Set up for "top side"

As I seem to have completed the bottom side operations without perpetrating any further outrages, it's time to set up the work for machining the top side. This entails roughing out and finishing the cavity between the cylindrical bores to form the space for the drive belt and tensioner pulley. There will also be some tapped holes for fixing the cover in place and some edge breaking / chamfering to finish it off.

As before, I will use the 3/4" hogger to rough out the bulk of the material, followed by a finish operation with the 10mm long series carbide end mill. With the cylindrical bores already machined, it shouldn't be such an issue clearing the chips out of the way. I now have my Jeton coolant hose system, so if I can arsed to get around to fitting it, I'm hoping it will be easier to place the coolant streams where they are useful and end up with less of it on my clothes.

The WCS zero for the top side is in the centre of the large bore, coincident with the (now finished) bottom surface of the part. I know the vise is still set up at the same height as the bottom operations, so I can just go 37mm below the previous G54 Z0 plane and set my new G54 Z0 there. And I could even check that I've got down to flush with the bottom face. Previously the stock height was bang on 38mm and the bottom ops took that down to 37mm. The final height will be 36mm, taken off in 2 facing passes again. 

And like last time, I've entered the heights data for all operations into my spreadsheet to determine the best table (knee) height, along with the quill extension for the G54 Z0. Without that, it's unlikely I will magically find a G54 that will accommodate all the moves and tools within my limited quill travel range.

I suspect my T01 reference tool is too short. It has the shortest stickout in the tool table and with the operations I've specified (including T01 for setup), I'd need over 150mm of quill travel. I think the limit is around 155 but the soft limits are currently 150mm. The solution is actually to touch off on the top surface of the part (which is Z37), entering the approved coordinate there ie 37.000mm. In the spreadsheet, I simply entered Zmin and Zmax as 37. The ideal G54 Z0 height is then around G53 117mm ie with the quill moved down 117mm from top position.

The G54 X0 & Y0 origin was set with my Martest (Haimer clone) indicator. Only needed to use it in X and Y, having already frigged the Z as detailed. Obviously, being the most expensive tool in the rack this is tool #13 but despite that, today it lived to tell the tale.

There we go - positioned at G54 X0 Y0 Z0:

Almost ready for action but first, set up the heights so that the top surface is 37mm from the base, not 36mm, otherwise it won't machine the required 1mm from the top surface.

Job done. On with the facing op:

Interrupted by a phonecall. This is the end of the finishing pass:

Done. Now support the overhanging end of the part, ready for the roughing op. It's noticeably weaker now that I've hogged out the large cavity. Obviously it will be a reasonably smart idea to remove the clamp before I do any more operations at the end of the part. Operation 6 (3.5mm drill) might be OK but operation 10 (1/2" chamfer) would most likely be an issue....

All this up-in-the air stuff might seem a bit bizarre. The reason the machine vise is perched on 5" parallel blocks is so that the machine guards don't hit the underside of the head or the controller console. Having said that, a lot of the swarf and coolant ends up going over the top of the guards anyway. So, with the loss of rigidity that results from lifting the vise up in the air coupled with the questionable effectiveness of the machine guards, I'm wondering if I may be better off doing away with them and making do with some bastardised shower curtains instead. What I really need is some of that clear, heavy PVC curtain stuff they use on retail refrigerated displays and industrial doorways. Must check out ebay.....