It actually has nothing to do with Bits from Bytes and everything to do with the fact that the United States is still not a metric nation. Do you know how difficult it is to find a metric wrench under 6mm? I didn't either. But, I do now. So, I have some advice...
If you live in the USA and you order a RapMan printer, I urge you to also purchase the RapMan Custom tool kit that they also offer for sale. Doing so will save you a LOT of time, trouble and probably money.
But, if you have ordered the Kit and not already purchased the RapMan Toolkit, then I hope I can save you at least a little aggravation and time by pointing you to places where you can purchase the tools you need. Just don't expect to get them all in one place.
SMALL METRIC WRENCHES
Neither Sears, nor any of the big box hardware stores normally carry metric wrenches below 6mm. However, in some stores and online they do carry a Craftsmen 10 piece metric ignition wrench set. It includes sizes: 4, 4.5, 5, 5.5, 6 thru 11mm and sells for $19.99 at the time this is being written.
I found a single Sears store that carried this set within a radius of 50 miles from my zip code. So, I looked elsewhere.
There are a few hobby stores near me. And, I was able to find the a set of tools that contained 5 small box end wrenches in sizes 4.0mm, 4.5mm, 5.0mm. 5.5mm and 6.0 mm. The set is also sold through Amazon as the #60008 21 PIECE MINI;TOOL SET EXCEL.
Fortunately, there is a Grainger near me and they just started carrying metric tools from ACU-MIN or Moody Tools. Here is the link to a set of 8 wrenches that cover sizes 2.5mm, 3mm, 3.2mm, 4mm, 5mm, 5.5mm, 6mm and 7mm. and what this set looks like.
This set is a higher quality than others and goes for $43.40.
Another alternative for metric box wrenches from 6mm and up are automotive stores. Here is a 6mm wrench by Autocraft that is sold through Advanced Auto Parts. This is part AC376 6mm wrench..
They can be purchased individually or in sets. Here is a set of metric wrenches that ranges from 8mm to 15mm.
Pricing on Autocraft parts varies, apparently, by location.
BALL-HEAD METRIC HEX WRENCHES
I could find metric hex wrenches relatively easily. However, that is NOT exactly what you need to complete a RapMan build. What you REALLY need are BALL-HEAD metric hex wrenches. And, finding these took me a lot of time and even more luck. I was looking for a set of small metric ignition wrenches when I went into Advanced Auto Parts. That is where I stumbled across a set of metric ball-head hex wrenches with every size that one needs to complete a RapMan build!
Finding the AC456 Autocraft 10-Piece Metric Hex Key Set Long Arm (Ball Head) made my day.
It includes the following sizes... 1.27mm, 1.5mm, 2mm, 2.5mm, 3mm, 4mm, 5mm, 6mm, 8mm 10mm. These cover, I believe, ALL the sizes we need to complete our build. The reason for the need of Ball-Head hex wrenches is due to the fact that some of the set screws that are used cannot be tightened from directly above. They have to be accessed from the side.
While it is possible to locate the proper tools to put together a RapMan 3D Printer in the USA, it is not as straightforward as it might be in Europe where metric is the standard for tools. So, ordering the RapMan custom tool set should save you a LOT of running around. And, it will put everything you need right in front of you in one compact package.