To be extra safe I normally make most holes 0.5 bigger than needed on 4mm parts, but for some holes where strength is important I have gone to 0.3 oversize through 10mm thick hardox (higher taper) and they have mostly been ok after a small amount of work with a needle file, for your design id say go 0.4mm or 0.5mm the intended size and it should be fine.
Like Andy says, clearance around holes is a must. A 0.5mm oversize hole is pretty standard (that's just 0.25mm clearance) for drilled holes and for laser or waterjet cut holes, as much as 0.75. Small waterjetted holes are often not particularly round and I like to clean them up using a Dremel with a tungsten cutter.
I see, well looks like I made everything 0.5mm too big from you guys have said.
Its not a big deal unless you are using soft material or really crappy screws
So it looks like I'm 'done' with CAD in regards to the hardox stuff. I just need to save up a few hundred pounds for it (he says not knowing the approx. cost).
So I said I was done with the electronics, but I still need to fit a power light. I've fitted a plug ready to connect the light but I would like to double check what light I should get. whats the minimum voltage I should get? if I need resisters what should I get it?
I guess you are going to use an LED? They all work on about 3V and will definitely need a dropping resistor. Some LEDs come in a mount with a resistor and you might be able to find one that matches your battery voltage - you really can't over-volt LEDs and expect them to last, so don't be tempted by something that's close.
Finding the resistor value is dead easy; just google 'LED resistor calculator' and pick one of the many choices. You will need a couple of details from the LED spec sheet and then the calculator will show you exactly what to buy.
thanks Nick I'll give that calculator a look
Looks like I need a 680 ohm resistor for a LED to run on a 4cell Lipo. Or 330 Ohm for 2 in parallel.
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