Tuesday, 22 May 2018

The new TR1 engine - tooling up, making a head fixture for skimming and milling (part 20)

Making the fixture to affix and also align correctly on my milling machine was one of those projects which I totally underestimated. The key problem is, that the cylinderheads on Yamaha XVs are case as one piece and don't have a valve cover in the common sense, which means I had to come up with a fixture to be able to fly-cut after welding them up.

Open the stage for four 60mm tall, 30mm diameter pieces of aluminium roundstock. 

Of course they had to undergo some surgery to be usable. Interestingly enough all came out within 0.10mm of each other in length, after just some eyeball measuring with a caliper. Before they are actually put to use, they will faced off once more.

All the posts had to be center-drilled and tapped M6 on both ends.

Have you ever wondered how you can hold a piece, when you can't use a bolt and nut to hold it down ?

Basically what I am doing here is applying the idea of an ER-collet in the opposite direction. So I sliced the stud and used the countersounk bolt as a spreader.

And as you can see, as the studs are turned 0.10mm undersize, about a quarter turn is sufficient for them not to go back into the hole.

Now this is all nice and dandy, but... this is not how I want to fix this to the milling table. So a baseplate was due.

Of course a mandatory "lifting" test was due and even without extraordinarly tightening the 4 spreader bolts it was an easy-peasy affair to lift the head up from the bench. Next up is some more trimming of the baseplate and then make some alignment pins, so taking the fixture of the mill and putting it back on is a quick affair that doesn't require the usage of DTIs or the like.


  1. Great thinking and execution!!!

    1. Thx, there's been quite a bit of extra progress already, but I gotta go through the pictures and finish some more steps, so it's a closed chapter and I can actually report some findings.