I will put my Metallurgists hat & dustcoat back on and make a very bold statement that will give 95% of the people here the shits big time .
The only tension wrench worth buying are the deflecting beam type as shown in the catalogue page below
deflecting beam tension wrenches
All of those ratchet style ones are shit and almost none are ever correct even if you do what no one ever does and back them off PAST the zero mark so there is no load on the spring
I bought a Repco branded 6" W & B wrench when I was 16 ( I am well over 70 now ) and it is still within 1% .
All of the micrometer adjustment ones are garbage unless they come with a signed original calibration certificate and for that you are talking 4 figures .
The spring loaded ratchet wrenches are for garbage mechanics who can not be bothered to lift the wrench off the fastener to take a second bike or so crippled they cannot manage to walk over to their tool box twice, ones for the standard ratchet then the second time for the tension wrench .
FWIW , I have 4 W & B deflecting beam tension wrenched and the last time we checked all were correct
The landlord , who takes meticulous care of his tools to the point he still has both the box & the carton that his tension wrench came in broke 2 head studs on the tractor and the repair cost over $ 300 in parts .
He put it down to the old studs never being removed and being 60 years old but when I ran his wrench against mine it was reading 40 % low at 120 ft lbs .
While my wrench when measured against his brand new W & B was spot on .
If you want to have some fun cut a 3" length off the end of a 3/4" allan key
Arm yourself with 2 x 3/4 impact sockets then go to your favourite tool supplier grab 2 tension wrenches set them to the same spec slip on the sockets then work them against each other . You will be lucky to find 2 that are within 10% of each other .
Jus like idiots who post their coil resistance was 22.3251 Ω because they have no idea about electricity . Ignorant clowns think because the tension wrench can be set to 224.5 in lbs it must be so much more accurate that the coarse scales on a deflecting beam.
Torques are only an approximation and the real number depends upon the slop in the fasteners, the materials, the presence / absence of lubricants and of course the weather & the temperature of the fastener and what it is holding together and of course the type of thread & the pitch of the thread & dimeter of the fastener and the surface area under the fastener, the size of the washers and a whole host of variables that have not come to mind at the moment .
