Topic: New thoughts about phillips vs. allen head bolts.

[Raul CB750K1]

We all have experimented the joy of destroying a phillips bolt head. Some of us have wondered why those bolts were so soft, and why didn't Honda installed stronger ones. I personally will use allen heads in my CB350 resto.

But it's true that those jap bikes had a very high attention to detail. I once read in a Cycle World article about the fuel vent tubes of the carburettors. They are not strictly necessary, but there they are, and the carb return spring have a rubber shroud to avoid the unlikely chance of pinching the vent tube. So, why using soft philips heads?

Then I thought? Is it possible to overtight a phillips bolt with only a screwdriver? Very unlikely. On the contrary, stainless steel allen head bolt against soft alloy will make it very easy to overtight them. Couldn't it be that they did it on purpose?

Furthermore, today it's possible to buy zinc-plated or stainless steel hard bolts. Wouldn't they be more adequate than the original or allen head?

Raul

[dusterdude]

actually raul i do believe they do that is because you have to dissimilar metals going together and there is a chemical reaction of some sort and of course the phillips head is not a strong head to begin with.

[Raul CB750K1]

That makes sense duster, but they have used hex heads in some other bolts. Why phillips heads only in the engine?

[Paul]

Allen head bolts made of the same material as the Philips would tend to round on the inside easier than the philips ?? and you can't swing off them ??
Should'v used one of these.

[Steve F]

actually raul i do believe they do that is because you have to dissimilar metals going together and there is a chemical reaction of some sort and of course the phillips head is not a strong head to begin with.

I was able to get zinc plated "Allen" SHCS from someone offering the complete set on eBaY.  They're not as pretty as the stainless is.  Remember to coat the threads with anit-seize compound before installing them.

[MikeDeB]

I believe they used the phillips head screws to prevent them from being overtightened (reduce the risk of a cracked case).

Mike

[paulages]

that being said, has anyone seen torque specs for all of these case cover screws, etc? are those specs in the honda shop manual? i would imagine 7 foot pounds would be about right.

[grumburg]

Paul: Where did you get that lovely bike lift?

[jotor]

This was on History Channel or Discovery or something.  Phillips head screws are used because they are the best for automated machinery.  First major manufacturer to use them was Henry Ford.

I personally like the chrome plated 8mm machine screws with the little 8mm hex heads.  They were used on 3 valve Hawks first, I think

Allen head screws ar so .............................déclassé.

 

[TwoTired]

True philips head screws are designed to "cam out" when over torqued.  They were originally designed for mass production as the head is self centering for machine power screw devices.  If the machine torque is set too high, you get rounded out heads (screw destruction) instead of stripped threads in the host part resulting in destruction/damage much more difficult to repair "as new".

Lots of cross point screw heads are not true phillips design.  There are variations on the design that have flat slots and tapered slots.  Also, the bottom of the "V" can be pointed, crowned, or flat. The Angle of the "V" can also be different.

The Phillips was the first widely used cross point head widely distrubuted.  Now, much like Kleenex, Xerox, Coke, etc. everything that looked similar got the layman's description of Phillips even though it may not be a true Phillips design.  I've seen people use a No 1 Reed and Prince tipped screwdriver on a type 1 Number 2 sized cross point and then curse the screw when the head striped out!

Using the properly matched cross point driver tip to the screw being serviced will go a long way to keeping the screws functioning as intended.

The cross point design is self centering, but not self aligning. Angular misalignment greatly increases wear on both the screw head AND the driver tool.  Wear is bad and reduces screw head performance.  Misalignment also reduces the maximum torque transferance capability from driver to screw head.  Part of the reason why impact drivers work so well is that angular alignment is often idealized due to the screw head being reformed by the impact process.

Finally, worn driver tips can destroy each and every screw head they are used on, even if properly matched to type.
Always have a brand new driver on hand.  Take a look at the tip's edges with a magnifying glass.  If the edges aren't sharp and well defined compared to the new one, it's worn!  Worn tips will improve the chances of cam out and usually deform the crosspoint head in the process.

I know, it's difficult to give up that favorite screw driver that has been your friend for many experiences.  I suggest a quiet and reverent funeral service just before the heave into the trash can.    You are more likely to enjoy life at least a little more with a brand new driver in your hand flailin' on screws.

Cheers,

[jtb]

What did he say?

[Terry in Australia]

What did he say?

G'Day John, where have you been hiding? TT's answers are always technically correct, just really looooong, ha ha! Cheers, Terry.

[ofreen]

I replaced a lot of the Phillips screws in the 750 engine with Allen screws, including the rocker cover screws.  All the Allen screws that I found in hardware stores around here (they all carry Midway) were smaller in diameter at the head than the stock Phillips screws.  Because of this, the bearing surface with the Allens was less than with the Phillips, so they tended to deform the the top of the hole when torqued down, even when using care in tightening.  I solved this by using wavy washers with the Allen screws.  The wavy washers are thin, so they look good, and the Allen screws have never loosened.

Greg
'75 CB750F

[mutters]

my bonneville (proper one from meriden) left the factory with alen head bolts/screws fitted in all the engine cases, and they've been screwed in and out alot with no probs.So guess what I've fitted to the old honda.And the man up the road gets them from work for me
for $0. 

[ElCheapo]

I usually replace the screws with a #8 or #10 hardened screw. These are hard to cam out and they will pass even the most picky show judges. On show bikes you have to remember that there are several different types of "phillips" or "cross point" screws. Panhead, cheesehead, taper point, etc.

[eldar]

As far as I am concerned, if the screw works, it is fine. The head is not that important.. The thread and length and pitch are the important things.

That said, I hate slot head screws. Philips and its variants work well but allen head is the easiest to use. You can keep the wrench in at up to a 15 degree angle on most screws and the screw stays on the driver better for those times when you are trying to get at something in small spaces. Nothing more frustrating than trying to put in a screw and it falls off and you have to try and dig it out!

[paulages]

Paul: Where did you get that lovely bike lift?

i got it at harbor freight, sold for about $200. i had an inside hook-up, so i got it for cheaper. right after i got it, i found out they had lifts for the whole bike, which would've been much nicer. oh well...

[TwoTired]

What did he say?

Okay, let me rephrase.  Some people don't like cross point screw heads because they aren't idiot proof.  They mutilate them and blame the screw.  Then they call them names like, phillips.  Allen head screws are less accepting of stupidity attacks when people attempt to use the wrong tool on them.  People are more likely to curse something else when they can't find a tool-like thing that will impale an allen head.

Allen head screws have better PR, as a result.

That better? 

[BobbyR]

I work for a Japanese manufacturer who also makes Mortorcycles. My division builds trains, but our engineers know a great deal about bikes. You will find most non critical parts assembled with Phillips head screws. There are a few reasons, first of all they are cheap,  the assemblers and techs on the shop floor can run around with screw guns and get things together pretty quick. The customer techs do likewise during normal maintenence. More stressed assenblies are mounted and are not taken apart with any regularity use Allen heads with red Loctite on the threads. Critical parts are of course assembled with bolts. Whiile our covesr are not stressed parts, they are not removed very often, so our guys use Allen heads on their Bikes since you have to give them a bit more torque when loosening them. To prevent overtightening just push down with two fingers.