Half-round Washer Bearing Alternative

1. Summary

10mm Brass rod is not always easy to get hold of in short lengths, and construction of half-round bearings from it for the Mk II Extruder^? may be beyond the capabilites of some home workshops. Fortunately, a servicable alternative can be made from M3 or 1/8 inch washers.

2. Materials & Equipment

• 3g Polymorph
• Very hot water
• approx. 6-8 x M3 or 1/8 inch washers. Steel or brass.
• Forceps or tweezers
• Bolt cutters or sturdy pliers
• Hair dryer
• Studding with smooth lands as per Mk II Extruder^?
• Motor-driven Screw Block as per Mk II Extruder^?
• Grease or Vaseline

Method

Take sufficent M3 or 1/8 inch washers to fill one of the wells intended for the bearings. Use robust pliers or (preferably) bolt cutters to cut them all in half.

Stacking half-washers in the bearing well

Stack the half-washers neatly in the well on edge, cut side uppermost; tweezers or forceps come in handy for this. Once the well is full, warm a pea-sized mass of Polymorph in hot water and firmly squash it into the channel formed by the washers. Allow to cool, then remove the stack intact. The Polymorph used here will be removed later - it is only to hold the stack of washers together.

Completed stack of half-washers

Put more Polymorph to warm, and pre-heat the bearing well with a hairdryer. This will keep the Polymorph workable for longer, but is only applicable to ABS parts - Polymorph ones would melt under this treatment!

Line the well with very soft Polymorph and push the stack of half-washers in, cut sides uppermost. Pull the solidified Polymorph off the washer stack, and push the smoothed portion of the threaded rod on top to line everything up. If neccessary, re-heat with hair dryer. Leave the bearing slightly proud.

Repeat the process with the other bearing well, finally re-warming both bearings, and settling them into their final position with the threaded rod as a guide. When cool, grease bearings very, very lightly with Vaseline or similar.

Half-washer bearings installed in the extruder.

-- VikOlliver - 04 Jan 2006
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