Grrrr wrong screws delivered

[rant]

In the middle of building the uArm, and need a bunch of M2x12-15mm screws. Bloody packet has M2.5 by mistake.

M2.5 is, according to what I read, one of the few (or only?) half mm sizes available. If it didn't exist, they would have been unlikely to pick M3 by mistake, but I can understand picking M2.5 for M2.

So there goes the uArm assembly for the day.

[/rant; thank you for listening]

JimboZA:
[rant]

In the middle of building the uArm, and need a bunch of M2x12-15mm screws. Bloody packet has M2.5 by mistake.

M2.5 is, according to what I read, one of the few (or only?) half mm sizes available. If it didn't exist, they would have been unlikely to pick M3 by mistake, but I can understand picking M2.5 for M2.

So there goes the uArm assembly for the day.

[/rant; thank you for listening]

Just nail it down. :wink:

Just nail it down.

Oh believe me I've done that many a time over the years Lefty.

Trouble is, these wee screws have to pass through existing holes in Perspex / Plexiglass and into the holes of servo horn fittings.

JimboZA:

Just nail it down.

Oh believe me I've done that many a time over the years Lefty.

Trouble is, these wee screws have to pass through existing holes in Perspex / Plexiglass and into the holes of servo horn fittings.

Well then just glue it down. :smiley:

One thing I didn't like about the uArm design was the number of different sized screws used; I would have much rather have seen a design that used only one or two screw sizes - it would have also been cheaper to source the parts (for them and us - plus for others that built it from the plans, they could purchase a single bag of screws and be done with it).

The only other thing I hate is the fact of metric sizes for the thickness of the acrylic or plywood used for the laser cut parts; here in the US it is difficult to get metric widths of acrylic/plywood (it is possible - just not something you can normally get - plywood tends to be easier, especially if you shop hobby stores or marine construction materials).

Most of the time you can only easily get standard size (imperial units) thicknesses - which are slightly different from the closest metric thicknesses. Enough to at least make me question and wonder whether that slight difference will be enough to make the parts impossible to fit together (or fit loosely, which would be worse). I won't know until I actually try building it, unfortunately.

The screws are only 2 diameters, M2 and M4, but yep there are a number of lengths. Sometimes the length isn't crucial, and say M4x12s could be used instead of M4x10s.

There are a couple of places I've seen so far where the material width is material 8), in many cases though it won't be crucial. For example in the end-effector, one piece slots into two others, and so the width of the slot obviously needs to be correct. On the other hand, where for example an arm swivels between two others, the gap is filled with washers so that would be easy to adjust.

Only safe way to convert from Metric though, would be to go through the whole thing with the proverbial fine-toothed-comb.