Pop Quiz 2 Update 4

chorl

Now that the lathe is better equipped to produce shiny, round objects, it was time to get back to work on Pop Quiz. Having a better tooling stup dramatically improved efficiency, and I was able to complete the motor mechanics today. Now I just await my SDP-SI order for the bearings and some shoulder screws.

Oh, and I also discovered that the lathe does indeed have back gears. They were rather well hidden, but now the operations which need <180 RPM at the spindle can happen

Boring out the 1/4″-walled steel tube to form the motor can, using the not-boring-bar.

A stiff toolpost does wonders for surface finish and accuracy. Here’s the finished can.

Next up was the motor mounting base and the hub for the can. I dug up the micrometer depth stop which helped stop the carriage at a repeatable, set distance. This meant I could manually feed using the carriage handwheel and not the compound slide, which eliminates the risk of accidentally cutting a taper. A DRO would make this unnecessary, but…

The mounting base begins to take shape… The same shape as the first try, but with provisions for mounting two stators stacked on eachother.

After cutting that part off (with a real cutoff blade!), I started working on the can hub. This involved two precarious internal boring operations. The larger one I could take care of using the not-boring-bar, but it couldn’t fit into the 1/4″ starting hole for making the circular bearing pockets (which are only 3/8″ in diameter anyway)

I should have bored these small holes on the milling machine, but instead I took the risk and used a 3/8″ endmill in the tailstock chuck. Oddly enough, it came out way *UNDERSIZED*, at .365 or so. This is weird. Very, very weird. What the deuce?

The three completed pieces after processing. The can presses onto the hub, and is retained by a healthy dabble of green Loctite. The whole thing sits over the mounting base, and a shoulder screw threads through the hub and into the mounting base to keep the whole thing together. I didn’t make the exterior mounting ring as seen in the 3d drawing yet.

Next steps: make the exterior mounting ring thing, as seen in the 3D rendering. Make a fixture for the UHMW slab chassis, then machine it. Get some carbon fiber and make the cover plates. Wait on Banebots and SDP-SI for the load of internal parts.

Now that I have at least part of the machine tools I used the most before, things should go much smoother. Dragon*Con 08 will be here in no time…

Ghettopost II.5

chorl

The second half of that aluminum billet was just sitting on the mill with the “make something using me to end your pains” look.

And so I did. Now introducing the other Ghettopost: a cutoff tool holder!

For the uninformed, the MITERS lathe has no parting /cutoff tool holder. As addressed in my Intro to Ghettomachining post, the only way to get your part off the stock you started was by hacksaw. Some would dismount the part and hacksaw it manually. I usually just slammed the hacksaw on the stock, with the spindle running, and slice it using power.

Either way, it wasn’t fun, nor particularly safe. And so with the relative success of my Ghettopost II from two days ago, I decided to complete the square blocks of aluminum and make a cutoff tool holder.

Using lessons learned from the turning tool holder, this build went much smoother and with more accuracy.

Sketching the outlines of the finished part in lieu of a full drawing helped alot. This was the other half of the giant aluminum billet that I bandsawed in half. First step was to shorten the height to 1.5″. For this, I used the giant shell mill, doing it all in one .400″ deep pass.

After the block was planed down to height, it was time to mill top features. The “stairstep” shape is to hold the tool as well as a clamping bar thing to lock it firmly into the holder. The large hole was started with a 13/16″ drill and then finished off to size with a boring head, just like last time.

After the top features were machined, I turned the block around to drill the horizontal clamping hole. Then around to another side to mill the Slit of Clamping. Finally, I flipped it over and cut 5/16″ out of most of the underside.

The reason for doing this is because the cutoff tool is a very tall and narrow tool. I sized this post according to the remains of a 3/4″ cutoff blade that I found. Because its cutting edge is correspondingly 3/8″ higher than the highest I accounted for. As a result, the tool has to sit lower than the flange on the 1″ post I turned.

The solution was to raise the contact surface of this holder to account for the increased height of the tool. The cutout is 2 inches square, which overlaps the 2 inch diameter flange and allows the little step at the bottom to hang off the edge of the compound slide.

After the holder body was done, it was time to make the clamping bar. This would have taken a few minutes if I had some 1/2″ steel square rod. Unfortunately at MITERS, everything is around when you’re not specifically seeking it out, but I couldn’t find a single square rod near half an inch.

I had to settle for a very odd-looking .5″ thick, 1.25″ wide bar. After taking a few test cuts, I realized it was stainless steel. Oh boy, work hardening. Slow and steady was the answer here, and I somehow trimmed this chunk down to 2.5″ long x .625″ wide x .375″ thick.

The complete clamping bar, with holes drilled. The first hole was accidentally drilled for a 5/16″ clearance because for some reason I thought I was using 5/16″ screws. Fortunately, it does not affect anything, as the tool will point out the other way.

The clamping bar reaches over the tool bit and has a little lip on the edge to prevent it from tweaking sideways.

And thus, with some added hardware, the cutoff tool holder was complete. Here’s a video of the inaugural cut, through nothing less than quarter-inch walled, 2″ diameter steel pipe. It was great.

This tool holder uses 1 5/16″ clamping screw instead of two 1/4″ ones (okay, one 1/4″ one.) I might rebuild the other holder, or at least rethread it, for a 5/16″ screw.

Now that I’m done making tools, I can start BUILDING ROBOTS! To complete the full complement, I’d have to have a dedicated solution for a boring bar. However, most of those fit in normal tool holders, so it’s not a priority.

Oh, here’s a picture of the ass end of a liquid nitrogen tanker truck. They go around every week refilling massive (20+ foot tall) tanks of LN2 around the labs. Shortly after I took this, the driver came around and chased me away.