I Really messed up collimating. Broken screw head.

[edjbrown]

Hello everyone,

I have an Omni XLT 127 SCT and despite the fact this wasn't exactly a cheap scope these screws always seemed extremely soft. I was doing a bit of collimating and accidentally turned one screw a bit too tight, not crazy tight, but certainly a bit tight. As soon as I tried to loosen it, (and I really don't think I tightened the screw tight enough for this to happen) it seemed that the screw head was willing to give way before the screw itself would. I then thought the best thing to do would be carefully remove the screw and see about getting some knobs, as these screws had always worried me. However... this screw would not budge .... It was at this point I panicked a bit and the screw head ended up as bad as you see in the image.

Does anyone have any advice? 

Obviously I want to avoid getting a replacement secondary mirror, but to be honest even if I did I can't seem to where to get one from.

Yours, a bit worried,

Ed

[Davey-T]

First thing to try is finding a good Allen key (not phillips) and file it to jam as well as you can in the screw head, then super glue it to the screw head and try to undo it.

Make a thin card template to protect the corrector plate first.

Dave

[Stu]

Normally backing off the other two screws should release the pressure on the third, have you tried doing that? At least it should turn more easily so Dave's suggestion is more likely to work.

[Pig]

There are some useful extractors that have got me out of some tight spots, the link below shows some. But as Davey point out rake care so no further damage occurs as a result of removing it.

https://www.amazon.co.uk/dp/B01E9ZC2K2?aaxitk=MAc-IFFL-gFk2wCnjY8Shg&pd_rd_i=B01E9ZC2K2&pf_rd_p=0e11f8c9-98e1-4a93-bd5e-367420b613ee&hsa_cr_id=9838264130102&sb-ci-n=asinImage&sb-ci-v=https%3A%2F%2Fimages-na.ssl-images-amazon.com%2Fimages%2FI%2F71Vr%2BZns1zL.jpg&sb-ci-a=B01E9ZC2K2

[paul mc c]

As Stu says,and if you have a fine pair of pliers that will grip the head,it just may turn ok.

[edjbrown]

Thanks very much for the advice! I will try that now. I'm just at that point of being very regretful for how I got here in the first place and a bit panicky to fix it and I know full well how that can lead to the situation just getting worse. 

2 minutes ago, Pig said:

There are some useful extractors that have got me out of some tight spots, the link below shows some. But as Davey point out rake care so no further damage occurs as a result of removing it.

https://www.amazon.co.uk/dp/B01E9ZC2K2?aaxitk=MAc-IFFL-gFk2wCnjY8Shg&pd_rd_i=B01E9ZC2K2&pf_rd_p=0e11f8c9-98e1-4a93-bd5e-367420b613ee&hsa_cr_id=9838264130102&sb-ci-n=asinImage&sb-ci-v=https%3A%2F%2Fimages-na.ssl-images-amazon.com%2Fimages%2FI%2F71Vr%2BZns1zL.jpg&sb-ci-a=B01E9ZC2K2

Hi Pig, I came across something like that whilst googling now but initially dismissed them because they looked too big? Are they fine for such a small screw? And dont you need to use a drill with them?

 

 Am happy to hear more advice if anyone has any.

[Zakalwe]

Unless you can remove the secondary from the outside you might have to remove the corrector plate to get access to the secondary mirror.

Take the other two screws out completely. Take the secondary mirror holder off the backing plate. This should expose enough of the remaining thread to wind it out by gripping it tightly with a (good!) visegrips or similar. Don't even think of using those easyouts....the best of them are generally rubbish and the chances of doing far more harm by trying to manually drill into a small screw are high. You'll feel like a right pillock if a drill slips and smashes the corrector.

 

[Taz777]

That looks pretty rounded to me. Was the screwdriver you used the correct size and type for the head? There are several sizes of Phillips and Pozidrive. Those screw heads are Phillips. You could try a smaller Phillips at it may go a bit deeper into the head to get extra purchase.

When I've head issues like this, I've had to drill the head out! You can also get a kit that will screw into the head a little using an opposite thread and a drill and then present a steel head which you can then screw out using a screwdriver. However, all of that is for equipment that isn't as delicate as a telescope.

[Edit] @Stu's suggestion is excellent and I would try that first.

[edjbrown]

OK all you guys are amazing. I was very worried. 

8 minutes ago, Stu said:

Normally backing off the other two screws should release the pressure on the third, have you tried doing that? At least it should turn more easily so Dave's suggestion is more likely to work.

This worked and I really dont think, in my panicked mind, that I would have thought of doing something so simple. Thanks Stu!

Screw is out, I will order knobs. 

Thanks so much everyone. I was pretty worked up about it. 

[edjbrown]

3 minutes ago, Taz777 said:

That looks pretty rounded to me. Was the screwdriver you used the correct size and type for the head?

It was pretty rounded, I think my initial attempt to loosen was with slightly the wrong sized head and it was not giving way. 

[paul mc c]

Nice one......?

[Louis D]

Be aware that many Chinese made screws provided with astronomy equipment are made from cheap cast pot metal rather than machined from high strength steel.  I've had multiple thumbscrews simply shear off in my fingers in eyepiece holders and finderscope alignment rings.  I now replace them with either nylon screws with large heads or steel cap head screws.

[RayD]

I think a big mistake often made with these screws is using the wrong screwdriver.  These are Philips heads, and most of the screws supplied nowadays, so most of the screwdrivers sold, are Posidrive.  whilst they look similar they are not the same and the Posidrive doesn't sit fully home in the Philips head.

Glad you appear to have it sorted.  Bobs Knobs are the way to go.

[Peter Drew]

Good result. Be careful fitting Bob's Knobs, fit one at a time to save the chance of the secondary falling inwards.   ?

[edjbrown]

7 minutes ago, Louis D said:

Be aware that many Chinese made screws provided with astronomy equipment are made from cheap cast pot metal rather than machined from high strength steel.  I've had multiple thumbscrews simply shear off in my fingers in eyepiece holders and finderscope alignment rings.  I now replace them with either nylon screws with large heads or steel cap head screws.

Not to downplay my own ineptitude in this situation, which is certainly not to be ignored, but nevertheless I was genuinely surprised at how soft these screws were. Even with gentle turning you can feel that it's not as solid as it should be, and all the while I was using a screw bit from a set where I had actually ruined other bits because the bits themselves were softer than screws I was removing!

 

[edjbrown]

12 minutes ago, RayD said:

I think a big mistake often made with these screws is using the wrong screwdriver.  These are Philips heads, and most of the screws supplied nowadays, so most of the screwdrivers sold, are Posidrive.  whilst they look similar they are not the same and the Posidrive doesn't sit fully home in the Philips head.

Glad you appear to have it sorted.  Bobs Knobs are the way to go.

You are right, I have a set of posidrive bits and tested a few to see which one I thought was correct. The first one that felt right in reality was not! Perhaps none of them are... I cant be sure anymore.

[edjbrown]

2 minutes ago, Peter Drew said:

Good result. Be careful fitting Bob's Knobs, fit one at a time to save the chance of the secondary falling inwards.   ?

Thanks for the tip! I will keep that in mind. 

[Stu]

18 minutes ago, edjbrown said:

OK all you guys are amazing. I was very worried. 

This worked and I really dont think, in my panicked mind, that I would have thought of doing something so simple. Thanks Stu!

Screw is out, I will order knobs. 

Thanks so much everyone. I was pretty worked up about it. 

Fantastic! I did have something similar with an Allen bolt that got rounded and my collimation got way out.

Glad it worked out

[Louis D]

1 minute ago, edjbrown said:

Not to downplay my own ineptitude in this situation, which is certainly not to be ignored, but nevertheless I was genuinely surprised at how soft these screws were. Even with gentle turning you can feel that it's not as solid as it should be, and all the while I was using a screw bit from a set where I had actually ruined other bits because the bits themselves were softer than screws I was removing!

 

Wait until you try to use a set of cheap Chinese made socket wrenches.  The walls are so thin, they often crack open!  I've also cut myself on the poorly applied chrome coating because they never go through a polisher to remove rough edges.

[Pig]

23 minutes ago, edjbrown said:

Thanks very much for the advice! I will try that now. I'm just at that point of being very regretful for how I got here in the first place and a bit panicky to fix it and I know full well how that can lead to the situation just getting worse. 

Hi Pig, I came across something like that whilst googling now but initially dismissed them because they looked too big? Are they fine for such a small screw? And dont you need to use a drill with them?

 

 Am happy to hear more advice if anyone has any.

Yes smaller ones are available, I have some made by “Wera” I did try to find the link but I couldn’t see it. I am sure other makes are available if the suggestions above don’t work.

[RayD]

7 minutes ago, edjbrown said:

You are right, I have a set of posidrive bits and tested a few to see which one I thought was correct. The first one that felt right in reality was not! Perhaps none of them are... I cant be sure anymore.

If you don't go the Bobs Knobs route (very good tip by Peter above BTW) and just replace the screws, make sure to check whether they are Philips or Pozi.  Below pic shows Philips left and Pozi right. They can feel like they are working fine, but the extra web on the Pozi stops it sitting all the way home, and it will cam out very easily.

[dweller25]

Here is my solution

I use a standard allen key to collimate