damaged grub screw removal

[RT65CB-SWL]

Hi all.

Not sure if this the correct place. I have a damaged grub screw, (hex head), on my 're-modded' ETX105 focus knob and after any tips for extraction/removal ?

 

BTW - I have hand drills & bits and other hand tools, but limited amount of workspace and no workshop/shed.

Tnx in adv.

Edited December 15, 2019 by Philip R

[johninderby]

Funnily enough I’ve just replaced a damaged grub screw in a focus knob. Typical rounded out head but I tried a new hex key with sharp edges and managed to loosen it. Lucky. 🙂

One of the best ways is to get a left handed drill bit that is a tight fit and you will usually be able to unscrew. Or get a screw removal tool if you can find a small one.

I think it’s a good idea to consider small grub screws as single use and replace it every time you remove the knob.

 

[JamesF]

10 minutes ago, johninderby said:

One of the best ways is to get a left handed drill bit that is a tight fit and you will usually be able to unscrew.

This has worked well for me on several occasions.  The bit starts to bite into the top of the screw and then turns it out.

James

[Davey-T]

1 minute ago, JamesF said:

This has worked well for me on several occasions.  The bit starts to bite into the top of the screw and then turns it out.

James

Needs a bit of care otherwise you can end up with a broken drill stuck in the hole as well 

Dave

[johninderby]

2 minutes ago, Davey-T said:

Needs a bit of care otherwise you can end up with a broken drill stuck in the hole as well 

Dave

Is this from personal experience? 😁

[Davey-T]

5 minutes ago, johninderby said:

Is this from personal experience? 😁

Very brittle some of those little drills 😂

Dave

[Neil H]

Get a bolt removal tool from a car spares p!ace they are hardened and made to remove bolts that the head has snapped off , you drill the bolt then insert tool and as it grips it unscrew bolt 

[Carbon Brush]

If the above methods don't succeed, time to get vicious.

Regard the focus knob as lost. Using a junior hacksaw blade or a modellers mini drill with a cutting disc, remove knob material from around the screw.

Oops. Before starting, mask off any holes in the scope to keep out swarf and mask any parts that might get impact from a tool.

The junior hacksaw requires care to make sure you don't put excessive strain on the focus shaft and end up bending it.

If you put the drill cutting disc along the length of the shaft, once you have a deep goove (almost full depth) you put a screwdriver blade in there and twist.
The knob will flex open allowing easy removal. Or it may just snap and fall off. Either way, job done.

A cutting disc will be necessary if you end up snapping a screw remover or left hand drill bit in there.

Drastic. But if the grubscrew is really stuck, the cutting disc will do the job without damaging the shaft or scope. That would be my choice.

HTH, David.

[johninderby]

5 minutes ago, Neil H said:

Get a bolt removal tool from a car spares p!ace they are hardened and made to remove bolts that the head has snapped off , you drill the bolt then insert tool and as it grips it unscrew bolt 

These are just tiny grub screws usually 3mm diamter not bolts so a bolt removal tool is way too big. You need minature tools for the job which you might need to buy from a model engineering shop. 

[markse68]

If you have any try a torx bit/screwdriver- you can usually find one that’s a tight fit- tap it in with a hammer if necessary- the sharp points grip the rounded hex hole 

[Skipper Billy]

Another method is to glue your allen key into the screw with good quality slow setting epoxy (Araldite standard) - then do not touch it for 24 hours. Then unscrew it - chuck it away and replace it.

[DaveL59]

if you do end up having to drill it out be careful not to damage the threads if poss. Not the end of the world tho as you can always re-tap with the next size up and use the appropriate size grub screw to replace it. Have had to do that on a couple of the micro size binoculars where prev owner had butchered the flat blade type grub screw and the threaded hole by using too much force and too wide bladed screwdriver. 

A LH drill bit you may be able to work by hand or using a pin wrench to hold it, rather than a power tool. As noted these small bits are quite brittle so beware. After all it's hopefully only nipped tight rather than over-torqued  

As Billy above mentions tho, glue can do it but you really want a tiny amount so you don't have the key stuck in the thread too. Another way is heat, a micro torch with a fine flame (jewellers type) just aimed at the screw area and a drop of WD40 while hot may break the thread free, but not good if the shaft its fixed to is plastic etc of course. 

Edited December 15, 2019 by DaveL59

[faulksy]

3 hours ago, markse68 said:

If you have any try a torx bit/screwdriver- you can usually find one that’s a tight fit- tap it in with a hammer if necessary- the sharp points grip the rounded hex hole 

what he said, get a tx bit and tap it in gently with a small hammer,then un screw 😀

[Ships and Stars]

3 hours ago, markse68 said:

If you have any try a torx bit/screwdriver- you can usually find one that’s a tight fit- tap it in with a hammer if necessary- the sharp points grip the rounded hex hole 

I was going to suggest the Torx method as well. That's the first port of call for me when a hex is stripped out. Can't think of a time it hasn't worked!

[RT65CB-SWL]

Just want to say "Thank you." in advance for all the advice. I think I have some small torx and allen bits, and will give it a try on my rest days.