Primary disaster!

[jezhughes]

Had an absolute nightmare with my 250p's mirror unit today. I was taking the mirror out the cell for the first time to clean it and flock the back. The grub screws holding the mirror clips were ridiculously tight, and after unscrewing 70-80% of the way i realised a lot of them were slightly bent.

2 of them eventually just sheared off. (maybe im too strong? Maybe they're just awful screws).

Does anyone know how i can get these out? I can't explain how tight they are in there, they literally won't budge. I've tried oiling down to loosen and cooling the base to try and free them, but they aren't going anywhere. Its like they're welded in!!

Worst case scenario can i just clip my mirror in with 5 clips instead of 6?

Oh yeah, and my driver slipped and put a 2mm chip at the edge of my primary... (i was being careful, honest )

I didn't have a good day today. I did how ever flock my tube! Needless to say i'm steaming and frustrated at the terrible build quality on the cell. No screw should be that tight.

Also i need to replace all of the clip screws - does anyone know the size or supplier i can get them from?

:mad: :mad: :mad: :mad:

[Daniel-K]

thats harsh i always feel sorry for people when this kind of stuff happens hope you get sorted

[cosmojaydee]

phone FLO

[nightfisher]

phone FLO

better still email them, and include pics of what you need, sorry to hear of your misfortune

[K3ny0n]

Have the screw heads sheared off?

**EDIT**

Just read your post again. Try getting some eagle beaks to see if they come out, but I can image they won't if they didn't come out with a normal screwdriver. If they don't come I would suggest you would have to re-tap/thread the hole. But you obviously need the screw out first, so file the screw flat and centre punch the screw. Get a drill peice slightly smaller than the size of the screw. Hopefully not touch the threads itself. The knackered screw should hopefully come out with a bit of persuasion. Then you need to check if the threads are ok. If they are not (I would suggest re-tapping anyway) find out the size of the screws and just re-tap the holes making sure you use plenty of oil when re-tapping them, take it slow when tapping the hole turning it half a clock then back a touch, half a clock again, ect. it shouldnt be too much bother re-threading them because the thread is basically already done.

Rob.

[8kids]

Looking at your pics, you may be able to grip whats left of the thread with molegrips, use some penetrating oil, wd-40 or the like and then tighten the bolt first then undo, and repeat. Hopefully this will ease the thread, if not you can drill out the bolt but you'll need to cut it flush with the surroundings first.

[Islander]

I'd contact FLO for advice in the first instance but if they can't help then as above, you should be able to get molegrips onto the broken ends - there's a needle nose version that would be ideal. Penetrating oil is a good idea too but not WD40 - it isn't a penetrating oil, it's a water dispersant. Use Plus Gas or similar and be careful not to overspray it. Leave it to soak overnight and then try the molegrips.

If you know what the thread size is, it might be an idea to clean the holes up after you've removed the broken screws by running the correct size tap through them.

[knobby]

Difficult to explain but at work, we use cutters to grip snapped or ruined screws... Sort of pointing down rather than across... Squeeze hard enough and they dig in to get a nice grip!

Mole grips as has been said would also be good but use the serrated grippy bit

all the best of luck

[John]

Sorry you have had these problems. Sounds like those screws were way over tightened - there should be a slight gap between the mirror clips and the mirror surface - enough to insert a business card they say !.

Just out of interest, why were you going to flock the back of your primary mirror ?.

[Moonshane]

Based on recent experience (although mine came out OK) I think SW use some kind of loctite on the screws hence their are effectively glued in. your chip is not a disaster as you could hide this under a clip.

I think they are M4 threads (standard 0.75 pitch). you'll be able to buy 50 stainless ones delivered for about £2. I use bolt from the blue on ebay. you might want to paint them black on the heads - I'd get cap head bolts.

[NGC 1502]

I had a 250p, it had 6 mirror clips like yours. Most other makers have 3 clips, so after you have got all the screws out, I'd just put back 3 equally spaced clips, and if you can, put the chipped edge under one of the clips.

Regards, Ed.

[scarp15]

Another solution to remove the damaged bolts, might be to carefully cut fresh screwdriver slots using a junior hacksaw as the sheared bolts appear to be protruding above the surface. However as with the advice above, permit a light lubricant time to work and try using a wrench or pair of grips, perhaps lightly tapping with a hammer first to free it up a little.

Worst case scenario would involve drilling and re-tapping the thread.

[moriniboy]

How about mounting with silicone instead, there are posts in SGL re this. Not sure if 250mm mirrors are too big to do this though.

[Budding Star Gazer]

if you want to avoid any more damage cut off the broken screw so they are flush or almost flush with the block with a smaller width drill bit drill down about 1/3 the depth of whats remaining and use easy outs to remove whats left of the damaged grub scres , it will remove the damaged part but as they have snapped they where cross threaded going in so the next step is to use a tap and remold the thread, you will need slightly bigger grug screws for the replacement but it's the best option.

[glowjet]

You have a diversity of suggestions to your problem, one that has not been mentioned, assuming you have not damaged the thread of the pan head screw, is to clean the end with a file and see if you can screw on a nut, I think Moonshane might be right in that they will possibly be ( poor quality ) M4, if you can do this, then put the nut on using some quick set epoxy resin, allow to set, then you can use a socket wrench on it. I think if you cut a slot for a driver the material is so soft it will break away, in any case, if they are stuck fast, it is going to mean drilling out and re tapping and if you have not the skills or the equipment this could be difficult for you. If you have a look at the sticky at the head of the DIY section there is a wealth of information on supplies of quality stainless goods, Abolt ( A bolt from the blue) is excellent for very small amounts of metric screws/bolts being often packs of 10 for less than a £1 post free. As a last case scenario you could consider cleaning off the old screws, reposition your clip as close to the original position, then drill two new holes to accept self tapping stainless pan head screws to fix the clip, the material you are to drill into, I am sure will be quite soft. Whatever you do to correct the problem, this time make sure your mirror is well covered and protected, it is just a pity you are not near hand as I would have been pleased to help

John.

[MAN or ASTROMAN]

This is an example of just how rubbish chinese metal screws and bolts are.I made the mistake of overtightening the screw that attaches one of the controls on my EQ2 (I should have known better).Of course the head sheared off.Not as bad a case as mirror cell screws though.You have my sympathy! Hope you reach a solution!

[Peter Drew]

I would expect to be able to deal with this problem myself as I used to do this sort of thing for a living (yes shearing screws as well!), but if you are not successfull with the easier of the good suggestions so far, why not just remove the offending clip and use just three equispaced clips. These clips only stop the mirror from falling out or moving too much from side to side, they should not exert any pressure on the mirror. The unfortunate chip can, as suggested, be hidden below a clip.

[jezhughes]

Thanks for everyone's feedback! I managed to get one out with a molegrip but when trying on the other it sheared it off even more, i've no option but to file down and drill out. Doesn't seem like too much of a disaster now but still a pain having to deal with it.

Looking back the chip/scratch isn't too bad, but it is too far out to hide under a clip, its just further out than the clip. I've never had any optic damage before so not sure how this will affect imaging/views, but it seems to minimal to have a large impact. Can anyone shed any light on how it might? The photo shows the scratch but there is a tiny chip above it in that dark area if you look closely.

[Spec-Chum]

I'd be very surprised if that makes any difference at all buddy.

Definitely wouldn't be noticeable. The coma from that part of the mirror would do more to degrade your view than that scratch

[jezhughes]

I'd be very surprised if that makes any difference at all buddy.

Definitely wouldn't be noticeable. The coma from that part of the mirror would do more to degrade your view than that scratch

Cheers! That's good to hear

It'll almost certainly be outside of my chip FOV for imaging anyway, so not too fussed about that.

[Moonshane]

bizarrely the generally recommended action is to paint the chip with a tiny dab of matt black. this will not affect the images at all (visually or otherwise) and may prevent glare from the damage (which may not actually be a problem.

try it and see if you can see it with the moon or Jupiter. if not, leave it.

[John]

That tiny mark won't make any difference. After all the mirror has a 60mm disk plus 4 support vanes hanging over it (ie: the secondary mirror !) and still works fine despite that obstruction.

[glowjet]

Some little while ago there was published on the forum a detailed account of trials that had been done with a beyond repair expensive auto camera lens, but with sound optics, this was in response to a question relating to damage to optical surfaces. Images were taken as gradual purposeful damage was caused to the lens surface, to see what effect it had on the resulting images, it was quite amazing to see the results, as very considerable damage had to be done, before it had any noticeable effect on the resulting images. I am not a mirror man, but I would put it down to experience and as John has suggested, forget about it

John.

[Spec-Chum]

That was me I think. I mentioned how my brother who had a few grands worth of camera lens' had no issue with cleaning his by spitting on them using his T-shirt and said you'd have to do something really wrong to damage them.

Someone then posted this http://kurtmunger.com/dirty_lens_articleid35.html

[Islander]

I think this one speaks volumes...

http://www.lensrentals.com/blog/2008/10/front-element-scratches