Thursday, November 17, 2011

Finishing the steering stem

It was way back in July that I turned the blanks for various length steering stems.  The various lengths allow me to adjust the amount of dive that happens under braking.

Here's where we left these parts:

Now these parts will be brought to the 4 axis mill and have the pivot holes and clamping faces machined.  then i'll switch to another setup and trim and chamfer the ends.

The first step is holding the parts in a 3J collet on one end and with a dead center in the other to ensure the part axis is coincident with the mill 4th axis.  That means that the zeroth step is to align the dead center to the 4th axis.  I machined a round adapter that helps greatly in this process:
I then remove this mandrel, reinstall the dead center quill and then clamp a part:
To check the alignment I held a .0001" indicator in the mill spindle and rotated the 4th axis.  the part was within .0003 TIR, which is an excellent runout for a 2nd operation clamping.
Now that the part is properly clamped and in alignment I can machine the features that mount the upper and lower control arms.  the machining is 4 pocketing routines and 2 reamed hole routines ending with the almost complete part:
Repeat this a few times with appropriate modifications for the various lengths and i have a bunch of useable parts:
Now there is a simple cleanup operation to do on each side to round and smooth the ends.  The part is held in the 4th axis in a 3J collet with the end just sticking out.
I profile the end, then chamfer it and repeat for both ends top and bottom:
The finished parts are pretty sweet lookin:
 Especially when assembled in the spider:
That's one more part to cross of the to-do list.  The front end is starting to take shape, i'm only missing the control arms which are next on the list of complex parts to do.  I may try to squeeze in a few simple parts before that, let's see what the next week or 2 bring.

That's all for now.

1 comment:

  1. Really nice parts Chris. We finally get to see the front end coming together. This seems to be what this project has been about from the beginning and it is reflected in your well thought out spider/steering stem/fork leg assembly. Easy to swap out to a different state of tune for the mechanic and even the novice mechanic at a track day.
    Keep on Truckin',