Thread percentage

[Jeff]

Anyone else have a customer that calls out abnormally small thread minor diameters?
I currently have a print that calls out a 17.5mm minor on an M20 x 2 thread.
That's about a 97% thread.

Maybe the bolt that goes in there has a special P.D. or something?

[JParis]

Don't do much in the way of outside work any more, however, that is a spec that would make me ask if it's correct...

75% is generally considered a "tight" thread"
65% is pretty normal
55% is a loose fit

at 97%, this would give me great pause, not only from the percentage of thread but actually cutting it successfully.

[Jeff]

Don't do much in the way of outside work any more, however, that is a spec that would make me ask if it's correct...

75% is generally considered a "tight" thread"
65% is pretty normal
55% is a loose fit

at 97%, this would give me great pause, not only from the percentage of thread but actually cutting it successfully.

Yeah it's a red flag for me too. But it's also the 2nd time I've seen it from this customer and last time the boss didn't want to call them and told me to take it to the high limit. Which, coincidentally fell into the low limit of a "normal" minor dia.

But this one has a stupid DIN ISO tolerance number for general tolerances and I don't have those kinds of charts.
DIN ISO 2768 -mk
DIN ISO 8015

[JParis]

and last time the boss didn't want to call them

Well, I would run it up the pole...and let them make the call or not....I would document it too so it couldn't come back on me

[Jeff]

Well, I would run it up the pole...and let them make the call or not....I would document it too so it couldn't come back on me

He's the owner. Can't run it up any higher lol. My main concern is thread milling it, but I should be ok.
I'm definitely going to bring it up to him.
Thanks!

I asked Chat GTP to define the DIN callouts and it gave me .pdf versions.
Hell yeah!