Baader UFC Tilter Issues

Removed the QHY268C and Baader UFC assembly from the SpaceCat built to make some adjustments, and to check the set screws of the UFC Tilter to see why they are so difficult to adjust. 

When checking the UFC Tilter set screws, I found that several of the screws were difficult to turn because their threads have been damaged.

This issue seems related to the design of this particular tilt mechanism. There’s a brass ring that sits between the two halves of the tilter. The set screws press against the bottom and top outer edges of the ring, shifting it up or down depending on whether the lower or upper set screw is threaded in further. 

Brass ring visible between the two halves of the UFC Tilter

The trouble is that the further the set screw is threaded in, the more likely it is that the threads of the screw will be damaged by the brass ring as it shifts toward the outer edge of the screw's cone tip. With threads nearest to the tip of the screw damaged, the screw then becomes difficult to back out. Forcing it will likely damage the threads of the tilter as well. 

It seems this issue may be unavoidable. The brass ring sits evenly between the two set screws at minimum tilt. To increase tilt, the lower set screw must be tightened, threading it deeper to offset the ring from center. Which risks damaging the threads. At the same time, the upper set screw is loosened to back it out, and is more likely to have its tip rounded off by the ring as a result.

Minimum Tilt (left), and Maximum Tilt (right)

It's worth noting that the Baader UFC Tilter, having a variable optical length ranging from 9.75mm to 10.50mm, was not intended to extend by more than 0.75mm, or one degree of tilt. It's possible that I may have exceeded this limit by overtightening the screws, resulting in damage to the screw threads.

The UFC Tilter uses M4 x 6mm stainless steel cone point grub screws. There are three pairs of these grub screws, six screws in total. All but one of the screws has damaged threads, and will need to be replaced. I placed an order for replacements earlier today. They should arrive in a few days.

Update 2024-01-19

Replacement grub screws arrived in the mail yesterday. Got them installed this morning, replacing the five damaged tilt adjustment screws. Applied a little Super Lube Anti-Seize lubricant to the threads to help minimize wear and tear. Made sure not to over tighten the screws when reinstalling.