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Drilling out stainless steel screws :(

6K views 31 replies 21 participants last post by  RainDog 
#1 ·
I had to remove 4 large stainless steel screws (with booggered up phillips heads) that PO fiberglassed to the hull of the dinghy I bought. Bought the best and hardest drill bits, best extractors, best taps. Shortly after setting out to do what I thought was going to be an unpleasant but not an impossible task I started to see how grossly I have underestimated this task.
My emotions raged on, going from wanting to cry like a little girl, to feeling like a Viking beserker after a good dose of Amanita muscaria mushrooms.
The hardest bits were spinning like mad, without making any progress. Now and then a tantalizing flake of ss would fly out of the hole, flirting with my maddened brain and trying to convince me that I'm making progress.
Finally, after a couple of hours and 2 ruined drill bits, I gave up. I dug into the fiberglass around the screws, and twisted of the heads of these little monsters with my best chanelocks. The effin resin held like a rock and the screws did not budge... :mad:

Which made me later think that maybe, just maybe, there is a better way... :confused:
 
#9 ·
I was pretty sure that cutting a groove in the heads would lead to them twisting off. The heads ended up twisting off anyway. I should have tried heating the screws, like aelkin said. I was thinking of using the torch for that and was worried that the transom will catch fire. did not think about soldering iron.
 
#10 ·
I have seen some bits that look almost like a deep mini hole saw. They basically drill around the screw, then it pulls out like a plug. You have a bigger hole to patch but saves a bit of agony. I think I saw them advertised in the back of Good Old Boat. One of the things you should order and have on hand before you need it.
 
#12 ·
The guys at the hardware store don't always know anything. Often, but not always.
Like Subaqua says, you need cobalt bits--they're yellowish and the package will say 'cobalt'. Accept no substitutes. Stop drilling and lubricate the points (cutting oil, 3-in-1, etc) frequently as you work, and go very, very slowly. Unfortunately, you may have work-hardened the SS by spinning the bit. You've obviously dulled the bit, too, so start with new ones, working up from small. Once a cobalt bit starts to cut, you can see the swarf just come out in little spirals. Buy some extra bits. Cobalt is the only kind of bit I keep on the boat just because it's all that works on stainless.
Good luck.
John
 
#13 ·
Another vote on drilling slow. The problem isn't overheating, it's the work hardening of the stainless steel that occurs when drilling too fast. Un-workhardened stainless steel is actually quite soft. You should always use a cutting lubricant, too.

My favourite ever tool in the history of all tools is the electric impact driver. I never knew this was my favourite tool ever until I used it one day to screw stainless steel philip head screws. It will also extract the almost most mangled of screws, and it never ever galls the head of the screw even when fighting a lot of turning resistance. I have a tiny 10.8 volt cordless model which has plenty of power but enough finesse to ensure that shearing the head off a screw is also a thing of the past. Have I mentioned I love my impact driver?

And one more suggestion. Vice grips - the actual Vice Grip brand or any other good quality copy - will usually remove the most obstinate of mangle headed screws as long as you have the access. In really tight spots,side cutter pliers can be used to grip the head of the screw from above. Just squeeze them hard enough to cut into the sides of the screw head and twist.
 
#16 ·
My favourite ever tool in the history of all tools is the electric impact driver. I never knew this was my favourite tool ever until I used it one day to screw stainless steel philip head screws. It will also extract the almost most mangled of screws, and it never ever galls the head of the screw even when fighting a lot of turning resistance.
Ha! Did not know that. I need to get me one of these.
 
#21 ·
While these are a great tool to have, and relatively cheap, they will not help you with removing an already buggered screw.
 
#24 ·
I have also used my cordless hammer drill, in conjunction with the torque setting, and heat from a torch to free uncooperative stainless screws.

Sent from my VS930 4G using Forum Fiend v1.1.3.
 
#25 · (Edited)
When you need to heat a screw or bolt like this, you need a small torch and a throw away screw driver or socket wrench. Heat the throw away driver or tool and then use it to transfer heat to the bolt/screw head. This will only apply heat where it is needed, along the shaft of the fastener. When you get the screw hot enough for smoke to start coming from around the head, try unscrewing it. If it won't come, heat it some more.

Using a tool to transfer the heat keeps the heat on the fastener and not so much burning up your gel coat.

Plan "B" is to use a dremel or similar tool to cut a straight slot for a flat screw driver and go for it as above.

Have water handy for putting out any fire that may start.

Be here by warned that the screw driver, socket and the extension will be annealed/softened by this treatment and will probably be useless for any other purpose after having been heated. The little ball in your extension that retains the socket has a spring under it. That spring will probably die early in this exercise and then the socket will just fall off.
 
#28 ·
I just had to remove a bolt from an alternator bracket. Slowly drilled a pilot with a bit roughly 1/3 the diameter of the bolt. Used reversed threaded drill bit to back it out. In my case, it just removed the remaining material around the pilot. Repeating this several times finally got the bolt out in many shards. I used compressed air and PB Blaster between each iteration.
 
#30 ·
Find a set of left handed drill bits, because they turn to counter clock-wise they will usually catch the thread helix at some point and back it out. Purchase a set that includes tap drill sizes for the common sizes and you can run a thread tap through to clean out and dress the threads for reassembly.
I found a cutting compound called Anchor Lube that works well on stainless, and because it is a semi-paste it stays where you put it and doesn't run off
 
#31 ·
Beat me to it... I love left handed bits, as they catch they could back out the screws. I have saved countless hours working that way. Also don't waste your money at local hardware stores for drills, go to a industrial (machining) supply store, you want TiN coated (gold) cobalt drills. The ones at Home Depot or Lowes or Ace just aren't made for real work, good for around the house but not stainless or any other hard alloy.
 
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#32 ·
Surprised no one has mentioned it, but anything you can put in your car you can bring to a machine shop and have them do it. They charge me 20 bucks normally which is totally worth it considering what a PITA it is to get them out. Just had them do this to all my hatches, which are 20 year old aluminum frames with stainless bolts. Genius design.
 
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