DIY dovetail bar

dikman (Richard) · #1 07-11-2022, 01:03 PM

The dovetail bar on my Celestron frac is a short one and I couldn't adjust the scope enough to counterbalance some of the camera gear, so I thought "why not make one?". I melted some aluminium (from BMW suspension arms, so good quality) and cast some bars. I machined the thinner one so it would screw to the scope rings and powdercoated it green. It works fine, although there are a couple of machining marks on it (I really need to buy a flycutter for doing larger flat surfaces), and cutting the dovetail angles was a bit tricky, although I've since thought of a better way (next time).
One problem with powdercoating is the parts are very slippery so after the tube nearly slipped out of the saddle I glued a piece of thin leather to a piece of ally bar that fits over the clamp part, which also saves marking the bar itself. Seems to work ok.

AstroViking (Steve) · #2 07-11-2022, 05:01 PM

Very clever work, Richard. Well done. I'd love to have a workshop where I could do that sort of stuff...

bojan · #3 07-11-2022, 06:11 PM

Very good

I don't have facilities to melt aluminium (yet..).
However, some time ago I used Aluminum angle 40x40x6 and formed a channel from two pieces like on attached sketch, joined together by couple of screws.
I also beveled the edge that goes into dovetail receptacle, however this is not strictly needed, because once the screw is tightened, the structure can't go out of the grip.

dikman (Richard) · #4 08-11-2022, 08:17 AM

I like that, bojan, simple and effective. Wish I'd thought of that, it would have been a lot simpler than my method and it would have saved a lot of machining!

bojan · #5 08-11-2022, 09:13 AM

Quote:

Originally Posted by dikman

I like that, bojan, simple and effective. Wish I'd thought of that, it would have been a lot simpler than my method and it would have saved a lot of machining!

Those extrusions are very useful for lots of things... I always try to use them first - to save time, effort, and very often, money ..

Boozlefoot · #6 12-11-2022, 06:43 PM

Melted down Beemers rebirthed as scope parts......love it.

I've been using this for weird and wonderful jobs, light and super-rigid, and takes t bolts for fixing gear. I grind the top lip off the lower quadrant shoulder in the clamping range. @ $22.00 metre, gets you a lot of jobs done. Surprising how handy it is. Available from any of the websites dealing with the "homestyle" cnc machines/engravers etc. 40 x 40, also 40x80 if you want extra height for your accessory.

dikman (Richard) · #7 12-11-2022, 09:51 PM

I first discovered that extrusion when I built my 3D printer (came as a kit, a large box of bits!) and yes, quite useful stuff.

dikman (Richard) · #8 14-11-2022, 09:04 AM

I may have found a better way of making a dovetail by casting. I found several .stl files on Thingiverse to 3D print dovetails. While I wouldn't trust a 3D printed piece to support a scope it should give me a suitable shape to give a fairly accurate mold to minimise machining the casting.
Something for next time.