# Adjustable Spotting Scope Swivel



## Badabinski (Jan 24, 2021)

I wanted to share this adjustable spotting scope swivel I made over the summer for my dad as a let's-all-stay-indoors-and-not-go-crazy COVID-19 project:



This was my first self-designed project that was more than 1 or 2 parts, and I'm pretty proud of how it turned out.

First off, some background. My dad does Palma rifle shooting competitively. Palma is shot from 300 to 1000 yards, and at the further reaches a spotting scope is an absolute must for reading wind mirages. There are plenty of dedicated spotting scope stands out there that are perfectly suited to the task, but they're often bulky and heavy. My dad began competing internationally a few years ago, and he just didn't have the space or weight allowance for a larger stand. Enter the tripod mount scope swivel, MK1:





This first version was made up of a commercially available swivel mounted to a tripod with a custom bushing. The scope was then attached to the swivel with an angle bracket. This setup mimicked the purpose built scope stands out there, but it was much lighter and could be broken down into pieces that were easy to cram into something airplane friendly.

The swivel itself has an interesting design. There's an aluminum bushing(?) that rides inside of a plastic cap that allows the bushing to spin freely. There's also a plastic washer that sits between the bushing and the aluminum body of the swivel. Set screws inside of the body of the swivel can be tightened to push the washer into the bushing, introducing some friction. You can tune the amount friction so the scope can be pushed to the correct position without needing to be locked in any way.

This setup had some distinct disadvantages, however:

The adjustment screws could be impossible to access on the swivel depending on how things were put together, meaning the friction bushings (making that term up) might be too loose and require a bunch of work to tear down and tighten up
The point of rotation for the scope was the top of the tripod, meaning the eyepiece of the scope would move away from or towards your face when you tried to pan the scope around
The angle bracket lacked rigidity and could vibrate annoyingly
It wasn't easy to adjust how far the scope sat from the tripod. The setup as pictured meant the tripod was a bit unstable when being used by someone sitting upright to spot wind conditions for another shooter. You definitely don't want your expensive spotting scope taking a tumble!
Angle brackets aren't as cool looking as custom machined components. This is clearly the most important consideration
My dad knew I was starting to get quite serious about machining as a hobby, so he came to me and asked if I'd be able to come up with something to address these issues. Here's what I came up with:



Some key things to note about this design:

The set screws are always accessible. There's enough clearance between the scope and the "vertical swivel" to fit an Allen key
The point the scope pans around is directly underneath the scope itself, meaning the eyepiece stays roughly the same distance away from the eye
The solid 6061 and 7075 aluminum construction is rigid and doesn't vibrate, while still being lightweight enough to travel with internationally
There's a ridiculously cool dovetail that can be used to adjust how far the scope sits from the tripod to help with balancing. Like, I seriously love dovetails so this feature is like catnip for me
The scope swivel is shiny and has a much better chance of attracting ravens, crows, and other competitors who are drawn to shiny things
(Do not shoot the ravens and crows, they *will* remember your face)

OK, with all of that background out of the way, let's get some more pictures and videos of the stuff we're all here for.

My first step was to rough cut all of my raw stock.


(Ignore the plastic here. I wasn't happy with the stock I had, so I went and purchased a nice delrin round bar from McMaster.)

I had some nice 7075 offcut blocks that I used for all of the square things. The round stock is some 6061-T6 I picked up at the same time.

I then went about squaring up my stock. My mill is very, very tiny and these pieces are somewhat sizeable, so I squared things up on my lathe using a superglue arbor:




If I'm being honest, this was terrifying:




(Apologies for my terrible camera work. The most charitable description of it would be that I'm trying my hand at cinéma vérité.)

I got some beautiful surface finishes, however:


(At least, they were beautiful until I scratched them to death with my general incompetence.)

I also got some excellently dimensioned stock. When I was careful, I was getting .0005" variation in thickness, which is pretty good for my sloppy shop!

Next came the layout:


(Yes, my drawings are terrible. My high school drafting teacher would be ashamed.)




(I was pretty inconsistent about getting pictures, so several pieces are missing. You can also see where I missed dimensions on my drawings and had to write them in after the fact...)

I then set about working on the dovetail pieces. I had never machined dovetails before, and it shows. I made basically every rookie mistake it's possible to make here. My cutter also wasn't big enough, so I had to relieve the top of the female dovetail to make it fit. I don't have a DRO on this mill and I'm terrible at compensating for backlash, so this operation was done by working up to the scribe lines.







(My mill has no power feed, so I wasn't able to grab any worthwhile videos of me cutting the dovetails.)
(Also, when I said "I had to relieve the top of the dovetail," what I meant was "I'm an idiot and I'm going to let the cutter RUB A RELIEF." I feel I had to make that confession. I hope you will all forgive me, especially because I made a very similar mistake on my next project...)

Next up were the vertical and horizontal swivels. I don't have pictures of cutting the bolt hole pattern, but I can assure you it was an exercise in tedium thanks to the lack of a DRO, forcing me to be reliant on handwheels that count .0625" a turn.


(I love spiral fluted taps. I'll never buy another straight fluted hand tap again.)



Next, I made this jig for my rotary table that was WAY too tall. It let me round off these parts fairly consistently, however:


(I know it's messy in this picture. Don't worry, I'm still just as terrible at keeping things clean and the squareness of my parts suffers for it.)
The parts were totally beat to death at this point. I spent quite a while lapping things on my beater surface plate and eventually got a presentable finish:


(Presentable, he says. I suppose it is if you ignore all of the deep scratches...)

With those done, the male dovetail was up next. This part is freaking cool, so it's a shame I don't have more pictures of making it.

First up, I drilled and reamed some holes to match this fixture I made:



Oops! I've hit my picture limit. To be continued in the comments, maybe. I'm pretty new to this forum, so I'm not sure if the 20 attachment limit is per post or per thread. I'm also not sure if I'm committing a faux pas here by attaching so many photos.


----------



## Badabinski (Jan 24, 2021)

Continued from above:

Next, I opened up the slot and gave it a nice chamfer:



The cool thing about this fixture is that it made it easy to round the ends off even though the radius at each end has a different centerpoint. The setup as pictured was used to cut the large round. The center hole and pin were used to cut the other end. (That's a terrible description, but hopefully it will be enough.) I could also cut into it when machining the dovetails, so everything was doable in a single setup.
Next, it was over to the lathe to make the hole in the end and form some radial features:


This setup was fun and also quite terrifying:




A few minutes after this video was taken, I found out that my house had flooded due to an unattended aquarium water change, so I'm missing quite a bit of footage from this point on. Stress sucks! I wish I could show the setup on the rotary table using my fixture. It was quite cool and I'm really happy with how the rounded ends turned out:





Next up is that SUPER COOL KNOB. I'll admit, I stole the idea from Hemingway Kits. I had just finished building their instrument-maker's vise when I was designing this project and I was quite smitten with the knob:




Not pictured here or anywhere is me turning up the Delrin housings, Delrin washers, aluminum bushings, and probably other things I've forgotten. I was still dealing with the flood, so I just wanted to get this thing done.
Some more pictures for funsies:






(Sorry for how blurry this one is!)

This thing has been in service since July, and apparently it's been working really well for my dad. This definitely stretched me quite a bit and I learned several important lessons. I'm sure I'll have to learn those lessons several more times before they stick, but this was a great intro into more complicated projects for me and my dad is quite happy.

I can make the original files available if people are interested (STEP and DXF), but be aware that my drawings are terribly dimensioned. Be prepared to fix them before you use them.


----------



## hotrats (Jan 24, 2021)

That is very, very nice! And appears well thought out also. I used to shoot service rifle comp. and never liked the scope stand adjustments. Your design looks like it takes care of that problem. Well Done!!


----------



## Badabinski (Jan 24, 2021)

hotrats said:


> That is very, very nice! And appears well thought out also. I used to shoot service rifle comp. and never liked the scope stand adjustments. Your design looks like it takes care of that problem. Well Done!!


That was my game as well! I went to Perry a couple of times (once as a junior), but I fell out of it after I got a full time job that required some travel. Still have my White Oak AR with the permanently-attached carry handle.

I always liked my dad's service rifle scope stand (which was pretty $$$!), but the fine adjustments on mine were a bit chewy and the locking knobs never got things rock solid. If I get into Palma then I'll probably make something like this for myself.


----------



## francist (Jan 24, 2021)

Nice job, and an equally great write up. I enjoy hearing people describe their thought processes as they work through some pretty complex design features, and I also know full well that the same thought processes don’t always work out as planned but we forge through anyway. I think you succeeded on a number of fronts here — 

-frank


----------



## Badabinski (Jan 24, 2021)

francist said:


> Nice job, and an equally great write up. I enjoy hearing people describe their thought processes as they work through some pretty complex design features, and I also know full well that the same thought processes don’t always work out as planned but we forge through anyway. I think you succeeded on a number of fronts here —
> 
> -frank


There was definitely a fair bit of forging ahead anyways with this project! I'm normally quite particular when I set out to do something, so taking a breather after making a mistake and then finding a workaround is challenging. Luckily, my day job (software development with some sales engineering in the past) has given me many, many chances to make lots of expensive mistakes and then recover from them. 

Glad to hear you liked my write-up! I'm hoping to finish my latest project soon (the world's most overbuilt 4140 steel yarn winder), so I'll try to do something similar for that.


----------

