Author Topic: Removing a broken lockplate screw (Read 7050 times)

bones92 · « **on:** October 03, 2016, 05:45:43 PM »

My apologies, if this isn't the right forum.

One of the lock-plate screws in my Kemper flintlock broke off right where the threads enter the lock plate. Fortunately, it is a standard 8-32 screw, which I was able to order from TOTW.

However, I want to be REALLY careful about extracting the broken screw. I have some left-hand drill bits, but would it be wise to use a Dremel tool to make a small divot in the center of the broken screw shank? It's flush with the inside of the lock plate, so I'm going to have to back it out with a bit.

Hungry Horse · « **Reply #1 on:** October 03, 2016, 06:05:34 PM »

I think the chances of putting a small divot with a Dremel in the middle of the broken bolt without bungling up the threads are pretty slim. If you have an automatic center punch, I would use that. The amount you might swell, and tighten, the broken bolt would be negligible. In most cases a left hand twist drill will walk the broken bolt right out, without an easy out.

Hungry Horse

bones92 · « **Reply #2 on:** October 03, 2016, 10:14:04 PM »

I've managed to drill a bit into the center of the screw, and bought an easy-out, but it's #1, and it looks like I need the next size larger.

T*O*F · « **Reply #3 on:** October 03, 2016, 11:21:08 PM »

Quote from: bones92 on October 03, 2016, 10:14:04 PM

I've managed to drill a bit into the center of the screw, and bought an easy-out, but it's #1, and it looks like I need the next size larger.

If you have a screwdriver tip assortment, use the appropriate Torx bit as an EZ out. There should be NO pressure on those threads.

Clark Badgett · « **Reply #4 on:** October 04, 2016, 12:15:50 AM »

I've never had a lot of luck with those broken screw extractors. I prefer to sharpen a small piece of round stock or use a prick punch to gently tap them back out.

Mark Elliott · « **Reply #5 on:** October 04, 2016, 12:50:51 AM »

With machine screws, I have usually taken Clark B's approach trying to back out the screw enough to grab it with some pliers. Otherwise, I have drilled out all but the threads and then picked them out.

Dennis Glazener · « **Reply #6 on:** October 04, 2016, 01:53:23 AM »

Not sure if you have enough metal to do this but my dad always used a small chisel sharpened to a chisel point then gently tapped it into the screw counter clockwise (for right hand threads). Never saw him use an EZ Out.
Dennis

Opps I see this is pretty much the same as Clark B's approach. Just remembered that daddy had several small chisels sharpened this way and I always wondered what they were for. He was a mechanic and always dealing with wrung off bolts/screws.

SingleMalt · « **Reply #7 on:** October 04, 2016, 02:24:41 AM »

There is another alternative. Bill Brockway showed this to me and I've used it several times. The broken screw is 8-32, so you can use either an 8-32 or a 10-32 screw. Track's screws work well for this, as they're not super hard, but have some "body."

First, disassemble the lock and take the selected screw and mic the shank, not the threaded portion. Select the closest wire gaged drill bit to that size and drill out the offending broken screw. Lightly counter sink both sides of the lockplate.

With a very sharp cold chisel, cut several grooves around each counter sink. Cut a piece of the shank of the selected screw 5/16" to 3/8" long and heat it to red-orange. with your torch. While it's still hot, place it in the hole from the outside and peen it until it covers the counter sink. Flip it over and peen the other side the same way. File both sides smooth and the repair is invisible.

Clark Badgett · « **Reply #8 on:** October 04, 2016, 04:56:14 AM »

Quote from: Dennis Glazener on October 04, 2016, 01:53:23 AM

Opps I see this is pretty much the same as Clark B's approach. Just remembered that daddy had several small chisels sharpened this way and I always wondered what they were for. He was a mechanic and always dealing with wrung off bolts/screws.

I'm sure your dad was a pro at it. I learned it many years ago when I did die work. Always broken bolts in dies. Still use the method when I can since I do a lot of emergency industrial machinery repair. Sometimes they are really stuck and have to resort to drilling out the bolt.

flehto · « **Reply #9 on:** October 04, 2016, 03:07:24 PM »

As a tool and diemaker have removed a few broken off screws using a sharp punch and backing the screw piece out....worked every time.....Fred

bones92 · « **Reply #10 on:** October 04, 2016, 03:29:00 PM »

Fred, can you elaborate?

At this point, I've drilled probably 2/3 the length of the screw, and I think I'm mostly centered. I'm hoping that if I can get it all out, I can refresh the threads.

If I need to refresh the threads, what style of tap would I need? TOTW advertises several variations of 8-32 tap. In this case, it is a hole that goes all the way through the lockplate.

Really hoping to not have to send this off for repair.

smylee grouch · « **Reply #11 on:** October 04, 2016, 03:49:14 PM »

If you get the screw out, would re-tapping to 10-32 work?

bones92 · « **Reply #12 on:** October 04, 2016, 04:02:35 PM »

Smylee, I think I may be able to get it out without ruining all of the threads. Maybe.

I'm hoping to get a bite with a #2 extractor so that I can unscrew the remaining threads closest to the exterior surface of the lockplate. I would then run a tap from the outside inward to repair any threads that may have been nicked near the internal surface.

I hope I don't have to go to a 10-32, as I would have to open up the hole on the anchor plate, and I'm trying to keep this Cornell Kemper rifle as original as possible.

flehto · « **Reply #13 on:** October 04, 2016, 04:56:57 PM »

The screw piece should just back out w/ a sharp punch. Can't understand how the screw broke off in the first place. It should be loose in the threads. Some other problems we're not aware of?

Whatever the thread size, just go in w/ the same tap size after the screw piece is removed.......Fred

bones92 · « **Reply #14 on:** October 04, 2016, 06:43:06 PM »

No idea. It was broken when I disassembled the rifle after firing. I had even disassembled the rifle a month earlier with no issues.

P.W.Berkuta · « **Reply #15 on:** October 04, 2016, 08:21:02 PM »

It is quite possable that the last time you reassembled the rifle you cross-threaded the screw into the lock which caused it to gall and bind into the threads. Then when you tried to dissemble it the screw sheared off that is why it is stuck into the lock plate. If this is a through tapped hole in the lock plate I would center up the sheared off screw in a drill press or mill then center punch the center of the screw the best I could then drill the screw with a drill bit two sizes under the original tap drill all the way through the screw then take the same size tap of the original tapped hole and using tapping fluid - re-tap the hole. If you were off center when you did the drilling of the sheared off screw then I would re-tap for the next larger size screw. This should not be an all day project

.

bones92 · « **Reply #16 on:** October 04, 2016, 08:22:27 PM »

Well, I ended up drilling all the way through. The replacement 8-32 screw won't enter in, so I think there is enough metal left to use a 8-32 tap. I hope I can retrace the original threads. I think there is remnants of the old screw still stuck in the threads, but it's hard to tell. No amount of EZ-out work seemed to retrieve any elements of the old screw.

JBJ · « **Reply #17 on:** October 05, 2016, 12:10:02 AM »

Use a starting tap and plenty of tapping fluid. It sounds like you may luck out and be able to rechase the 8-32 threads. The tap should easily push the remanants of the screw out of the way. Hold it straight!
J.B.

bones92 · « **Reply #18 on:** October 05, 2016, 01:59:08 AM »

Really don't want to screw this up.

Anyone here have a tap and the know-how to do this right? I'll pay for the service and return shipping.

flehto · « **Reply #19 on:** October 05, 2016, 02:16:32 AM »

Use a small tap wrench w/ a new tap and try entering from the bottom side and if it doesn't turn easily, try the top side.....one should work. Use plenty of oil. Don't force the tap and make sure you're at an approx. right angle to the plate. You can do this.....just take your time.....Fred

MKemper · « **Reply #20 on:** October 05, 2016, 03:30:02 AM »

Bones, if you want to send me the lock plate I'd be happy to cut the thread and send it back.

bones92 · « **Reply #21 on:** October 05, 2016, 04:31:31 AM »

Marvin,

Thank you. I will email you.

horologist · « **Reply #22 on:** October 16, 2016, 05:41:44 PM »

A lot of good suggestions here, I thought I might add a couple of additional ideas.

First, broken screw extractors.
Tools used to remove broken screws from watch plates after the screw head has been sheared off. Only useful with parts having a through hole, allowing the tool to grip booth ends of the screw.

A detail view of the business end.

These tools are scarce but the important feature is that the tool clamps down on both ends of the screw and then is turned to loosen and remove the broken portion of the screw. Modified C clamps or even a drill press could be used. Don't power up the drill press, hold the chuck stationary and turn the object with the broken screw by hand.

Second, if your broken steel screw is in a nonferrous part (brass or nickle) then you can dissolve the screw in a concentrated alum solution. Heat some water and add alum until it you can't dissolve anymore. Then drop your part in. Heat and solution concentration all speed up the process. Make sure you have removed any steel parts you want to keep. This stuff will make short work of spring steel. My mentor demonstrated the technique on a clock plate but left the springs for the strike and chime levers attached. He said it wouldn't be in there long enough to hurt them and ended up making new springs. It won't damage but may discolor nickle and brass, experiment on any other metals before trying with an important part.

Troy

bones92 · « **Reply #23 on:** October 17, 2016, 07:25:37 PM »

Happy to report that Marvin Kemper was able to re-tap the threads, and I managed to cut down one of the replacement TOTW 8-32 screws (without maiming myself

). Again, my thanks to Marvin.

The head diameter of the replacement TOTW screw is larger than the original screw. I ordered 2 from TOTW, but I noticed the thread journal length (if that's the right term) on the new screws is about 1/8" less than the originals Cornell used. Not a big deal, except the old screw broke right at the end of the threading, so using a new screw would have been tricky as the unthreaded shank might prevent tightening the screw enough.

I was able to use the original front screw in the re-tapped rear screw hole, and cut one of the new TOTW screws to length for the front. But, if I end up having to replace the other original screw, I'll have to find one with a bit more thread journal than what TOTW offers.

FDR · « **Reply #24 on:** October 20, 2016, 03:12:33 AM »

If Marvin doesn't, I have the die to extend your 8x32 threaded portion to any length you might need. I can also reduce your screw head diameter. My email is in my profile.

Fred

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Author Topic: Removing a broken lockplate screw (Read 7050 times)