What exactly is an "Acorn" lug nut?

[SteveM]

I have always considered Acorn lug nuts to be the closed end type of lug nuts.

However, it seems that I have recently seen other descriptions, based on the shape of the lug nut.

I just don't want any surprises at inspection/tech.

I am using common (Summit), open end OEM replacement type lug nuts with tapered seats on steel wheels and OEM studs. (Record is 105 mph in my class).

Any clarification on the "Acorn" thing would help.

Steve.

[38flattie]

Steve, you are correct-acorn nut is the closed end type of lug nuts.

Good luck!

[cagedruss]

Here is an example, a long Acorn type.

[Captthundarr]

A pretty one at that.

[Stainless1]

Throw it in the lathe, cut the end off and it's legal... depending on wheel size and speed 

[jimmy six]

Lathe? Hacksaw!!!...make sure the threads go to the end. JD

[RichFox]

I drilled some through and ran  tap afterward. Few more threads can't hurt.

[Geo Metro Racer]

I have always considered Acorn lug nuts to be the closed end type of lug nuts.

However, it seems that I have recently seen other descriptions, based on the shape of the lug nut.

I just don't want any surprises at inspection/tech.

I am using common (Summit), open end OEM replacement type lug nuts with tapered seats on steel wheels and OEM studs. (Record is 105 mph in my class).

Any clarification on the "Acorn" thing would help.

Steve.

What class are you running in?

[Ron Gibson]

The open nut is required so the inspector can see the end of the stud to make sure there is enough threads in use.

Ron

[dw230]

Class doesn't matter, rule states no Acorn style lug nuts.

DW

[Milwaukee Midget]

I drilled some through and ran  tap afterward. Few more threads can't hurt.

Rich, that works provided it's solid all the way through.  My Dodge came with acorn nuts, but they're simply a chromed aluminum cover over a standard lug nut.

I'd bet the anodized picture in cagedruss' response is the same.