Tap drill size wrong (?) for 0.5625" UNF-18

[WilliamLYJH9]

Hello,

Novice user here, but I don't think this is "operator error". The hole tool gives a tap hole size of 0.481" (see attached screen capture), but every published reference I have seen lists it on the order of 0.5156" (75% thread, alum). Am I missing something?

Regards,

Bill.

[johnptc314159]

0.5156 is what i would use.   i never paid much attention to the hole size 😞    there is a look up table for most thread info which can be modified in fusion 360.

[HughesTooling · Accepted solution]

One problem is the dialog doesn't update the core diameter when you change the pitch. If you check the actual hole after creation you get this.

Mark