NSW 'B' class mogul

[Roger]

Hi David,
Good progress then, and I agree with your cautious approach if you think it's going to go badly.

I'd dispose of the 15% Silver Solder, I can't see you'll ever use it.

I'm not sure that it's necessary to machine sheet metal brackets after Silver Soldering. Getting them right before Silver Soldering is usually enough. I'm not sure why you're 'cleaning up' with a Ripper, they're roughing cutters that don't leave a good finish unless you have a very small overlap indeed. You need a conventional milling cutter for that sort of operation.

[David]

The 15% was for caulking larger gaps in the boiler. It's no good for anything else and certainly doesn't work on steel! I made the same mistake on my 0-4-0, used it to solder the valve rods together and they broke in service. I didn't know it was unsuitable back then and had bought that lot it because it was so much cheaper than the good stuff.

I only used the ripper because it could go the full depth in one pass and nothing else I have could do that. As I said this part can't be seen so the finish doesn't matter as long as it has been brought back to square. A rub with sandpaper has made it 'good enough'.

[JonL]

Jan 22, 2019 20:56:16 GMT David said:

...As I said this part can't be seen so the finish doesn't matter as long as it has been brought back to square. A rub with sandpaper has made it 'good enough'.

I think I just heard Roger faint!

I'm halfway between you two; I like a nice finish even when the item can't be seen, but I won't spend much time making something pretty if it doesn't gain me anything.

[David]

Today was window rim day. I spent many hours on getting toolpaths how I wanted them and thinking about how to hold the stock down on the CNC machine, but eventually it occurred to me that these being round the lathe was probably the correct machine to use. And I thought I'd try them in steel rather than the hopelessly expensive brass I bought the other day when I was still going to do it on the CNC mill.

I made the first one to check the sequence of operations before I photographed the second one.

So, after cutting a blank and using the first part as a check to see it was a good right size it was off the the mill, obviously!



First to square up one side with an edge from the original stock because the tracking on my bandsaw is way off.



Face a flat surface with the just milled straight edge against the fixed jaw.



Drill a hole in the middle just clearance size for an M12 stud.

Trim the edges on the bandsaw.



Finally to the lathe, making it round and leaving it a bit oversize.



And face it off to give a second flat face and leaving it a bit thicker than finished size. One hour at the end of this step.



Now start enlarging the hole in the middle. First with drills, up to 20mm - the biggest I have.



Then with a boring bar. The lathe has about 40mm bore in the spindle and I have to go to 56 at this point so I put the topslide all the way forward, touch the tool to the chuck and then bring the saddle back a tiny amount, checking it isn't touching by moving the chuck by hand.



This leaves a thin foil to break off on the inside.





Put the chuck jaws on the inside and bring the outside to size. Again touching the tool to the jaw and using the topslide to leave a tiny remnant of material to file off the perimeter.



Checking with the cab side as it gets close. Also a lot of fiddling trying to get the depth of the step correct. Two hours now.



After turning the chuck key the wrong way, stretching the part so it isnt' as nice a fit anymore (did that to both!) and cleaning it up with a file it goes back inside the jaws to have the bore enlarged until there is about 0.5mm wall thickness of the part that goes through the cab window. This is the only part of the sequence I'm not happy with as I can't get the part concentric on the move from outside to inside the jaws so the wall thickness will be a bit variable.

Using the usual trick to not cut into the chuck.



This takes a long time with light cuts and constant checking of wall thickness.

Close enough and now more filing and fitting to get it in the window.





I went to start this last night and found the 'reversing screw alignment tool' half-finished in the lathe so had to get that done first. So that's in the photo too, with the screw bracket sitting in place to see if there is sufficient clearance around it. Three hours for each side. I thought the second side might have gone faster, but it was 9:00 - 12:00, and 13:00 - 16:00.

[JonL]

Can't argue with the results, lovely.

[Jim]

Lovely work David. On another tack that's an interesting mod you've done to the Hafco band saw's table.

Jim

[David]

Thanks guys. I'm pleased with them.

The bandsaw table is a piece of scrap I took out of Bruce Beasley's scrap bin. The only thing I did was cut the slot and drill the holes, so there is no special reason for the shape other than that was the shape that came out of the bin.

It has a larger area and is stiffer than the original is much better to use.

[Jim]

Bruce is a great source of all things handy.

Jim

[David]

I drilled and tapped a hole in one of the eccentric straps to drive the lubricator, a job that's been waiting for a couple of months now. So I think I can put the loco back together now if I want to.

I couldn't live with the eccentricity of the wall thickness on the window rims. They just weren't good enough.

I didn't have any steel bar of a large enough diameter but I did find a short end of 63.5mm brass - exactly what I should have used. I hate using brass because it's so expensive but I'm going to have to get over it or it will just sit unused anyway, an even worse use of the money!

So 45 minutes later I have two much better window rims. I left the walls at 1mm because that looks more like the photos.

[Jim]

They look the good to me David. The portholes were such a feature of many of the NSWGR locomotive cabs that they do have to 'look right' and yours ceratinly do David.

Jim

[uuu]

By using the brass, you've wasted the steel, which is a lot cheaper.

Wilf

[David]

Thanks Jim.

I guess a trial run showed me I preferred the thicker rim.

I'm wondering if they're sticking out a bit too much this time but I've just looked at my father-in-law's P class and the rims on that are both thicker and stick out about the same amount. The black paint seems to subdue them a bit so I'll try and move on to the next bit.

As you say Wilf, much better to waste the steel on the 'one to throw away!'

[David]

Soldered the reversing screw bits together today. I like to think it looks better in real life than the photos show it.

It was done in two steps. First the bigger bit was soldered at the back, then the alignment rod was put through to hold the front piece in line and that was soldered on.

A couple of hours in the acid and it came out looking sludgy and brown and I was worried for a minute but the sludge mostly wiped off with a rag.

[Roger]

That came out well, a good result.

I'd caution against leaving anything made from Steel that long in acid. I've scrapped a part in the past that ended up with deep etch method that were too bad to clean up.
If you completely cover every part in flux, you will only need to soak it in water to remove it. You only get the black oxide where the Steel is exposed.

[David]

I lost a part too when I forgot about it. Luckily it was just a handrail bracket on the tender.

I had your comments about covering the part in flux in mind when I did this but was worried the solder would go everywhere and be too difficult to clean up. There are a lot of corners I can't get into on this piece.

[pclass]

Nice work David, I used Brass when I made my window edges, I agree there was a lot of waste but that's what I wanted in the end cheers Dennis PS my engine is a 32class

[Roger]

Jan 28, 2019 22:29:16 GMT David said:

I lost a part too when I forgot about it. Luckily it was just a handrail bracket on the tender.

I had your comments about covering the part in flux in mind when I did this but was worried the solder would go everywhere and be too difficult to clean up. There are a lot of corners I can't get into on this piece.

I wouldn't worry about that. You can always paint around the areas with Tippex if necessary. If you only put just enough Silver Solder in scraps around the piece, there won't be enough to go far anyway, and it will be a wafer thin coating if it does run. Cleaning that awful black Oxide is something I avoid at all costs.

[David]

Thanks Dennis. I bored in all of 15mm so in the end it was ridiculous trying to 'save' the material - the short length is barely any shorter!

I'm just glad I didn't do the ineffective 6 hour process using the 5 x 72mm brass I'd bought because that would have been the same as tearing up $30.

[David]

The plan for today was to drill 4 clearance holes in the bracket that the reversing screw sits on that allow the screw to be bolted to the bracket. That plan lasted about one minute in contact with reality.

I put a square against the faces of the bracket that bolt to the cab to be sure they were okay and they were not. So a bit of milling and filing and they didn't seem much better. I think using steel angle for these two faces is stopping me from being able to machine it them properly square, or that's my excuse. Being heated up bright read a few times might not have helped.

So I made a new one from from 3 x 30mm steel strip. Took a couple of hours but it is better than the first one. I used a 90deg welding magnet to hold over-long strips in place while soldering. I had to shim two lips of the magnet because of course they did not hold the steel strips perpendicular to the 'ground'. 0.5mm brass did the trick.

Back to the original job of the clearance holes, double checked all my numbers, fixed the misunderstandings, confirmed on the 3D CAD model and drilled the holes. Tapped the holes in the fabrication the reversing screw runs in and they went together nicely.

While looking down the length of the whole thing I convinced myself the front bearing part (that one I did on the CNC machine a couple of times) did not seem to be lined up properly with the rear one, and didn't looked centered on the I beam that goes between them. Either it moved after clamping it down with the 'alignment tool', said tool was eccentic, or warped while the soldering was being done.

I unsoldered it, cleaned everything up, scribed a center line on the I beam and lined things up by eye before resoldering. I think it's still off but hopefully better than before. If I knew how much it was out I could make an eccentric bush at the rear where there is some room but I might just make the front stub of the screw undersized enough that it rotates smoothly.

2.1 steps backwards and 2.1 steps forward! While I now have the holes to attach the screw to the bracket I now have to drill the holes in the bracket that allow it to be attached to the cab, which had already been done on the old one.

After those holes are done I might try milling or grinding a square thread cutting tool. Asking the expert today he said a square thread would be fine as opposed to an ACME thread which I have no hope of grinding a tool for. Square flanks should be easier to grind. I bought some 4mm round HSS last year for this threading tool.

Will a carbide cutter cut HSS?

[David]

I decided to put the loco back together a few days ago. This is the most "complete" it's ever been with the cab screwed on. I forgot to put the buffers on and I don't think I've made a drawhook for the front yet. While doing this I made the bracket that holds the little brass 'thing' on near the brake cylinder, another job that's been waiting for a few months!



This was done as a bit of a morale boost and to check the fit of the reversing screw mechanism. Sadly the firebox is about 10mm too wide! This means I'll need to do at least the firebox cladding before I can figure out the final location of the reversing screw. It also means the loco will look less like the prototype than it already would have with the firebox being far too wide compared to the barrel. I'm not too put out by this because I'd never know if I hadn't been told.

The cab barely fits within the rivets on the running boards - there is absolutely no gap there - but it does fit.



I had a go at making a square thread cutting tool the other day too. It's 4mm HSS milled down in with a 6mm carbide cutter that had the end blunted on the CNC machine but is still fine further up the sides. This is a square thread, not trapezoidal - I have no hope of grinding or cutting anything else. The holder is a piece of hex with one side milled down for the clamping screws. I tried to buy an ACME thread cutter, but the prices are insane.



The first effort in brass was poor but consultation showed I needed to grind more off the front so it didn't rub. I'd left a flat there for strength. The tool may also have been too high, I was having trouble seeing the centre of the brass rod. I also ground the lower part of the front away so less cutting tool was in contact with the work in case that was a problem.

Tonight's efforts were much better but unfortunately still not good enough for the final product.

First I tried a single start right handed thread. This was encouraging although the thread crests and roots are different widths so there is an immediate problem with the cutter or it's helix angle setting, which was just a guess.



Next I tried a double start right handed thread with a normal 60deg tool to ensure I had the technique correct where you move the compound slide forward half the lead cut the 2nd start. It looked about right, and I was very pleased.

So left hand double start time. I scratched a single lead with the normal threading tool so I could see the helix angle. I used some type of measuring instrument with two legs - one on the bed of the cross slide and the other rotated until it lined up as well as I could judge with the scratch on the work. Then this was put next to the cutter loose in its holder and the cutter pressed against the leg to get the same angle.

The result wasn't as good as the first RH single start. You can see the crests on one of the starts are significantly thinner than the other. This is 8mm with a 3mm lead, so 1.5mm pitch.

Could it be I didn't get the top slide adjustment correct?



The tool isn't as good as it could be either. It's 0.75mm at the tip, using guessing sticks, which I thought was pretty good. But it's more like 0.85 or more not much further back which won't be helping.

However, for a first attempt at this stuff it went much better than it could have!

The bigger challenge will be creating an inside threading tool to cut the nut. I'm not convinced I can make a tap. At least this is a square thread, not ACME or trapezoidal, so the flanks are at 90deg or as close as I can get. But it's a small hole to fit a cutter into - about 7mm! So not sure what to do there yet.