When I was at the airport daily, my wrenches were calibrated every six months or after an accidental dropping. The calibration shop knew all of us by first name. The Snap-On truck guy would test, but not provide certification, but after a drop that got me back in service quickly. The torque between them was virtually the same. Now I get them done every 5 years or so. Mind you I have 6 different wrenches of different flavors, Snap-On.
I do take accurate torquing seriously, from CV bolts to lug nuts and a bunch in between. As well as valve cover nuts. My range goes from lb in to 300 lb ft with a torque multiplier I can accurately torque to over 1200 lb ft.
https://www.ebay.com/itm/Snap-on-YA391-1-2-drive-Internal-3-4-EXT-Torque-Multiplier-1200-ft-lb-MAX-Exc/283962152921?hash=item421d7697d9:g:CTYAAOSwOntfIhx 5
Mind any error is multiplied, but at those levels +/- 10% is usually acceptable.

I would suggest for everyone to pick up one of these little bad boys: https://www.amazon.com/gp/product/B004VYURT0/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

They are certified at sale and very good for checking your other wrenches (stick the gauge on a normal torque wrench) to see how they are. I found my craftsman 1/2" clicker was creeping up in torque every time it reached the limit until I spun the ratchet some, and max torque depends on how quickly I turn it.

Anyway, using the gauge I did my joints a little while ago and a couple hundred miles later each one is perfect. No moon washers and no schnorrs.

Edit: I used only the hardware that came with the GKN/Loebro units through pelican.