Ideas needed - screw removal

[peter_4059 (Peter)]

My Moonlite focuser kit arrived today ready to install on the Meade SN10 I recently acquired. I was all ready to make the change tonight but came upon a snag - the button head cap screws holding the corrector cell in place are either full of paint or are rounded off so the allen key cannot take hold. The same screws on the mirror cell are ok so I'm confident the allen key size is correct (3/32").

So the question is - what is the best way to remove these screws? I'm assuming I'll be replacing them with new ones.

Help greatly appreciated.

[iborg (Philip)]

For the slot, I have had success using a small triangular file.

Also, if you are using ball headed Allen keys, sometimes a straight one will go in that bit further, allowing you to then undo it.

Good luck

[killswitch (Edison)]

Dremel in notches and use a flathead.

[mental4astro (Alexander)]

I misread the original post.

If the screw heads are totally exposed and not recessed, Ed's suggestion is what I would suggest too. You'll need to prepare the corrector plate covering it very well to protect it from grit and dust that will be created. A little drop of WD-40 will also help loosen the screws, but it can leave a little residual stain if not wiped off afterwards.

If the heads are recessed, you will need to use the Dremel in another way. You will need to use a tungsten carbide 'fissure bur' (see picture) to cut the slot into the head. A steel bur will have no significant cutting capability on these stainless (?) steel screw heads. Again, you will need to protect the corrector plate. Will need a steady hand to control the Dremel.

[blink138 (Pat)]

is it at all possible peter that they have used both an imperial and metric sizes in the same job?
i have found that on a couple of things i have
pat

[peter_4059 (Peter)]

On closer inspection, I have now formed the opinion that a previous owner has replaced the screws holding the mirror cell as they are button head whereas the ones holding the corrector cell are pan head. There are also some marks/scratches around the screws on the mirror cell that might be from a previous screw removal attempt.

I'm not sure if they are the same thread at this stage however my plan is to replace them all. The ones on the mirror cell seem to be 8-32 UNC.

If anyone has the measurements of the original SN10 mirror cell retaining bolts handy I'd really appreciate confirmation of the thread/bolt size.

Here's a couple of pictures - first is the corrector cell with what I believe is the original bolts and the second is the mirror cell with the new bolts.

[peter_4059 (Peter)]

Ended up using a small pair of mutigrips - worked a treat! For future reference the bolts on the SN10 holding the mirror cell and the corrector cell to the tube are 8-32 UNC - approx. 12mm length. Do yourself a favour and get some stainless steel ones from Small Parts, part number: SC0417C-013-B-SK-S4.