This won’t work, when they make a PCB, there is a limit on the number of drill sizes used in the process and in a cheap fab, you are sharing these with the other customers. This means that drill substitution happens and some of your holes won’t be what you planned.
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thank you for the information! I wasn’t aware of this.
Project thrown away!I will continue with drill bits.
Salvatore
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I was looking at capabilities here:
but I haven’t found any mention to a limit to the number of different drill sizes on the same board.
Salvatore
???
I think I told you twice already that the cheap pooling services substitute drill diameters.
The big machines in those factories, have automatic tool changers with hundredths of drills, but most often a lot of duplicates in a limited number of diameters. The machine counts the number of holes drilled with each drill, and automatically changes to a new drill after a predetermined number of drilled holes.
Some explanation
I have seen machines with 12 tools. They don’t want to stop the process to keep fitting rare sizes
I know you are getting some conflicting advice . . . but one thing is for certain, copper and solder are much softer than FR4 fibreglass and resin. Simulating hole sizes by drilling into FR4 is not simulating what you will get with a plated through hole . . .
interesting…
Salvatore
ok, good to know this.
Salvatore
I already mentioned in the discussion that JLC told me that if I request, for example, a 1 mm. hole, it will be 1 mm. (+0.13mm/-0.08mm. tolerance) plating included, that’s to say: finished, but maybe this is not what you meant to say; maybe you were referring to force needed to insert the pin in the hole?
Salvatore
I though you were planning to buy some drills to try some different size holes and test fit some pins ? if you do that in plain FR4 the result will be different to the same size hole after plating.
A 1.2mm hole in FR4 will not take a 1.2mm pin easily, a hole plated with a finished size of 1.2mm will give more and accept a 1.2mm pin.
mmmh, you are right but let try another approach:
if a 1.2mm hole in FR4 will not take a 1.2mm pin easily, I will try a 1.25mm hole. If it will fit in FR4 with some friction, this will indicate that 1.2mm plated should be ok.
Does it sound right?
Salvatore
No, not really.
If you drill the holes yourself, then they are not plated, while if you order a PCB the holes are plated, and if you solder them, they will be much stronger, regardless of whether there is a press fit or not.
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probably I’ve been not clear: that the holes will be stronger it’s a matter of fact,ok, but I asked if my trick could be good only to determine the correct diameter when the hole will be plated. If it’s ok, I finally expect only a bit more friction.
Or maybe I’ve not understood…
Salvatore
Again?
Again: For the cheap pooling services, they substitute drill diameters for other (nearby) diameters, so the holes may have a different size from what you order. Drilling holes at home is not going to change anything about that. So you either use the cheap pooling services and live with what you get, or you pay more to get exactly the hole size you want.
In my experience, those pins have quite a bit of leeway. If you only care about them not falling out, just specify a hole that’s in the middle of the spec, and if it ends up on the small side, you will have to use more force to insert the pin, and if it’s a bit big, they will be easy to insert, but the retention force only needs to be a fraction of a gram.
ok, not the “correct” diameter, but the best.
Salvatore
yes, I only care that the pin doesn’t fall down. I will try to specify a middle value. The square part of the pin 0.9mm for a diagonal of 1.2728 mm and the datasheet specifies 1.2mm for the hole.
Salvatore
This off-topic ( =not about KiCad at all) thread is already exceptionally long, has many good viewpoints and helpful answers, so it’s time to close.
Consider that an average Human Hair has thickness of 0.2mm
Machines that make PCB’s have Motion tolerances, Hardware tolerances, Tooling tolerances, cost’s associated with tolerances and their passing/not-passing inspection to customer geometry and tolerance requirements…etc
You’re inferring theoretical dimensions of a delta 1.2728-1.2 = 0.0727mm. What about thermal expansion/contraction…
Before Closing - last bit of Info…
Do you really need a Hole dimension with value/tolerance tighter than a small percentage of a Human Hair?
Whose going to make it and, for a price you can afford…
Grab a junk PCB and drill some holes and do some common-sense testing…