A bit of a milestone reached this evening as it’s almost ready to reassemble. I just need to cut some lengths of M6 studding to fasten the bottom slide bars on with. Then once the basic carriage is reassembled and fitted on the ways, I need to mark out, drill and tap the carriage lock before reassembling the cross and compound slides.
There wasn’t a lot of depth and I wanted them countersunk to retain as much cross slide travel as i can also I doubt if these will ever get unscrewed again once finally fitted so I used M6 button headed cap screws instead of the usual deep headed type.
This is what it will look like when all fitted together.
The end support piece and the bottom of the carriage lock are made from the same piece of bar (eBay purchase) and must be free machining as recommended by Mike Evans, because they machined, drilled and tapped so much easier than the steel that I made the other parts from.
Next comes the most daunting part so far, machining the carriage casting to square up the cut outs in each side to take the extension pieces which will support the carriage stop.
Being a casting, the very nature of it is rounded corners and rough finish. At the very least the faces needed flattening to take the machined block which is to be let into each cut out. As I was studying the cut outs to determine how best to machine them, I noted that at the side where the inverted V was machined into the base there was a distinct slope to the edge of the cut out.
When I check this with a protractor it was almost 80 degrees. There wasn’t enough casting left to make this edge vertical without cutting into the inverted V so it made sense to machine this edge to 80 degrees. I reasoned that cutting the opposite edge to the same angle would also help relive any potential stresses on the M6 screws that I plan use to fasten these infill blocks to the carriage, when the lock is tightened down.
I then machined the ends of the infill blocks to suit the angled cut outs.
All this was made less stressful by the knowledge that a replacement carriage casting is only £23 plus P&P.
Although I have been waiting for delivery of various bits of metal and fixings which have been trickling in over the last few days (I have everything I need now, I think or should that be hope). I haven’t been idle.
I got the stainless steel lock nuts for tensioning the Gibs on the two slides and managed to get those ready to refit.
The last photos also show an anti backlash nut/block which I hope will take out the backlash from the cross slide lead screw. It’s an idea I got from the US YouTuber that I mentioned (username of Dr Jim) who made his from oil impregnated bearing bronze. I looked into getting some and nearly had a heart attack so settled for testing the concept in acrylic as I had seen another person do who had fitted anti backlash blocks to a home made CNC Mill.
Whilst making the anti backlash nut/block was quite simple. Finding out the thread size/pitch was a bit of a challenge and I am grateful to members of the Model Engineer forum who between a few relies gave me the information that I needed to work it out.
Why was it so difficult you might ask. Well, I have previously mentioned that the machine is imperial but fitted with Digital Read Outs on the cross slide. From what I have read, when fitting the DRO kit’s the lead screw is replaced as part of the upgrade. I rang Chronos who are the supplier of DRO kits in the UK who told me that the lead screws included in the kits are metric. On this basis it seemed logical that the cross slide leadscrew may in fact be metric.
As you might imagine a query on the ME forum elicited quite a few helpful answers and a few less than helpful ones thrown in for good measure. Ultimately I was pointed in the direct of a US site and advised that some of the machines actually came factory fitted with DRO’s and they retained imperial lead screws. With the help of replies that were specific with information I finally worked out that my cross slide leadscrew is a left hand thread 3/8″ 20TPI. Part of my difficulty was that I had no idea of how BSF threads were actually measured as I have never had cause to buy or measure any BSF fixings. All my experience has been in Metric or for modelling purposes, BA screws etc. Where we specify the whole thread length.
A set of taps was duly ordered from RDG engineering supplies (£10.96 inc. postage) and the job was done.
A friend who models in 4mm scale asked me if I would draw up some injectors for GNR tank engines (J52/53) so in between working on the lathe improvements while waiting for bits and pieces to arrive through the post I had a go.
He provided me with an annotated photo to work from which didn’t have every dimension on it so while I don’t think that it’s 100% accurate, it’s good enough for small scales.
Of course we need a handed pair which was the last job.
For my birthday/Christmas present from my Son last year, I received a Stuart Models 10 V Stationary Steam engine Kit. Although I knew it was coming they didn’t get to visit us until yesterday so I have only just got my hands on it.
Saying it’s a kit is stretching it a bit in terms of the kits that I am used to in 7mm modelling but I don’t know how else to describe it.
Here is what you get in the box
Last but not least the hardware and sundries in the form of nuts and bolts, gaskets etc.
I had a first go at Fly cutting with the mill last night. The pieces of bar in the last post are what’s known as hot rolled steel. Hit rolled steel is the cheapest way to buy steel but you do get an outer coating of oxidisation and the edges are far from flat/square
For the two larger pieces I needed to square up the edges and then flatten one face. I had two options use an end mill or fly cut them. I used an end mill on the edges bt for the larger area it would have taken a fair amount of time to flatten it with my largest end mill with is 10mm. With a fly cutter I could do the whole area in one or two passes at each cutting depth. The other thing that appeals to me about fly cutting is that it uses a piece of tool steel similar to a lathe tool and is something that I can confidently re-sharpen in the workshop on the grinder. I have no means of re-sharpening end mills so they become quite expensive consumables.
This is the fly cutter in action, it was spinning at 740 rpm and I was taking off 0.04mm per pass