Stuck grub screws

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xwhatsit

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Hello,

I'm having a bit of difficulty working out how to remove seized or stuck grub screws.

I thought I'd post this here as I'm sure you come across this problem regularly on old and abused lenses.

I've now had this problem twice and both times it's prevented me continuing repairs. Once on a nice Minolta E-Rokkor 50/4.5 with dodgy aperture blades, and now on my recently-acquired Yashica YF's shutter speed dial. Tiny brass screws can't take a great deal of torque from a screwdriver!

If it was one of my motorbikes, I'd soak the offending bolt in penetrating lubricant for a day or two, maybe apply a little bit of heat, and in the worst case scenario I'd drill it out. Now applying penetrating lubricant to a lens or shutter speed dial doesn't seem sensible, nor does heat. And drilling out a grub screw -- is that even possible?

Any advice would be much appreciated.

Cheers,

-Tom
 
I use a tiny tiny drill, preferably new so it's ultra sharp and just roll it between finger and thumb. On brass it doesn't take long to drill out and then clean up.
 
nobbylon said:
I use a tiny tiny drill, preferably new so it's ultra sharp and just roll it between finger and thumb. On brass it doesn't take long to drill out and then clean up.
Click to expand...
I can understand drilling the head off a bolt so you can pull the casting or whatever off over the exposed bolt shaft, but how does this work with a grub screw? If you drill right down to the end, aren't you left with all the threads still there? Having a bit of trouble describing this, I'll draw a picture.

In the attached picture, if you drill away what is marked in solid black, won't the remaining bits of grubscrew still stop you from lifting away the shutter speed dial (or whatever else you can imagine a grub screw holding)?

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There is an old trick you may be able to try. Find a small electric soldering iron - commonly available in Tandy stores and the like. These are designed for soldering sensitive small parts like circuit boards. They come in various levels of power. Place the hot element directly on the stuck screw and allow it to heat up. This may break the bond that is holding it. Try turning the screw when its hot and then again when it cools. The idea is to heat the screw without heating the surrounding metal so as to get differential expansion. Not guaranteed but it may work, especially if lok-tight has been used on the screw.

In relation to drilling out the grub screw, this may be possible and as you say you are left with the screw threads intact. But you cna buy a screw extractor - a small tapered tool that has reverse threads. As you screw it in it works to tighten onto the surrounding hole you have drilled into the screw so you can then pull it out. Not sure if you can buy from small enough though - try a specialist tool supplier like Micro Tools who sell tools for fixing cameras an other delicate equipment. I would use this as a last resort for obvious reasons.

http://www.micro-tools.de/
 
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If you have a very small pin punch ... it needs to be the same size as the head of the grub screw ... place it squarely on the head of the offending screw and tap it reasonably sharply a couple of times with the flat side of a pair of pointy nose pliers or something of similar weight.

This works at least ninety percent of the time if you're careful.
 
The screwdriver has to fit properly in the slot. Too small is likely worse than too large but neither is good. Anyway file the blade to fit, set it in the slot & tap it with a small hammer, knife handle, rock etc. The shock should set it free.
 
with the drill out method i use there is usually just a tiny amount of metal left in the thread and in your example will pull past easily. The tapping a sharp screwdriver method works aswell.
 
This is a good tip. Additionally, many types of Loctite will give up if the soldering iron is hot enough. On big bolts, heating the bolt with a gas torch then quenching it with WD40 works well, but obviously not on little grub screws.


peterm1 said:
There is an old trick you may be able to try. Find a small electric soldering iron - commonly available in Tandy stores and the like. These are designed for soldering sensitive small parts like circuit boards. They come in various levels of power. Place the hot element directly on the stuck screw and allow it to heat up. This may break the bond that is holding it. Try turning the screw when its hot and then again when it cools. The idea is to heat the screw without heating the surrounding metal so as to get differential expansion. Not guaranteed but it may work, especially if lok-tight has been used on the screw.

In relation to drilling out the grub screw, this may be possible and as you say you are left with the screw threads intact. But you cna buy a screw extractor - a small tapered tool that has reverse threads. As you screw it in it works to tighten onto the surrounding hole you have drilled into the screw so you can then pull it out. Not sure if you can buy from small enough though - try a specialist tool supplier like Micro Tools who sell tools for fixing cameras an other delicate equipment. I would use this as a last resort for obvious reasons.

http://www.micro-tools.de/
Click to expand...
 
I run into a lot of set screws that someone already broke the head. Nothing to grab onto. I use a hand drill with a triple-zero drill bit. Not the prettiest way, but it works. Usually the threads are intact, but sometimes ther screws are just corroded into the metal. Worst case: resort to a dremel and cut a slice into it. Had to do that with a 1939 CZJ Sonnar in Contax mount. The set screw for the rear module was not screwed in all the way, and the optics module was forced into the mount. No amount of force would get it out. On a good note, it is now in a J-3 LTM mount and works quite well.
 
I deal with bad screws a lot myself (mostly at work). If heat doesn't free them up, I drill a small hole in the center (like your diagram) then tap a torx driver or bit into that hole with a small hammer. I have sets of T1-T10 bits that I ONLY use for screw extraction. This method (provided I could drill a decent hole) has never failed me. I drill out a LOT of screws at work.

If I am at home and have some time, I will make a left hand drill bit (just a split-point type) to drill the hole. This way I can get the bit to the exact size AND use a left hand bit that usually backs the screw out on its own. This is only if I do not have a left hand bit handy already. I also use a small pin vise to hold the drill bit and just drill the hole with finger power.

Good Luck Sir!

Matt (who is very serious about torx bits working wonders with renegade screws)
 
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