What's new
What's new

Countersink standards

ron_jh

Aluminum
Joined
Oct 8, 2007
Location
Toronto
Hi All,

When you have to drill a hole and countersink for a particular flat head screw or drill and counterbore for a particular bolt, where do you find the standards to go by. I can't seem to find it in my machinist handbook. Is there a website that has a good reference?

Thanks.
 
I just measure a SHCS or test fit a FHCS. :confused:

May seem Old Skewl, but never had it fail for me yet. :Yawn:


-------

Think Snow Eh!
Ox
 
I just measure a SHCS or test fit a FHCS. :confused:

May seem Old Skewl, but never had it fail for me yet. :Yawn:


-------

Think Snow Eh!
Ox

You and I went to the same school - sorry I mean skewl:D OX

CSKs are a nightmare

FWIW - I had a drawing 3 weeks ago with some holes maked ;- xdia csk to fit XX screw.

Knowing the general crap standard of hardware these days I asked for a definite size, which after a bit of umming and aaahing I got.

Did job to spec, (inc csks,) which was isnspected and passed,............ then get phone call ''Your csks are all wrong.'' .............. suffice to say the mistake wasn't down to me.;)
 
You and I went to the same school - sorry I mean skewl:D OX

CSKs are a nightmare

FWIW - I had a drawing 3 weeks ago with some holes maked ;- xdia csk to fit XX screw.

Knowing the general crap standard of hardware these days I asked for a definite size, which after a bit of umming and aaahing I got.

Did job to spec, (inc csks,) which was isnspected and passed,............ then get phone call ''Your csks are all wrong.'' .............. suffice to say the mistake wasn't down to me.;)

Seen that happen a few times as well, the most common mistake made by the guy drawing the print that the diameter of the csk just has to match the dia. of the screw head, right?
Well, put a .375 screw in a .375 csk and tell me what you see?
The screw isn't flush - it sticks up .010 - .020.
People who machine for a living know better.
 
socket head cap screw c'bore depth

I noted long ago that the depth of the head of a non metric shcs is the same as the major diameter of that screw. C'bore should be at least +.01" for this nominal dimension for the screw to lie below the surface.
:scratchchin: Assuming (I know it's dangerous) that the screws are AMERICAN Made!
 
:scratchchin: Assuming (I know it's dangerous) that the screws are AMERICAN Made!

We've had problems with customer supplied 'cheap' screws; sometimes had to machine the heads to get them to fit. Often the heads are not concentric with the shank and are all different sizes and who knows what material they are made from?

We now exclusively use Holokrome or Unbrako (US made) screws; more expensive but when the customer sees the difference in quality he will immediately agree with us.

Regards,

Mike.
 








 
Back
Top