Snapped bolt in block - how deep can this be drilled?

I would first grind a flat area on the end with a carbide burr in a pencil grinder.Then carefully center punch a mark right down the middle to give You a new start.Get some left hand drill bits starting about .125.Slowly work Your way up in drill sizes,and eventually a drill bit should grab and spin it right out without damaging threads.Mcmaster Carr for bits if You cant find them local

Perhaps you could measure the center to center of the holes and the location of the dowel (or maybe use the old bracket as a template, I can't picture it so I'm not sure), find a piece of 1/2" (or whatever) stock and drill it to to act as a guide to keep your drill square and on target?

The hole in your temporary guide (for the hole you need to repair) would be left at either the size of the repair tap, or maybe 3/16" to use as a pilot to drill out to the proper diameter afterward.

Bolt that up to the engine and drill through it. I think it would help to control wandering. As far as depth, I would guess that you could go the same as the adjacent holes, though I'm not positive about that. You should "feel" it when you're through the steel bolt and hit the cast iron. Looks like water back there.

Another thing that often works are the left handed drill bits, as above. If you're lucky they bite into the broken bolt and spin it right out. I have had no luck with the so-called "easy-outs".

Nasty job digging those broken bolts out, hope it's not hardened.

What I usually use at work for this kind of little "accidents". Never failed for me so far...

I was going to try the left handed bit but I figured the threads were so chewed up from the previous drilling, nothing was going to just back out of the hole. Pilot tube sounds like a good idea, once I figure on the depth and diameters I want. Depot run...

I threw it back together for a cruise tonight, not even going to put the bulkhead back on, just the engine cover, and leaving the dash area open, must be crazy but I gotta ride tonight, even without A/C. gotta ride...

Angelo

jeffsmachine has this one correct. You must get a flat spot in the center of the stud/busted bolt and then center punch. Left handed bits are the answer -- I've never had any luck with easyouts either; but the broken stuff has ALWAYS come out with left handed bits; but it is incredibly important that you start the pilot hole in the CENTER of the broken bolt. Can you get straight on the area, or is this an engine pull thing? Cannot tell from the photo.

Best of luck -- just be patient and it will come out without damaging the threads. Also, you will know when you've went through the bolt or stud, but again, you need to have this thing centered.

Mark

Heating the block around the bolt can help too as it expands the metal making the bolt move easier. It also helps draw penetrant in.

I have never had much luck with easyouts, a small oxy-acetylene torch is usually my savior. If the threads are shot after then a helicoil or stepped stud is the way to go.

If it's any help I meaured the depth of the holes in my spare block and they are 0.97" deep.

Good luck,
Julian

Hmm, strange why you guys seem to have so much trouble with easyouts (as you apperently seem to call those things). Due to my work I get to do a lot with snapped (Loctited for that matter) bolts, and easyouts do the trick for me (sometimes in combination with some heat I must admit)...

Thanks for some good ideas. Looks like my first step will be to try and get a good flat surface on the bolt, or what is left of it. Looks like there are at least 5 different drill indentions in this hole, someone should have given up sooner, would have made my job a bit easier. Once I get the flat surface I will TAP a center punch to help keep the drill bit centered. Don't want to flare out or expand the metal any more than I have to. Will work up from a small bit as far as I can (Left handed bits when I snag them). I might also freeze the area after soaking with WD-40 or the like. I don't believe heating this area will help, like mentioned earlier, it will expand the metal making things tighter, heating could work on a bolt/nut, shaft/bearing,etc. where the surrounding metal had somewhere to expand to other than the object it is jammed on.

Thanks for the depth information, gives me a place to mark for a stop. I can get a straight shot in to this location since it is in the front of the engine and everything will be out of the way. Just another project to fix while waiting for A/C parts and hoses. sigh.

Thanks everyone

Angelo

I do have a set of easy outs or extractors, but in this case, the threads on top of the bolt seem to be quite buggered up which I think would jam the bolt nicely. I might give it a try carefully with about a 20% pilot hole, any larger and I would most likely expand the bolt into the threads, it would not take much to do that at all. Will see when I make the holes in the bolt.

Thanks,
Angelo

Don't know why, but extractors and heat never works for me, I always end up drilling and cutting new threads...

...Now Your going to hear from a Professional Machinist; if You Care to Listen! DO NOT use a 'EZ-Out'(Very Very HARD!)if and when it Snaps off, Your NightMare has Just Begun! As well as making a good living Machining Parts for, Assembling, and Calibrating in; 'Power Transmission' Gearboxes, from 500 HP up to 17,000 HP; a very small part of My work has been to fix the blunders of other 'Mechanics' who have tried and failed to remove a 'Broken Bolt'. I.E. FIRST Remove the Hardened EZ-Out AND then the Broken Bolt! There is Only ONE way to Remove a EZ-Out! Clamp the 'Part' down on the Milling Table, find the 'Dead Center' and Mill the EZ-Out, Out, with a 'Carbide End Mill'! The Carbide Endmill can be used only once! Because as It 'Cuts'(actually Wares away)the Very Hard Steel, the Carbide Mill itself Desintigrates!

NOW! Your Bolt problem stems from the use of a Bolt that was Too long; when screwed in it 'Bottomed Out' Before Clamping, so then more force was used, snapping off the Bolt where the shoulder meets the threads!

To remove the Bolt: This will be difficult because You will have to use a 'Hand-Held' Drill motor. The Bolt is a 5/16-18. The 'Tap Drill' for it is an 'F' drill, Decimal=.257" If You do not have an F drill, You may use a 1/4". This is the largest drill You will use and NOT harm the Threads. Yes! Get the Top of the Broken Bolt as Flat as You can (a 1/4" end Mill in a drill Motor will do the job enough to get a centerpunch centered). You won't need Carbide Because the Bolt is Soft. Then, Start with a 1/8" Drill and drill all the way through! Will be 1-1/2" to as deep as 2.0". Be sure to use Oil to keep the Drill Bit from Burning up!! Move up to slightly larger drills, and finish with the 'F' drill. Now Your at the 'Root' Diameter of the 5/16-18 Thread, and the 'Old' Bolt Threads are all that remain. All You do now is use a 'T' Handle Tap Wrench with a 5/16-18 TAP. Now Try to 'Retap' the threads! You'll most likely get it in a couple of turns and then the Tap will JAM!! This IS What we want! Now Unscrew the Tap and 'if 'it's' Cooperating', the Old Threads will come out with the Tap being unscrewed! May take a few times of tapping in and out! WD-40 Helps! When All of the Debris is removed; use some oil and clean-up the threads by running the Tap Down-in a couple more times. This should leave You a Clean Bore with Fine Original threads! If the Remaining Threads are too 'Buggered-Up' to be of use...Your last resort would be; to drill and tap for the 'Next Larger' Bolt! That would be a 3/8-16, TapDrill 5/16". Ofcourse; 'That' Hole in the 'Mounted Part' will have to be drilled to match 3/8". Good-Luck with it!!

Marlin

Thanks, I was kinda hoping you were going to chime in before I started this chore. Having snapped 'easyouts' before, I had already decided I did not want to go that route, even if I had to redrill and tap completely, and definately did not want to apply heat. I have both left and right drill bits and was going to start off with the left handed bits hoping to get lucky. I have been spraying the hole with WD for a couple of days hoping it will seep into the threads and make life easier during the chore. Thanks for your reccommendation/procedure, will follow as close as possible when I get back to it. Hopefully my next post will be a happy one. snicker

Angelo

Well, this isn't coming out as planned... After grinding on the top of the snapped bolt for a few hours trying to get a flat surface to center a drill bit, I find that the previous person had snapped what looks like 2 drill bits into the bolt! From the hardness and look of the bolt, I am going to assume it is stainless since I have found quite a few stainless bolts on this engine. At this point I am at a loss, do I continue to slowly grind away for the next week? I don't think I can thread another bit between the 2 snapped ones, I'm not that good. Can/should I weld a stud into this hole? Do I have to pull the engine for a friggen snapped bolt and bring it to a machine shop?

Depression is setting in.

Angelo

quote:

Originally posted by MARLIN JACK:
...Now Your going to hear from a Professional Machinist; if You Care to Listen! DO NOT use a 'EZ-Out'(Very Very HARD!)if and when it Snaps off, Your NightMare has Just Begun! As well as making a good living Machining Parts for, Assembling, and Calibrating in; 'Power Transmission' Gearboxes, from 500 HP up to 17,000 HP;

Professional wise I'm into transmissions dealing with torques up to 1.000.000nm and more (yes, one million nm and more)

But never, never had troubles with easy-outs. They do not always do the trick (mostly they do though), and never broke one. Wonder how others do make them break...? But true, if broken, you could get in even bigger trouble.

ANGELO B,

Sounds like you should take the advise of Marlin and use an end mill, so yes, it has to come out if you want to use the same hole again. If there are two broken bits in there, end mill is the best solution.

Mark

...There is ONE more way to remove the Bolt!! I only mention this because 'It' does exist; But Will be Very Hard to Locate a Machine Shop that would even Have this Machine, And that Machine may NOT be Portable enough to work on Your Block while it is Still in the Car. The Machine I refer to is Called a 'Electronic Disintigrator'. Basically one probe clamps to the Block, the Other Probe (Pointed) is placed in Contact with the exposed end of the Broken Bolt. Similar to 'Reversed Electrolosis'; ONLY the Bolt, itself Disintigrates into easily removed 'Pieces' and Leaves the 'Parent' threads in the Block, absolutely UNtouched!! Don't know if this will help You. A Second Idea would be to 'Friction Weld' a Stud onto the Broken Bolt, which could then be Clamped upon, to unscrew the Bolt. This procedure would be the Most Difficult, as You would need a 'Highest Speed' Motor and it would be 'Hand-Held'! One last suggestion! A CARBIDE DrillBit!! Hard enough to drill the Other drills and EZ-out! But still hand-held. Also Very Brittle, Very Expensive. Run it at a Fast Speed, with NO lubricant!! Last: Have You ever seen a 'Magnetic Base' Drill Motor? I wonder if there would be enough room to Mag Mount it to the Front Face of the Cylinder Head, if everything was removed, out of the way?

Marlin

quote:

'Electronic Disintigrator'

I have used these in the past. The particular model I have used was a "head" mounted to a drill press style feed.
The disintigrator uses a hollow sacrifical tube to ping away the said bolt or broken tool in the hole. Coolant flows through the sacrifical tube for cooling and washing away the waste materials. These tubes come in various sizes to fit the particular job being performed. I have taken the head of the disintigrator off of the feed unit and used freehand on jobs that the unit could not be mounted due to location interferences.
Good luck on finding one.

quote:

'Electronic Disintegrator'

Until Marlin shared this with us, I had no idea such a tool existed.

Here is a You Tube video that gives a pretty good idea of how they work.

http://www.youtube.com/watch?v=FgDscaUOQnc

Larry