Extracting broken let off screws

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Bruce Dornfeld, RPT

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Feb 27, 2021, 12:53:18 PM2/27/21
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We all know let off screws can get too tight in the rail.  On a S&S grand I recently serviced, many were way too tight.  I tried using a soldering iron, but it did noting perceptible.  Question one: is the soldering iron we use for electronics what the old timers referred to or should it be one of those old style really big soldering irons?   The one I used is 25 watt.  So what watt?

Two or three of the let off screws broke off in the rail.  The top and bottom of the screws are now broken in the rail with nothing to grab at all.  What do you do to extract the screw?  I found a kit for extracting broken screws from StewMac (Stewart MacDonald) the guitar repair folks.  This includes a screw extractor which will cut the wood around the screw.  It works just fine in my shop, but the Steinway rail has that brass covering the wood.  How do you deal with that?  I don't think the screw extractor will go through the metal, but I haven't tried it there yet.  What has worked for you?

Joe Garrett

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Feb 27, 2021, 1:06:22 PM2/27/21
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Bruce,
The soldering iron thang anneals the metal screw stem. i.e. it softens it and makes it more prone to breaking off. Not the method I'd use as a first effort. Tapping on the let off screw, top and bottom would help it to loosen in the rail more effectively. However, you'll need to be very creative to do that. That has worked for me before.
IF the let off screw is corroded, then you've really got a problem as the corrosion tends to weld the screw to the wood core of the rail.
Screw extractors are usually very hard metal. If you use one for the above purpose, then you'll have to insert a new piece of wood where you extracted the screw. That is accomplished with dowel stock. However, that gives you another dilemma: end grain to insert a new screw. That can be fixed by drilling a hole across the rail to intersect the vertical dowel stock. Then you'll have a cross grain for the screw. Hope that's clear. I've done this a few times it's a royal pain in the patoot, but, if care is taken, will work.
Best,
Joe

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Captain of the Tool Police
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William Monroe

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Feb 27, 2021, 1:10:24 PM2/27/21
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Hi Bruce,

The screw extractor will cut brass, moving slowly and ensuring the bit stays on a straight path of travel, lest it break.
25W Soldering Iron is plenty. If the screw gets hot, that's all you need. I don't think I've met a soldering iron that wouldn't make a letoff screw scorchingly hot if left on it for a bit. But, as Joe mentions, it will weaken the screw.

I've used a fine punch before, with success, supporting the rail with a 2x4 cut to fit between the letoff rail and the bench.

And if you drill it out, you can avoid having endgrain by cutting your own plugs to fill the hole you created. This avoids coming in from the side of the rail to create cross grain. Plug cutters are cheap, a piece of 4/4 maple, and you're ready to go.

William R. Monroe, RPT




On Sat, Feb 27, 2021 at 11:53 AM Bruce Dornfeld, RPT <bdor...@earthlink.net> wrote:
We all know let off screws can get too tight in the rail.  On a S&S grand I recently serviced, many were way too tight.  I tried using a soldering iron, but it did noting perceptible.  Question one: is the soldering iron we use for electronics what the old timers referred to or should it be one of those old style really big soldering irons?   The one I used is 25 watt.  So what watt?

Two or three of the let off screws broke off in the rail.  The top and bottom of the screws are now broken in the rail with nothing to grab at all.  What do you do to extract the screw?  I found a kit for extracting broken screws from StewMac (Stewart MacDonald) the guitar repair folks.  This includes a screw extractor which will cut the wood around the screw.  It works just fine in my shop, but the Steinway rail has that brass covering the wood.  How do you deal with that?  I don't think the screw extractor will go through the metal, but I haven't tried it there yet.  What has worked for you?

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Joe Garrett

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Feb 27, 2021, 2:18:43 PM2/27/21
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Hmmm? That would require a really small plug cutter. The smallest I've seen is 3/8" which is way too big for the existing rail imo. Just saying.<G>
Best,
Joe

Joe Garrett

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Feb 27, 2021, 2:31:38 PM2/27/21
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Just did a search on plug cutters. I did find a few sets with 1/4" plug cutter. Probably would do the trick if the screw extractor matched to the same size.

Les Koltvedt

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Feb 27, 2021, 2:40:46 PM2/27/21
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Metal workers use spot weld cutters...


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Bruce Dornfeld, RPT

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Feb 27, 2021, 5:53:45 PM2/27/21
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I neglected to say that the Stew Mac set comes with a plug cutter.  It is to cut 3/16" plugs.  It works well and the plug it cut fit well after using the extractor.  I just did some test on scrap so far, the Steinway I won't see for another couple of months or so.  I should mention too, that I found the appropriate thickness of leather and glued it and the let off buttons to the rail until I can do a proper repair.  Most screw extractors I see advertised are too big to use for a let off rail.  The Plexiglas guide that comes with their kit may work fine on guitars, but cannot be used on a let off rail, so I made my own guide.  The drill that comes with their kit is another thing we probably don't need.   Thank you all for your thoughts on this.

Bruce Dornfeld, RPT

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Feb 27, 2021, 5:57:02 PM2/27/21
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Another question, would you use a good penetrating oil on tight let off screws?  Certainly the stuff would stay in the wood, but is that bad?

Joe Garrett

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Feb 27, 2021, 6:01:15 PM2/27/21
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Please explain. That doesn't make sense with my post.
Joe

Joe Garrett

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Feb 27, 2021, 6:07:49 PM2/27/21
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Bruce,
Hmmm? You have me wondering why you requested a method for this repair, if you have already done so. Not sure where the "Stew Mac" thing comes in. Suspect I need to do another search.<G>
Best,
Joe

-----Original Message-----
From: "Bruce Dornfeld, RPT"
Sent: Feb 27, 2021 2:53 PM
To: pianotech
Subject: Re: [pianotech] Extracting broken let off screws

I neglected to say that the Stew Mac set comes with a plug cutter.  It is to cut 3/16" plugs.  It works well and the plug it cut fit well after using the extractor.  I just did some test on scrap so far, the Steinway I won't see for another couple of months or so.  I should mention too, that I found the appropriate thickness of leather and glued it and the let off buttons to the rail until I can do a proper repair.  Most screw extractors I see advertised are too big to use for a let off rail.  The Plexiglas guide that comes with their kit may work fine on guitars, but cannot be used on a let off rail, so I made my own guide.  The drill that comes with their kit is another thing we probably don't need.   Thank you all for your thoughts on this.

On Saturday, February 27, 2021 at 1:40:46 PM UTC-6 Les Koltvedt wrote:
Metal workers use spot weld cutters...


On Sat, Feb 27, 2021, 2:31 PM Joe Garrett <joega...@earthlink.net> wrote:
Just did a search on plug cutters. I did find a few sets with 1/4" plug cutter. Probably would do the trick if the screw extractor matched to the same size.
Best,
Joe

-----Original Message-----
From: William Monroe
Sent: Feb 27, 2021 10:10 AM
To: pian...@googlegroups.com
Subject: Re: [pianotech] Extracting broken let off screws

Hi Bruce,

The screw extractor will cut brass, moving slowly and ensuring the bit stays on a straight path of travel, lest it break.
25W Soldering Iron is plenty. If the screw gets hot, that's all you need. I don't think I've met a soldering iron that wouldn't make a letoff screw scorchingly hot if left on it for a bit. But, as Joe mentions, it will weaken the screw.

I've used a fine punch before, with success, supporting the rail with a 2x4 cut to fit between the letoff rail and the bench.

And if you drill it out, you can avoid having endgrain by cutting your own plugs to fill the hole you created. This avoids coming in from the side of the rail to create cross grain. Plug cutters are cheap, a piece of 4/4 maple, and you're ready to go.

William R. Monroe, RPT




On Sat, Feb 27, 2021 at 11:53 AM Bruce Dornfeld, RPT <bdor...@earthlink.net> wrote:
We all know let off screws can get too tight in the rail.  On a S&S grand I recently serviced, many were way too tight.  I tried using a soldering iron, but it did noting perceptible.  Question one: is the soldering iron we use for electronics what the old timers referred to or should it be one of those old style really big soldering irons?   The one I used is 25 watt.  So what watt?

Two or three of the let off screws broke off in the rail.  The top and bottom of the screws are now broken in the rail with nothing to grab at all.  What do you do to extract the screw?  I found a kit for extracting broken screws from StewMac (Stewart MacDonald) the guitar repair folks.  This includes a screw extractor which will cut the wood around the screw.  It works just fine in my shop, but the Steinway rail has that brass covering the wood.  How do you deal with that?  I don't think the screw extractor will go through the metal, but I haven't tried it there yet.  What has worked for you?

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Captain of the Tool Police
Squares R I
gpianoworks.com


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Bruce Dornfeld, RPT

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Feb 27, 2021, 6:33:42 PM2/27/21
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Hi Joe.  I just did a test with some scrap.  I did not try cutting through brass with it and just because I think I found a way to repair it doesn't mean it is the best way.  I figure this happens to others and others have found a way to deal with it.  Stew Mac used to be called Stewart MacDonald if that helps.   Stay well my friend!

Joe Garrett

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Feb 27, 2021, 6:51:52 PM2/27/21
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Bruce,
My experience is that oil, (whatever kind), makes wood "spongy". Also, "penetrating oils" have a nasty habit of traveling to places I don't want them! I prefer dry lubes for such.
Best,
Joe

-----Original Message-----
From: "Bruce Dornfeld, RPT"
Sent: Feb 27, 2021 2:57 PM
To: pianotech
Subject: Re: [pianotech] Extracting broken let off screws

Another question, would you use a good penetrating oil on tight let off screws?  Certainly the stuff would stay in the wood, but is that bad?

On Saturday, February 27, 2021 at 4:53:45 PM UTC-6 Bruce Dornfeld, RPT wrote:

David Nereson

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Feb 28, 2021, 4:17:03 PM2/28/21
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If there's at least an eighth of an inch of the let-off screw protruding from the top of the rail, it can be filed on opposite sides of the screw to fit a drop screw regulating tool.  Or, you can unscrew the let-off button from the screw and either file the bottom of the screw  to fit the drop regulator or grab it with Vise-Grips and turn it up or down out of the rail a quarter-turn at a time, until you can grab it on top.  If it's broken flush with the wood both top and bottom, further surgery is required (see other posts).
--David Nereson, RPT

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