Fastener choice and why...

[peejay75]

If space allows, why [would a manufacturer] choose a Philips head button screw over a hex head (with or without Phillips) flange screw?

The tools part is, I'd feel more confident tightening or removing a hex head fastener than a Phillips, or next, a socket head fastener.

 

[AA/FC]

Where is the fastener located in this example?

 

[chevy.stroker]

Other questions are:

What material is this fastener screwed into?

What type of threads: machined or tapping?

 

[JradM]

Assuming you're asking what reasons might possibly exist:

1. So the driver will cam out during installation if over-torqued. After all, that's allegedly why the Phillips screw was invented.
2. Ease of maintenance. I'm not suggesting a Torx or hex-headed fastener is hard to turn, but Johnny Homeowner is more likely to have a PH2 than a T15.
3. Overlapping use of two different tools - e.g. if you have a bolt and nut, it might be best to use a 1/2" bolt and 9/16" nut so you don't have to have two 1/2" wrenches. Maybe that could happen with two screw types. More likely, just an application where you don't need high torque so the Phillips head is just to hold the fastener steady while you apply torque to the other side.
4. Where debris might collect? A hex head screw is more likely to fill up and is a little trickier to pick out.

I'm not suggesting these are good or common reasons to pick a Phillips screw (well, except #2), just a reason why it could be chosen.

 

[VolvoRyan]

IIRC, phillips is designed to be self-limiting in how tight something can be, as the tool will cam out.

Some fastener choices are preference, but mostly it has a lot to do with the tooling being used. Lots of legacy involved, too.

-Ryan

 

[niget2002]

Is there room to twist the torx head, or is there only vertical access for a long philips screw driver?

 

[speed bump]

Cost, tool access, and application. Flange screws cost more so you don't use them unless you need the clamping area. A pan head Philips screw requires no area around the head to turn. Nice thing about a Philips is you can turn a lot of fasteners with one driver versus needing a dedicated driver for size with a hex.

 

[cmandp]

They'd use phillips heads for cost of the fastener plus lower cost (easier) assembly. Phillips (Torx too and others but are more expensive to makes) are self centering better than a hex head or even a internal hex. Typically Phillips will be a low strength fastener because of the torque you can provide with a phillips drive. Clamping force the fasteners can provide is where the strength in a bolted connection comes from.

If it's a low strength application you're not going to use a more expensive Grade 5 or 8 (Metric 9.8 or 10.9) for a mass produced product.
That's my quick 2 cents. There will be many design considerations that come into play when design a bolted connection.

 

[Firebrick43]

From a repetitive maintenance standpoint hex head is better than Phillips bar none and torx is even better yet.

I hate Phillips machine screws

 

[peejay75]

Where is the fastener located in this example?

Ooops, forgot to add that, thanks! Valve/rocker cover on an engine.

 

[peejay75]

Is there room to twist the torx head, or is there only vertical access for a long philips screw driver?

Plenty of room to twist the torx head, all fasteners (valve cover) are "canted". Not accidentally overtorquing seems to be the most logical reason, I'm assuming now.

 

[Wamsutta]

Button head screws can be good looking. I'd switch to an Allen button head. Monster Bolts is a good source.

 

[peejay75]

From a repetitive maintenance standpoint hex head is better than Phillips bar none and torx is even better yet.

I hate Phillips machine screws

Just curious, why is torx better than hex? (Now, again, I'm playing into my "fears" of it being easier to "accidentally" round off a torx head than a hex head.)

 

[peejay75]

Button head screws can be good looking. I'd switch to an Allen button head. Monster Bolt is a good source.

That was my thought (keep the aesthetics similar), but for easiest removal (less likely to, ahem, "screw" it up), I would imagine the hex head would be the "safest"?

 

[JradM]

Just curious, why is torx better than hex? (Now, again, I'm playing into my "fears" of it being easier to "accidentally" round off a torx head than a hex head.)

It's actually the opposite. Torx allows for greater torque.

 

[peejay75]

(A pic of the fastener in question...it's just a screw, no built-in washer/flange):

 

[peejay75]

It's actually the opposite. Torx allows for greater torque.

hence the name?

 

[Firebrick43]

Just curious, why is torx better than hex? (Now, again, I'm playing into my "fears" of it being easier to "accidentally" round off a torx head than a hex head.)

Opposite. I was a CNC machine mechanic on very large CNC 16 axis gantry milling machines.

Hundreds is screws would be removed and replaced every day for access. The factory screws were flange head Allen (hex) screws.

We replaced these screw with some regularity and required replacement dropped way off when we switched to torx

 

[chevy.stroker]

Ooops, forgot to add that, thanks! Valve/rocker cover on an engine.

Just curious what engine, and are you having issue with leakage?

 

[peejay75]

It's actually the opposite. Torx allows for greater torque.

Now my apologies, I'm confusing Torx/star with socket-head/allen (are those the same?)

 

[peejay75]

Just curious what engine, and are you having issue with leakage?

Nissan VG series, yep, valve cover leak, I want to go back with the "easiest" to service fastener, since this thing is already a PAIN to work on.

 

[chevy.stroker]

Nissan VG series, yep, valve cover leak, I want to go back with the "easiest" to service fastener, since this thing is already a PAIN to work on.

Just a recommendation. Do with as you want.

If using cork or paper gaskets when resealing apply a little Permatex Aviation Form A Gasket No. 3 on both sides of the gasket.

I would also degrease the holes and apply a little purple locktite/vibratite to each bolt.

We did that often on old Corvair valve covers.

 

[jayemm]

Opposite. I was a CNC machine mechanic on very large CNC 16 axis gantry milling machines.

Hundreds is screws would be removed and replaced every day for access. The factory screws were flange head Allen (hex) screws.

We replaced these screw with some regularity and required replacement dropped way off when we switched to torx

I can identify with what you're saying. On my floor jack I replaced the cheap button head (Allen head) screws that stripped out easily because the hex was shallow and the metal was soft. Only had to piss me off once. Hardened allen head capscrews were substituted.

 

[Firebrick43]

The only real issue I have seen with torx is there is a T27 size. Some driver bit sets don’t include this side and therefor guys will misjudge the size and use a T25.

Harley motorcycles is the biggest user of T27

 

[Firebrick43]

I can identify with what you're saying. On my floor jack I replaced the cheap button head (Allen head) screws that stripped out easily because the hex was shallow and the metal was soft. Only had to piss me off once. Hardened allen head capscrews were substituted.

Full height socket head cap screw wouldn’t have worked on the panels as they would lead to stuff catching on them but I don’t see why they wouldn’t for the OP engine cover?

 

[WildBill]

I replaced the ones on my old Pathfinder with button head torx and lock+flat washers because I hated the screws, and the leaks. I didn't tighten them very much but got the biggest washer I could in hope it would add clamping area. The screws always seemed loose. Stopped the leaks for the next couple years.

 

[peejay75]

I replaced the ones on my old Pathfinder with button head torx and lock+flat washers because I hated the screws, and the leaks. I didn't tighten them very much but got the biggest washer I could in hope it would add clamping area. The screws always seemed loose. Stopped the leaks for the next couple years.

This, all of this...

Update, I got the screws removed/cover off, and as WildBill stated, at least one was kinda loose, none of them felt "torqued down" (factory max spec is 2.2 ft-lbs (this could be the reason for phillip--reduce temptation to over-torque?), probably could've removed them by hand if I'd eaten my wheaties this morn!

Also, as much as I'd like to ditch the phillips head in favor of something else, got a feeling me local hardware store is probably not gonna have a unicorn that is the correct length and has that "speed taper" (what is the proper term for that?) on the end:



May hafta give the OEM hardware a thorough cleaning and reuse. On a positive note, the Tekton #3 phillips 1/4 socket and GearWrench 10" 1/4 extension coupled to the Hart 1/4 90T ratchet (all recent purchases, "thanks" to GJ) worked like charms, no sinking feeling of rounding the head!

Thanks as always for all the replies and help!

 

[Firebrick43]

This, all of this...

Update, I got the screws removed/cover off, and as WildBill stated, at least one was kinda loose, none of them felt "torqued down" (factory max spec is 2.2 ft-lbs (this could be the reason for phillip--reduce temptation to over-torque?), probably could've removed them by hand if I'd eaten my wheaties this morn!

Also, as much as I'd like to ditch the phillips head in favor of something else, got a feeling me local hardware store is probably not gonna have a unicorn that is the correct length and has that "speed taper" (what is the proper term for that?) on the end:



May hafta give the OEM hardware a thorough cleaning and reuse. On a positive note, the Tekton #3 phillips 1/4 socket and GearWrench 10" 1/4 extension coupled to the Hart 1/4 90T ratchet (all recent purchases, "thanks" to GJ) worked like charms, no sinking feeling of rounding the head!

Thanks as always for all the replies and help!

https://www.mcmaster.com/products/m...torx-screws/?s=Torx+Metric+Button+Head+Screws

 

[JradM]

I doubt that tapered/unthreaded portion is necessary. I suppose if the original hole has threads cut with a tapered tap, then the tapered end of the fastener could let it reach farther inside. Hard to imagine a purpose for that though, because it wouldn't help the fastener any. Maybe to line things up?

I wouldn't sweat finding a fastener with that same unthreaded taper on the end.

One thing that might be important from the photo you posted is not switching to something with a significantly wider head, or it might not fit within the flange on your valve cover. E.g. they make nice bolt/washer combos that can give a valve cover a nice "custom" look, but that wouldn't work here.



Even too wide a flange could be an issue.

 

[chevy.stroker]

Just out of curiosity I'd measure the depth of the hole and the length of the screw. I wonder if those are bottoming screws so you can't over torque.

Anyway, the shape makes me curious.

 

[WildBill]

This, all of this...

Update, I got the screws removed/cover off, and as WildBill stated, at least one was kinda loose, none of them felt "torqued down" (factory max spec is 2.2 ft-lbs (this could be the reason for phillip--reduce temptation to over-torque?), probably could've removed them by hand if I'd eaten my wheaties this morn!

Also, as much as I'd like to ditch the phillips head in favor of something else, got a feeling me local hardware store is probably not gonna have a unicorn that is the correct length and has that "speed taper" (what is the proper term for that?) on the end:



May hafta give the OEM hardware a thorough cleaning and reuse. On a positive note, the Tekton #3 phillips 1/4 socket and GearWrench 10" 1/4 extension coupled to the Hart 1/4 90T ratchet (all recent purchases, "thanks" to GJ) worked like charms, no sinking feeling of rounding the head!

Thanks as always for all the replies and help!

I used ones the length of the screw without the tapered part.

 

[Dave455]

Also, as much as I'd like to ditch the phillips head in favor of something else, got a feeling me local hardware store is probably not gonna have a unicorn that is the correct length and has that "speed taper" (what is the proper term for that?) on the end:

In the U.K. we’d call that a “dog point”. In this case a “dog point grub screw”.

I suspect that’s an American term anyway, since most of these designs originated with the Allen Screw Company.

 

[chevy.stroker]

@Dave455 thanks! Learn something new everyday.

 

[peejay75]

In the U.K. we’d call that a “dog point”. In this case a “dog point grub screw”.

I suspect that’s an American term anyway, since most of these designs originated with the Allen Screw Company.

Ditto! You made me Google it, but every "dog point" search brings up exactly what it looks like! ("Body bolt" works, too, I recall reading somewhere that it is to speed production/location).

 

[chevy.stroker]

@peejay75 duh! Of course a body bolt. I feel my alzheimer's kicking in.

 

[wyb2]

I doubt that tapered/unthreaded portion is necessary. I suppose if the original hole has threads cut with a tapered tap, then the tapered end of the fastener could let it reach farther inside. Hard to imagine a purpose for that though, because it wouldn't help the fastener any. Maybe to line things up?

I wouldn't sweat finding a fastener with that same unthreaded taper on the end.

One thing that might be important from the photo you posted is not switching to something with a significantly wider head, or it might not fit within the flange on your valve cover. E.g. they make nice bolt/washer combos that can give a valve cover a nice "custom" look, but that wouldn't work here.



Even too wide a flange could be an issue.

This longer unthreaded tip seems to be very common on automotive fasteners, but I haven’t noticed anywhere else (not a thing on mil/aero spec fasteners for example). My theory is it’s one of the few industries that gets fasteners actually manufactured for them to their spec, and the long lead-in helps ease assembly and reduce the risk of cross-threading for high-rate assembly.

Agree that there is no value in trying to find a replacement with this feature.

 

[larry_g]

(A pic of the fastener in question...it's just a screw, no built-in washer/flange):

Are you sure that is a Phillips head? Could be a JIS standard.

 

[peejay75]

Are you sure that is a Phillips head? Could be a JIS standard.

Ah, forgot about JIS, it could be! The #3 Phillips fit snug but perhaps I should see if U have a JIS bit that will fit, thanks! (also heading to the hardware store tomorrow to see what my options are.)

 

[JradM]

JIS should have a dot.

 

[rust in the eye]

(A pic of the fastener in question...it's just a screw, no built-in washer/flange):

Looks Japanese. Get yourself a JIS screwdriver, it will be an epiphany.