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Ball Bearing of 4mm-Shafts

Rotating metal kit shafts usually are beared in perforated strips, angle girders or gear plates.
For shafts with a higher load furthermore solutions with some parallel mounted strips or cranks are used; in individual cases one can find also shafts with a larger diameter. All this methods increase the bearing area and so reduce the abrasion - but they are not able to avoid it.

Optimal is an abrasive-free bearing with ball bearings, which can be realized simply and universally for a lot of applications. For this only some drills and an adequate bench drilling machine is needed - a lathe is not necessary!


1. Example

This alternative requires a standard miniature ball bearing (approx. 2,50EUR) and a crank (e. g. from METALLUS).
In the actual case a ball bearing with an inner diameter of 4mm, an outer diameter of 8mm and a thickness of 3mm is used.
The flange of a METALLUS-crank has an outer diameter of 10mm and a length of 9mm; so there is enough material to insert the ball bearing.

The drill hole of the crank is to enlarge to a diameter of 8mm for a depth of 3mm. It remains a collar with a wall thickness of 1mm, which will have an adequate stability for the most applications.
Because brass is a soft material which tends to pull in sharp drills one should be very carefully; possibly sharp drills are insignificant to blunt by using a sharping stone.
5kB (38kB)
Ball bearing with crank

The result is a simple and solid appearing ball bearing, which is difficult to distinguish from an original crank.
If the drill hole is a little bit too large the flange can be pressed slightly in a vice; possibly the bearing also can be fixed with some glue.


2. Example

For this a miniature ball bearing with a flange (approx. 5EUR) and any construction part as a holder is needed.
In the actual case a ball bearing with an inner diameter of 4mm, an outer diameter of 7mm, a flange diameter of 8mm and a thickness of 3mm is used. The holder is a cheap perforated strip with 3 holes.

After enlarging the intended drill hole to a diameter of 7mm the ball bearing simply can be inserted, but is isnīt still fixed sufficiently. For this the part e. g. can be mounted to a gear plate or another construction part. Hereby the distance shall be adjusted (by means of washers) to the thickness of the flange to avoid mechanical tension.
The benefit is, that no expensive construction part is to modify, but only a short perforated strip.
Another advantage is the small installation height compared to the 1 example.

5kB (26kB)
Ball bearing in strip
  
7kB (38kB)
Ball bearing mounted to gear plate

Because the 4mm holes of the bearings are very closed tolerated, some shafts possibly will not fit into. In this cases ths shafts can be adapted by means of a smooth abrasive paper.

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