Countersunk holes are wrong size

[andrew.smithPWL2Q]

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

[ryan.bales]

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.

[TrippyLighting]

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

[andrew.smithPWL2Q]

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

[ryan.bales · Accepted solution]

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

[andrew.smithPWL2Q]

Thanks!!

[johnAMKDR]

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).