Here we go again . . . MK4

[routercnc]

I managed to finish off the remote grease extensions. The threads were tied up so the grease nipples now sit flush on the end of the tubes:


Then machined 2 flats (8mm AF) which were aligned to the flats on the grease nipple. This is to allow the tubes be inserted after the bearings are fitted, making it easy to fit/remove the Z axis - something which might happen quite a lot when setting the machine up:


Here they are complete:


The single straight one (left side) is to service the lower bearings and is fitted to each unit as required, then removed.

Then onto the Z axis. These are the large side pieces, each 30mm thick. I'm machining them as a pair to get whilst I get them to size. Outer dimensions on most edges are critical as they will hold a pair of Z axis rails and need to be parallel, true, and hold a tolerance on the dimension.

They are too wide to go on their side on the bed or vice, and too thick to sit flat on the bed, so had to set them up on the edge:


Dialled them in roughly to avoid having to machine too much material away


Tops machined flat - left a tiny bit next to the vice which I filed away by hand:


As the parts were too thick to machine the ends, I marked a datum on the left end (+0.5mm longer than final dimension), and one on the right end.


Then set up a parallel edge. This was so I could flip the parts over and rest the machined edge against this. Took a long time to set it all up and be sure it was good, but them machined the other side.


I was pretty relieved to get to this point with both edges parallel and part to size (96 mm). However what I didn't know at this point was that this new top surface was actually on an angle and it was more like 95.7 mm (!) on the other side. Don't know if the fixture slipped during machining or what. But it is out by way too much for the linear rails.
I think my recovery plan will be to re-machine both parts to 95 mm (1.0mm underside) , and then use machine epoxy behind one set of bearing carriages to fill in the ~1.0mm gap. This might turn out to be a blessing in disguise as this will ensure perfect alignment.

Then onto drilling and tapping the holes. Not much to report here, standard stuff tapped to M5. But I did make this tap guide from a bit of aluminium round. The last part of the hole is tapped to M5, then there is a 6mm clearance. This guides the tap into the thread perfectly. Might make so more for other sizes:



I didn't get a picture of the last ops but I basically machined the ends to final size using the datums machined on an earlier op. I had to flip the part to do both sides.

Once I sort out the edge machining problem, there are some straightforward holes / counterbores to come, then I need to figure out how to machine some detailed features onto the ends. I think I will cut a hole in the table the machine sits on and poke most of it through into the draw space underneath.
The final op after that is to drill an 18mm clearance hole about 200mm long through the centre of the part (ballscrew sits inside). I think I'll do that on the lathe . . . bit more thought required.