Mast Overhaul - Replacing Delrin Inserts in Collars

Replacing Delrin Bearing Strips in Collars

1.	Inspect the Delrin and the machined keyways of the collar for wear.  If the keyways of the collar are badly worn, the collar should be replaced.  If the Delrin strips are worn down to the metal collar, they should be replaced.
2.	To remove the old Delrin strips, remove the nylon screws from the collar.  Pull out the Delrin strips and clean the collar Note: Most masts manufacured before 1986 have glued-in Delrin bearing strips.  For replacement of glued-in Delrin refer to Service Sheet #424
3.	Press the new Delrin strips firmly into the groove.  Align the holes in the Delrin with those in the collar.  Refer to the illustration below.  Install new nylon screws through the collar into the threaded holes in the Delrin.  Apply Loctite adhesive P/N 49450 or equivalent to the nylon screws before installation.  Do not overtighten the nylon screws.
4.	Cut off or file off the ends of the nylon screws protruding through the Delrin until they are flush.
5.	Carefully file off any excess Delrin which may protrude into the keyway of the collar.
6.	Before reassembling the mast, slide each collar over its mating mast section.  If the collar does not slide freely over the tube, it will be necessary to sand high spots on the Delrin to fit.  The high spots will be evident by shiny or gray marks on the Delrin strip.
7.	Wipe the collars clean before reassembling the mast.

1.	Wear rings are preformed split synthetic bearings which fit around the butt plate above the seal on each interior mast section.   Wear rings can be replaced when the mast is disassembled for seal replacement. Check the wear rings wear.  If the wear ring is worn down to the butt plate surface, it must be replaced.
2.	Clean the butt plate and wear ring groove.   Slide the wear ring over the mast and into the groove.  Press the wear ring into the groove to make sure there is at least 1/8" clearance between the two ends.   If necessary, cut enough off one end to get the required gap.
3.	The wear ring must be held in place until this mast section is inserted into the receiving mast section.  It may help to put a drop of glue on the two ends to hold the wear ring in place.
4.	On masts manufactured before 1986, Delrin bearing strips were cemented to the butt plates of the mast sections.  Wear rings can be used to replace the old Delrin bearing in many of these masts.  Consult the factory with your model and serial number for verification before ordering replacement wear rings.

1.	Inspect the collar insert and the machined keyways in it for wear.  If the keyways of the collar are badly worn (elongated), the collar insert should be replaced.
2.	Using a knife, remove the flat rubber external bumper which is glued to the top of the collar.
3.	To remove the Delrin insert, remove the (3) 1/4-28 socket head cap screws from the collar with an allen wrench.
4.	With a hammer and flat punch or chisel, carefully tap around the top edge of the insert to drive it out the bottom of the collar.   Note that the insert can only be removed from the bottom of the collar.  After removing the old insert, clean the collar.
5.	Install the new insert into the collar.   Make sure to align the holes in the insert with the holes in the collar.  It may be necessary to gently tap the insert into the collar.  Do not damage the insert.
6.	Apply thread locking compound, such as Loctite Super Bonder #495, to the ends of the 1/4-28 socket head cap screws.  Replace the screws.
7.	Replace the external bumper. See Service Sheet #422.
8.	Before reassembling the mast, slide each collar over its mating mast section.  If the collar does not slide freely over the mast section, it will be necessary to sand high spots on the insert to fit.  The high spots will appear as shiny or discolored marks on the inside diameter of the Delrin insert.
9.	Clean the collars before reassembling the mast.