# How much axle space for the cap nuts and chain tugs?

I am investigating whether I can insert cap nuts with too short axle attaching area. The image below is exaggerated but the attaching areas are about 1.2cm and 0.95cm. The difference 0.45cm meant in 6 months that the left cap nut became broken, metal spaghetti. I squeezed about 0.2cm from the past configuration due to the wrong conf, now the difference is about 0.25cm, but suppose I place there a chain tug, it will take away about 0.2cm and the problem may re-emerge: again metal spaghetti and broken cap nuts. So how much space should be reserved for cap nuts in axles?

The cap nut is about 2.1 cm deep.

1.23cm with the right cap nut, no problem, the nut in good condition. After placing there a chain tug, the space is about 1.0cm. 1.04cm with the left cap nut. With chain tug, the space is about 0.8cm. Even with 0.9, I got metal spaghetting and broken cap nut after 6 months. A problem?

Related

• question about naming of cap-nuts here