80mm long focal length refractor

[Matthew Gregory]

Excellent project - subscribed!

 

[savarin]

First job with the 10mm aluminium plate.
2 large flanges to make the clamps that hold the scope.
I opted to document all this for the thread on cutting aluminium plate and as I didnt want the hassle of cleaning up all the fine swarf from the table saw I elected to use the jig saw. Not as clean cuts but still pretty quick.
I've kept the dates and times on the photos so you can see how quick the cuts are.
Rough marked out on the 1500x160x10mm plate

first cut with the jig saw approx half way through

finished, 2mins

long side and 4 corners off, 14 mins including a blade change for the saw.

Using a hole saw on my p#$% weak drill

at last we're through. This is probably the longest part to do. I seems to take forever particularly when the drill stalls easily at it slowest speed but highest torque. Also incredibly messy.

Into the lathe and turn round, 2 flanges. Now I have to mount them to the face plate and bore them out to just over 80mm for the tube and some foam padding.

 

[savarin]

The two flanges bolted together with four 8mm stainless rods.
Now I have to bore the holes for the tension screws, mill the sides for the 8x40mm strips (cut on the table saw) that will bolt on and hold the bearing trunnions and then split them in half.
Thinking again about all this I have a feeling I should have drilled the plates for the clamp bolts then split them whilst they were still square, then turned and bored them.
If it doesnt work I will revisit and do it again that way.

 

[savarin]

Took a break from the stand etc and made a sun finder.
A quick dive into the scrap bin came up with 3 off cuts of 12mm thick aluminium and a bit of thin tube.
I wanted the sun end to fit into the tube with a 1.5mm dia hole but how to hold the off cut.
Centre popped the middle and held it tightly against the chuck jaws with the rotating centre and some double sided tape.

Drilled with a 1.5mm dia for the sun to peep down and made it an interference fit into the tube.

The sun spot has to hit an opaque screen at the other end of the tube so the screen holder needed a threaded insert to hold it in place.

Made a small internal threading tool and cut a 0.7mm thread inside and on the outer clamp ring.

The screen is cut for a plastic milk bottle, scratched with dividers and inked.

Then I polished the lot.

It works a treat. now back to the stand.

 

[12bolts]

Nice work Charles,
Did you use the double sided tape and centre because of the lack of a 4 jaw? And then hold the round to cut the centre out?
Thats a pretty high polish inside the "cup" Im impressed with the finish!

Cheers Phil

 

[savarin]

Nice work Charles,
Did you use the double sided tape and centre because of the lack of a 4 jaw? And then hold the round to cut the centre out?

The off cuts were too small for the 4 jaw (original piece of crap) so I used the tape and centre. Then mounted the now round piece in the 3 jaw and used the bearing pusher to get it aligned flat, turned down the push fit part for the tube, reversed it to drill the small hole and bore out the taper.
The other two pieces for the screwed end were drilled first, both mounted together on a long bolt trapped in the 3 jaw, turned to size then individually bored and the threads cut.

Thats a pretty high polish inside the "cup" Im impressed with the finish!

Thanks, 600 wet and dry with wd40, then 1800 jewelers abrasive paper and wd40 then solvol autosol.
There are still some marks left so when I set the polishing wheels back up and use tripoli followed by rouge then all the marks and micro scratches should disappear.

 

[savarin]

Back to the stand and bits.
Milled the side slots out of the rings using a small end mill I had been given years ago and my vertical slide.

then drilled the chord for the clamp bolts once the rings are split.

Straight all the way through with no wander.

milled out the corners and enlarged the hole to 5mm

The finished rings before polishing with one 40mm wide side plate resting in the slot and a 5mm rod in the bolt hole.

Now I have to cut the rings in half.

 

[savarin]

I thought I had it nailed.

I need 8 stainless knurled nuts for the clamp rings.
The first was ok, the second and third were very nice.

The knurls are even and regular.
That's when I assumed I had solved all the variables. Bad assumption.
The fourth one started fine, the thread cut smoothly and all was going well until it came time to use the knurler.
It kept walking itself out of contact.
It just wouldn't stay at 90 degrees to the work piece and the tension on the central tightening bolt of the QCTP was as tight as I could get it.
Its a double or maybe a triple start, hardly any knurling in the centre.
The fifth one (still in the lathe ready to be parted off and thrown away) is what could only be politely called an abortion.

Its making me believe that a purpose built fixture that cannot swivel at all would be the way to go.
Anyone foresee a reason not to?

 

[savarin]

Split he scope clamp rings today.
I only had a hacksaw so to keep the blade straight I clamped two lengths of angle iron to them and sawed through the gap.


This kept the cut pretty clean for a by hand saw cut.


A quick rub on some wet and dry and a load of WD40 for approx 8 mins


And the ends are nice and smooth and clean.

 

[Matthew Gregory]

Nicely done! Great idea on the angle iron guides, too.