What's the right way to drill out a broken screw or bolt shank?

[Tinkerer]

For a change, this isn't something I've stuffed up. Yet.<br /><br />I'd like to know the right way to do this instead of creating another problem when the drill bit wanders off centre and bites into the surrounding material and leaves the shank in etc etc. Or I break the screw extractor (also known absurdly as an Ezy Out), which is harder than any bit, and there's no meat left in the shank to work with. Now I'm stuffed, so I just ruin everything drilling and hacking it out and hope JB Weld and/or helicoils will perform their usual magic.<br /><br />A lot of the problem is that I can't get heat onto the shank, which is flush with or below the surrounding material, without risking melting the alloy around it. Also I can't get any penetrating fluid in there. So I'm trying to budge a frozen shank.<br /><br />I've got a stainless steel 1/4" shank left in the hole of an alloy gearcase where the head had broken off before I got it. <br /><br />Can't put it in a drill press so it'll be a hand held power drill. Or maybe I should start with a hand drill for better control?<br /><br />This is what I normally do but it ain't always successful.<br /><br />I have a spring centre punch that puts a tiny hole on mild steel (and less on stainless) but do it a few times and it puts a bigger hole there, which I then make bigger with a normal punch hit with a hammer. About this stage we're often already starting to wander a bit off centre as the hammer hit punch seems to move a bit sideways.<br /><br />Then a thin bit about 3/32" (I usually break them if they're much smaller no matter how careful I am) for a pilot hole and then a bigger bit.<br /><br />I use a cobalt bit.<br /><br />Then the screw extractor, which has a good chance of breaking and now I'm stuffed again.<br /><br />Anybody got any advice on how I could do it better?

 

[rodbolt]

Re: What's the right way to drill out a broken screw or bolt shank?

leave the screw extractor at the store. save the money for decent drill bits and taps. I have a set of bullet boint bits with no-slip shanks and a set of carbide tap drills. the bullet points are throw away bits butI dont care cause the customer buys them. a dremmil tool can be invaluable with a tiny carbide burr to help a hole someone else mis-drilled. a quality drill with a good chuck and spindle bearings is a must.<br /> I drill 4 or 5 a week during the summer and never have a problem. if its 10mm(3/8) or bigger I sometimes drill a 5/32" starter hole for the tap drill center relief.<br /> but you have to remember I have done this a year or so <br />actually my father taught me when I was still in elementary school. a good transfer punh kit is helpful. I have a few drill bushings I have welede to pieces of steel with slots for doing exhaust cover bolts and head bolts.<br /> mostly its a matter of common sense and experience. but leave the easy outs at the store.<br /> hardest bolts you will ever drill are the bolts holding the trim units on jonnyrudes from the late 70's to the mid 90's. man them is some hard bolts.

 

[JB]

Re: What's the right way to drill out a broken screw or bolt shank?

Non-boating Tech topic.

 

[Paul Moir]

Re: What's the right way to drill out a broken screw or bolt shank?

I just wanted to add to rodbolts suggestions. I do pretty well exactly what he does. Except if I've got access to the top of the bolt, if it broke off flush, I'll use the dremel with a carbide bit to carve a little pit for the drill to start. I find this works much better than trying to flatten the top of the screw and center-punching it. If it's slightly uneven I find the bit is going to wander. The dremel bit I use is essentially a tiny end mill and it works very well for re-centering holes.<br /><br />I've also gotten a lot of milage out of titanium and cobalt drill bits - even HSS in a pinch just by going slow and using lots of lube. I've never had to tackle the T&T bolts rodbolt mentions though.<br /><br />The 'weld a handle/nut on and turn' method works well too where applicable. I've only got a little wirefed fluxcore welder but it does the job nicely. Whatever you do, stay away from 'Easy Outs' if you don't want to learn about electro-discharge machining.

 

[one more cast]

Re: What's the right way to drill out a broken screw or bolt shank?

Heres a little secret guys. Buy a set of left hand twist (reverse twist) drill bits and a lot of times the bolt will spin out when you drill it. Yes there is such a thing and no I don't know where to buy them. We had them at work.<br /> Update: Here you go. Left hand drill bits

 

[rayjay]

Re: What's the right way to drill out a broken screw or bolt shank?

Snap On sells an extractor set that has worked pretty well for me. The main difference with this set is that you drill the hole all the way through the broken shank. The shank then shrinks a little . Their extractor piece is driven though the shank and then a hex adaptor is slid over the extractor piece and the shank is [hopefully] turned out.<br /><br /> http://buy1.snapon.com/catalog/item...&group_ID=1254&store=snapon-store&dir=catalog

 

[Laddies]

Re: What's the right way to drill out a broken screw or bolt shank?

Something I have with a lot of success with in hard to get at places, Left hand drill bits and torx bits the don't expand the bolt, like some eazy outs do, use a little heat around the fastener not on it--Bob

 

[snapperbait]

Re: What's the right way to drill out a broken screw or bolt shank?

Then there's the mental aspect of busted bolts.. <br /><br />Lots of people freak out, but you gotta keep cool and take your time... Even with the right tools, lose your cool and/or rush, the problem gets worse every time..