Monday 19 January 2015

Shortening (QR) skewer


BEFORE             and               AFTER
a small bicycle plastic surgery
Skewer is a rod (essentially a long bolt) that fits into the hole of a hollow wheel axle and fixes the axle in the fork dropouts. On one end the rod is threaded and has a corresponding nut, on the other end it usually has QR (quick release) handle, but can also have just a hex head. The skewer is often too long, so that the threaded end extends well past the end of the nut. This is an aesthetic fault more then anything else, although in some extreme cases – as in the picture here– it could be considered as a cold weapon, potentially causing serious injury or damage to the property. The obvious remedy is to cut the excess end of the threaded end, but many will be reluctant to undertake this task, fearing that the cut threads would damage the nut. I was sceptical too, but now, after I pacticed it a few times I can say it is quite safe, if you follow some simple, logical steps:  
  • With the skewer on the bike note the length of the threaded end that you want to remove.
  • Remove the skewer from the axle and re-thread the nut past the desired cut point. It is advisable to use another,“heavy duty” nut for this purpose, but the original nut is good too.
  • Hold the skewer in the bench vise and cut the desired length with fine hacksaw.
  • File the cut surface so that no sharp edges remain.
  • Remove the nut to “clear” the remaining threaded part. Then install the skewer.

By the way, the procedure is applicable to any bolt that you want to shorten. Weight weenies will be particularly interested in this, and that is why I add a table showing how much mass (not  weight!) in grams you will drop by shortening a bolt of diameter D by length L= 1cm. For different length L multiply the number from the table by L expressed in cm.

Material
Diameter D
 
2 mm
3 mm
4 mm
5 mm
6 mm
8 mm
Steel
0.25
0.55
0.98
1.53
2.21
3.92
Titanium
0.14
0.32
0.57
0.88
1.27
2.26
Aluminium
0.08
0.19
0.34
0.53
0.76
1.36