Rounded 8mm bolt on drive sprocket cover

[deniv]

Before I drill it out or anything drastic, does anyone have any suggestions for removing a rounded out bolt on the drive sprocket cover?

I just got this bike running and am trying to make it driveable but it apparently the Neanderthal of a PO ruined the bolt. It appears as if they tried to notch it, but a screwdriver won't bite. Wouldn't be bad if it wasn't is such a tight spot. Any suggestions?

On mobile so it won't let me attach photos via the usual method so here's an imgur link. https://imgur.com/a/J4H0i

 

[usmc5811]

Find PO, make him remove it - punch him in the back of the head everytime screwdriver slips.

 

[amc49]

LOL...................if you can get to it then use a very sharp chisel and hammer and dig in relatively straight to start then swing sideways while forcing a cut on the outside edge of the screw head to slowly knock it loose. I did so many on Jap bikes I couldn't count back in the day. Almost 100% of them come loose.

 

[dirtdigger]

I cut a slot in the head with a dremel tool then use a hammer driver.

 

[deniv]

I cut a slot in the head with a dremel tool then use a hammer driver.

This is usually my go to method, but unfortunately I wouldn't be able to get at the bolt without damaging the cover. I'm trying to figure out another solution before going that route.

 

[usmc5811]

This is why I'm seriously considering investing in a metric shit ton of Allen head bolts

 

[dirtdigger]

i only run allen head bolts anymore after i get the stock phillips bolts out.

 

[Medyo Bastos]

Set a nut over it, and slowly build some weld through the center of the nut until the nut is welded enough for you to put a socket on it.

 

[amc49]

The bolts are not grade bolts, if that is a DOHC (by your previous posting) then centerpunch a divot and drill the head loose to get only the stem of bolt left, which is a 6 mm.X1.0 and should come out pretty easy after the head is gone. Use more than one bit, small to get all the way through the head of bolt then bigger to eat away the outer part. Pick the second bit to be slightly smaller than the bolt flange and then even if you have to go deep enough to slightly cut the cover the new bolt will hide the scar. Use oil, the bit then stays centered better, so many people butcher work like that just for the lack of grabbing a bit of oil to lube the hole for straighter drilling. Carefully done virtually guaranteed success and maybe in 10 minutes.

I used to be a big press printer and many years of drilling bolts out that idiots messed up at the drop of a hat. Some people quite literally need their hands bolted down to metal plates with all fingers flat to keep them from touching things. Touch = destroy.

Somebody has to be more than the normal butcher to chew those up, I NEVER change that type. The earlier phillips head, yeah, they are utter crap. The hardness is about the same, as in below grade 5. The bolts easily twist in two at over 10 ft.lbs.

 

[grepper]

A couple of suggestions here..
1. Get an impact screw driver, they are less than $10 at Harbor Freight, https://www.harborfreight.com/impact-screwdriver-set-with-case-37530.html A must have when working on old bikes.

2. If that doesn't work, drill it just enough for the head to the screw to come off. Then take the cover off and there should be enough of the screw left over to grab it with a set of vice grips.

 

[deniv]

Thanks for the suggestions everyone. It has been frustrating finding little surprises of butchery all randomly all over the bike. Hoping that this is the worst of them.

I was able to get it loose with AMC's process and left handed drill bits. After 15 minutes of careful drilling the head was mostly gone and the bit managed to bite the stem and pulled it out loosely enough for me to remove it with some needlenose pliers.

I'll try to post a build thread for y'all later today to see my progress so far on this bike, what I plan to do next, and hopefully offer suggestions for things I may be missing since this is the first time I've ever worked on a bike before.

 

[amc49]

Yay.

The procedure will work with right hand bits as well.

 

[saratim2020]

If you’re having problem with your screwdriver bit slipping against the screw head due to try this simple method. Start by utilizing a hammer to tap the screwdriver deep, lodging it straight into the screw head. This should provide more grip you need to twist the fastener, especially if it’s made of softer metal. If that doesn’t work, to get a firm grip on the screw, cover it with a rubber band or a little piece of duct tape with the adhesive part against the screw head, as this will give extra grip. Press the material into the hole with the screwdriver and then try again.
Another option is that, if your screw has a Phillips head, is to use a flat-head screwdriver that is small enough to fit within the Phillips head hole. To pull this off easily try utilizing the rubber band method mentioned before.

 

[amc49]

The later DOHC don't use a pan head screw with phillips slots, rather, an 8mm. hex head that requires a socket.