9 replies to this topic

[JulianS]

Hi, I need to remove this screw that presses the spring on the declination arm. It's rusty and nothing will come out. But I need to know the characteristics of that screw—length, diameter, and thread type—so I can find one before removing the other. Do you know the characteristics of that screw? Thanks.

[DLuders]

You didn't say what telescope mount you own.  Did you try some automotive sprays, like PB Blaster , to loosen your existing screw?

[JulianS]

Screew

Attached Thumbnails

• 

[DLuders]

You still did not say what MODEL of telescope mount you own.  Your closeup picture doesn't say either.

[Julian Sanz]

You didn't say what telescope mount you own.  Did you try some automotive sprays, like PB Blaster , to loosen your existing screw?

Hi, sorry. lx200gps 10"

[Julian Sanz]

Sorry.  Telescope,and mount LX200GPS 10". 

[Mike G.]

PB Blaster has worked well for me in the past, but sometimes it needs to work overnight or a couple days on really rusted parts.

[Piet Le Roux]

Hi, I need to remove this screw that presses the spring on the declination arm. It's rusty and nothing will come out. But I need to know the characteristics of that screw—length, diameter, and thread type—so I can find one before removing the other. Do you know the characteristics of that screw? Thanks.

The screw does not, "presses the spring", it only determine the amount of travel. You dont need to adjust it if you want to remove the drive, but what is the problem and why do yo want to disassemble the drive? 

[MikeBY]

I agree with Piet. Why are you needing to mess with this limit screw? I see from the picture there is rust in the threads. You need a good penetrating lubricant. PB blaster is one,  but some of these are very hard on plastics. PCBs, paints and aluminum. 

Start with WD40.

Protect nearby components and everything else in the arm.  Remove connecters and just put a drop or two on the threads and let it soak in 24 hrs. Rewet with a bit more lubricant. 

Fit a SAE hex driver and gently and repeatedly tap down  on the grub screw. Add lubricant if lubricant goes down into threads. After tapping for a few minutes start applying horizontal tapping and torque in the counter clockwise direction  on the grub screw to break it free.

Do not apply excessive force in any of this as the steel grub screw is threaded into relatively soft aluminum and you risk damaging the threads. 

If the grub screw doesn't start to rotate, try tapping and applying applying torque in the clockwise direction, then back again in the counter clockwise direction. 

Again keep the threads at the top wet so that lubricant can flow down into the threads. 

 

If you still have no movement move to a penetrating oil designed for loosening rust and metal corrosion caused

frozen parts. 

 

I'd avoid PB blaster and strong solvents as there is a risk of corroding the aluminum threads. Be sure the penetrating oil is safe for aluminum.

 

Again, soak the connection in penetrating oil 24 hours.

Rewet and follow the same procedure.

 

Take your time,  don't cause more damage. Vibration is the key to breaking the screw free. If you have a hammer massager or hammer drill with very low force clutch that will work faster. Just remember, use low torque settings.

 

All LX200s are SAE English threads.

 

The next thing is to use heat, but you must be careful not to overheat the circuit board or nearby parts or the motor. Heat the housing while using a hex driver that's been in the freezer to keep the grub screw cold. If you've got a heat gun for SMB soldering that will work. 

[OzAndrewJ]

Gday Mike

Why are you needing to mess with this limit screw?

If i read this thread ( and another on another site ),

it appears he wants to unscrew the bolt that fits inthe PCB

This has a really large head on it, and using my engineers hat

unscrewing it can be used to apply more compression to the spring,

but to do that, you also have to backoff the grubscrew that sets the lash.

( The RA has an adjustable bracket to do this, but DEC appears to use the PCB

as the spring support )

I have never understood this mechanism, as unscrewing the "?" bolt in the PCB

means it wont be very strong unless you pack it with washers????

but who knows what Meade was thinking :-)

Andrew Johansen Melbourne Australia

 

edit

Drat, try 2 to attach piccy

 

 

 

Edited by OzAndrewJ, 22 May 2025 - 11:48 PM.