This started almost a decade ago when I worked at a machine & engineering shop. I made a jig to hold the TB in their big lathes, but I had nothing big enough after I quit. I never refined it to the stage to make the plate properly until recently.
I made a new jig for my little lathe to hold a Honda throttle body (D/B/H and K). It allows me to center the TB, thin the brass sheet I use for the throttle plate, and even cuts the throttle plate with a bevel on the ends. I first used it to make the tb-manifold adapter plate for my K20A PRB manifold to seal a B-series throttle body perfectly. After that I made my first 64.39mm throttle body plate.
The center cylinder is removable when I bore the throttle body. When I cut the TB plate, I test the fit by slipping the bored TB over it. If it's too tight, I shave the plate another thousandth.
This TB was bored years ago with a crappy bit at the machine shop, but the plate was cut on my new jig. Future TB bores will be much smoother.
Here's the bevel, which is about a 6.5 degree cut. Stock is about 8-9 degrees, but the larger bore at that angle would put the plate past the first EVAP hole (bottom nipple in above pic). The gap around the plate is less than a human hair, and there is no sticking since the edge of the plate sits flat against the inside bore.
FYI I don't plan on boring TB's for anyone else, it's not worth the time. Maxbore's service or 68-70mm Omni TB will be a better deal for most people anyways. I made this primarily since I needed to make a thin TB spacer.
Author
Topic: Throttle Body boring jig (lathe) (Read 8022 times)