Seized small hex heads

[LewisM]

Recently got an SBIG ST-2000XM with a CFW-9 filterwheel. I went to take the filterwheel face plate off last night to clean the filters and install an H-a in the place of a second Lum the prior owner installed, but 3 of the tiny hex-head screws holding the cover plate on are seized.

I gingerly tried using the long side of the allen key for leverage, but I fear it was going to strip the hex hole before undoing. All the others "snapped" open (distinct click when freeing them), but show no signs of Loctite, so I assume just alu-alu seizure/corrosion.

Seeing this is a filter wheel, with rubber traction wheels, delicate Astonomik filters and other electronic wizardry, I dare not try direct application of heat or even a heated rod directly to the head. I fear the only option will be a small left-hand twist drill. (I have never seen an Ezy-out with a small enough shank either). Once I start, there is no turning back.

Suggestions from the Peanut Gallery?

Also, what size are these screws - I assume imperial sizing - so I can source replacements.

[multiweb]

what size hex?

[glend]

Can you not email the company support folks to ask about removing the grub screws? Is it under warranty?

[trent_julie]

If the screws can be replaced, use some diagonal pliers to pinch the hex head and turn, if you are concerned about the surface put some thick tape down.

Trent

[gts055]

I wonder if the hex head is briefly hit with a spray of circuit board freeze spray to shrink the fastener then quickly attempt to crack it free. Maybe insert the hex key first before freezing. Jaycar have this spray. https://www.jaycar.com.au/freezing-spray-can/p/NA1000 It is used to find dry solder joints or cracked circuit tracks. Mark

[LewisM]

I drilled the recalcitrant ones out. I had 7 spare correct sized blued ones to put back in, so all good. Cleaned the 5 filters, checked the sensor. VERY clean inside.

My replacements are philips head, so no more worry about darned tiny hex heads. I also rubbed pencil graphite on the thread to avoid this in future.



Err, whilst SBIG is a pretty good company (or WAS), I doubt it is under warranty after 15 years Glen :P

Bill at SBIG told of this one's history (was atually owned by a NASA tech), and he said it was absolutely immaculate (he was actually surprised) and faultless.

[LewisM]

Tried that - no go. I actually already had a can from another project (as well as a can of air duster, which gets pretty cold too).

Brute force in the shape of a left-hand micro drill did the trick. Ruined the screws, but I had replacements on hand.

[gts055]

Excellent, that will be very satisfying.

[LewisM]

Indeed - nothing more annoying than stuck screws when you need to get at something.

For anyone needing to know (crickets chirping), the screws are 4-40 x 3/16ths

[Rainmaker]

For future reference, using a slightly oversized Torx bit will work, with a light tap using a hammer (very light indeed) its 6 points will dig into the very corners of the hex socket and Voila !!!

[LewisM]

Tried that Matt. No go. Was going to strip the socket.

These were in there gorilla tight and I think SBIG used cheap a$$ chinesium screws (post mortem proved this)

[multiweb]

Good to hear you got them out. I was about to suggest to drill them through. That releases the pressure then an extractor or inverted drill does the job. Matt has a point with the "ajusteur". One sharp tap usually jiggles a seized thread axially, follow up with a bit of WD40 or aerosol and wait a little for it to sip in before getting it out. Does the job 90% of the time.

[LewisM]

What I was worried about was the shank breaking. These screws are NOT good quality, so am actually glad to replace them.

I went on eBay and bought another 12 as spares for a mere $19...OUCH...

[multiweb]

Poor quality screws actually help because they're easier to drill. Proper screws you're usually screwed. Literally. Oxy torch screwed. :lol:

[LewisM]

Good point Marc.