Drilling out a stainless screw from aluminum

[Jim Fitch]

I need to replace the out-haul sheaves on my boom and, even with letting the PB Blaster sit for days, the stainless steel screw heads just snap right off when I try to free them.  Does anyone have a technique to share on drilling out the screws without destroying the aluminum that they have completely bonded themselves to?

Thanks,

Jim
Sunshine
1103

[Ray & Sandy Erps]

I tore apart a Honda outboard several years ago and ended up breaking several stainless steel bolts.  I ended up taking them all out, screwing up the first couple so I had to use thread insert kits to repair the hold but I got better at it as I went along.

I used a small grinder to grind the broken bolt/screw flat.  Accurately center punched and then started out with new, small drill bits.  I leared that drilling stainless required a slow drill speed (I thought fast was better and ended up ruining a few bits)  I kept the bits sharp.  Once you get through with the first drill bit, you can get a soaking compound on the otherside of the bolt in the case of blind holes.  At any rate, I kept going up in drill bit size as I approached the size of the bolt.  I bought a set of reverse drill bits from Snap-on years ago and often these spun the broken bolt out when drilling out the bolt the next size up.  If it didn't, I started applying easy-outs.  That was kind of a do-or-die situation, as the easy outs kind of pressed the drilled out bolt outwards as they dug in.  Most the time it worked but on a few occasions the easy-out wouldn't do it.  Then I would take a small sharp chisel and start catching the outer edges of the broken bolt and driving them inwards to loosen them up.

I hate broken stainless in aluminum.  As a preventive measure, I was told that permantex number 2 should be applied to the threads of stainless bolts going back into aluminum.  That's the brown sticky gasket material that's hard to get off you fingers.  Anyway, I practiced that and have had not more seized bolts.  The permatex cleans up with rubbing alcohol.

Good luck.

[Jim Fitch]

Thanks Ray, it sounds like fun.

Jim

[Tom Soko]

Jim,
Once you get the SS screws out of the boom and end caps, you might want to re-drill and tap the holes for a 1/4-20 hex cap bolt.  With a little never-seize, the bolts are easy to get out the next time.

[Ron Bukowski]

I tackled this job over the winter. My out-haul was "stuck" and I couldn't get it to move either way. As I tried to remove the SS screws from both ends of the boom, one at each end broke off. The phillips head screw driver chewed up the remaining screws. I used a vise-grip pliers on the heads that didn't break off and carefully backed them out. Where the screws had broken I drilled them out not really caring too much about drilling into the aluminum castings underneath because I knew that Tom Sokoloski's idea to drill and tap for 1/4-20 hex-head screws was a winner and that was what I was planning on doing. When I got it all apart, there was more than enough "meat" in the aluminum to allow for the larger screws. BTW, I found that the out-haul lines had twisted around each other and that was why it was jammed. I straightened out the lines but I didn't make any other changes at that time. With the hex-head screws in the ends it will be a simple matter to take it apart again when I decide what I want to do or if it becomes jammed again. Thanks, Tom.

[Jim Brener]

How did you get the end caps off.  I removed the 4 screws from the forward end of the boom but the cap seemed frozen in place and I did not want to crack it (if possible).  Have not tried the aft end yet but need to replace or free up the outhaul as described in a mainsheet article.

[Ron Bukowski]

Work a sturdy screw driver or small chisel into the seam between the end cap and the boom then drive the end cap off with some heavy hammer blows. It takes quite a bit of force to start the cap moving. As the cap moves away slightly it will require less force. Work around the perimeter of the cap so that it doesn't cock in the mast. I was afraid that I would damage the cap but don't worry it's not so fragile.

[Jim Price]

I used a flat blunt chisel with hammer, tapping all the way around evenly.  Also used liquid wrench soak prior to using tools.  Don't know if it helped but once the cap started to move, it just popped right off cleanly.