Question about drilling broken bolts

[Frankencelery]

When I took my 250SX rear end apart, I had to remove the trailer hitch to get to the bolts for the final drive. One of the bottom bolts was broken off, and naturally the second one broke as well. I've completely sworn off easy outs...they always break on me, leaving me with a hardened chunk-o-metal in the hole. Instead, I decided to drill out the holes until it was large enough to re-tap.

My question is maybe a newbie one, but I really don't know how to do this properly. First, I use a punch to mark the center to start my drilling, but the resulting hole is NEVER in the center! I didn't have a large enough bit, but I'm wondering how to get it back to where I can tap it, especially with the hole being off center. Do I drill it larger and tap a bigger size?

Also, the trailer hitch was not the stock one. Does anyone have an extra SX trailer hitch they want to get rid of?

[leevarnado]

here's an easy way to fix your problem.drill you holes,take a bolt run it through the hole and put a nut on the other side.this is on the hitch,right.

[BERT306]

i don't think its possible!!

Last time i tried to drill completely center i purposely made my center punch OFF CENTER so maybe it would magically go straight. Nope. dang. although i knew that wouldn't work anyway its just me being bullheaded. Why try to make a perfect center punch when it'll NEVER drill center anyway:mad:

I just waisted your time and helped u none, sorry. :beer

[knsmodels]

try the punch and drill the hole with a left handed drill bit.....usually the heat generated by the hole being drilled combined with the reverse drill bit the bolt will come out.....jmho

[Dirtcrasher]

From an ex machinist here:

Use a nice sharp center punch to start with. Begin drilling with a 1/16th or so "pilot drill". Just barely start drilling and LOOK AT IT!! If it's off, use the same center punch on an angle to FORCE THE CENTER correctly. If you drill too far, you won't be able to force or walk the drill bit towards the absolute center. It's also general practice to sharpen that center punch each time you use it so you have a sharp clean center to drill into. You also HAVE to start with a small drill bit or it won't hold the center.

Drilling things out by hand is hit or miss. If you have a hole next to or close to the broken bolt hole, put the longest bolt you have in there and use it as a guise to keep things centered (make sense??)

And last, heat really helps get stuff out. We don't all have oxy/acetylene and for years I was so-so with propane. Mapp gas was a bit better but O/A hands down is one of the most used tool I have and use!! I think I paid 400$ for a set complete and it was the best $$ I spent :D

[racerxxx]

Frankencelery,

With the tube off you can put a 32mm or 1-1/4 socket on the square standoff that you hitch bolts to. Then use a transfer punch to go thru the 1/2" drive hole of the socket. You can get transfer punches at http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=3577
Or Graingers of MSC. Harbor is probably the cheapest. to make sure you are keeping the transfer punch straight you can use another socket on top to sort of center it better. I have used this method many times with success. If ther is enough of a nub sticking up flip the socket and use the transfer punch that way. Also start with a small drill bit and work your way up, chuck up the small bit so that only about a 1/2" of the bit is showing, that way you won't get much flex out of the bit. I use a 3/32 or number 43 drill for a starter drill, and then slowly creep up, I may "size up" 5 to 6 drills until I reach my finish drill size. I know its a lot of work to do it that way but you have a less chance of your bit walking on you. Once you get close you can tap out the hole, but you'll probably have to use a bottom tap(or grind the tip off to a flat_ to be able to get all the way down.

Best of luck, if you can't see the picture let me know and I'll email it to you.

Racerxxx

[Frankencelery]

This is in the axle, so there's no backside to put a nut on. And I'm afraid I already drilled the holes, though there's still some of the original bolt left in the hole.

Thanks for the info, DC. I don't have O/A but I do have mapp. I might try some heat and, I know I'm going to regret this, one more try with an easy out....

[honda250sx]

racerxxx. excellent work.

I to myself a machinist. I utilize transfer punches all the time. Especially if its broke off in a deeper hole. I will pencil grind it flat with a carbide bur to insure I have a flat drilling surface. I will then use which ever transfer punch that fits in the hole snug. Then give it a tap. Always on center. Never fails me. Again start small and work your way up in drill size. Remember if its steel on steel. HEAT IS YOUR FRIEND. I have had a ton of success with left handed drills as well.

Good luck

[leevarnado]

can u send us a picture of the axle,may be other options,but the machinist guys sound like they know what they are talking about.

[Frankencelery]

Racerxxx, sorry I didn't get your message before I went back out there to beat on it some more. I guess my question was academic, because I had already drilled the holes. I will definitely take your advice next time though.

Leevarnado, look at the pic that racerxxx posted. That is exactly the part I'm working on. However, as I said, I'm afraid the damage is done. I already have off center holes in both bolts!

DC, I went out and put the Mapp torch on it full blast. I then proceeded to ruin one easy out and I'm no closer to getting the remains of either of the bolts out. I managed to NOT break off the easy out in the hole, so that's a victory for me.

[honda250sx]

you need real heat. Map gas is alright for heating up cases to put bearings in but thats about it. you need a O/A setup. get it CHERRY.

[MonroeMike]

Couldn't you just grind that whole part off and weld a nut in it's place there?

[hublake]

I have an OEM hitch from an 85 sx. If you are interested PM me your address and I will get it in the mail ASAP. $5.00 plus shipping.

[Erics350x]

Not trying to steal your thread but, what if you are drilling Grade 8 bolts? I tried drilling a foot peg bolt the other day and didn't even dent the dang thing.

[racerxxx]

Not trying to steal your thread but, what if you are drilling Grade 8 bolts? I tried drilling a foot peg bolt the other day and didn't even dent the dang thing.

Erics350x,

These are like the starter drills I use:

www.mcmaster.com item# 2860A57

They're a bit pricey at $7.75 ea. but when I'm out in the field I need bits that can perform! I drill alot of holes in our equipment that is stainless steel and aluminum, drilling and tapping a 4-40 screw into SS by hand is dicey but we do it almost daily. Alot of your standard drill bits just can't handle a hardened bolt, also drill steel slow, let the bit do the work and used pleanty of oil.

I drilled a grade 8 out (twice) of the crankshaft on my John Deere lawn mower that hold the clutch for the blades on, no problems. Like the old machinists always told me "don't rush it, you'll only cause more problems".

[BigRed_Ryno]

I'm with D.C on this too, decent sharp center punch, then start with a nice small pilot drill. did it on my mates CR250 cylinder just last week, slowly uping the drill size till literally just the thread of the bolt was left, and that came out with a screwdriver! didn't even have to re-tap it B) just take your time with it

[brapp]

i have always used an end mill if you can get the part clamped to drillpress or millign machine, or drill your pilot hole i prefer 1/8 inch cause 1 /16th basters anways break on me, but drillyour pilot hole then get a reverse twist drillbit and i have actualy used reverse taps as an easy out if the drill doesnt work. or drillit out wayyyyyyyy bigger and weld a nut into the hole so you ahve a nice threaded place to bolt to. btu it shoudl be a good weld and make shur eu have enough area aroudn the nut to hold the bolt.

[Dirtcrasher]

^ Oh, ABSOLUTELY. If I can get the part in the mill, there isn't a bolt in this world I can't get out. Big, small, short or tall a mill does it ALL!!!!!!!!!!

You can get things so close that you can literally wind out the dead threads like a helicoil.

As far as transfer punches go, they work great. But, in a case like this where that piece is punched out and basically a nut is welded underneath, whose to say that the threads are dead centered within that almost rectangular mount??

I guess I take my eyes for granted. I'm basically able to find centers by eye, especially if you grind it flat with a cut off wheel or similar to what Jeff suggested. I have really really good eyes, if I wasn't so stupid I'd do AOK :D

And IDK if I mentioned it, but you really want to drill that thing out as big as you can. THEN heat it up because that that point you have a very thin wall that heats easier.....

[Frankencelery]

I finally got it cleaned out...some of the hardware you guys were talking about is beyond me, but I needed some good cobalt drill bits, so I bought a left handed set, and drilled it out a little at a time. On one, it was just like Dirtcrasher said, the threads just wound out like a helicoil. on the second i had to get in there and sort of scrape out the bits. i then re-tapped it, but I hadn't planned ahead properly, and the drill bit size was too big for the tap I used, and the threads are rather shallow. I'm not sure if I should just run with it, or try to go bigger.

I did find the original problem though. These bolts didn't rust in place...someone used American bolt sizes in the holes. This is a major pet peeve. If you put a bolt in the hole, and have to lean on it to get it go in, either you're cross-threaded, or YOU'VE GOT THE WRONG SIZE! AAAAAAAAAAAHHHHHHHHHH!

Ok, I'm better now. I just can't get over people doing that.