Warning!! Epic tome ahead.
I had the day off work today, so I got to spend much more time in the workshop.
Before I start on cutting the tapers I wanted to cut out for the gear, as you can see it will not do as it is at the moment.
Also I tried the fit of the new gib brackets on the lathe and found that the front bracket fouls the rack by just a little.
So I took about 1.5mm off that bracket and then, after measuring the offending gear as being 17mm, I used a 16mm endmill ( the biggest I have ) and made the cutout.
And here it is in place.
Now that's done it was on to cutting the tapers. In Bog's thread about Darren's lathe he temporarily glued a 1.5mm pin on one edge to set the taper, and I was going to do the same when I discovered I didn't have any superglue. So I came up with an alternative version, and verified it using my little digi-angle-finder. I used a 1.3mm drill bit to space one end ( circled in red )
Then I rough milled it with a 3/8" roughing endmill and then finished it with a 10mm carbide cutter. Then I did the same on the other bracket, remembering to get the taper going the right way.
I was hoping to mill up the gibs themselves, but when I looked through my stash-of-scrap I didn't have any suitable pieces of brass. ( I did have some that was way too big, but the price of brass is too much to mill that much into swarf )
So instead I decided to press on with another little mod, the cover for the handwheel gears on the carriage. As supplied, it looks like this.
I was going to get all technical and start measuring up and marking datums, but then I realised that I could do it much simpler. I measured the shaft to be 17mm and, after cutting out a suitable piece of 1.5mm ali sheet, I bored a 17mm hole in what seemed to be roughly the right place. Then I had to file a little radius on one corner (red circle) so that I am able to manipulate it in and one edge fits nicely under the half-nuts.
Then, while holding the ali in place, I traced out the outline of the casting with a pencil. (actually I had to do this twice as I smudged it the 1st time )
Then I rough cut it on the bandsaw, remounted it on the casting and held it in the vice and carelessly filed it to shape, and then drilled the cover for mounting screws (and gently marked the casting too)
Then it was over to the mill to align by eye and then drill 2.5mm. I was only able to get one clamp on it so I took it really gentle when drilling. ( this casting drills and taps like a dream )
I seem to remember seeing someone else doing a similar mod and they found that the gears sit a tiny bit proud, and their solution was to mill a recess in the cover to prevent the gears from binding. My lazy streak kicked in and I thought I could make it a little simpler. Both gears have shoulders to space them out from the casting, and I measured the shoulders at just over 1mm.
Now if only I had a working lathe !!! But I do have a vertical lathe, of sorts.
As you saw, I even aligned the tool with the very same ruler I use to set the toolheight on my lathe. Actually I had to do this twice as the above tool was the wrong geometry.
It worked just fine, all I needed to take off was 0.25mm from each gear's shoulder.
Then after tapping the m3 holes in the casting I was able to mount the cover.
This what it looks like in situ
Sadly the brass I've ordered for the gibs wont be here until at least tuesday, so I will have to think up some other mods to be getting on with in the meantime.
Tune in next week to see what happens.
Tim
