Small hex half (.5) sizes?

[Buckgnarly]

Recently ran into a Chrysler mini van sway bar end link being a usual PITA. Found a 5.5mm hex in our Tekton set at work, fit perfect. I've seen really small stuff like 2.5, but Tekton has stuff up to 5.5mm. Is this something I have missed, or is 2.5, 3.5, 4.5, 5.5 hex a common thing?
Needless to say I ordered all they had in drive and length sizes....hahah!

 

[BlakeTheCarGuy]

I’ve used the 5.5 hex never any of those other sizes. I believe I have the 2.5 and all of those others in my Capri set of the torx and hex bit sockets and I have a ton of really small Allen wrenches.

 

[four.cycle]

The proliferation of different types of fastener heads wasn't enough with slotted, phillips, torx, Posi-Drive, clutch-head, "E-torx", Robertson, and all of the other various and assorted types.
They felt the need to go with HALF millimeter sizes on hex fasteners.

I am saving up my money to buy the new SAE hex wrench sets in /128th sizes.

 

[Komet]

I know I can buy them individually, but I still think there should be a 1/4" drive 6pt shallow and deep socket set of 4.5mm and 5.5mm so everybody with a typical starter kit can fill out their socket trays.

 

[KnurledNut]

7/32 will work on 5.5mm.

 

[Dave455]

The only one I encounter regularly is 2.5mm.

In most standards it’s the size used on M3 cap screws and M5 grub screws, both of which are fairly common.

The other sizes I can’t say I’ve ever knowingly encountered.

 

[NoahG]

7/32 will work on 5.5mm.

That’s the reason I keep the 7/32” nut driver in my box.

 

[superspec]

I have a Bondaus brand ball end set that has half sizes. I use several at work depending on what brand equipment I’m dealing with

 

[Meursault74]

3.5 mm Hex key for Campagnolo Delta Brakes

 

[Tools4Me]

US made Bondhus L wrench sets 12195 (regular hex) or 10995 (regular hex on the short leg and ball hex on the long leg) are great options for people who want to have good quality tools ready and available to use, but don't want to spend too much money on them since they won't be used very often. The sets include 1.27mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 7mm, 8mm, 9mm, and 10mm. The sizes listed in bold are all harder to find sizes that many sets will skip.

https://www.amazon.com/dp/B000E7XJGG/?tag=atomicindus08-20

https://www.amazon.com/dp/B000E7ZMSE/?tag=atomicindus08-20

 

[Lassen Forge]

How about those %#&#% 18.5 MM Mopar lug nuts? When they had their chrome covers they were 19mm. the covers eventually wallered and fell off, leaving you with these damned oddball sized lug nuts... where a 19 would round them off and an 18 wouldn't fit.

 

[Tools4Me]

How about those %#&#% 18.5 MM Mopar lug nuts? When they had their chrome covers they were 19mm. the covers eventually wallered and fell off, leaving you with these damned oddball sized lug nuts... where a 19 would round them off and an 18 wouldn't fit.

That's what half sized lugnut flip sockets are for. The 18.5mm end is for when the chrome covers have already come off and the 19.5mm end is for when the covers are still on but they are a little bit swollen from corrosion underneath them. I know what you mean though, they could have just made normal lugnuts and avoided the issue altogether.

Amazon.com

 

[Mirage]

I know I can buy them individually, but I still think there should be a 1/4" drive 6pt shallow and deep socket set of 4.5mm and 5.5mm so everybody with a typical starter kit can fill out their socket trays.

The Capri 1/4 drive set does, 4-15mm with both 4.5 and 5.5. I picked one back in November for this very reason

 

[dutchgray]

The standard 9 piece metric Hex key sets that every company sells come with 1.5mm and 2.5mm in the half millimetre sizes, anything else is unusual.

 

[Steve_P]

1.5 and 2.5mm are standard sizes and are why they are with most/all L key sets. I have the Tekton bit sets with the other half sizes but I'm not sure I've used any other than possibly 2.5

 

[AdAstra]

At these small sizes there's nothing wrong with them standardizing on a half mm size.

If something needs to be 1.5 mm for engineering reasons, why would they round that to 2.0 mm (33% too much length, ~75% too much head volume) to make a round integer?

Even at 5.5 mm, that's 10-20% extra head mass, tool size, material cost, access clearance, etc, which adds up if you are making literal billions of fasteners.

Additionally, for external wrenching sizes, they target having a consistent ratio of under head bearing area to thread area across fastener sizes. The thread progression is the primary variable, the head just comes along for the ride.

Do you also think a 5/64" size is somehow wrong? 1/64" is a smaller step than 0.5 mm. Sizes larger than 5.5 are whole numbers, because by then the difference is less important than the convenience, just like 64ths sizes drop off.

 

[mikey03]

I notice 5.5mm is common on hex key sets but snap on 3/8 hex bit sockets only go 4 to 10 in full numbers no 0.5

usually snap on skips sizes that aren’t real useful but I’m wondering about 5.5 and found this thread from last year