Drilling out stainless steel bolts.

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ChasB

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I have a M8 stainless steel bolt embedded 2" in resin that needs drilling out and replacing.

Do I need a special diamond tipped drill bit for this?

Drilling it out will make the area hot, and that will melt the resin won't it? Won't that then cause a problem with the bit getting covered in molten sticky goo?

In theory I could heat the bolt up with a soldering iron at either end, thus melting the resin and so pull it out, but there's a thick metal backing plate that will act as a heat sink and maybe even allow the resin in the surrounding area to melt - which I don't want. So that option's a non-starter.

Any tips appreciated.

Cheers!
 
You can drill stainless but you will need new drill bits, a slow speed and a lubricant, and the problem is that the drill bit will wander and it's very difficult to drill out completely. Try drilling a small hole, say 5mm diameter x 5 mm deep and then knock the bolt out with a drift. I've done the above but it was stainless in aluminium.
If you cannot knock out then drill as deep as possible with the 5mm bit then increase to 7 or 8mm diameter.
Good Luck!
 
If it's not actually bonded in then I'd follow the advice and drill it out to ~5mm then use an extractor. If you think that may crack the resin then you could tap it to M6 and start it by screwing in a bolt and locking nuts, then use an extractor to unscrew it once it's moving. If it's well and truly bonded in then I guess the small hole will act as a pilot for a larger drill. Depends on what you want to do with the hole afterwards, as well.
Another thought, re-reading your post, would a narrow hole saw, without a drill bit, to remove the material around the bolt help? You could probably then get some molegrips on it or file flats and use a spanner.
 
Thanks.

It's well and truly embedded in with resin. I think any attempt at turning it will crack the surrounding resin. A lubricant will create a problem of cleaning the hole ready for a fresh layer of resin and then the replacement bolt. Maybe I could run a hose of cold water on it (with a bucket inside underneath for when I break through!) to cool it as I drill, thereby stopping the resin melting.

I think the pilot hole with a smaller bit is the way to go.

I still wonder whether a conventional bit will last long drilling into a high chrome content bolt.
 
I think you are right about a normal bit burning out, I don,t envy you the job at all, I think unless your incredibly lucky the drill will run off. I have a similar problem, I have been putting off on the stem head fitting. I dont think the heat is as big a problem as the running off part. In my case I think I will end up butchering out the bolts and having to repair the subsequent damage. Please pm me if you come up with a solution, I will be most interested. Bill.
 
Buy yourself a cobalt drill bit. They are not especially expensive, I recently bought a set 2 - 6 mm for £7 on Ebay. I have a collection of them up to 10 mm permanently aboard. There is nothing to compare with them for stainless steel. When you drill, keep supplying water to the area from a hosepipe, not so vigorously that you swamp the drill, and the heat will be conducted away.
 
I don't envy you the task of drilling, I think it will cost you a fortune in broken bits and take ages.
I would go the heat route, you only need to soften the resin.
I take it you can get to both ends of the bolt and the bolt head isn't encapsulated (if it is, you can chisel the head out) and that the plate is behind the head.
I would apply heat through a funnel (cone) to the thread end and at the same time put some torque on the head. Once it starts to turn, get some leavers under the head. The plate will make a good base for the leaver fulcrum.
 
I had to do this last winter to remove/replace the winches. The first 5 bolts took about 4 hours starting with a small bit and getting bigger. For the second winch I invested in some Bosch Titanium bits (from B&Q), the job took 20 mins.

Invest in the right gear and life is a lot easier.

Hope this helps
 
From the West epoxy manual:
"Remove a permanently bonded fastener by applying heat to the head of the fastener with a soldering iron or propane torch. Use a heat shield to protect the surrounding area. Heat will travel down the fastener, softening the epoxy in contact with it. At about 120°F the epoxy should soften enough to allow the fastener to be backed out. Allow more time for heat to travel down longer or larger diameter fasteners."

120F is less than 50C. That's surprisingly low. I'll try that first.

But surely boats must sometimes sit in hot sunny places and the resin embedded fittings might get that hot...? Couldn't that be a problem?

I found this intriguing item
http://www.atvconnection.com/Departments/ATV_Tech/Tech-Tip-14-Drilling-out-Exhaust-Studs.cfm

And this on cobalt drills http://www.fairburyfastener.com/norseman.htm
Don't know where you'd buy these here though

Or maybe just plain old fashioned titanium will do?
http://www.drillbitdepot.com/HSS_DRILL_BITS2253.htm
Cheaper than regular bits at my local hardware store...
 
Ah, so maybe titanium it is then. /forums/images/graemlins/cool.gif So were the Bosch drills titanium coated? As opposed to a solid titanium alloy...?

(And I bet there's different grades of titanium coating... /forums/images/graemlins/frown.gif )
 
[ QUOTE ]

120F is less than 50C. That's surprisingly low. I'll try that first.

But surely boats must sometimes sit in hot sunny places and the resin embedded fittings might get that hot...? Couldn't that be a problem?



[/ QUOTE ]

One reason why epoxy hulls usually have polyester decks. And why even these should be white in the tropics.
 
The trick is pressure and slow speed especially the latter. Centre pop the end of the bolt as accurately as possible on the centre. Start the hole with a centre drill (ordinary HSS) but really lean on the drill. I use a long lever braced against something. Then switch to the appropriate diameter for the final hole. Forget about special drills. I have drilled around 300 Ø6.5 holes through 316 stainless 6mm thick with an ordinary HSS drill. But don't let the drill get hot. That will work harden the SS and the only solution is a new boat.
 
It's a titanium nitride coating. TiN coating is commonly used for edge retention on drill bits and milling cutters, often improving their lifetime by a factor of three or more.

M42 high speed steel contains 8% cobalt and is by far the most effective of these steels for drills.
 
How about a hole-saw. You can get a 16mm one and if you don't put a drill in the mandrel the S/S stud should keep it roughly on course. Then just refill the hole with resin.
 
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