Jerry......50+ years ago I commenced my apprenticeship in a non ferrous metal works [a division of the British BICC]
Melting, casting, drawing of copper & brass tubes [big stuff...up to 8" diameter] ....then on to wire production
Absoutely common place in workshops were shadow boards with..'
flogging spanners' [one piece forged ring hexagon with a forged handle with the flogging pad as a part of the forged process]......all neatly and sequently mounted by size
The weight of a 3" AF flogging spanner was maybe 25 lbs........the Fitter would engage the flat faced nut over the machined high tensile washer, , the Foreman would mark the nut & the pad......... the Fitters Mate would swing a 15lb or 28lb spanner until the Foreman agreed, an induced torque had been created or attained by tightening the nut so stretching the thread
The proof of the Pudding was when an Inspector checked the height of each large bolt that confirmed the tension [height] growth achieved
Always quite a Ceremony when the first revolutions were made
during or after any major refitThe Davey/John Brown steel mill drive in the video clearly shows
machined flat washers under the heads of Mill Stand drive retaining bolts
Calibrated/adjustable torque wrenches were not introduced for every day use in the steel industry until the mid 30's?......however hydraulic tensioning devices were commonplace in the mill industry in the early 20's.........
So the purpose of the high tensile machined flat washer was to ensure any galling between surfaces did not include the entablature of the machine ...ie., the Nut & the Washer were of lesser cost to replace than rectification to the machine spot facing on the bolt hole
Same applies to any machined model component...the use of a flat washer can protect machined surfaces from damage...keep like for like...a brass washer over a bronze tapping, a steel washer over a steel tapping
Then must agree with George here, no real need for a locknut.....just achieve your estimated level of applied torque....a pump spray of IPA, then a drop of
Loctite 243 Derek