NSW 'B' class mogul

[Roger]

Hi David,
These sorts of things are hard to get really neat, the eye is wonderful at seeing errors where there are things in a row!

Can't you use your CNC mill for this sort of thing? If the part can't be taken to the mill, there's nothing to stop you using it for made a drill jig so you can transfer the accuracy to the piece in question.

[David]

Thanks Kerrin, much appreciated!

Roger, plan C is to spot and drill 1.2mm holes in another strip while it is still clamped on the (manual) mill. I put it back on the mill and cleaned up the edge after I wrote the last message so I have a datum line. I've loaded the CAD drawing that was used for the laser cutting and calculated all the hole locations from the bottom and left edges of the strip. Then the strip can be cut from the parent stock on the bandsaw. I'm not in the mood to do it now so it can wait for tomorrow.

Plan D is start with a strip of 1mm steel and machine a 5.5mm strip down to 0.75 or so and then do the hole drilling performance again. That should give me a ledge to rest along the top of the cab sides while riveting that will have to be milled or filed away later.

I considered the CNC machine before I started and thought it would be over-the-top. However it is plan E, possibly D depending on how I feel. If I had decided to go that way this morning it would probably be done by now but I didn't expect it to be this difficult. There isn't anything it would do the manual mill won't fairly easily - it's just an edge and some holes in a line!

I note superglue has not been working well in this case. It is cheap no-name stuff but surely the formula is basically the same. It has failed to hold in any useful sense, with and without accelerant. Epoxy might have worked if given long enough. In either case something nasty will happen when the silver soldering is done.

[Rob]

Jan 1, 2019 7:01:40 GMT David said:

For now I've left the workshop and am pretty discouraged at how the first day of the year has gone in there. It's days like this when I don't understand people who say they find their time in the workshop fulfilling and relaxing! I like looking at bits I've finished but struggle to see how anyone actually enjoys the journey. As far as I'm concerned it was just a wasted day.

David, I know exactly how you feel. When things start going wrong for 'no reason' there's always a danger that I'll lose motivation and shift focus to one of the hundred other things that need doing around the house etc. and then the engine sits for another 6 months with no progress.

I was at a particularly low spot when I discovered my crank pins were at 45 degrees instead of perpendicular, but the process to fix the bores actually appeared to work OK and it meant I made use of the face plate which I never do, so proved to be a learning experience too. 

I also tend to find something 'easy' to do instead - quick turning jobs with fewer operations so any cock up doesn't result in hours of wasted effort. That way you get the satisfaction of a well made part and the enthusiasm levels stay high. Not to mention maintaining progress!

[suctionhose]

From my daughter's year 4 teacher: FAIL is "first attempt in learning"!

[Jim]

Totally agree. We've all been there and in my case the problem niggles and niggles away in the back of my mind. A nice cold soothing ale or two helps greatly.

I find things seem to sort themselves out overnight and the next attempt all falls into place. You'll be right David.

Jim

[Deleted]

just to echo what others have said, step away and try again fresh another day, I think you'll find that you'll be asking yourself what all the fuss was about the first time around... good luck and happy engineering...

Pete

[Roger]

Jan 1, 2019 9:51:34 GMT David said:

Thanks Kerrin, much appreciated!

Roger, plan C is to spot and drill 1.2mm holes in another strip while it is still clamped on the (manual) mill. I put it back on the mill and cleaned up the edge after I wrote the last message so I have a datum line. I've loaded the CAD drawing that was used for the laser cutting and calculated all the hole locations from the bottom and left edges of the strip. Then the strip can be cut from the parent stock on the bandsaw. I'm not in the mood to do it now so it can wait for tomorrow.

Plan D is start with a strip of 1mm steel and machine a 5.5mm strip down to 0.75 or so and then do the hole drilling performance again. That should give me a ledge to rest along the top of the cab sides while riveting that will have to be milled or filed away later.

I considered the CNC machine before I started and thought it would be over-the-top. However it is plan E, possibly D depending on how I feel. If I had decided to go that way this morning it would probably be done by now but I didn't expect it to be this difficult. There isn't anything it would do the manual mill won't fairly easily - it's just an edge and some holes in a line!

I note superglue has not been working well in this case. It is cheap no-name stuff but surely the formula is basically the same. It has failed to hold in any useful sense, with and without accelerant. Epoxy might have worked if given long enough. In either case something nasty will happen when the silver soldering is done.

My Plan A is to use the CNC machine to either make a part completely, or to make jigs or fixtures if that's not possible. No human is a match for machine accuracy, so if you want it made as accurately as possible, I'd say machine it. There's no such thing as 'over the top' in the world of tech. We can flick a light switch or say "Alexa, turn on the light" which uses the internet over WiFi and AI to process the command and then communicate with the light. Is that "over the top"... well, no, if you've got your arms full of washing!
I use the tools that will give me the most accurate result with the least effort and disappointment. I use the surface grinder sometimes rather than draw file. It's not necessary, but it's dead easy and so what if it's more accurate than you need.
I can't remember the last time I marked anything out or used a centre punch. Why guarantee it's going to be less accurate than it could be?

[David]

I'm pleased to report plan C worked, with an improvement I thought of last night after going to bed.

I drilled all the rivet holes while the stock was clamped to the mill after cutting the straight edge and I then went and made the holes that will eventually have 10BA screws through them 1.6mm so I could use 1/16 rivets to hold the strip in alignment while riveting it on.



I used the bandsaw to cut along what will be the top edge of the strip, leaving it wide so I can draw file to the top of the cab side. Then offered it up to the cab side and put the 1/16 rivets through to get the alignment. I sailed a bit too close to the wind in places with the bandsaw but I'd given myself enough leeway (extra width) to get away with it.



Then I put the 3/64 rivets in, trying to space them evenly in case that helped reduce warping and stress. I also didn't make them very tight. Then the draw filing to bring the top edge flush with the top of the cab side.



Greatly relived when that all worked, obv! It took a fraction of the time and worry it took to do the first side too.

I spent the rest of the day turning the CAD drawings used to laser cut the plate work into a 3D model and modeling the reversing screw and its brackets etc. This is to ensure I understood the drawings and to find out what I still needed to do to the cab sheets before I put them together. It is just as well I did this because I found 5 holes and a modification to the reversing screw cut-out I hadn't noticed before and a number of things I would have made a mess of if I'd just tried to make them. So it was certainly time well spent.

[steamer5]

Hi David,
Another day &a great success! Well done.

Cheers Kerrin

[Jim]

That's a good technique you've used David and it can be applied to other similar situations too. It's all looking great, I can almost hear the exhaust beat now coming up the ruling grade from Leura, where I was born to Katoomba, where i grew up.

Jim

[JonL]

Fantastic work, well done!

[Roger]

Hi David,
That's a much better result. Personally, I'd have used the CNC to cut the edge too rather than use the band saw and then file it. It wouldn't have taken much time, you wouldn't have needed to mark it out, and it would only have required a few nibs to be filed away. The more you can do on the CNC mill, the easier life is and the more accurate too.

By the look of it, you ought to be able to profile each of those cab pieces and add all of the holes on the CNC

[JonL]

Jan 2, 2019 11:14:51 GMT Roger said:

Hi David,
That's a much better result. Personally, I'd have used the CNC....

I reckon you brush your teeth and stroke the cat using CNC!

[Roger]

Jan 2, 2019 11:21:07 GMT JonL said:

Jan 2, 2019 11:14:51 GMT Roger said:

Hi David,
That's a much better result. Personally, I'd have used the CNC....

I reckon you brush your teeth and stroke the cat using CNC!

Now there's an idea.... must get a cat first though.

[Jim]

Please don't try to CNC one Roger they are easily obtained and in good working order at any RSPCA shelter.

Jim.

[simplyloco]

Jan 2, 2019 22:51:01 GMT Jim said:

Please don't try to CNC one Roger they are easily obtained and in good working order at any RSPCA shelter.

Jim.

Of course he can: he just goes to the Cat Neutering Centre...

[Jim]

Nuts to that idea John.

[David]

I thought the front reversing screw support would be ideal for the CNC machine so did the programming last night and got started on it about 8:30 this morning. I've just come in at 16:30!

I started with a rectangular piece of stock but didn't like the thought of holding the finished part to mill the back off it, so decided to try Roger's part on a stick idea. The backplate on the chuck is for mounting it to a rotary table and the holes in it do not line up with the t-slots so I used the clamps that came with the vise to hold it down. It seemed ok.



It went to plan overall but there were a lot of speed bumps along the way and the finished result is almost but not quite good enough due to the parting off marks on the back which is sadly the visible side. I've filed and sanded it but they're not going away and it's getting a bit thin! I'll just live with it because I don't have the cutters or patience to do another one. The finish on the other side is rubbish too but you can't see that on the finished assembly. The finish around the edges is excellent.

The first 6mm cutter was blunt so after it had gone for about an hour I changed it for another one I hoped was sharper. That one was worse and after about 90 mins I noticed the part didn't look as deep as the DRO was saying the Z axis reading was and it turned out the 2nd cutter was so blunt it was rubbing and getting forced up into it's holder. So at this point I'd managed to get down to between 4.5 and 5 of 10mm depth. I went to a HSS 5.5mm cutter that seemed sharp to the touch, redid the toolpaths with that and it took a few hours but got there in the end.

A cleaning up cut around the web below the boss with a 2.5mm cutter and drilling the hole took no time. You can see there is a problem in the offsets between the 5.5mm and 2.5mm cutters - I don't have much luck getting these figures correct.

Other things I should have done:

1. Made the round stock as small as possible. Shaving say 4mm off the diameter may have change the toolpath to save some time.

2. Parted off further back. I was juggling the position of the parting tool at the start but I should have just left myself 0.25mm or so to file/sand off. I didn't realise how bad the parting off marks would be as they're not usually that bad. I've had to do a ton of sanding anyway so it would have been nice to have the part at the correct thickness at the end of it!





I was able to do a couple of other things while it was going but it required pretty constant attention so not much to show for a full day's work.

First I made part of the bracket that holds the reversing screw in the cab. The plans show it made from 3 pieces but I had some angle that looked like it would work for the vertical parts of the bracket and save one soldered joint. I just milled it square and to size/thickness.

Then I started on the I beam that guides the reversing screw nut. This is 15mm high, 15.5mm at its base, 73.4mm long. I started with a piece of 25mm sq steel and now have it to size. It will probably take a while to cut the channel out, 5.5mm deep each side and 11mm wide but I think getting it down from the 25mm sq stock was the time consuming part. I took equal amounts from both sides and took them down evenly to avoid distortion, even though it was black steel. That probably added 30 mins to the time rather than just tearing each side down in turn.

I'm hoping my approach to cutting parts is wrong because if this is the correct way to do it, it takes an age and only uses the end of the cutter and whatever the depth of cut is of the flutes, say 0.5mm. Next part I'm going to try to make a toolpath that cuts fulls depth but comes in from the sides in steps. I doubt it will be quicker but at least it will use more of the cutter.

[Roger]

Hi David,
That's a solid way to hold round stock, and I see nothing wrong with your approach. If you're having problems getting a smooth cut, it will probably be worse if you go any deeper before you figure out what the problem is. Is the bar Free Cutting Mild Steel, because it's not cutting very nicely? Possibly the feed and speed is too aggressive, I'd be inclined to slow the RPM right down and try to find something that cuts smoothly. Machining parts with light machines without coolant is a very different prospect to what you see on YouTube with people tearing through material. They're probably using brand new carbide cutters too.

If you're still using HSS. I'd strongly suggest you give something like this a try, you won't regret it. It's inevitable that you're only going to use the end part of most of the cutters, I wouldn't fret about that. I used conservative feeds and speeds and the cutters last pretty well.

[David]

The two blunt ones were carbide, but that's all the carbide I had so I had to fall back to HSS. I'll buy some more carbide cutters soon, I'm trying to find some ALTiN on eBay Australia. There is an Australian company that makes them but the prices are not suitable for learning with!

I doubt it was free cutting stuff, it was something I bought as an offcut years ago. I'll price some 12L14 next week.

The feed was 50mm / min, spindle speed 1000rpm. Do you just accept cutting times of 3 or 4 hours for a clearing operation as normal? That's where I am at the moment when things go well!

I might just give the CNC a miss until I have the cutters and free cutting steel. There is the rear screw support to do which is a slightly simpler shape that might be a good project when that stuff arrives. It's only 5mm deep too, not 10 so will be quicker.