focuser slippage

[mat,v]

Hi all,,I recently bought a second hand W/O 2speed crayford focuser in great cond,,when i load it up with a large EP and W/O 2" Diag the focuser SLIPS and won't adjust,,It works with "lighter" EP's,,I have completely loosened the silver "hold" screw and tightened the black focus pressure screw,,it has made a mediocre difference,Is there anything else i can do to "tighten" it up more to stop it SLIPPING,,,Thanks all,,,MAT

[marki]

Hi Matt

Turn the scope upside down and adjust the focus so the tube is completely out. You will see the a flat machined into the focus tube. Is this smooth with the anodising in place? If you can see the metal the focuser is worn. Also this surface should be free of grease which will cause the tube to slip. As it is second hand you do not know what has been done by the previous owner. If the surface looks ok give it a good clean to remove grease etc. If it still slips the bearings may have been fiddled with.

Ciao Mark

[mat,v]

The anodising is still in place with no metal showing,,a little bit of white gunk that wipes off easily,,,I read on another post that the black screw should be tightened as much as is physically possible,,:shrug:,,Doesn't sound quite right,,there is tight & there's over tight,,is there anything inside the unit that i could tighten,,,,,Cheers MAT

[marki]

Hi Mat

As the draw tube is still in good nick thats good. Do not tighten anything up as far as it can go as you may bend the rod that turns against the draw tube. It should not be necessary unless the focuser is badly worn. I have very little pressure on mine and it works fine. I suspect that the "white stuff" is lithium grease and this is probably the cause of the slippage. You will need to take the focuser apart (only if you feel competent to do so or get a shop to do it) and clean all of the grease away. The milled flat and rod must not have grease or it will slip.

Ciao Mark