I think I mentioned that a couple telescope parts did not survive the move undamaged. One of them was the refractor's focuser. I bent the damaged parts back into what looked to be the original shapes, but the focuser is rough and it binds. before the move, I had considered replacing the focuser with a dual-speed focuser. These have two knobs; one is the coarse focus typical on telescopes; the other turns at 1/10th speed, allowing very fine focus changes. So I ordered the GSO 2" Linear Bearing Crayford Focuser (made in Taiwan). It is an gorgeous piece of machining:
The only downside is that the flange is 112.5mm OD and the refractor's tube is 125mm ID. So, I need to make an adapter. To quote the opening sequence from The Six-Millionaire Dollar Man:
Gentlemen, we can rebuild him. We have the technology.
At least, I do. I have a 6" 4-jaw chuck. No, Sherline lathes do not normally go this large. In the past, I have made riser blocks for the headstock and tool holder to allow turning big stuff.
1. I will start with a 6" x 6" aluminum square.
2. Drill and tap a 3/4"-16 center hole. (This is the Sherline headstock spindle size as well as the size of the rotating table adapter.)
3. Remove 6" chuck.
4. Rotate workpiece onto headstock spindle.
5. Turn workpiece to 124.8mm OD.
6. Make riser block for the tilting table on which rotating table will sit. (I need the clearance to rotate this large of a workpiece.)
7. Tilting table to 90 degrees.
8. Put workpiece on rotating table adapter.
9. Turn workpiece 120 degrees at a time.
10. Center drill each hole.
11. Repeat for two more holes.
12. Replace center drill with twist drill for a through hole deep enough to get through the 112.8mm layer.
13. Return workpiece to 6" chuck on headstock spindle.
14. Use cutting tool to cut 105mm hole.
15. Use boring bore to enlarge center hole to 112.7mm.
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