Monday, 16 May 2011
Lugwork - 2
I thought I'd show the process of putting a cutout in a lug.
The lug I'm working on here is the upper head lug for Ben's bike. It's a Llewellyn Cadenzia XLH lug, and I'm doing a little work to it to make it look more like a classic Bocama Professional.
I start by roughly marking where the cutout will be, using a sharpie. Then I put four center punch marks in; one in a little from each of the triangle vertexes, and a third right in the middle.
Next I use a pillar drill to drill a 1/8" hole where each vertex will be, and then a bigger hole in the middle, as shown below:
Next step is to open out the holes to form a rounded triangle. I predominantly use a 1/8" diameter Swiss No. 2 round file to move the vertex around, and a three square Swiss No. 2 file to bring the sides down towards the vertexes:
Once I'm reasonably happy with the shape, I swap to needle files. These are mainly used to reduce the diameter of the vertexes and smooth everything up:
These cutouts have a matching one on the other side, so I do them both at the same time, doing plenty of measuring to ensure they match. The final step with this lug is to round out the cheeks a little to soften the look. Here's how it ends up looking along with the lower head lug, which I did previously: