The Offshore Voyaging Reference Site

Why We Need a Torque Screwdriver

Stainless steel is not as strong as it looks. For example, the recommended torque on a 10-24 (~5mm) 316 SS machine screw is just 23.8 inch-pounds (2.68 newton-metres).

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Karl Lewis

My brother, when he was an auto mechanic, used to suggest that you could just tighten a bolt until it snapped, and then back off a quarter turn.

James Greenwald

Wera superfan

Dick Stevenson

Hi John and all,
Do Snap-on tools enter the realm of preferred tools?
Decades ago, whiles still working, I would treat myself to a Snap-on tool or two every year as a present to myself. I immediately felt the difference with the wrenches: they were a joy to hold in one’s hand and did the job. The ratcheting screwdriver made many jobs faster and easier and was strong and well-built and kind to the hand for longer jobs. All the tools brought pleasure when used.
Unfortunately, all my boat tools were stolen off the boat and replacing with same was not in the budget. A trip to Sears and buying Craftsman (and Stanley) met my budgetary position and work needs (still does) and were much more in line with my skills (I liked to believe that using Snap-on tools automatically made me a better mechanic, carpenter technician  etc.) (The ratcheting screwdriver was the only tool I replaced with another Snap-on.
Casual observation seems to have Snap-on to be the preferred tool by professionals in the US (perhaps also CA) and I am curious why they were not mentioned that I remember.
Thanks, Dick Stevenson, s/v Alchemy

Dick Stevenson

Yes, really lousy. I will go back and re-read more closely.
Thks, Dick

Niels Rasmussen

Calculate the required torque.
When i was at university study engineering one of the courses was covering how to calculate the required torque for nuts and bolts in various situations. The text book was in German and very detailed with long list of equations, tables and plots to be used. In the end, after completed the procedure and finally could conclude the correct torque, the result was timed with 0.9
Why? Because, per experience, technicians always torque the bolts more than the specification. To have the right torque the engineer therefore specify only 90% of the calculated required torque.

Matt Marsh

Yeah…. the whole process gets *very* sensitive to tiny variations in friction, material finish, temperature, etc. as you get close to the “ideal” torque.
It’s increasingly common to see sensitive items specified as “torque to 17 and then tighten another 40°” rather than “torque to 30”

On applications where even a torque plus an angle isn’t accurate enough, you’ll often see hydraulic tools that directly tension the stud, and then release it once the nut is snug.

For what we do on our boats, torque wrenches and torque screwdrivers are the right tools – but I would add a torque angle gauge if my engine’s service manual called for one.


I am easily convinced that proper torque on nuts, bolts and screws will improve the sailing life of my boat. Not being groomed as a mechanic, I appreciate the intro into this mystic world of metal stress. Certainly the WERA tool line looks amazing (when compared to my Harbor Freight cheap salt water throw away tools that came with the boat).

Not wanting to empty the cruising kitty for a whole new tool box, do you have a NM measuring range for a torque tool that will serve most of the on boat demands. Keel bolts are not an issue on my 1974 Cal 35. The needs would be engine, aluminum spars and hardware attachment to the fiberglass deck.


Thank you.