Turns out that most people have no skill when it comes to olt torque, sometimes that is not that important sometimes it is critical. Most parts (outside of the engine) on E.G. lawnmover are not bolted with defined torque and then it does not matter. Modern cars and motobikes pretty much all matters. E.G. some Ford engines have spark plugs that have a tapered seat. Nearly 100% of DIY mechanics do it wrong and nearly same amount of skilled mechanics that don't use torque tools. This has caused many problems and net is flooded with videos where people swear at "stupid" sparkplugs that seize/rust up and broken threads.
Another problem is wheel/rim torque. Most people just don't get it right by feel. Many will get away with it, but this year I have helped three friends to open up the wheel bolts. One was solved with brak bar, another needed an penumatic impact wrench and last one need to weld 3/4" socket onto special bolt (After two diffeent garages tried to open it and broke two special keys). Yes aluminium rim, taper head bolt and tamper proof bolt, guy who tigtened it said that he did not use torque wrennch or too much force.....there was nothing wrong with the bolt or anything, just too much uumph.
Now to this project.....I have measured TIR of various ER chucks and collets. Ebay ones are pretty much lottery....Individual parts may have TIR from almost acceptable to nearly 0,1 mm of TIR. I have thrown worst out and use marginal (0,02-0,03 mm of TIR per standard) for less demanding aplications or "specials" like scored drill shanks. The ones from reliable vendors or western brands (that has not moved manufacturing to low cost countries) seem to work fine. I have bought half a dozen MT3/ER25 cheap collet chucks. One is good, two marginals and rest ready to bin. All brand ones were good as they arrived.
I have noticed that torgue has effect on some chucks/collets. Pretty convinced that on cheap chucks the nut is often problem and some collets are faulty in every way.
Good collets/chuck seem to work on almost any torque setting, bad ones on none. There is a little indication that carbide mills are more sensitive to TIR and bad tool holding. I have broke few 3-5 mm carbide mills, some of them dumb errors, some of them left me buzzled.
Why does TIR matter? If you take very small carbide mill (or one with acure abgle like a grooving bit) the excessive eccentricity might cause your four flute mill to work as a fly cutter. Hand feed on the mill is uncertain and I always try observe the chips to see if they are anything near that they should be. With new (to me ) tools I use cutting tool feed/speed calculations to find out that a) mill has very limited top speed (somewhre a little over 2000 rpm) and b) with the small mills tooth load will cause pretty slow feeds. Now, if only one tooth cuts, that produces oversize groove and feed/speed calculation tooth load will quadrupled.
Now I have a means of torquing the ER collet nut to same torque (small mills I am aiming well below recommeded torque), plan is to check if somewhere 50% of max. torque value is good for small carbide mills that has smooth and hard shanks.
This has been checked in industry, there it has definate effect, maybe there is some truth in my home work shop where I have inferior tools and I don't have best practices. But I am workng to improve.
Maybe it is cost effective, maybe not. So far spent: 25€ on torque wrenc, 5€ or ER 25 wrench, few hours on garage and maybe this helps me to weed out bad tool shopping from good ones. Least I know now how to mod torque wrench for hook spanner and such, if I ever need to rebuild machine tool spindle.
