Screw Identification

I just found this short article that explains why sometimes our screwdriver fails to fit even if it appears to be in good condition.

Screw Head Identification
On the carbs, you’ll notice the cable support screws and choke housing screws often have “dashes”
stamped into the screw face. This is to designate that the screw is not actually a Phillips, but rather a Pozi Drive. See
included pictures. Pozi Drive #2 screw drivers are available from professional tool suppliers. Most techs are unaware of
the difference and use a Phillips screw driver, which strips the head on these screws.



On the carb sockets, you’ll notice the screw used for tightening the socket to the carburetor has a “dot” stamped into
the head. This is to designate that the screw is not Phillips, but rather JIS (Japanese Industrial Standard). See included
pics. If the techs switch to a JIS screw driver or driver bit for the carb sockets, they’ll notice a much better fit. #2 JIS
screw drivers are available from professional tool suppliers. Often people strip the carb socket screw head, because
they use a Phillips screw driver. The screws are not available as a spare part, forcing the technician to replace the whole
socket assy.



This article was written about identifying carburettor screws but I found it interesting that I've never had the difference in these screws so clearly explained. I hope you find it useful the next time you a screw that you can't get a grip on. Perhaps you've selected the wrong screwdriver?

I did my time as a mechanic/diesel fitter, never new that. Very good info.

Thanks for that Phil..... I always thought my Phillips bits and screwdrivers were just worn. Actually, using them on the wrong screw head types wouldn’t do them any good either, just like the screws themselves.

JIS-type screws are apparently universal on Japanese motorcycles and I've personally come across them on Engel fridges. The problem now though, is that the JIS designation has apparently lapsed, so Japanese screwdriver manufacturers can no longer sell JIS-designated screwdrivers!

Pozidrive is a better fit, less slippage than a Phillips. Pretty much every screw used in Cabinetmaking applications is Pozidrive. Square drive is also excellent, particularly in construction and high torque applications.
The old slot is almost obsolete, more a decorative thing in restorations now.

Very good info thanks. The slot screw would have to be the worst invented

Well I'll be screwed.

I find i can torque down a slotted screw more so than Phillips head but slotted are terrible when using with a impact screw gun driver..
When ever i`ve stripped an old phillips dome head i use a 4`` grinder & a thin grinder blade to create a groove for a slotted driver. Works every time.
It must have been near 30 yrs ago when i first discovered various types of star heads ect when working on a Peugeot 405 so figured that is where the new ideas came from France.
What a selection we have now days but i think those square heads are the bests."
Still have a Yankee screw driver in my box high tech they were in their day.
All the best for Christmas Folks.

I think the google search filed Philips head and mine with a bit of knowledge

thanks for that Moneybox. Never knew that either!