Topic: Broken off screws advice – Antique Outboard Motor Club,Inc

This topic has 9 replies, 8 voices, and was last updated 2 years, 3 months ago by Blake Monroe.

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January 11, 2022 at 7:50 am #252740
Blake Monroe
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US Member - 2 Years
I have a couple of small screws small bolts that are broken off inside the block do the corrosion when trying to remove them. I’m sure a lot of you guys have some tips and tricks on removing them. I have limited experience with helicoils from many years ago but I’m assuming that’s where I’ll have to go is to drill and tap and Helicoil unless there are 0ther recommendations.
January 11, 2022 at 7:56 am #252742
Tom
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US Member
If you can center drill them accurately with successively larger holes, you can pick out the pieces and save the original threads. If not, you’ll have to drill enough out to remove the screw and use a HeliCoil.

One method of increasing your chances of drilling accurately is to make a steel plate with the exact hole pattern of the block you’re working on. Drill the holes in the plate so that the holes for good threads are the size of the bolt, the holes for the bad threads are much smaller. Then bolt the plate to the block and use it as a guide to center drill the broken bolts. Once you have the small holes drilled, use larger and larger drills until you can remove the pieces of the broken bolt.

Time is your friend here. Be patient.

T

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2fast4me, Blake Monroe
January 11, 2022 at 8:20 am #252749
frankr
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US Member
Amen. I think the most important thing is make sure you get all the old pieces out before running the tap into the hole. Failure to do so invites a broken tap. Then you are in trouble for sure.

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2fast4me, Blake Monroe
January 11, 2022 at 12:10 pm #252767
DAN UMBARGER
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US Member - 2 Years
Depending on what bolts broke I’ve had success taking blocks to my welder and he welds a nut to whats left of the bolt…heats it up and pulls the broken piece out. Otherwise whats been said above works with a lot of patience and time!!!

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2fast4me, Blake Monroe
January 11, 2022 at 1:35 pm #252770
green-thumbs
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US Member - 2 Years
Take a look at article on page 26 of January 2022 edition of Antique Outboarder. Your situation may or
may not lend itself to a similar approach.
Methods vary, some will work in one situation
and not in others. Also depends upon resources
A friend had a cutting torch and a steel bolt broken
off in a cast iron engine block ( starter bolt on bottom
of engine.) preheated the bolt and gave it a puff
of oxygen…bolt came out as slag without damage
to thread in cast iron. Slick Trick, but, better get in
a lot of practice first if you do not know how. I say
him do it. Very much like magic…it is one thing to
know how and another thing to actually pull it off.
Louis

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Blake Monroe
January 11, 2022 at 3:05 pm #252772
Mumbles
Participant
Here’s where a set of left hand drill bits can come in really handy. Quite often the drilling alone will unwind the broken bolt out of the hole, as long as it isn’t corroded in place. Depending on the size of the broken bolt, Easy Outs or other fluted style screw extractors can be used to remove it. Any drill bit used shouldn’t be much larger than the tap drill size for that particular thread so the threads in the block aren’t damaged. If those threads get damaged or drilled out, then a Heli Coil insert is the next step.
January 11, 2022 at 4:08 pm #252776
johnny
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US Member
A friend of mine is a machinist and he drills a hole in the end of the broken off stud then taps it with a left hand tap, but not all the way to the end of the broken off stud. Then he can thread a left handed screw into the threaded hole to remove the stud.
January 11, 2022 at 4:26 pm #252778
Blake Monroe
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US Member - 2 Years
That’s a clever idea!
January 11, 2022 at 8:47 pm #252785
joecb
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US Member - 2 Years
All good advice, each suggestion may prove best for a particular situation and/ or availability of critical resources. In general, if the bolt or stud broke off in a failed attempt unscrew, forget about easy-outs or left hand drills. If you have access to a welder, the “weld a nut” on the stub is about a sure fix. When resorting to the drilling out approach, accurately centering your drilled hole is essential for success. Rigid machine tool set-up ( bridgeport !) is best if you have the tools. When doing free hand or common drill press, the use of a guide bushing is best. A steel plate was suggested, good, or a jury rigged bushing as green-thumbs used. Another good bushing plate, use the mating part ( like a cylinder head) bolted in place using the good bolts, fit a bushing in the subject hole to suit the tap drill size of the broken thread.
Another unusual fix.( not tried) … search use of alum to desolve steel fastener from aluminum part.

Joe B
January 13, 2022 at 1:03 pm #252863
Blake Monroe
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US Member - 2 Years
Thank you Joe for the info. I had not considered a bushing or the alum. I will have to look into that some more.
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