Last updated: 10 September 1999

DEC lock mod

From: Jim Chambers (ucjttjc@ucl.ac.uk)

I finally got really fed up with the poor Dec. locking, especially with a camera onboard. If one takes off the Dec knob and degree plate, you will be presented with a mechanical absurdity, a 3/16 th Whitworth thread on a 4 inch knob. To compound this the threaded insert is very short and pressed into the inner shaft with just a knurl to hold it. The leverage is over 10 to 1 ! no wonder things break with the grip you need for the clutch to work.

My answer is as follows, providing you have mechanical help.

1 Undo the 4 screws and slide out the optical tube.
2 Remove the black arm on the dec side with it's gear wheel.
3 Drill a 6mm or 1/4 inch hole right thru the centre.
4 Find a long bolt 6mm or 1/4 inch diameter about 2 inches long.
5 Trim the black plastic so the head of the bolt sits down on the inside flange of the dec arm.
6 Place the Dec locking knob upside down and level, fill in between the the black spokes until you get a full fill of epoxy resin.
7 When hard get a machinist to grip the knob in a chuck in a lathe and turn away the brass thread and bore a recess for a full hexagon nut to suit the bolt. Epoxy the nut in situ with more epoxy. I used double sided sticky tape on the chuck jaws to grip the Dec knob periphery.
8 De-greaseand roughen the faces that grip the gear wheel and assemble with the bolt. Place a one inch washer with a 1/4 hole on the protruding bolt, add the Dec degree plate, then a final thin ordinary washer to stop the knob scuffing the alloy degree plate.
9 The protruding threaded portion of the bolt will have to be reduced to about a 1/4 inch proud with a fine junior hacksaw.
10 Then screw on the Dec knob with it's new nut. Make sure you don't have too much thread or you will drive the nut out.
11 If all goes well you will have a perfect lock with the minimum force, and it will last forever!

Meade won't speak to you any more but I don't mind. I want a scope that works. I just hope they tell the makers in Taiwan! This bolt idea would not cost 20 cents.

Clear skies folks

Jim Chambers. North London. England.

Go back to the Tech Tips page.

Go back to the ETX Home Page.

Copyright ©1998-2000 Michael L. Weasner / etx@me.com
Submittal Copyright © 1999 by the Submitter
URL = http://www.weasner.com/etx/techtips/declock.html