Bending fork blades

[Chik]

A recent thread about RIH having difficulties sourcing a fork crown reminded me of the question that I had after watching the opening sequence of this clip some years ago:



I thought that the standard practice is to bend them without heating them. I assumed there are metallurgical reasons for this.

Anyone here bend fork blades like van der Kaaij, by heating them up until they are glowing?

[Paul Jacobs]

I bend fork blades by cold setting.

The book "Made in England" - the Artisans behind the handbuilt Bicycle by Matthew Sowter and Ricky Feather, published in 2012 contains an interview with the late Ron Cooper who started building frames in 1947, at the age of 15. Below are a couple of extracts from the Ron Cooper chapter.

[Chik]

Thanks, Paul. Have that book, with Matt's and Ricky's autographs :) I read Ron's chapter first, and obviously forgot about that detail...

It sounds like it's a bit trickier to execute properly. Am I understanding it correctly?

[Paul Jacobs]

It sounds like it's a bit trickier to execute properly. Am I understanding it correctly?

I don't suppose it would be very difficult to do and I would be interested (as you asked in the first post) to know if anyone here does this. I presume heating most steel alloys to red or orange and then allowing them to cool in air (without quenching) just makes the metal softer and reduces the tensile strength. It should not make it brittle which would be bad for a bicycle fork. I would not want to do this with something like Reynolds 853 (for example) without knowing a lot more about the effects. The problem with heating with a hand torch is that this can be a bit variable without skill and practice. You would also need something other than a wooden or aluminum fork bender unless you do it free hand which Ron Cooper may have done. I can imagine how careful distribution of the extent and degree of heat would determine the resultant curve when a straight fork blade is bent but that is not a skill I feel inclined to try to acquire.

[Chik]

I guess a related question is, why would one do it with heat when one can cold set?

[Cynikal]

In the opening segment of the video, he is only heating one side of the blade. Wouldn't that cause an issue as well?