topic Re: Countersunk holes are wrong size in Fusion Support Forum

Countersunk holes are wrong size

andrew.smithPWL2Q — Mon, 21 Mar 2022 14:15:10 GMT

Hi!

I've been using F360 since late December pretty much daily and I think I'm getting the hang of it...

Recently I noticed that when I use the 'Hole' command to generate countersunk holes, the cone-shaped cutout for the countersunk screws is too large.

As an example: I want to make a countersunk hole for an M4 screw. The screw-head's diameter (which I measured from a McMaster-Carr screw that I imported is 7.5 mm.

Other software that I've used in the past could also auto-generate countersunk holes - here's a screencap of such a hole (in cross section):

The diameter is 8 mm - so, slightly larger than the screw head itself.

If I generate an M4 hole in F360, this is what I get:

... depending on the chosen standard the diameter is 10 mm or 9.4 mm ... This is way too big. What am I doing wrong?

Best regards,
Andrew

Re: Countersunk holes are wrong size

ryan.bales — Mon, 21 Mar 2022 21:30:51 GMT

We might be using the maximum values for countersink allowance. I agree its rather large compared to what i'd expect and i'll log this with the team. In the meantime you'll need to manually pick the diameter of the countersink you'd like.

Re: Countersunk holes are wrong size

TrippyLighting — Tue, 22 Mar 2022 11:12:15 GMT

According to the engineers bible, the ISO Standard for the top diameter for a countersunk hole for a M4 screw is 9.18 mm.

Re: Countersunk holes are wrong size

andrew.smithPWL2Q — Tue, 22 Mar 2022 13:06:56 GMT

Hello Ryan,

Thank you for your response. How do I manually change the diameter? The corresponding values are 'greyed out' meaning I can't edit them...

I also find it a bit annoying that every time I change a setting in the 'hole' dialog, the 'Size' jumps to a (seemingly) arbitrary value, instead of staying at M4 where I put it.

Best regards,
Andrew

Re: Countersunk holes are wrong size

ryan.bales — Tue, 22 Mar 2022 13:08:04 GMT

Change the hole tap type to 'simple'. Then you can manually specify the countersink diameter.

Re: Countersunk holes are wrong size

andrew.smithPWL2Q — Tue, 22 Mar 2022 13:13:38 GMT

Thanks!!

Re: Countersunk holes are wrong size

johnAMKDR — Wed, 22 Feb 2023 19:00:55 GMT

But what if you still want clearance? Besides editing the countersink diameter, you have to alter the hole's diameter (after noting what it should be for your choice of fit).