What you will need
The main part (core) is made from the engine intake valve (its diameter is larger than the exhaust valves). The valve moves along the hub of the front wheel of the bicycle. For the convenience of the core punching process, two springs are used, the diameter and length are selected taking into account the dimensions of the valve stem and the parameters of the bushing, all parts are fixed with a washer for welding.
Punch manufacturing technology for long-term work
Secure the grinder with the grinding disc in a vice in a horizontal position, fix it carefully, do not damage the plastic body of the tool. Sharpen the valve tip to a cone. Make its top as sharp as possible. The rod is made of especially strong alloy steels; sharpen slowly and do not allow the metal to temper.
Using WD, clean the bike axle of dirt and old oil. Check the completeness and dimensions of the parts: two springs, a washer, a valve and the front wheel axle. The washer should fit easily onto the stem.
Place one spring on the valve and insert it into the axle.
Place the second one on the reverse side, squeeze it a little and place the washer on top.
In this position, it is necessary to fix all the parts of the device.
To do this, place the valve with the lower spring and axis on the guide of the movable jaw. Compress the lower spring until the upper spring drops below the valve retainer groove and clamp the vice in this position.
Place a washer on the spring at a height just below the groove. Grab the parts in several places.
Clean the weld from scale and allow time to cool. As we mentioned above, do not overheat the metal, otherwise the crystallization will change, it will become soft and unsuitable for core punching.
The device is ready, test its performance.
Make some marks on the round pipe and the metal strip.
Check the condition of the core. If it is not dull, everything is fine, you can use the device for its intended purpose.
Conclusion
If there are no old valves, no problem. Instead of them, you can use any available products made of hardened steel: files, axles of special mechanisms, etc. If you are not sure of their strength, make a few marks for testing before starting work.
