with a new threaded headset in hand, I thought of asking about technique people have for not marring the top locknut. It is difficult to avoid at least rounding a couple corners a bit during the final tightening because of the spring in the adjustable wrench. I figure this is either that my wrench of worn out or I am being heavy-handed.

My technique usually consists of adjusting the headset a bit too tight, then backing out incrementally either until the bearing seems right or it becomes too loose, in which case I retighten to the last increment and call it good. In short, this is a good number of cinching, providing ample opportunity for trauma to the locknut.

To address this I actually bought a non-adjustable 32mm wrench, but it turned out to be a bit wide enough to reliably round corners. My current wrench is 12" with jaws that open to 33mm and until now because of its heft, I have only thought of trying another 15" that may very well have less spring.

I'm not sure I understand.
A proper headset wrench - like a bigger version of cone wrenches - was one of the first specific bike tools I bought.
So headset wrench to hold the bearing race in place, then a regular wrench to tighten the locknut.

If you really think you need a 12" or 15" adjustable wrench to tighten the headset's locknut, you are tightening it WAY to much. Also, many locknuts are octagonal, not hexagonal, so the usual open end or adjustable wrenches don't seat properly.

Even with an adjustable wrench, I have never bunged up a headset locknut.

A good quality adjustable wrench will work without damaging the nut, as it will not have the large amount of play that a cheap one does (I assume that's what you mean by "spring").

This ^^.

However... if you *really* want to get obsessive about it, you could cut up an aluminum drink can and put strips of the can between the wrench and the nut.
Steve

A good quality big adjustable wrench has the advantage you can snug it to the top nut. Just be careful and don't tighten too much.

.
...for an adjustable wrench, these work pretty well on the majority of headsets:




Channellock 8SWCB Slim Jaw WIDEAZZ 8" Adjustable Wrench
Channellock 6WCB WIDEAZZ 6" Adjustable Wrench

Another thing that helps a lot is to have the fork ends clamped in some sort of holding device similar to this:

Fixed size head set wrench.. 32mm for 1" , 36 for 1.125" are 1/8" thick .. alloy lock nuts can always be substituted for Steel.
The one I got from Tange,(in 1990) had a O ring seal to reduce water leaking down the steerer.. promoting rust/corrosion.

To keep the fork from rotating during headset work with only one wrench I place a lever (2"x4" or my Park pedal wrench with it's padded handle) between the blades up close to the crown. This lever is then braced by my torso's side.


But if you just leave the front wheel in place you can straddle the front wheel and trap it between your legs.


I always start my headset adjustment with a slightly loose set up, then tighten bit by bit as needed while confirming the adjustment by rocking the bike fore and aft while locking the front brake on.


Since threaded headsets usually also have a quill type stem stuck inside with the wedge bolt tightened any adjustment made without the stem tightened will be wrong by the amount of distortion the tightened stem produces. So do any headset adjustment with all installed. Usually this adjustment is one of the last I do on a bike service, not the first as some believe is the way. Andy

Spanners will always round nuts because they act on the corners. Other stuff.

Aluminum headsets are particularly prone to such damage. Some designs of headsets and/or tools can minimize this, e.g.:

The Park Tools Professional Headset Locknut Wrench (HW2) is worth it! I just was doing a quick internet search & it does not appear to be in stock anywhere.

That thing is really horrible in my opinion, just poorly made and loose fit on everything. If you can find the J.A. Stein version that came before it they are awesome, wrench openings are broached and fit nice and snug.

Interesting - 32 mm threaded headset locknuts I have no complaints with the park Tool. I like that it has a design like a flare nut wrench, where it engages all the flats. I never experienced any slippage or looseness. Now I'm curious about the design of the J.A. Stein one. I know the Park Tool one is hugely more precise & efficient than even a well made (slop free) adjustable wrench.

Over the years, Park made at least two different threaded headset wrenches. The chromed steel 32 mm headset/15 mm pedal wrench (HCW-6) was indeed not well made nor a precise fit.

The far better quality "laser cut" HCW-15 is a 32 mm/36 mm double end (1" and 1-1/8" headset) wrench that is a precise and properly octagonal and works very well on those headset locknut and upper race flats.

yeah you're doing it wrong

you get two Headset Wrenches -bike specific tool, not an adjustable crescent

one to hold the cone
one to hold the locknut
and you set the preload then countertorque them against each other to lock up, none of this incremental-back-and-fourth-too-loose-too-tight bullcarp home mechanic kludge job

no, the keyed washer isn't enough

if you're cheap,
at the very least you need ONE headset wrench - to hold the cone, and can use your old adjustable crescent to hold the locknut. but at any rate, without at least the one headset wrench on the cone you've been doing it wrong all this time.

disclaimer: some really old bikes don't have wrench flats on the cone, instead they have a knurled surface. you still need to grab that and keep it from spinning.

I used to do it this way but it was explained to me (here on BF) why it needed to be done from looser to tighter, as described above by Andrew. I can't remember the reason, but it made sense at the time.

I think the issue with the Park is the quality varies wildly, I've seen at least one early one that fit great. Bought 2 myself that were completely useless, one was so bad Park actually warrantied it. Don't recall ever bothering to open or test the replacement, just sold it I think.

failed to mention the wrench on the top race because I considered it a given although I usually hold it steady and cinch the top nut against it because it can be used as a kind of reference. I would like to know how you are able to finalize the bearing without what you refer to as the incremental-back-and-fourth-too-loose-too-tight bullcarp?

start with slightly too tight because I am much better able to detect an appearance of play as opposed to the other way around. I figure slight over-tightening will not have a lasting effect the way leaving a headset tight develops race brinelling, though perhaps this is delusion or dare I say home mechanic kludge.

feeling lazy, so in brief:

spin the cone down by hand, checking the fork as you do so to feel the point play is gone.

hand tighten the locknut down on top of it

place heatset wrench onto cone, 2nd wrench onto locknut
it's convenient (but not required) if you place them such that both handles can be grasped simultaneously with a single hand

with the fork held from rotating, torque the two wrenches into each other, being careful that each one moves the same number of degrees against each other -by doing this equally, the cone maintains its preload position, since the motion from locknut vs cone threads cancel each other out
feel for fork play as you do this, and bias the wrenches if needed (noted earlier: one hand squeezing both wrenches together. frees up 2nd hand for testing play)

so, all the hard wrenching force is done in one motion at the very end, greatly reducing the amount of back and fourth marring of the flats
the preload was mostly found by hand in the first steps

overall its a very quick and smooth process - no back and fourth

yeah, it takes practice. work in an LBS for a while, when you need to get things done both quickly and correctly you figure these things out.

i guess, outside of that context there's nothing 'wrong' with doing it the fumbling slow way - other than chewing up the flats.... you still get the headset adjusted in the end