Well it's been a busy week or so here and I have been pushing my tiny Unimat to the limits (and beyond) again!
I got the aluminum linear bearing supports made but unfortunately the Unimat wasn't up to the task of cutting the slots using a burr from my Dremel (no metal cutting end mills available) so I had to resort to the old skills and cut them out by hand using a hacksaw and a flat file. I have a medical disability that leaves me extremely tired after only a small amount of effort and all that hand working meant that I had to cut one pair of flats and then go and rest for a couple of hours to recover! Nevertheless I got them done and I just need to get the hardware to mount the skate bearings.
Next up was the adjustable blocks for the rails/pipes. This again turned out to be a big task as my material was slightly wider than required which meant I had to machine them all round using a 1/2" wood router in the Unimat. Once I had them square and to size it was on to the holes (all 108 of them!)
The mounting holes were nice and easy as I set up a jig on the Unimat so that I could just slide the corner into position and drill. The only downside was the whopping 3/4" of travel on the Unimat Z axis. The material was 3/4" thick and by the time you add in the point length on the drill and a bit of clearance above the part it meant that I had to flip the parts over to get a hole that went all the way through. Thankfully my jig was spot on and the holes lined up perfectly.
The large central hole was next which meant tearing down the Unimat mill/drill set-up and reconfiguring it as a lathe. All I had to make the holes were wood cutting spade bits so that was what I used.
The first problem I encountered was the fact that I could not 'swing' the larger of the blocks in the 4-jaw chuck as the corners of the block fouled on the bed. After some head scratching and pondering I wondered just how much I would have to remove from the corners to get it to 'swing'. Out came the Exacto knife and I started to pare small amounts off one corner until it cleared the bed. As it turned out I only needed to remove 1/8" at 45° so the corners of the four larger blocks got a quick trim and away we went!
The next problem to raise it's head was the fact that the Unimat just didn't have the power to cope with a 1-1/4" spade bit straight into the nylon. This meant that I had to work my way up in size but it also meant that after the first hole was drilled there would be nothing to guide the spade bit. I also placed a variable speed controller in the line so that I could slow the Unimat down as the slowest available belt speed was way too high for the spade bits. As it turned out the spade bits ran nice and true and didn't really need the point to centre themselves in a rigid lathe set-up. The finish was very good, almost glass like, and I was impressed with the way they cut nylon. It took a while to machine all the holes with having to go up in steps of every other size but I got there in the end. It helped that the smaller blocks only needed a 1" hole too.
Once the large holes were done I had to reconfigure the Unimat to mill/drill mode again so that I could drill and tap the adjustment screw holes. After the large holes this was a breeze and only took half a day to drill and tap all 48 holes.
I have attached a few photos and have more of the various set-ups if anyone is interested in seeing what I had to do to make these parts.
If things go according to plan I should be starting on the woodwork next weekend as my buddies woodshop is finally free (he has had an active project going on and wanted that out of the way first). More updates as they are available!
Larry