Jump to content
Sign in to follow this  

What drill bits needed to drill a bolt out ?

Recommended Posts

I snapped a bolt off in my sub-frame (The bolt that holds the muffler/silencer on) and the drill bits i have don't seem to do anything to the bolt...

So what type of bit do i need ?

Share this post


Link to post
Share on other sites

a left-handed bit is your best bet. A lot of times the bolt will spin out as you are drilling the hole for the easy out. The other thing you can do is just simply drill it out and install a heli-coil. In either case you need sharp drill bits.

Share this post


Link to post
Share on other sites

Get a nice sharp center punch and make sure u are dead center on bolt. Start with a tiny drill bit.Dont press to hard and snap your bit:foul:. And gradually work your way up till u get most of the bolt. At that point try an ez out, but once again do not snap it. Nothing worse than broken ez out in the bolt u just spent a half hour drilling thru:banghead:. If ez doesnt work. Keep going up on drill sizes. If u have been drilling dead center u may get lucky and be able to pick the threads out at the biggest drill. If not. Go up a lil more and tap a larger size. If its an insert they make a replacement tool for them . Good luck

Share this post


Link to post
Share on other sites
I snapped a bolt off in my sub-frame (The bolt that holds the muffler/silencer on) and the drill bits i have don't seem to do anything to the bolt...

So what type of bit do i need ?

You need sharp ones of good American quality! If you did not cross thread the bolt and just snapped the head off due to fatigue, you may be able to use a pick and spin out what is left of the bolt. If not, as stated earlier, center punch and start with an 1/8 good quality, sharp bit. Work your way up to a 9/32nd if it is an 8mm bolt. You should be able to pick it out from there or tap up a size to 3/8 or 10mm.

Share this post


Link to post
Share on other sites

Can you see the other side of the bolt? If so, try to grab it with vice-grips and turn it "in" the rest of the way. Even if you can get it to move 1/2" a turn you're making progress. It'll be somewhat tedious at first, but you'll get to a point where you can remove it the rest of the way with your fingers.

If not, the best bet is left hand drill bits, start with a 1/8" and you'll probably get to a point where it just comes out. If not, move up to 3/16" and finally 1/4". If you get that far, just give up, drill it out the rest of the way with the correct bit and re-tap it.

If you don't own metric taps, you should. Available at any hardware store, the last set I bought had from 3mm to 10mm in common threads with bits and taps for $40-50. Like someone else said, buy quality tools once instead of Chinese crap repeatedly.

Well, taps are consumables, but quality ones last longer and some places even will replace them at no charge (rare, but don't look a gift-horse in the mouth).

IMHO, there's nothing easy about an EZ-out, especially when it breaks off. I can't remember the last time I used one cause they're more trouble than they're worth.

Share this post


Link to post
Share on other sites

Could need to resharpen, or may need a carbide tip. If youve been drilling like crazy you could have tempered the bolt. Just means it will take a bit. Try the left handed bits like mentioned, or you could take a dremel tool and grind it out. Ive dremeled small bolts like that then just picked the rest.

Share this post


Link to post
Share on other sites
I snapped a bolt off in my sub-frame (The bolt that holds the muffler/silencer on) and the drill bits i have don't seem to do anything to the bolt...

So what type of bit do i need ?

Sharp for starters.. (so new unless you sharpen your own)

Left hand is best for this as it often will spin the fastener out while drilling, though heat and friction.

If the broken fastener is above surface, grind or file top so it is a flat surface, then center punch in the center (filing it flat helps center punching dead square, and keeps the bit from walking off center)

Start with an 1/8 or so bit, and go up in size till you get to just under the fastener minor dimension (so that’s the dia at the base or “inside” the threads)

Of the fastener has not come out by now, use an easy out or other type broken fastener extractor.. CAUTION,, if the broken fastener is cross threaded, bottomed out, or otherwise physically fixed in that hole,, it may take more tq to remove then the easy out can handle.. Heat may be needed, or other more advanced removal methods may be required.

Share this post


Link to post
Share on other sites

A cobalt bit is what you are looking for. They aren't cheap, but they are very hard and won't dull as quickly.

Share this post


Link to post
Share on other sites

Thanks for the answers guys, The bolt is stuck in there and there is no way to grab it with anything like you can with a lot of other broken bolts so drilling is my only option...

Will try your answers,

Thanks

Share this post


Link to post
Share on other sites

I see you're in the UK, so instead of 1/8", 3/16" and 1/4", 3,4.5,6mm bits. I like the titanium coated ones, but any left-hand bit will do as you don't use these often and are hard to find locally. Now if you have to buy them online, get the titanium coated or cobalt alloy ones. Skip "bright"/uncoated or black oxide as these are cheaper and more prone to breaking and wear out faster.

Share this post


Link to post
Share on other sites
A cobalt bit is what you are looking for. They aren't cheap, but they are very hard and won't dull as quickly.

+1 Cobolt bits work much better on hardened bolts.

If the bolt can be spun "in" completely through the hole and out the other side, there's really no reason for a left-hand drill bit. If the drill bit spins the bolt through and out the other side, just unchuck the bit and pull it out the back side.

Share this post


Link to post
Share on other sites

Not the answer but a common issue I see is people use way too high rpm's and press too hard when drilling, which causes excess heat and premature dulling of the bit. Ever notice how slow a drill press turns compare to a hand drill?

Share this post


Link to post
Share on other sites
a left-handed bit is your best bet. A lot of times the bolt will spin out as you are drilling the hole for the easy out. The other thing you can do is just simply drill it out and install a heli-coil. In either case you need sharp drill bits.

^^^This. I have a set of left-handed drill bits and EZ outs. The left-handed drill bits work so well, I've never had to use an EZ out.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×