Best Method To Remove a Stainless Steel Broken Screw Corroded to Aluminum Frame

[josa1]

 

Well, I'm in the midst of hoeing a hard row!  Servicing a Penn International 50SW for my friend.  Started to remove the reel mount from the frame, turned the first 8x32x7/16" screw about a 1/4 turn and the screw head fell off in my hand.  Had better luck removing the two front screws.  Started on the remaining screw, difficult to turn, did all the normal stuff with penetrants, heat and so forth with no luck.  Finally, it too broke under too much pressure from yours truely.  These screws are absolutely frozen and have to be removed by drilling them out.  To make things worse, the screws seem to be made of the hardest stainless I've had to deal with.

I have a drill press (Min Speed about 500 RPM) and a set (actually several) of the cobalt drills and they will drill the stainless screws SLOWLY, but on my first attempt the drill bit bounced off the screw and went through the aluminum frame like it was butter.

I've tried several different things to no avail.  Finally have a hole through the first screw, but not very straight.

Just wondered if this has happened to you.  And if so, how did you resolve the issue.

Guess the question is "What is the best way to drill out a stainless steel screw?"

Any help would be greatly appreciated.

josa1

[Ron Jones]

The BEST way is with a mill and stub bits and a very strong hold fast arrangement but I doubt you have access to that (mst don't.) With the bit wandering I'd bet you are using a regular length drill bit and possibly not pre-drilling with a smaller bit? This will probably have to be done in steps, small diameter short bit, small diameter long bit, medium short bit, etc. A lot of work but it is the best way to protect the frame. At the end of the day, the holes in the frame may be shot and then you are looking at tapping oversize holes.

Tough row to hoe.

The Man

[josa1]

Thanks Ron.  I used to say in the Commercial Air Conditioning Industry that knowledge is expensive.

I am closely informed that the same is true with drilling these stainless screws.  It's agonizing to know that there's only about 1/4" of the screw remaining in the frame.

I don't have access to the machine shop equipment/tools that you mention.  So, I'll either have to make use with what I have or send the frame out to get the screw extracted.

A couple of things I've learned.  Slower drill speed is better than faster.  And, water is a better lubricant for stainless than drilling/tapping oil.  Those from stuff I've watched on YouTube.

Thanks for your comments.

josa1

[oldmanjoe]

  I have a blue point / snap on set # 1020 that i use .      It has bushings that have steps in each bushing to aid you to center drill .
   One side you drop in to the hole or flip it over to slide over a broken bolt .
   You can use copper tube or small sockets as bushings ...  or make a tape bushing on the drill bit .

[josa1]

That's a very nice set of tools there Joe.  Something I could have used many times in the past.

Just too large for my needs.

I appreciate the ideas on centering the bit on the broken screw a lot. That was my first mistake, not getting the drill bit absolutely centered on the broken screw.  Probably the most important first step in drilling out a broken screw!

Thanks a lot!

josa1

[oldmanjoe]

   First step is to see if you are looking at a icicle or a flat top .  So you can drill it ...

[PacRat]

Whenever removing broken bolts and screws I always use left handed drill bits. Halt the time they will come loose while you drill them.
McMaster-Carr is a good source for left handed bits. Some auto parts stores carry them but they are not always high quality.

[josa1]

Hi pacrat,

I can assure you that these screws are so tightly bound that they may as well be welded to the frame.  There is only a very short portion remaining in the hole in the frame.  I could not budge them when the head was still attached to the screw, the frame was heated, the screw was heated and I used an impact driver to try to break them loose.  The only remaining solution I can see is to totally drill out the remaining portions of the screws and retap the screw hole.

I appreciate your assistance and have put your helpful suggestions in my list of things to remember for future use.

Thanks!
josa1

[alantani]

been there......

i use a propane torch and blast it until it glows.  the problem is that any plastic even remotely in contact will melt.  you  have to strip it down as much as possible.  now i ALWAYS torch the soft brass clamp bolts in the old internationals.  it's just not worth taking a chance anymore.   

[josa1]

Hi Alan,

Thanks a lot for your comments. And, I can sense, your understanding of the current predicament I find myself in.

I am always certain that the best way to loosen stuck parts is to heat them or the body around them.  In this case, I am just concerned what that amount of heat would do to the gold anodizing on the reel body.  The aluminum is such a good heat conductor that it's pretty much necessary to heat the whole reel body to obtain the required result.  I have considered putting the part in the kitchen oven to evenly heat it to some predetermined temperature.  I might yet do that.

Have you had the "opportunity" to apply that much torch heat to an anodized part?  If so, what was the cosmetic result? 

At the present time the minor damage I've done to the body is going to be covered by the rod mount, should I ever be lucky enough to remove the damaged screws and get to the point of reinstalling it!

Thanks again!

josa1

[alantani]

the anodizing will hold up.  there might be a slight discoloration, but there is really no other choice.  you could soak it in penetrating oil for months and get no results.  you are stuck, literally, and i think that this is the best way out.  and have patience while drilling. 

[Ron Jones]

It is hard to argue with the Boss!

The Man

[josa1]

I agree!

Thanks Alan!

josa1

[josa1]

This might come under the heading of "Stuff I Don't Want to Know About".

But....

Because I was wondering how hot I needed to get the aluminum reel body to cause it to grow enough to release its hold on the stainless steel screws, I learned a little something about the "coefficient of thermal expansion" this morning.

My first question was "What if the stainless grows more than the aluminum as it is heated?"  Seems that would be a bad thing as to my uneducated mind that would make the screw more difficult to remove.

Coefficient of thermal expansion is defined as a product's fractional change in length divided by its rise in temperature.

Turns out the coefficient of expansion of the different aluminum products mentioned range from 11.9 to 13.1 for AN AVERAGE of 12.83.

The Coefficient of expansion of different stainless steel products range from 5.7 to 9.6 for AN AVERAGE OF 7.24.

So, in general the aluminum grows at a must faster rate than stainless.  It then seems that if the reel body was heated to about 250-300 degrees Fahrenheit it should loosen the bond between it and the stainless screws.


josa1

[Ron Jones]

J will be along to comment shortly I'm certain.
The Man