Making technic parts

[StormFalcon32]

I was wondering if it is possible to make custom technic pieces out of acrylic or something? For example, buying a sheet of acrylic the same thickness as a lego technic and then drilling the appropriate holes in it?

[JJ2]

That would be possible but the Lego tolerances are very small so one mess up will make the part too lose-too tight. Another option is 3d printing, mainly using Shapeways.

[aeh5040]

Efferman has developed an extensive catalog:

 

[bonox]

it would be relatively easy to get 'correct' tolerances with some proper machining equipment or especially a small NC mill. Obviously you're guessing and it's very much a near enough is good enough approach if the parts work (just like the 3D printed parts) because I doubt anyone has access to TLG's manufacturing tolerances.

There are some things to remember though - broaching axle holes will be tricky and you'll need to remember the spot face around every hole you want to put a pin into. 

If you're planning on free hand drilling a sheet then you may be disasspointed in the outcome, however I would think it's still possible to make simple items like train connecting rods by this method. Making a 20L liftarm with all holes in it would probably be a nightmare.

[Boxerlego]

I've hand made my own Technic parts. The Best way to make your own Lego Technic parts is using the Lego Technic Parts you have available around. By using the already made Technic parts you will have a better Connection with other Lego parts and this way making your own Technic parts will come together better.

[Boxerlego]

Here is a couple of Pictures of a LEGO Technic Part I made. 

  

[BusterHaus]

18 hours ago, bonox said:

it would be relatively easy to get 'correct' tolerances with some proper machining equipment or especially a small NC mill. Obviously you're guessing and it's very much a near enough is good enough approach if the parts work (just like the 3D printed parts) because I doubt anyone has access to TLG's manufacturing tolerances.

I remember reading that the parts have a tolerance of +/-.001".  This is pretty tight for machined parts (especially in plastic) but doesn't sound unreasonable for injection molded parts. 

Machining plastic has a slew of challenges.  Clamping can deform stock material, cutting tools that are not sharp can push the material instead of cutting it, resulting in insufficient material removal, and the internal stress present in the material has to be considered when making long, thin parts like Technic beams. 

I could see machining being useful for making some parts, but it has its limitations. 

[allanp]

If you want to machine out of raw stock I would use delrin as in my experience it is a good strong plastic that can be machined easily to a high tolerance and good surface finish much better than any acrylic I've machined.