HB2 Construction

The PPEX as I dubbed the PDJ kit was designed for constructors who do not have a metal mill or lathe available. Phil does the necessary machine work and has a work around for other things like large holes. Since a machine shop is no problem here at THMS, I can do some machining a little more professionally.

Here I am spot drilling for the 3/4 in hole for the Z axis screw bearing. The other holes seen here were done on a drill press. Once I spot the center the X and Y are never moved. I have a way to remove, test fit, and replace the part in exactly the same place without moving the axis. Yes, it can be done.

After the spot drill, I drill a hole large enough to clear the boring bit. Drill bits do not bore round holes. The holes in fact are generally three side. Drill bits this long whip around like wet noodles without a starter spot.

The boring head is inserted without moving X and Y axis. I prefer to start slightly over the diameter of the clearance hole so the tool isn't hitting the high spots inside the non round hole.

The first pass has started and I increase offset 0.020" each pass which is 0.040" removal. The scale calibration in the boring head is accurate enough to get close. I check the ID with my dial caliper. I can remove the part and replace it by loosening the vice jaw if I have to. I point the tip of the boring tool to the right and just touch the right side of the hole when re-tightening the vice. Works for me.

Here I test fit the 3/4" x 1/4" bearing without removing the part. The bearing is stuck here because it is so crooked but it is a light press fit into the hole which is what I was attempting to accomplish. It was all the way in and I am trying to push it up from the bottom. No can do but this hole was done anyway. I bored two more holes into this part with a very tight press fit for the 1/2" guide rods . Success!

These parts are too big to hold in the vise. This is the gantry side where the stepper motor will be installed. A 3/4 hole is need here for the bearing.

As with the smaller parts I start with a spot drill and then drill a bigger hole to clear the boring tool.

There is a little blur in this photo as the mill is running. As with most milling operations, the setup takes longer than the actual cuts.

I am taking a measurement. I can always take away more but extremely hard to put back if I go oversize. The reading here is 0.627". I am looking for 0.750".

This is a different cut. Just a slot with a rounded inside end. Here I am dead center over the spot. I set the hand wheel at zero and made the first cut backing out toward the camera.

Almost finished. All cuts after the first were inward cuts stopping at zero on the hand wheel dial. The suggested process for folks without an end mill is to drill the hole then make saw cuts to the sides of the hole.

Finished, and you can see the very clean cut that was made. I made two more of these cuts on another part. Yea-boy! Real machining!

The assembly of all the HB2 parts that need assembly! :-) What I have left to do is the fine detailing, draw filing the edges, final deburring. Good job for tomorrow...