Understanding Metric Schematic Dimensions

[aeroencychris]

Hi all,

Quick question: trying to do some work in Fusion 360 modelling a Pi Zero case, but I can't fully understand the dimensions in the sheet below. How exactly do M2.5 holes work? What would the diameter of the screw holes be? Tables online aren't giving me a straight answer and are mostly referencing drill sizes.

 

[tlink]

the diameter is 2.75 MM with a standard differential of 0.05mm

[aeroencychris]

1 minute ago, tlink said:

the diameter is 2.75 MM with a standard differential of 0.05mm

Oh, I thought that meant the depth it was drilled to. Thanks.

[W-L]

4 minutes ago, cdsboy2000 said:

Hi all,

Quick question: trying to do some work in Fusion 360 modelling a Pi Zero case, but I can't fully understand the dimensions in the sheet below. How exactly do M2.5 holes work? What would the diameter of the screw holes be? Tables online aren't giving me a straight answer and are mostly referencing drill sizes.

 

The holes are basically larger than the nominal 2.5mm screw so there is clearance. with a +/- of 0.05mm so a min of 2.45mm and a max of 2.55mm

[aeroencychris]

1 minute ago, W-L said:

The holes are basically larger than the nominal 2.5mm screw so there is clearance. with a +/- of 0.05mm so a min of 2.45mm and a max of 2.55mm

Okay, just planning on putting some mounting pins through them so 2.2 should work fine. Thanks!

[tlink]

2 minutes ago, cdsboy2000 said:

Oh, I thought that meant the depth it was drilled to. Thanks.

you can see it in the second most top left number, next to the 6. it shows an arrow pointing towards lines linear towards the exact hole with 2.75 above the arrow. it took me some looking but i found it eventually

[Squish4058]

M2.5 is the diameter its classed by, this does not mean the diameter of the hole will be 2.5mm

m2.5x3 would be a Metric 2.5mm diameter hole with a thread pitch of 3

 

The M numbers have nothing to do with hole depths and they should always be specified elsewhere

You can convert M2.5 to an actual hole diameter online

The idea is that when you want to make a M2.5 hole, you drill an UNTAPPED (unthreaded) hole of 2.5mm diameter, then put a tap tool in, this tool removes material, and makes the hole wider in order to add a thread

[aeroencychris]

2 minutes ago, tlink said:

you can see it in the second most top left number, next to the 6. it shows an arrow pointing towards lines linear towards the exact hole with 2.75 above the arrow. it took me some looking but i found it eventually

@W-L this kinda contradicts what you were saying but he has a point, didn't see that measurement in the top left saying 2.75. Should I just try a diameter of 2.5 and reprint if it's too snug?

[aeroencychris]

2 minutes ago, kris2340k said:

M2.5 is the diameter its classed by, this does not mean the diameter of the hole will be 2.5mm

m2.5x3 would be a Metric 2.5mm diameter hole with a thread pitch of 3

 

The M numbers have nothing to do with hole depths and they should always be specified elsewhere

You can convert M2.5 to an actual hole diameter online

The idea is that when you want to make a M2.5 hole, you drill an UNTAPPED (unthreaded) hole of 2.5mm diameter, then put a tap tool in, this tool removes material, and makes the hole wider in order to add a thread

Makes sense, thanks

[W-L]

1 minute ago, cdsboy2000 said:

@W-L this kinda contradicts what you were saying but he has a point, didn't see that measurement in the top left saying 2.75. Should I just try a diameter of 2.5 and reprint if it's too snug?

Oh sorry I mis-read it the min is 2.70mm and max is 2.80mm.