The fight to remove my Mak SCT converter

[JamesF]

As I've had the Mak apart to sort out the loose mirror and it now needs collimating I thought I might as well go the whole hog and remove the SCT converter at the same time so I can go back to using 1.25" kit directly.

The SCT converter ring (about 12mm tall, 3mm thick and threaded on both sides) absolutely would not budge by hand, so I had to resort to tools. They allowed me to turn the ring, but also turned the ring fitted to the end of the baffle tube that the SCT converter screws onto. Gingerly I took both off together thinking I'd just unscrew them from each other and put the baffle tube ring back on.

The baffle tube ring is about 5mm high and 10mm thick, also threaded on both inner and outer surfaces and fits almost entirely inside the SCT converter. It has two 2mm holes through the face on opposite sites, presumably to allow it to be screwed on to the baffle tube with a matching tool. Obviously I don't have this tool and there's no real way to get a grip on the baffle tube ring otherwise.

First I tried putting a steel pin through one hole and turning it, but the pin bent. As did a second. Then I came up with the idea of nailing the ring to a piece of wood through the holes and turning the SCT converter. That just pulled the (40mm) nails straight out of the wood again.

My mind was starting to wander towards the application of heat (kettle full of hot water first, probably, but a blowtorch would possibly have been a last resort before I got the saws out) when I hit upon the idea of clamping the baffle ring between two nuts on a threaded rod, clamping the nuts in a vice and turning the SCT converter around them. I couldn't find any rod of a suitable diameter, but hunting through one of my "plumbing spares" boxes I found a straight through 22mm compression fitting. Sure enough, that went through the middle and allowed me to do up the nuts on either side to clamp the ring in place and clamp them in the vice. Out with the biggest pair of adjustable pliers before I'd have to move up to stilsons and off it came without any further trouble.

It's never going to look quite as pristine as it did, but somehow I don't think it would have done if I'd got as far as the blowtorch either. I'm still not sure why it was so hard to get off. Either it was not a very good fit originally (it was in place when I bought the scope, so I don't know) or there was some dirt in the threads causing them to jam.

To sweeten the ending, I found a lid on the floor of the workshop that should work nicely as a collimation cap. Having drilled the centre and cleaned it up, it looks like it will just fit nicely over the outside of the newly-replaced baffle tube ring.

James

[Merlin66]

On threaded parts like this a very slight smear of boot polish on the threads minimises the possibility of binding...good to know for the future....

[DoctorD]

I use a pair of Baby Boa strap wrenches to loosen the SCT adapter on my MAK.

HTH in future.

Paul

[JamesF]

Good idea. I should perhaps pick up a couple of those. I have a strap wrench, but it won't adjust small enough for the SCT adapter.

James

[Mike Hawtin]

I sympathise, my atlux had a lovely cast polar scope cover about 130mm diameter which has a very coarse thread. One day the cover locked solid when I tried to unscrew it. I had no choice but to hacksaw it off to be able to use the polar scope and found a small flake of ali had broken off the leading edge of the first thread consequently locking the cover in place. It was a drastic solution but the only thing I could do to remove it. Mount still works fine but its looks are spoilt for ever!!