[smdubovsky]

Here's what I've been up to today - twin plugging my own heads. Instead of the common DIY approach of tilting the mill head over in 2-axis (which is a PITA to repeat and then retram straight), I used a large universal dividing head to machine a fixture that holds the head at the compound angle required. I even put a pair of 5/8" pins on the bottom to keep it aligned in the T-solts of the table so the translation to the 2nd plug was along the X axis (it was a B*TCH to figure out that calculation.)

The extra work at the beginning to make the fixture saves LOADS of work while doing the heads. It also allows moving the knee up/down to change tools w/o losing center. The work becomes not much more than a series of straight down 'hole drilling' operations. W/ a piloted counterbore (instead of an endmill) it might even be possible to do it all on a heavy duty drillpress.

It also turns out that all the plug angles listed on all the pelican threads are for <=2.7 heads. The 3.0/3.2L heads are different from earlier ones. Took quite a while to figure that one out. I went though the trig several times and couldn't figure out why the results were off.

Anyway here are the pics:
1&2) the fixture itself. It locates using the step where the cyls fit.
3) tap drill (after a pilot drill and bore operation.)
4) Using a piloted tap wrench w/ M12x1.25 (those things are the bomb for tapping a straight hole.) Wish I had a spiral point tap in that size though...
5) Counterboring for the socket clearance
6) inside shot. Still need to grind a small pocket around the backside of the tip.

[Rick V]

Nerd.
Looks like you should hang onto that rig. I can see it paying for itself very fast.

[Jazzbass]

Dorki style? Stephen, Dorki style would be drilling it out with a DeWalt hand drill after half a case a beer, egging the hole out with the bit, then using JB Weld to secure the new spark plug. Then wondering why it went **boom** the first time it started.

I mean really. Vertical mill? Precision jigs? That's for guys who "do it right" and "want it to work".

Nice work. What kind of mill?

[VaSteve]

Originally Posted by Jazzbass

Dorki style? Stephen, Dorki style would be drilling it out with a DeWalt hand drill after half a case a beer, egging the hole out with the bit, then using JB Weld to secure the new spark plug. Then wondering why it went **boom** the first time it started.

I mean really. Vertical mill? Precision jigs? That's for guys who "do it right" and "want it to work".

LOL!

[Trak Ratt]

Originally Posted by Jazzbass

Dorki style? Stephen, Dorki style would be drilling it out with a DeWalt hand drill after half a case a beer, egging the hole out with the bit, then using JB Weld to secure the new spark plug. Then wondering why it went **boom** the first time it started.

OK, OK it went boom the first time but once we "scored" the bore some and put a notch in the plug thread it ran... sort of

[markwemple]

Originally Posted by vasteve

lol!

x2!

[Clarke]

Nice work Stephen.

[Dr K]

Originally Posted by VaSteve

LOL!

x3

Originally Posted by Clarke

Nice work Stephen.

x2

[Lupin..the..3rd]

That's one serious DIY. Well done.

[smdubovsky]

Originally Posted by Jazzbass

Dorki style? Stephen, Dorki style would be drilling it out with a DeWalt hand drill after half a case a beer, egging the hole out with the bit, then using JB Weld to secure the new spark plug.

LOLZ! Nearly spit my coke out.

Mill is a '69 bridgeport. 2J head, chromed ways, servo X feed, sony magnescale dro. I can't easily get a rollback up to my basement doors (deck) so until I have the urge and time to take it partially apart it lives in the back corner of the office. Even fully disassembled the base is ~700# so its going to take a heck of an urge to want to move it again.