Member postings for Muzzer

If you are doing any maching using the edges on the end of the cutter, the helix angle will be related to the material it's intended for. So aluminium would require a fast helix, copper and brass a slow (or parallel) helix and you can even buy a reverse helix. I suspect the latter is actually best used for thin sheet material, as it will push the work against the table.

Of course, you could have a parallel flute cutter with any kind of cutting angle if you are mainly cutting radially and I expect you can get different combinations of helix angle and cutting angle according to both material and type of cut. But one advantage of the spiral is a smoother cutting force which is presumably why parallel edged cutters are best used for light finishing cuts.

Murray

Just taken delivery of my X and Y ballscrews with double ballnuts for my BP clone CNC conversion. Took just over a week to arrive from China and cost $207 all in (inc carriage) - that's about 125 quid. That also included having the 3 ends machined with shoulders, keyways and threads to my drawings. Pleased to see that between my drawings and their machining, I have ended up with leadscrews that seem to be the right lengths and accept the intended bearings, pulleys etc. It may take a little longer for me to complete the machining of my mating brackets etc.

It's easy to slag off Chinese suppliers but for the likes of me, they have proven to be a very useful source for some of the critical parts of the puzzle - and they CAN provide viable parts. In the end, I will have sourced parts from the UK, China and North America. No single country or continent seems to have a comprehensive and affordable solution.

Murray

Most modern electronics are washed in aqueous cleaner nowadays. Gone are the liver-destroying days of Genklene and other volatile solvents. As you say Neil, as long as you get the batteries out quickly you are likely to avoid lasting damage. Some compts like relays have breathers that might admit water but other than that, warmth and time should do the trick.

That reminds me I have an iPod that needs to go back together. It went through a full washing machine cycle and already had a broken screen but I was able to repair it with parts from Hong Kong for a few pounds. You can't remove the batteries in those quickly but we seem to have got away with it. I'm getting too old for micro surgery like this.

Murray

I resorted to cutting the thread in reverse like that. although with the tool at the back of the work and not upside down. Mainly due to the long time it takes my Bantam to coast to a stop. My VFD can't be configured to stop any quicker, so threading can be rather fraught. If cutting metric on an imperial machine you still need to get the tool back to the starting position without disengaging the half nuts (ie under power) but you can do this with fewer distractions going on, so slightly reduced chances of screwing it up. That's the theory at any rate.

I have almost completed a variant of Graham Meeks' clutch I designed for for the Bantam (see my albums), which should help considerably. This operates on the spindle, not the leadscrew and gets around the problem. I'll finish it once I am no longer preoccupied by the latest distraction...

Merry

It's often tempting to believe that you can create a robust design simply by stringing together black boxes and devkits / eval boards. However, if you have no real, profound understanding of what the black boxes are doing, you are sort of hoping they do what you expect them to do. That would be nice. Unfortunately, there are often several ways for a manufacturer to achieve a given "black box" functionality and it's often essential for you to put the time in to figure out what's happening if you are to avoid those sticky moments.

As Andrew says, you can't possibly get right to the bottom of what's happening in ICs but as he mentioned there are often a few critical details hidden away in the app notes that will bite you if you don't pick up on them - and even a few that aren't! You soon learn that it's less time consuming in the end to do that homework up front than to rush the first stages and deal with the issues later. To my mind, the cost of rectifying underlying issues increases something like logarithmically, the later in the program you leave them.

Murray

Interestingly, you may have spotted that Anders Wallin's blog is linked to from Dan's site. It looks as if they have been collaborating on some aspects of the project. Presumably Anders' toolpath algorithms are made use of. I also get the impression that FreeCAD was felt to be close in terms of values/aspirations. Presumably that work was what the "Opencamlib"(?) references were about. HeeksCNC is more of a standalone spinoff from that, by the sounds of it.

I tried FreeCAD some months ago. I may have been unlucky but the features I was attempting were plagued by crashes (of the program!). I hope it evolves and delivers a comprehensive feature set. Many of these open source projects are staggering in what they have achieved.

Although I'm fairly mathematically literate, I just couldn't get on with OpenSCAD. It just isn't how my brain computes. It's not as young as it used to be, which probably doesn't help either.

Murray

Has anyone tried this out yet? Generates g codes from a variety of file formats like step, STL etc. Some interesting background too on toolpath generation techniques if you look into the blog links.

I'm fairly new to CNC but this looks pretty interesting. Pretty amazing considering it's largely the work of one person (Dan Heeks). I suspect it may be limited to 2.5 / 3 axis operations but that's enough for the likes of me for the time being.

I was looking at HSMXpress recently which is free for 3-axis CNC but it's much more of a heavyweight product and requires Solidworks.

As I said, pretty amazing to have come up with something as capable looking as this.

Heeks CNC website **LINK**

Youtube demo **LINK**

Murray

That Airbus story as recalled seems to have been passed through the "Daily Mail Science Correspondent" filter. I'm not an aviation expert but even so I recall there were a few more details to the plot. I seem to recall they were both disoriented and weren't even aware the plane was in danger of stalling until too late. A mechanical coupling wouldn't have made the slightest difference. IIRC there had already been reports of problems with the Pitot tubes icing but nothing was done in time

As for cars being somehow controlled over Bluetooth and going doolally, I don't think you would believe how many layers of safety and redundancy there are in modern cars. Apart from the schadenfreude from the US car companies over the supposed problems with Toyota's throttle pedals (which turned out to be mostly false reporting and hysteria), I don't recall hearing of lots of issues with robustness on the engine control front. Cars nowadays are far less likely to suffer from loss of control than in the good old days (sticking throttle cable, anyone?) and nobody is about to throw all those babies out with the bathwater. Makes for an easy chortle down at the pub but quite simply there is no likelihood of that ever happening.

Murray

After much digging about, you will find eventually that the modern equivalent of the factory recommended oil for the Bantam is ISO AW32, which is usually sold as hydraulic oil. Sounds suspiciously like "Nuto H32" and is available for peanuts (by the gallon) at most auto factors. It's also what they recommend for lubricating the slides, BTW.

Murray

For stuff like linear guides, head over to AliExpress and have a look around there. You should be able to get something delivered in a week or so for not a lot of dosh. AliExpress is not a complete Wild West experience, as there are some safeguards in place to protect buyers like us.

If money is not the issue, how about Misumi. Talk about playgrounds for grownups!

Murray

Rather you than me. It's 30-32C and sticky as hell in Guangdong right now. Just right for hanging around in hot factories!

Merry

A component like yours would naturally clamp to the table, using pieces of aluminium strip as spacers to save the table and the cutter - wood might be a bit too spongy. It doesn't look as if a vise would do it much good. Once you have machined the cavities, you could move the clamps without disturbing the work so they are bolted through the cavities, allowing you a clear run at machining the outside profile.

Thinking carefully about workholding before you start machining can save hours of setting up between operations. If the finished article has fixing features you can often use them to hold the work down, and thus simplify matters. Alternatively it may be worth leaving a couple of hold down lugs which you can remove at the end, manually if necessary.

There are times when you can't avoid removing the workpiece and you have to be very careful getting it set up again. This is where gadgets like DROs can save lot of time and improve accuracy.

Murray

I find that climb milling allows a heavier cut before the onset of chattering is provoked, which is another reason for going that way. I have a life to live, which doesn't involve taking longer than necessary on operations like this, even though it's a hobby.

There is a balance between tightening up the slides enough to prevent the work being drawn uncontrolledly by the cutter (helping itself to the backlash) and being so tight that it makes turning the handle difficult. With practice you can back off the slide locks so that you still need some margin of effort to turn the wheel but you can feel that the cutter is assisting with the feed. If (like me) you have noticeable backlash, you can break the cutter very easily by climb milling without remembering to tighten up the slides. I take great care to avoid this!

The pulling force exerted by the cutter is affected by the radial depth of cut, so there must be a "neutral point" with climb milling where the required feed force is zero in the direction of feed. So, taking light cuts is more hazardous in some cases than taking the plunge, so to speak.

Murray

They are for retaining the cams within the spindle nose. Certainly shouldn't be loose. Unless your system is unconventional or not original, I suspect there should be a spring and a pin behind them that mate with a groove in the cam. It may only be the spring force that is preventing them from coming completely undone.

On my Bantam (and in the spec) the bolt is a cheese headed thing that bottoms out hard against a counterbored shoulder, so I'm not convinced your grub screws(?) are original or correct.

Perhaps a Boxford owner could confirm.

Here's a link to the spec for the Camlock system **LINK** showing you how it works and the recommended components. See 33.5.2 and 3.5.3 for the bolt and pin. No spring is shown unless I've missed something.

Murray

My Bantam has metric threads and dials on the cross and top slides and the tailstock but is otherwise an imperial machine ie has imperial leadscrew and gearbox. It seems this was quite common and is most likely something to do with the number of machines that were supplied to schools and colleges. I'm ashamed to say I've owned this machine for nearly 20 years now and it was only recently that somebody pointed this out to me....

BTW, there are various Bantam / Colchester owners active on the homeworkshop.org.uk forum. It's good to check in there from time to time.

Murray

I have to say I have never made a model and will almost certainly never will. I'm more of a machine builder than a scale modeller but I've been reading ME since the mid seventies as then it was the only way a boy could read about how to make stuff at home.

I'm fine with the shared content, even in MEW. However like a lot (some?) of the current readership, I move with the times and so 3D CAD, CNC etc is definitely on my current radar.

And cars, bikes, engines, steam, machine tools, welding, electronics.... It's all fine by me!

Murray

If you look at how technology has exploded over the last 50 years, it's difficult to imagine what will happen in the next 50. However, you can be sure it isn't about to suddenly come to a complete stop just because we (here) can't imagine what will happen next. The way it will continue is by the next generation(s) starting where we left off. Our kids grew up with computers, powerful software, smartphones, internet etc and they take them almost for granted. It's come to the point where no single individual can claim to understand every aspect of a modern product. Even the software has got to that point. Modern cars have between 50-100 microprocessors in them (you possibly didn't realise that). It's not about to stop...

I started out playing with discrete transistors like the OC71, AC128 and was messing with switching power supplies back in the late 70s. Now I develop smart motor drives, chargers etc that have dedicated SMPS controllers, microprocessors, comms ports, displays, diagnostics, data logging, thermal protection etc. Things have come a long way! SMPS and other switching power electronics products can be very reliable indeed, not least because we understand a lot more about failure mechanisms nowadays. Modern components are effectively defect-free as far as product reliability is concerned. Generally, failures are the result of poor design or inappropriate application. Might sound controversial that statement but that's the long and the short of it.

Today's engineers have to design with highly integrated devices, like it or not. There is still the need for discrete devices in almost any product but there's very little these days that you can do with a handful of discretes alone. Apart from inverted snobbery or nostalgia, there's really no benefit from sticking to decades-old technology. That's not to say I'm not nostalgic myself (I have "several" boxes full of nostalgia) but what has always really, really excited me is thinking about what we could do if we build on what we have - and going out and making it happen. In this context, that's perhaps the difference between an engineer (tackling new challenges) and a technician (sticking with the same)? No disrespect meant to technicians, BTW.

Murray

This is the carriage stop that came with my Bantam. No idea of the parentage but it likes to be nipped up tight. I fitted the keyway and replaced the bottom piece so that it sat better on the ways. It's loose here, so not sitting square but you can see the idea. I've never found the micrometer dial worth bothering with. Instead I usually finesse the position using the top slide.

As ever, the picture is sideways as a testament to Windows 8 which knows better than me which way to orientate the photo.

And here's my cross slide stop. It is pretty basic and only works for feed direction away from you due to impatience when I made it but it can be pretty handy when facing with power feed. There are 3 tapped holes which allow it to be fitted in 2 positions, giving me all the adjustment required in combination with the threaded stop bar. The transverse and longitudinal power feeds will trip out in both directions against any firm stop.

Murray

Edited By Muzzer on 30/05/2014 04:47:01

I doubt you can actually see the index mark but if you connect the display up and use the "index detect" function, you can locate roughly where it is. On my system, the display stops blinking and the unit beeps when the index is found. I think that's fairly typical.

This is what the slider looks like. The orange plastic thing is a disposable keeper. The ball on the end of the spring biases the slider against the scale. You can see three of the rollers too. It produces a classical encoder signal.

This is the extrusion with the seals removed and the scale visible. It's held in with small pieces of soft plastic beading

There's a few more pics over on this external site: **LINK** and in my albums on the ME/MEW site **LINK**.

Hope this helps.

Murray

If you take the end caps off (4 screws), the little bogie assembly comes out, PCB and all. That just leaves the glass scale in the extruded housing. Mine was just held in with rubber wedges or similar. It came out easily enough and I was able to use a new carbide insert tool to score the glass, then snap it off. Shortened the housing, retapped the holes and off I went.

Be aware that there is an index mark on these scales. It will work without the index but if your DRO display can pick it up (to reclaim the origin after power off - useful function sometimes), it's worth checking where it is and making sure you don't accidentally chop it off in the process!

I have some pics if you want reassurance! I shortened a spare scale to fit the head of my Bridgeport clone so I now have 2 (alternative) Z-axis scales which I change by swapping over the connectors on the display. I have to say I use this quill-mounted one 99% of the time, so it was an excellent mod.

Murray