Have I misunderstood metric size hardware?

Glen

When I ask for an M5 washer from standard content, I expect 5mm + clearance.
I see an interference highlighted by red.
When I check the ID of the washer I get 4.55.
Doesn't look right to me.

nick_papageorge073

I just tried and its the same on my end. Except when I pick chamfered washer, it is a clearance size. Yes, that does not seem right? Maybe submit a help request?

GWS50

This is the case for some M4 washer too, I haven't had time to submit yet though

nick_papageorge073

I submitted a helpdesk request.

nick_papageorge073

I heard back from support. The washers we were finding were actually captive washers on screws (SEMs). That's why their diameter is smaller than the screw's major diameter. The traditional washers we were looking for are ISO 7089 or 7090.

glen_dewsbury

Thanks or checking that out Nick

jmoellers

 I replied to Nick's helpdesk request, but thought I'd share for the rest of the group.

I'm guessing you're using Plain washer large grade A ISO 10673 (or normal or small). This is the table from ISO 10673 for the small size (the ID is the same for normal and large sizes as well). M5 is 4.55 mm nominal. 
 

 
The reason for this is because washers from ISO 10673 are Plain washers for screw and washer assemblies, aka SEMS. I think you're actually looking for ISO 7089 or 7090. These are the more common ISO washers and have a 5.3 mm ID for the M5 size.