topic Re: How does Fusion 360 calculate hole size? in Fusion Support Forum

How does Fusion 360 calculate hole size?

CAD.OneFD9UA — Fri, 15 Dec 2023 18:35:00 GMT

I was getting ready to send a part to be machined and I noticed that the actual hole size for a threaded hole doesn't seem to match up with what I find when I look up drill size for the respective thread. I.e. 6-32 should be 0.107" vs 0.109" modeled. This is super close and I'm guessing doesn't matter unless the tool center interprets it as a non-standard tool. Out of curiosity, I build a part in Inventor (2023), added holes, exported it as a STEP file, pulled it into Fusion, did the same thing and measured the results for comparison (see picture attached). The holes on the left are Inventor, holes on the right are Fusion.

I guess I have two questions. 1) What standard is used when generating threaded holes? 2) Does it really matter?

Thanks,

Re: How does Fusion 360 calculate hole size?

HughesTooling — Sat, 16 Dec 2023 10:16:46 GMT

What Fusion produces is the mean size for the minor diameter of the thread not the drill size. Fusion does actually have the drill size stored in it's XML thead files but does not use it! Hopefully at some point you'll get the option to use the drill size or the minor size.

Mark

Re: How does Fusion 360 calculate hole size?

HughesTooling — Sat, 16 Dec 2023 10:15:20 GMT

Looking here it seems like Fusion is using the mean diameter and Inventor is using the minimum minor diameter. Neither of these are the actual drill size you get from a thread chart, for a 1/2-13 drill would be 27/64 or 0.4219"

1/2-13 UNC-2B
MINOR Ø.434-.417
PITCH Ø.4565-.4500
MAJOR Ø.5000 MIN

Re: How does Fusion 360 calculate hole size?

CAD.OneFD9UA — Tue, 19 Dec 2023 23:26:16 GMT

Thank you for your reply. I really don't want to be making some lucky machinists life harder by feeding them nonsensical dimensions. I know this is a small thing but it seems an odd bit to leave hanging considering Fusion is "the future of design and manufacturing". Might be a good candidate for a setting in preferences.