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pfrederi

Removing Broken bolts in aluminum/alloy

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One of my winter projects is to pull the engine on my 418 and solve the loose engine tin issues.  At least 5 of the small 1/4" bolts that hold the tins on have been sheared off flush with the block or  the head over the years .  In a Magnum 18 the block (and heads) are some aluminum alloy.  I know that most recommend welding a nut on the broken bolt ( I like Rangers comment about using a washer with a smaller hole first to avoid welding to the base material). 

 

This is a big project as you can't get  straight access to a lot of bolts thus having to pull the engine and put it on the engine stand so I can spin it around to get straight shots at the broken bolts. 

 

Recently i tried to get a sheared tin bolt out a head.  Pulled the head clamped it in a vice drilled it and used and easy out....which broke off.  Had to move over drill a new hole and helicoil it then enlarge the hole in the tin to get things lined up.  Not pretty.  would like to avoid that this time.

 

Any tips warnings about welding on an aluminun alloy  block???  i have a Miller MIG and an older Miller Thunderbolt AC/DC wleder but I am not at all good with either one.

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Anything in this thread help you out?

 

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I usually start with the smallest drill I think I can get by with, drill it all the way through and soak them with a good penetrant before trying to move them. Then they can be step drilled, the penetrant helps with the drilling,the drilling can possibly provide a little heat for the penetrant,and that usually makes a difference. I've also used "Tapeze"?& that seems to help some. I've also wondered if one of the mini-torches on them would help the penetrant to get to the heart of the matter. 

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Once the corrosion starts with different metals being mixed together it's pretty tough to break it loose - the parts basically weld themselves together . Best is to try to spot weld a nut to a broken bolt - you can use a copper washer below the nut to absorb the heat and prevent melting the aluminum - it will sacrifice the washer first before damaging the aluminum . Easiest way is to use 7018 stick rod in 3/32" size or smaller - I have used 6011 1/16" rods in a pinch on really small bolts - just be careful since that rod is has a very aggressive arc and prefer to run it on ac polarity . Immediately after welding the nut apply some paraffin canning wax around the nut - as it cools the wax will be drawn into the threads and help knock them loose . Using penetrating oil and too much heat in combination will turn the oil into hard carbon - don't do that , the wax is far better although it does make a mess . If that doesn't work - then it's onto drilling the bolt out . I use cobalt bits and TD Foamy cutting oil - it's designed for annular cutters and threading work - works far better than anything I've found in 40yrs besides trichlorethane-based cutting fluids , which are now banned completely . At times the bolts are broken off in a very irregular shape and it's nearly impossible to center punch them well enough to keep the bit from walking off into the softer aluminum - for that I use a rotary tool of appropriate size (die grinder or Dremel) and a carbide burr to put a center guide hole in the bolt . I also try to use a 118-120* bit - they will hold their center a lot better than the common 135* bits - but they can be more prone to breaking as they cut more aggressively . Patience is key - take your time and use lower rpm's on your drill bit to prevent breakage .

 

One of the most commonly replaced and updated tools I keep around is a set of carbide burrs - they are not cheap but nothing else will cut through broken easy-outs or extractors due to their alloys , carbide is all that will cut it . I stick to either known US made high quality or Swiss/German bits - they not only last longer but have a far less tendency to chatter . Double cut for steels/iron , single cut for aluminum . A Dremel or other small rotary tool is nearly a must for this stuff as well as a solid quality die grinder for larger work . Air die grinders are ok and they last longer than most electric tools but their excessive speed can be a problem (they can be turned down with the screw adjustment valve/regulator - all these rotary air tools have that screw) . Electric die grinders have a lot more torque and can operate at much lower speeds - this is key when using carbide burrs to prevent chatter and breaking a burr bit - they are very brittle . I can't count how many times I've cut out broken drill bits and extractors here for myself and other folks - plenty of practice as I get a lot brought here that no one else will touch . I do some removal work for machine shops as well and those are the worst since the machinist has already exhausted all his tricks . On broken hardened tool steels such as drill bits and extractors a welding rod can blow it out of there with the arc on through holes - never do that on a blind hole - the trick is not damaging the area around the bit and especially on cast iron - if that rod hits that iron you'll draw up the carbon and create a spot so hard almost nothing will cut it .

 

Cast aluminum is a real problem - it's highly porous and attracts oils and carbon which will impregnate it and make hard spots . Trying to re-tap a hole is tricky and tough to keep the tap from galling . Mystic Metal Mover has a specific aluminum tap lube available in small cans - it's a good idea to keep some around and it works well for drilling aluminum as well . Other than that - I use TD Foamy on everything else , even on lathe work as it clings to the surface a lot better than most lubricants for cutting . Hunt around for broken parts that are junk and practice techniques on that first before attempting something on an expensive or hard to find part . Scrap yards are a great place to get practice stuff and it comes at scrap price - then get returned per market for some money back to boot and I do that pretty often if I want to practice on something with new welding procedures .

 

If nothing else , send it here and I'll get them out....lol . Keep in mind that welding shops are a great source of getting broken fasteners out - that is a staple in their business and those guys deal with it every day .

 

Sarge

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20 hours ago, pfrederi said:

One of my winter projects is to pull the engine on my 418 and solve the loose engine tin issues.  At least 5 of the small 1/4" bolts that hold the tins on have been sheared off flush with the block or  the head over the years .  In a Magnum 18 the block (and heads) are some aluminum alloy.  I know that most recommend welding a nut on the broken bolt ( I like Rangers comment about using a washer with a smaller hole first to avoid welding to the base material). 

 

This is a big project as you can't get  straight access to a lot of bolts thus having to pull the engine and put it on the engine stand so I can spin it around to get straight shots at the broken bolts. 

 

Recently i tried to get a sheared tin bolt out a head.  Pulled the head clamped it in a vice drilled it and used and easy out....which broke off.  Had to move over drill a new hole and helicoil it then enlarge the hole in the tin to get things lined up.  Not pretty.  would like to avoid that this time.

 

Any tips warnings about welding on an aluminun alloy  block???  i have a Miller MIG and an older Miller Thunderbolt AC/DC wleder but I am not at all good with either one.

Hi pfrederi

If you have a broken bolt in a component which has other threaded holes close by, cut a piece of steel bar/plate whatever,that will cover all the holes,  drill larger holes roughly where the holes in the component are, they don't have to line up exactly, then, if you have a lathe, cut some short pieces of round bar, say 1" or so long, drill holes larger than the threaded holes, on the lathe machine inserts to fit the holes in the bosses, make some spare inserts. Drill the inserts to a close fit with the bolt size for the threaded holes, drill the spare inserts with smaller drills, up to the tapping size for the broken bolt. Bolt the plate and bosses to the good component using the correct size inserts,then weld the bosses to the plate. You now have a drilling jig which should allow you to drill out any broken bolt/stud on that component, or another the same. Start off with the insert for the actual bolt size, run the drill into the end of the bolt, this will give you a true centre for the smaller drills to pick up from, the bosses should hold the drill perpendicular to the part being drilled. Be extra carefull with the smaller drills,"peck" at the bolt and withdraw to clear the swarf, tiny drill bits work best at high speeds.

Your question regarding welding aluminium/aluminum, if you are using an ac tig you will have the "cleaning" effect which you won't get with the mig, the answer is "Clean" "Clean""Clean". Don't just wire brush the part, if it's a broken boss with a threaded hole, drill it out first, use a rotary burr to remove the oxide build up, after cleaning the oxide will begin to re-form straightaway. Bolt the part down to reduce the chance of warping, preheat with a small gas torch, especially if using the mig, "Alli" will suck the heat away very quickly, you find you have no fusion at the start, then you burn through.

you could also try one of the alloy " brazing" kits available which work using only a propane torch, again remember, "CLEAN" or it won't work.

Good luck and have fun.:UK:

Regards Doug.

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