stuck screw heating question

[btbarb]

Greetings all,

I'm trying to replace my front sprocket cover screws with SS allen heads and they all seems to be stuck pretty good. I've shot 'em with penetrating oil and have been trying to loosen them with the Craftsman hand impact driver, but they're not budging at all. I haven't mangled the heads yet.

When applying heat, do I just keep the torch flame on the screw head and not the area around it? How long do you heat the head or can you heat too long?

Thanks,
Bryan

 

[chuck hahn]

If your gonna replace them anyways, you can drill off the heads then remove the cover. Then at that point you can apply heat and penetrating oil directly where they go into the engine case. Vice grips to back the bolts out. Very unlikely the oil or heat will travel the full length of those long bolts to have much of an effect. Drill just big enough around to get the heads off the bolts and your good to go.

 

[keman]

What has worked for me is to focus heat on the head of the screw till they start getting red, then allowing them to cool. Then I hit them with some pb Wait an hour our so and heat them again, cool, then try the impact.

If that fails, go for the drill like Chuck said.

 

[chuck hahn]

Gotta remember the aluminum covers right there too!!! I seriously doubt that he would ever get them hot enough to have the heat migrate the lenght of the bolts..some are over 3 inches long. My vote is for drilling the heads off, heat at the engine cases and then the oil. More direct heat where its needed..oil exactly where its needed..they will then just uncrew easily.

 

[Nessism]

Get a bigger hammer. And make sure your impact driver is loosening, not tightening. They will come off with the impact. No heat needed, and pent lube doesn't make it back to the threads.

 

[shinzon1]

I agree with Nessism. I had one stuck on mine with almost no head left and i used my impact driver and three good hits with my 2 1/2lb. mallet. came right out. sometimes the best motto really is "if it doesn't work, get a bigger hammer."

 

[chuck hahn]

Hopefully a previous owner didnt use locktite on them...in which case i can understand them not loosening even with an impact. Well if he rips the heads up he has the option of drilling them off and starting anew.

 

[btbarb]

Thanks for the input guys, I'll give the bigger hammer and whack a try and double check (again) the direction of my wrench, and then if I still can't get it, go for revenge with a drill.

 

[shinzon1]

I'd like to hear how it goes. Keep us updated.

 

[1_v8_merc]

1.) Triple check Impact, make sure it's set to Loosen.
2.) Test out the Impact on a wooden block and make sure it's twisting to Loosen
3.) Get bigger hammer or hit harder with a small one

 

[btbarb]

Lesson learned

Lesson learned

I'd like to hear how it goes. Keep us updated.

A bigger hammer solved the problem for 3 of the 5 screws, the two that wouldn't budge were just slightly altered from my first attempts so the bigger hammer just rounded the threads and fubar'd 2 of the 5. Lesson learned, if I would have used the big hammer first on all of them, there would have been no issue on any of them.

Once I could feel how the big hammer was causing the bit to bite, I changed the phillips head to a flat head and beat a cross-cut into the head. There wasn't a lot of bite to the cross cut, but it was enough on both screws. Not sure of how heavy my hammer is.

Thanks again for the help.

Bryan

 

[Normk]

My grandfather used to say, "Use a bigger hammer or you'll break it!". Having repeated this many times, it amazes me that people laugh as it seems that they misunderstand physics.

If one needs to move something, use a big hammer. If one needs to break something (i.e. breaking up a broken off thread cutting tap) then use a small hammer.

Cutting a screw slot into the head may help you rather than pounding a slot in by hammering through the impact screwdriver. The driver turns or attempts to do so which can make the slot created less effective.

You are on the right track with that big hammer if the impact screwdriver is the best available option, however given the location that may not be so.

As for concerns regarding the use of Loctite, IMO this is an over stated concern. Blue Loctite only increases the break-away torque by about 10% which is typically much less than the break-away due to even a small amount of corrosion of the thread and parent metal. The use of Loctite is often a benefit due to its sealing of the theads against corrosion.

Chuck is right on target regarding the length of the screws being an issue. It will compromise any heating attempts and is likely damping the impact screwdriver's effect. There is also a concern regarding compressing/flexing/bending a screw sufficiently to break the cover.

Drilling the heads off as recommended gets my vote also.

I agree with Nessism. I had one stuck on mine with almost no head left and i used my impact driver and three good hits with my 2 1/2lb. mallet. came right out. sometimes the best motto really is "if it doesn't work, get a bigger hammer."

 

[btbarb]

...<snip>
Cutting a screw slot into the head may help you rather than pounding a slot in by hammering through the impact screwdriver. The driver turns or attempts to do so which can make the slot created less effective.
<snip>...

I did try to cut a slot into the screws but I could'nt get the dremmel cut out wheel into the area for those two bad screws. I figured I was going to have to drill them out, so I tried the all-or-nothing rude approach with the impact driver to create the slot and that ended getting them both out.

 

[shinzon1]

glad it worked!

 

[chuck hahn]

You may want to get a BOTTOMING tap in that thread size and chase all the holes..easily. When the tap bottoms out dont force it any further. This will get any oxidation from in there loosened. Spray the holes out with some compressed air and then use some anti seize on the new bolts..youll be glad you did this later on when you need to change the sprocket or a chain.

 

[Normk]

Glad you got them out! A thread chaser is to be preferred to a tap for cleaning up threads although if using a tap, a bottoming tap is the choice.

A tap is designed to cut away material which lies between the threads which means that chasing with a tap will cut away some or all of the metal which has been displaced.

A thread chaser is intended to realign and reform displaced metal which means that some or all of the displaced material will be forced back into threads. In a badly damaged thread, the chaser may save the day while the tap can remove too much material.

Another advantage is that a thread chaser is less brittle and so less likely to snap off in the hole. An additional advantage is that a thread chaser has little in the way of flutes so there is less opportunity for loose material to wedge and jam the tool.

Hansen and most professional tool lines have thread chasers. Here's a photo of one: http://www.mactools.com/ShopOnline/Product/tabid/120/productid/323970/variantid/314729/Default.aspx

Of course, you require metric but this is the style to which I was referring.

For crossed spark plug thread restoration it is difficult to beat Mac Tools expanding restoring tools which fit into the good threads at the bottom of the hole and move upwards, ironing out the damaged threads. These require that one starts with a loose fit and takes several passes with each a bit more expansion on the tool but they are super! I use my set from time to time to bail people out of difficult situations: http://www.mactools.com/ShopOnline/Product/tabid/120/productid/320132/variantid/310891/Default.aspx