Chapter 4

Top Plane facing, detent hole, buffer tube threading

Finally got a chance to sit down and write the program for the top plane. I also got my ER-16 spindle in for my Taig mill and am loving every second of it. If you have a Taig and don't have the upgraded spindle, get it! You'll be kicking yourself for living without it for this long! Now I am finally able to use 3/8" cutters with some real cutting speeds and not have to worry about chatter.

Now onto the good stuff. For the top plane I drew a basic solid of what the top plane looks like from the left side of the lower reciever. I then imported this drawing into my CAM program and wrote the tool paths. The first revision took too large of a cut and kicked the forging out from its fixture - I had removed the locating pins for some reason on this one. So I backed it down 50% and changed some other parameters of the operation and now I'm getting a silky smooth surface on the top plane. Its really amazing how much the ER-16 spindle improved the accuracy and performance of the Taig.

As I said in Chapter 2 I chose to do the operations in this order to suit the machinery I am working with. Having done the shallow magwell and FCG pockets earlier really helped the top plane facing operation. True, you do have to do the same setup twice, but I feel that this is the best way to do it given my machinery. If you're working with larger, more capable machinery, by all means, do it in the least amount of setups!

Here's a pic of the top plane operation setup on the mill:

Chips flyin'!

Another great advantage to the ER-16 spindle is the runout, which is practically zero. I haven't measured it yet with a dial indicator, but a buddy of mine that has also upgraded reported that his was less than a quarter thou! The surface finish really reflects this too.

Smooth as glass!

The buffer detent hole is pretty straight forward. Only "tricky" thing about it is that it sits at a 6 degree angle. Nothing that some trig calculating and shimming can't take care of. Luckily enough, with the height of my vise floor, and the length of the set up blocks, I just needed a 2.125" shim on one end while the other end rested on the vise floor. A 1-2-3 block and a scrap piece of 1/8" plate took care of that and pretty soon, bam! A buffer detent hole! I also chose to drill the detent hole before creating the threads in the buffer tube hole. This made starting the hole very easy as compared to trying to get the drill to start a true hole on the crest or valley of a thread - wherever the hole ended up needing to be placed. I didn't even have to use a center drill to get the hole started. Just a 1/4" drill and a G84 command took care of it.

Side note - I also had to make a drill chuck adapter so I could use my existing Jacob's chuck with the new ER-16 spindle. I just took a 3/8-24 grade 8 bolt, cut it down on both ends, turned a piece of round stock true in my lathe, tightened the Jacob's chuck onto the stock, threaded the shaft into the rear, made a center drill, chucked a live center in the tailstock, and turned the shaft true to the Chuck's axis. This keeps the runout nice and low for a true drilled hole. (Still need to measure it with a dial indicator) Since the ER series collets are full collapsing, the OD of the shaft wasn't particularly important, as long as it was within the range of the 3/8" collet it would be fine, and it was. Now I just chuck the Jacob's chuck into the 3/8" collet, and tighten her down. Simple!

Here's a pic of the 6 degree angle setup:

And the drill chuck and adapter in action:

Now onto tapping the buffer tube, which is again, pretty straight forward. Now here's a glimpse of the setup I was going to use for making the 1-1/8" buffer tube hole on the lathe as mentioned before. Using some shims to get the correct height to be centered on the buffer tube hole I then used the cross slide to center it horizontally. Used a tap guide to guid the 1-3/16 16 tpi tap supplied by William at The Tannery Shop to create the holes. Thread milling would have been a nice alternative to this method along with a good learning experience, but since I don't have enough Z clearance on the mill, I would have had to tilt the spindle 90 degrees, retram it, and do some trickery with programming thread milling on a different plane, both of which I have never done before. So I took the easy way out and just used a tap. Cutting these threads required quite a bit of elbow grease. I couldn't imagine tapping the threads any other way than with the reciever firmly locked in a machine with a centering guide of some sort on the other end.

The setup:

Buffer detent and buffer tube hole threaded complete!

Next stop, hoggin' it!