please see attached photo..

i believe the best way to get the sheared screw remains out from inside the threaded shaft is to take the shaft out and put it into a lathe.

then drill hole into the broken thread big enough to use a screw puller..

if this is the case, how does one remove the shaft from the tuner,

in order to be able to put it into a lathe?

otherwise we may need to cut a slot into the top of the shaft to enable us to use a screwdriver to draw it out..

not preferable, but may work...

any advice welcome please!!


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I think I would start by putting some penetrating oil on that screw, and let it sit until you decide on a solution.

Slotting the top very carefully sounds like a workable plan, but I think the penetrating oil is an important first step.

Of course, if someone recommends using heat, SKIP THE OIL.

Hi Tony, heaps of ways to skin this cat - and we all have our faves.  Firstly, why did the screw break in the first place - the answer to this will largely determine the preferred method of extraction,  but some preliminary activities will be much the same for any fix.

Firstly remove the shaft from the mount so its easy to work with - the slotted collar is a ferrule by the look and should screw out with the appropriate tool or some tapping with a pin punch and small hammer.

Soak the shaft in some penetrating oil (I use "Nutcracker", but there are a heap of similar products) - heat it if you can but not over an open flame.   Then apply a hot, heavy soldering iron tip to the end of the shaft and cycle some heat expansion and contraction through the shaft and bore area, dump it back into the oil while it is hot and leave it for a while.

Lightly tap the end of the shaft with a pointed punch to apply some longitudinal movement to the threads and break up any corrosion that may be bonding the threads to the bore.

At this stage you can drill a hole and use an extractor,  you can use a dremmel cut-off disc to make a screw slot and back the screw section out or you can use the same cut-off tool to take a couple of mm off the outside shaft and expose the end of the broken screw - which can then be grasped by a heavy set of serrated pliers and rotated out.  

That sort of thing ...there are probably better ways and I'm sure you'll hear about them here - but patience and precision is probably a good place to start when doing this stuff.

Good luck Tony, keep us posted,


thanks so far..


nice to hear from someone on this side of the globe..and in the same timezone!!

it occurred as i was attempting to undo the screw a bit to then reseat the mop button had some play in it that i wanted to get rid of.

seems like the penetrating oil is a definite start..after getting the shaft out.

i've engaged a fellow to look at this for me, and any or all ideas are welcome.


My first attempt would be to drill it with an appropriate size LEFT HAND drill bit.  Often enough the bit will snag the screw and power it out.  "Kroil" or other super-penetrating oil would be a wise addition to the project.  For anybody in the repair  biz, an assortment of lefty bits is a good investment:

Left Hand bits from McMaster-Carr

thanks for the idea frank.

will pass it to the guy doing the work.

being in small town regional australia doesn't help, as experienced talent is thin on the ground..

do you have a tool dedicated to getting the worm assembly apart, allowing the post to be removed? there's a slot on either side if the post..

in the meantime i decided to request support from the maker/supplier...either new complete set or a new post and the tool to get bad post out and new post in..

i have had an unresolved issue with these tuners a couple months maybe they'll switch 'em over for me.

It's a teeny screw broken off flush, so getting in there to do anything can be a big problem.  Here's another, lower tech idea:

Using a little jeweler's saw, cut a  slot across both the open end of the tuner shaft and down into the screw itself. That won't hurt much, and it may give you a good shot at unscrewing the broken piece with a tiny flat blade screwdriver.

Oh, yes, Stewart MacDonald can provide you with the small spanner necessary to take that collar off.  It's usually installed with Loctite, so it can be a bit stubborn.

thanks again frank,

yeah, cutting the slot across the top was the fallback plan here i think..

they flatly said no way on the spanner, because they don't people easily fooling around with them..

and the loctite..

someone clever maybe needs to make them up?

Don't overlook asking Stew Mac for help.  I have a set of these tuners and asked them if they could provide the tool to adjust the little collet so I could lighten the tension.  They said they prefer that I send the tuners back to them for adjustment or replacement because they use loctite on the collets.  They might equally be willing to work on your set and replace the shaft.

I didn't take them up on it because the tuners soon loosened up a little from use and because I needed to gig with the mandolin.  But if you can take the time to send them the tuners, that might be the way to go.  Give them a call or email.

StewMac has great customer service (which they should have on a $500 set of tuners).


thanks larry,

yes they have agreed to replace them, which is great..being in australia, sending them away would have taken at least 6 weeks....just quietly, the 500$. cost of them is a bit overdone to say the they have a good $$ cushion for the service they give on them..

one thing tho, the g strings have been very hard to turn (.40 or .41 strings) which i think is unusual??  

so you reckon by loosening off that collar will make them turn easier under tension?


That's the problem I had with a couple of button shafts on my set--hard to turn.  Ask Stew Mac to check and adjust that before they send the replacements to you and tell them your preferences--some players like them tighter than others.  As Frank says, the collars are installed with LocTite (ACC formulated to anchor threads) and SM told me that because of that they prefer to adjust them themselves.  Mine have eased up with use, but they'll make it good if you alert them to your preferences.  A little lube on the button shaft and the gears might help, too.  Even the very best tuners need some from time to time.  If you have one of those speed winders that fits in a power drill, a few minutes in each direction before stringing up might ease them up, too.

Re the cost, they're pricey but once mine loosened up, I haven't thought about that.  The work so well that I just use them and smile.  After the Gotoh's that preceded them, they're a wonder.  I might have bought SM Elites instead of these but at the time, these were the only really good ones that looked like the original Loar tuners.


thanks again larry...

i've asked SM to pre-adjust them to suit so we'll see..

with the cog, i noticed there is a bowed washer under it.

is there an adjustment there to ease up the button shaft?



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