stuck mounting screw

Hi , I'm trying to remove the rib on my Marvel conversion to replace it with the iron sight rib. The front screw nearest the muzzle won't budge . So far I've managed to twist a high quality allen wrench , thankfully without rounding either the wrench or the screw itself. It's been soaking in PB Blaster penetrating oil for a couple days now. The other two screws released without any signs of thread locker or epoxy on the threads. I've tried heating the screw with a soldering iron and a cigarette lighter , to no avail. Any suggestions?

More heat 
I use map gas with a mini torch

I use PB Blaster a lot on vehicles, but I wonder if Kroil would be a better choice for your purpose.

Since you've already used a soldering iron to rule out loctite, then drill the head out. What happens is the screw stretches, and the head sticks tight to the surface it's seated on. The remaining threaded shaft will usually spin out with finger force. Not uncommon.

Use something that can bring more torque. Allen bit head on hand or electrical screwdriver or drill. They do not twist out and in absolute worst case will strip or round the hole, then you will know the only other option is drill.

Try an impact drill with a allen bit. The hammering will break it free easier than a standard drill and can be easier on the bit.

It's not talked about a lot, but I have 2 techniques that works on recalcitrant fasteners. 

1) Alternate between trying to loosen and trying to tighten.  Sometimes that wiggling is sufficient to start to break whatever adhesion is holding the fastener in place.

2) A lot of people feel like you apply torque evenly as you turn the wrench.  My process is similar to staging the trigger - you take up all the slack and get the wrench fully loaded and then you apply a burst of force to the fastener.  This often gets fasteners with Loctite to instantly release.  With small Allen wrenches, I actually will see the wrench flex in step 1.

It is important to use a high quality tool, cheap tools will deform taking up the force you are applying - meaning the force never actually gets to the threads.  

It is also helpful if you have worked with machinery and developed a feeling for when fasteners will respond to these methods vs. a needing more aggressive approach.


Another approach some have used (usually on larger cap head screws)  is to hammer a Torx bit into the Allen head to make sure there is no movement possible between the tool and the threads.

Lot's of good advice. My top 2 are Kroil and impact-type tool.

Joel

Richard Benoit wrote:Hi , I'm trying to remove the rib on my Marvel conversion to replace it with the iron sight rib. The front screw nearest the muzzle won't budge . So far I've managed to twist a high quality allen wrench , thankfully without rounding either the wrench or the screw itself. It's been soaking in PB Blaster penetrating oil for a couple days now. The other two screws released without any signs of thread locker or epoxy on the threads. I've tried heating the screw with a soldering iron and a cigarette lighter , to no avail. Any suggestions?

thanks all. I'll start looking for Kroil locally, plus a bit I can use with some sort of impact.

A cheap hammer driven impact driver comes in handy in many areas.

Be careful using power impact tools. The normal 1/4" hex bits are most often not made of good steel. It is difficult to find truly "impact" quality bits.

On the other hand, the trick mentioned above hammering a suitable size torx bit into a socket head screw is perfect with normal hardness bits.

You might also try putting the bit in a vise and turn the slide instead of the tool.

I sent mine back to Marvel for the same thing. They just charged me for the shipping.

If they break it they can fix it. If I break it, I can't.

Outthere wrote:I sent mine back to Marvel for the same thing. They just charged me for the shipping.

If they break it they can fix it. If I break it, I can't.

After trying a number of the suggested methods , I finally managed to round out the hex in the screw. The head drilled right off with a 9/64th bit, leaving a little stub that screwed right out. No damage to anything except the already ruined screw. Piece of cake, thanks all for the advice. Should have saved myself a lot of trouble my just drilling it out in the first place , as was one of the suggestions.

Another method I've had good luck is to give it a good whack with a punch and hammer. Especially in an aluminum rail, I think it sinks the head of the screw a bit and takes the load off of the threads.

The other fun 'fact' I've run into is that anodized aluminum and black oxide steel seem to form a chemical bond of some sort. So torque alone might not be enough, especially on small socket heads.