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 (Marc)]

what size hex?

[glend (Glen)]

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 (Mark)]

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.

Originally Posted by glend

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

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

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]

Originally Posted by 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

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 (Mark)]

Excellent, that will be very satisfying.

[LewisM]

Originally Posted by gts055

Excellent, that will be very satisfying.

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 (Matt)]

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 (Marc)]

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 (Marc)]

Originally Posted by 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...

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

[LewisM]

Good point Marc.