May 22, 2019 3 Comments
Among excellent makers of allen wrenches (think: Bondus, Allen, PBSwiss, Pedro’s, Park, Wihus, and others) only one has addressed engagement geometry like external socket wrenches have.
Historically, allen screws arose for embedded fasteners. The wrench inserts into a fastener rather than surrounding it. But the hexagonal interfaces have similar limits. In order to transmit maximum torque to a fastener without deformation drive shape was devised for external sockets, often known as "flank drive." That name belongs to Snap-On, a socket drive pioneer but you'll find such drive geometry everywhere today.
As this idea is nearly universal for external socket wrenches, why are internal allen wrenches all plain hex shapes driving on their corners? As allen screws dominate in bicycles, we need to ask about this situation!
Damaging or stripping out the screw is a real threat. All of us have seen bad fits (slightly undersized wrenches, slightly oversize screws) and bad materials (less hard wrenches and screws of softer metals). External drive wrenches on hex heads see far less trouble. How can the allen screw interface be improved?
Wera (German wrench maker) has done this! In their 1997 patent , wrench faces have a non-flat surface such that the corners do not drive the allen screw.
If the faces of an internal drive wrench are subtly modified, over 20% more torque can be applied before deformation. Experience with Wera tool geometry has made me a believer. The difference is real and important.
I challenge you to test this. As smaller size wrenches seem to exaggerate the effect, try testing with 2, 2.5, or 3mm wrenches. Overtighten sacrificial screws with various wrenches and notice the obvious difference. Or enjoy this excellent test by Matt Fields.
It's time to benefit from this trick. Wera is well distributed but you won't see it in many channels. We've decided to offer Wera L-keys but the least expensive model with total function—steel, black laser, long L, ball point, from 2mm - 10mm, selling from $0.90 to $5 each.
As you build your box and workshop, color is an important option. You can decorate tools with vinyl dip or tape, buy pre-colored models, or use shrink tubing. They all work but shrink tubing is my preference. Color choice can be artistic, functional, or individual.
To empower this fun and games, we now sell 12" (30.5cm) lengths of shrink tubing in six colors and diameters to fit 2-10mm wrenches. For a modest cost you can decorate, repair, change, and play. Shrink tubing is tough, tactile, and slightly rounds the hex key center for ease of turning. One foot of shrink tubing will make many short sections for a bunch of wrenches. A standard heat gun does the shrinking.
See the wrench and tubing product listing for all details, and get started.
Please share your solutions. Toolbox Wars can now move beyond foam cut inserts and factory anodizing.
November 02, 2021
I also hope it can help with the soft screws sometimes provided with various SPD cleats (Time comes to mind).
November 02, 2021
Maybe this will help reduce the amount of stainless cylindrical cap bolts rounding out because they’ve been stuck in aluminium.
If they’re not rounded off they’re often chewed up.
If only the allen wrench (or bolt) manufacturers looked at how standard hex wrenches are made today and how they engage the flat sides of the bolt heads earlier.
Great article as always!
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November 02, 2021
As a mech/tech, autos professionally, drag racing motorcycles, bicycles and much in between, Snap-on’s Flank Drive Plus wrenches have saved my bacon many, many times.
Despite their even way more than normal Snap-on pricetag, they have been worth every cent.
They have cracked bolts loose that had been rounded by flare nut, regular wrenches, vice grips and other.
Its about time the tech is being applied to this.
One thing to always consider is the application, some things come with substandard hardware as a way of limiting the force their component is subjected to.
Patience and diligence is always the primary factor, and better tools should help, if you wield the tool correctly, the outcome is more likely to be correct.