Drilling out a broken stainless steel bolt....

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BlueSkyNick

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... which was seized in the alloy mast. several years of weather induced corrosion and the two were welded together, a common problem I know.

What is the best drill bit to use? I tried a standard HSS steel bit and hardly made a dent.

Then I am planning to overdrill the mast to fit a helicoil for a new bolt, having tapped the new hole.

Of course, the battery in the cordless drill died after 30 seconds as usual!
 
MoodyNick said:
... which was seized in the alloy mast. several years of weather induced corrosion and the two were welded together, a common problem I know.

What is the best drill bit to use? I tried a standard HSS steel bit and hardly made a dent.

Then I am planning to overdrill the mast to fit a helicoil for a new bolt, having tapped the new hole.

Of course, the battery in the cordless drill died after 30 seconds as usual!
Click to expand...
Its hard enough drilling SS with a pillar drill, I would tap, bash, worry, try different easing fluids, heat etc on the darned thing until it comes loose. Then think about an over sized bolt/self tapper.
Stu
 
MoodyNick said:
... which was seized in the alloy mast. several years of weather induced corrosion and the two were welded together, a common problem I know.

What is the best drill bit to use? I tried a standard HSS steel bit and hardly made a dent.

Then I am planning to overdrill the mast to fit a helicoil for a new bolt, having tapped the new hole.

Of course, the battery in the cordless drill died after 30 seconds as usual!
Click to expand...
you need a sharp drill bit and slow speed, if your battery drill is 12v you could wire a lead, from the battery pack to plug into the boats 12v system. My 14v drill works OK like this.
 
You'll need 2 cobalt drills with constant speed and pressure, first drilling a smaller pilot and the other as near the diameter of the bolt you can get, with plenty of lubrication; make a plasticine(?) sump of oil that you can drill through. The stainless will work- harden if too high a speed is used or pressure not kept constant. the so-called Easi-out bits are not likely to be of use as if they break off you have an even bigger problem.

An alternative solution may be to use a hole cutter and repair the enlarged hole with a stainless patch pre-drilled to the original size, and pop rivetted to the mast.

ianat182
 
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Seized bolt

If you do manage to drill a hole through it close to the bolt size do not try a cheap tapered "Easy out". Bite the bullet and buy, beg or hire a "Snap on type" parallel key extractor. They do not spread the remaing bolt and at the worst can be hammered through should they snap. Maybe should be renamed "Snap Off"!
 
Maybe I'm missing something here but I have found pouring boiling fresh water on corroded together threads often allows them to part very easily. Use a lot (an eletric kettle plugged into the marina supply is useful) and give it time to remove the corrosion and salt. Cheap and easy and often works in sea salt corroded areas.

got to be worth a try::cool:
 
PabloPicasso said:
Maybe I'm missing something here but I have found pouring boiling fresh water on corroded together threads often allows them to part very easily. Use a lot (an eletric kettle plugged into the marina supply is useful) and give it time to remove the corrosion and salt. Cheap and easy and often works in sea salt corroded areas.

got to be worth a try::cool:
Click to expand...

.
 
Personally I wouldn't use a hand drill - as someone has already said, even drilling out a s/s stud with a pillar drill is difficult enough.

Suggest cutting a slot in the remaining stud with a dremel, then using an engineer's screwdriver (hexagonal handle) and a large adjustable wrench wrapped around the hex handle, press hard and try to work the bolt loose - back and forth. A blowlamp and some plus-gas (not at the same time !) might help too.
 
Salt water, ally and stainless steel, always try hot water as pablo says above first.
We often sort out pulled off fittings like that ,if there is just enough to get molegrips or cut another slot with a junior hacksaw,the alluminum oxide often releases far better in fresh HOT water before anything else.
Cindy
 
If you can cut a slot after the hot water and anything else you chuck at it use a small cold chisel on an angle in the slot and tap it gently with a light hammer so it is trying to turn the bolt. The impacts will often break the corrosion 'weld'.
 
Having tried the hot water trick, try (if you can) cutting a slot in the broken

stump exposed. Then with a hammer through screw driver and a small hammer

give it a sharp tap.This will often upset the bond between the offending

parts.

If that fails get a small tct drill bit and grind off the cutting edge back rake

with a green or diamond grinding wheel.Works great on broken manifold bolts

too.

Ray
 
SS Bolt

Dont even attempt to drill this without a good drill and sharp cobalt drill, ensure plenty of lubrication while drilling or the drill will lose its edge straight away, if you can position the drill so you can use a lever against it, not too long or you will strain the drill but enough to slow it down if you press hard than this is as good as a pillar drill.You have not said what the bolt is for, could a smaller size be used if you drilled and tapped out the damaged bolt body?if you damage the alluminium thread is there an option to helliciol?
try the drill first with plenty of lubricant on and that will get through eventually, but, as already stated make sure you go with a small pilot hole first.
...........have fun.!!
 
MoodyNick said:
... which was seized in the alloy mast. several years of weather induced corrosion and the two were welded together, a common problem I know.

I'm not sure how the bolt (or screw) fixing thro' the mast was made.
If there is no thread in the alloy mast involved, then the bolt should drift out without turning. If part of the mast is theaded, it won't drift out.
To break the inter metal corrosion, would it be possible to use stillson to turn the mast - sharply - first one way, then the other, at the same time applying heat to the alloy to expand it as others have suggested. To prevent damage to the mast, wrapping with emery cloth (rough side inside) should help.
Sounds crude but it could work.
Good Luck, Ron Dean.
Click to expand...
 
Quality cobalt drills are the way to go, a proprietary cutting lubricant and very slow drill speed as well. Quality cobalt drills are expensive a 6mm one will be about 6 quid.

It's possible to use a Torx bit driven into the stub as an easy out.
 
MoodyNick said:
... which was seized in the alloy mast. several years of weather induced corrosion and the two were welded together, a common problem I know.

What is the best drill bit to use? I tried a standard HSS steel bit and hardly made a dent.

Then I am planning to overdrill the mast to fit a helicoil for a new bolt, having tapped the new hole.

Of course, the battery in the cordless drill died after 30 seconds as usual!
Click to expand...
Try a weak acid - the obstruction is caused by hydrated aluminium oxides which are all bases.

The application of heat sometimes helps.

Only as a last resort would I try drilling out (I know I've had to do it)
 
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