken from the fact that they were used by the British Empire that your forefathers wanted to cut ties with :-) (with interesting differences between US and British measurements introduced mainly in units of volume and mass)

BTW, For a window into why the rest of the world thinks metric is better, try understanding the Burmese system [en.wikipedia.org]

---Rant ends---

Anyway, history and jargon aside, in 1959 the yard was redefined as exactly 0.9144m meaning an inch is exactly be 2.54cm or 25.4mm so if you want you can do an exact conversion and then find the closest fit to your "standard" measurements (which is essentially what the SAE design is). Most parts are designed so that there is a good fit between standard metric and US nuts and bolts sizes so it isn't too much of a problem but pay attention to the size of nuts and the holes for them when looking at the trapped nuts.

Edited 1 time(s). Last edit at 11/13/2011 05:36PM by reece.arnott.

Thanks bdcannon, I just ended up spending hours mix-matching the two measurement systems for different parts of the printer. Damn America makes everything unnecessarily difficult.

Is there a reason no one has made abs screws and nuts with their printer?

Aside from SAE conversions, you're in the US so you should be able to order parts from McMaster-Carr. They have all the metric sizes you need. I'm in NYC and I got all my screws in metric from them, though I got my threaded and smooth rod in SAE from local hardware stores (diameter wise 5/16in rod is a few hundredths of a mm smaller than 8mm, more than close enough, though the thread pitch is significantly different so you have to recalibrate your firmware for an SAE leadscrew).

can you use a solder gun and melt the part into place? thread the part onto the screw bolt/ heat up the bolt and pull the part into the space the smaller nut would fit with a pair of pliers, and let it cool...

kyleeamonahern Wrote:
-------------------------------------------------------
> Thanks bdcannon, I just ended up spending hours
> mix-matching the two measurement systems for
> different parts of the printer. Damn America makes
> everything unnecessarily difficult.
>
> Is there a reason no one has made abs screws and
> nuts with their printer?

A couple people have experimented with printed M8 nuts. I had a crack at it myself and found that the size of the features and the 60° overhang means you end up with a chunk of plastic that mainly gets its threads when forced onto a screw or threaded rod. That said, I do think that a lot could be accomplished threading screws directly into plastic parts instead of using captive nuts everywhere. Self-tapping screws should grip printed parts pretty well. An awful lot of R/C car kits use self tapping screws in ABS parts.

Actually getting what you need now, I would also recommend McMaster-Carr. Their deliveries are quicker than you might expect. Also, every new build that doesn't use inch fasteners is a step in the right direction.

Just a note about Canada being metric. Although we ARE a metric country I have found it extremely difficult to find metric bits. Almost all of the shops still use SAE. I have considered going to Mcmaster Carr to solve my metric problems which is ironically in a country that uses the imperial system.

Hey, I'm from Canada too and have had issues finding the metric pieces needed. I ordered from McMaster Carr and had that order cancelled with this message. "Due to the complexity of U.S. export regulations, McMaster-Carr accepts international orders only from businesses. This decision also applies to orders shipping within the Unites States, because it is based on the final destination of the items. We cannot accept this order or future orders" Looks like I will have to create an account under a business. Just wanted to let anyone from outside the US know.

Yeah, a few people here have mentioned that canadian individuals couldn't order from McMaster.

Have a look at Fastenal, they have local stores in many canadian cities and they carry metric hardware.

+1 for mcmaster. Best source in the US. That and it can get a little addictive shopping there...

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

Quote
NormandC
Yeah, a few people here have mentioned that canadian individuals couldn't order from McMaster.

Have a look at Fastenal, they have local stores in many canadian cities and they carry metric hardware.

i will agree with the Fastenal i have used them, i was even in ackland grangers the other day and i mentioned that i am looking into buying some more metric stuff and they will be getting in more metric.

but yes in a metric country it is a royal pain in the ass to find metric parts in this country.

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[mike-mack.blogspot.com]