Dovetail Adaptor for Old EQ3-2 Mounts

[JamesF]

My EQ3-2 is one of the old models that has fittings for scope rings, but doesn’t have any form of dovetail clamp. I prefer to use dovetails as it makes swapping scopes around between mounts easier, so I decided to modify my mount to add a suitable saddle. I’ve seen this done by mounting a saddle on a section of dovetail that is then bolted to the mount using the holes for the rings, but I wanted something with a little more lateral stability.

I bought a new saddle from Sky’s the Limit and after some hunting around discovered that it’s possible to buy small sheets of aluminium on ebay for very little money. I bought some 5mm sheet and cut out a piece that would support the entire base of the saddle as well as resting on the sides of the mount head. The plate extends out far enough to reach the holes for mounting scope rings. I drilled out matching holes in the plate and tapped them to accept an M6 thread. When fitted to the mount the bolts then hold the plate tight to the top of the mount without it being able to rock or twist.

Four more holes tapped to M6 take the screws that hold the saddle to the plate. Tapping M6 holes squarely in 5mm plate is tricky. I discovered the way to do it is to put the tap into the chuck of a pillar drill with the plate clamped to the table and then turn the chuck by hand. This keeps the tap square to the face of the plate. Doubtless there’s some clever way to do this, but it worked for me.

Here’s what it looks like when assembled:

You can just see the edge of one of the flanges that rests on top of the mount sticking out underneath the lower edge of the saddle. There's a similar flange on the other side.

For the obvious reasons, I've not had a chance to try this out yet. Hopefully that will come soon. In the meantime I shall be attempting to make a similar plate to fit my AZ3.

James

[Gina]

Yes, I've used a pillar drill to hold a tap to get threaded holes at right angles to the surface - works well with plate

[Stardust]

My friend wanted to do the same thing, I only made this and the dovetail bar yesterday. Just need to drill some holes to fix and give a new lease of life to an old mount.

[JamesF]

*Sigh*

If I had a lathe I'd love to make the parts myself too. The little demon whispering in my ear is getting increasingly difficult to ignore. Looks like a very nice job you've done. Did you use stock bolts or make them yourself too?

Actually, I have a plan as regards the lathe. I'm going to save up little jobs that need things making until I've reached the point at which the cost of a small lathe would come fairly close to the price of buying the bits to complete the jobs. Then I'll buy the lathe and make the bits I already want a couple of pier heads making up and in the workshop I have a 4" Parkinson F No. 7 Fitter's Vice that sits unused because the half-nut is worn to the point where the vice mechanism jumps. Could easily be 100 years old. Replacing that with a modern one won't be at all cheap, so if I could make up a new half-nut to fix it and machine the two pier heads that would represent a fair chunk of the lathe price

James

[steppenwolf]

Excellent - I love the DIY approach! I'd love a lathe myself but all I have for metalwork is an old Black and Decker two speed drill in a vertical drill stand but I've made plenty of good mounting hardware with that and have got quickly up to speed with tapping threads too.

[JamesF]

I have a pillar drill and it does see a lot of use. If I had to kit a workshop out from scratch again, a pillar drill would quite possibly be the first static power tool I'd buy.

James

[Stardust]

Yep made the bolts, knurling wasn't great on the first one but they all look the same in the dark. Made some pier heads too which was fun. I've only had the lathe a couple of years, so wish I'd bought one a lot sooner. It has paid for its self in that time with saving me money and making a few parts for people. Has a lot of use as my other hobby is live steam garden railways.

Be nice to get the old vice going, I prefer old tools to a lot of the modern stuff.

You could do some light milling in alli with a verticle drill and a cross vice, but being able to drill and tap makes a difference.