How to avoid boogered up Phillips head screws


Bryan Bosch

We all have one or more Philips head screw drivers in our tool boxes. It's pretty much impossible to be a DIY'er without them. But, if you own an a vehicle that was manufactured of Asian origin, chances are, the screws on it are not "standard" Phillips head. So, if you find that your Phillips head screw drivers are ruining your fasteners, it very will might be because you're using the wrong tool for the job.

Lesser known is the Japanese Industrial Standard (AKA JIS). Bottom-line, a standard Phillips driver will not go into a JIS screw all the way because the corner radius of the screw is smaller than that of a standard Phillips driver. Because of this, it leads to what is referred to as "cam-out". In fact, the standard Phillips was created to allow this, so that you know when max torque has been reached, avoiding over tightening or worse, snapping fasteners.

The differences between Phillips and JIS are not easily seen, so this illustration should help.

jis_vs_phillips.PNG

Sometimes screws will be identified as being JIS if there is a dimple or dot on its head. But, this isn't always the case. But chances are, if you're working on a Japanese machine, the Philips head screws will be JIS.

jis.JPG

JIS screw drivers are not hard to find, ranging in price from the mid to high $20.00 for the budget stuff, on up to 3x (or more) that for the good stuff. Good tools, if taken care of can last a lifetime and the right tool for the job saves time and money in the long run.




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I find that even when using the correct screwdriver, sometimes the head still cams out and causes the driver to slip. If i know that the screw has been in the part for a long period of time, I will dip the end of the screwdriver into some valve grinding compound to eliminate all slippage. (Especially when removing engine case screws that have endured many heat cycles and are covered in oil)

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I find that even when using the correct screwdriver, sometimes the head still cams out and causes the driver to slip. If i know that the screw has been in the part for a long period of time, I will dip the end of the screwdriver into some valve grinding compound to eliminate all slippage. (Especially when removing engine case screws that have endured many heat cycles and are covered in oil)

 

Now, you know that this is a "wiki" system. If you click the "edit" button, you can "add"to the article. FYI if you were not aware. :)

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You might find it works top use an impact driver.  Its my go to tool for fasteners while in the shop.  In the field is a different story.  The sharp impact breaks just about everything loose.  If not pay attention to whats happening at the bit and adjust the angle by touching against a bench grinder. Support ISO standards so your kids don't suffer the same fate!.  Most of the cheap Asian products are suspect as they don't adhere to common standards.  I keep a partitioned drawer full of common fasteners  so I can replace any suspect parts before I have a failure in the field. 

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I find that even when using the correct screwdriver, sometimes the head still cams out and causes the driver to slip. If i know that the screw has been in the part for a long period of time, I will dip the end of the screwdriver into some valve grinding compound to eliminate all slippage. (Especially when removing engine case screws that have endured many heat cycles and are covered in oil)

Thats a really good idea.  But to make it even better.... give the screw-heads a squirt with brake cleaner before applying some "grip compund".

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I always since 1971 had removal of carburetor bowl screws a big problem with stripping them.  Geeze, why not ALLEN guys?  I really hate phillips head anything, and my last name is Phillips.. ha ha  Thanks for the tip about the proper TIPS to buy.  But no matter what or how careful you are, sooner or later you are going to strip out either a carburetor bowl screw, or a throttle mounting screw, they both suck.  buy back up screws, and maybe replace them with Allen or STAR screws if available.   I wonder why in 45 years someone has NOT changed this configuration.. silly isn't it.

Gary

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Best value I've found is the Hozan (Japan) drivers on Amazon, work the best on Kehin and Amal carbs for me

Those look pretty good, going to get me a set.

 

I have seen that dot on there, but makes perfect sense.

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One common problem with both Phillips and JIS screws is the screw coating whether it be phosphate, cadmium, zinc, or powder.  The coating will build up in the bottom of the screw head and will not allow even the proper screwdriver to seat to the correct depth.  I have several screwdrivers I've filed the tip flat on to solve the problem.  The flattened tip allows the shoulders of the screwdriver to take the pressure as they should so that the screwdriver doesn't "cam out" of the head.  It makes a huge difference.  I remove damaged screws all the time by using this simple modification.

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One common problem with both Phillips and JIS screws is the screw coating whether it be phosphate, cadmium, zinc, or powder.  The coating will build up in the bottom of the screw head and will not allow even the proper screwdriver to seat to the correct depth.  I have several screwdrivers I've filed the tip flat on to solve the problem.  The flattened tip allows the shoulders of the screwdriver to take the pressure as they should so that the screwdriver doesn't "cam out" of the head.  It makes a huge difference.  I remove damaged screws all the time by using this simple modification.

 

I know what you are talking about, metals that don't mix well or corrode due to being exposed to elements or cleaners/chemicals.

 

I am fixin to get me a set of these JIS screwdrivers myself. I have Snap-On screwdrivers and the tips are more broad, as the example shows. Looking at a set on Amazon.com site.

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I know I'm a bit off topic,but the Robertson screw was used extensively on industrial,automotive and military equipment. Its much less prone to striping than a Philips.

Henry Ford recognized this as well.He tried to control production of the Robertson screw.When the owner disagreed, Ford chose the less effective Philips, hence its widespread use to this day.

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I have replaced all the phillips head screws on our yz125's with cap screws.  They use allen wrenches to install and remove and solves all the problems.  They are on the top and bottom of the carb, on the brake line brackets on the swing arm, on the chain guard  around the front sprocket, on the timing cover and on the power valve cover.  Makes life a ton easier. 

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I find swapping the phillips/JIS screws for allen heads the best method of dealing with this problem. I have done this since day one and never had one strip. It is just easier than replacing already stripped screws on second hand bikes with more JIS screws. Luckily most of the new bikes don't have many, if any of these screws anymore (with the exception of the Yz). None of my bikes have any of these screws anymore. 

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verry valuable information,  i never knew ther was a different variation of the philips head fasteners. looks like i found out why i have had stripped out screws for years.

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Quick tip is to seat the bit into the screw head with a small hammer. Pushes past the burrs. These screws are not hard at all so a simple hacksaw slot and a flat head screw driver and you are there. Dremel will work too of course but in the shop the heal all is to tac weld a nut to the head of the stripped screw and use a socket to back it out.

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A quick tap on the face with a parallel punch can restore crosshead screw faces and shock the thread enough to shift them,then chuck them in the bin and replace with stainless cap heads.

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Tip from Aviation Maintenance department. Use household comet cleanser on the tip of your cross tip bit to help prevent the dreded 'cam out"

 

Isn't cam out designed in so that you don't over-torque the fastener?

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