Member postings for Marcus Bowman

Can you fix a piece of steel just behind the cutting edge, to force the ribbon sharply upwards, so that it breaks? That might be a piece of steel taped to the toolpost, or it could be clamped in place along with the tool, by the screws that secure the tool in the tool post. Mind you; I use a polished carbide tip designed specifically for aluminium, and it is just as good at filling the place with long strips of swarf. That tip has a built-in chip breaker, but its tiny. I'm thinking of something much larger.

Marcus

Loctite Detach removes Loctite (as the name suggests), and there is a similar thing for Superglue (which I have used on my fingers once or twice.....). They are commercial products, but designed for the job.

The superglue remover is supposed to live within arm's reach of my bench, but I can't see it at the moment, which is a bit worrying.

Marcus

Up to about 1.5mm I use Makita electric shears. They are my go-to tool for speed. There is a little bit of a knacjk to these, to hit the "sweet spot" where forward movement is easy, and you do need to exercise positive management of the curling waste strip on longer cuts. Electric shears remove a thin strip to create a channel which forms the cut. They are great for straight or gently curved cuts.

I also use a Makita nibbler for up to 1mm sheet, and that works well on tight curves down to about 50mm diameter. As Ian S C says, the nibbler generates millions of tiny crescent-shaped SHARP waste, and leave a SHARP edge just perfect for slicing flesh.

I also use a pair of good hand shears, up to about 2mm (tough on the wrists at that thickness. I prefer my big Gilbows for that, but tight curves need the aircraft shears which grip one edge more securely, but do leave tiny serrations on the top surface just next to the edge of the cut. The Gilbows tend to slip sideways just a little on the tight curves (Speed and old habits means I am using straight-jawed Gilbows, rather than the curved-jaw versions which might be better for curves).

Fine-toothed jigsaw blades work well. Coarse-toothed certainly do not. Support the sheet next to the edge of the cut.

Marcus

You may find that if you are using inserts you will get better results when threading at higher speeds. That's true of non-insert tools too, of course, but more so with carbide inserts.

If you are using a partial-form insert, the extent to which you will need to deal with the shape of the thread crests afterwards will depend on which threadform you are cutting. Whitworth crests are rounded (unless you are cutting a truncated Whitworth form) while metric threads are flat-topped (although just a smidgeon of corner rounding is both allowable and helpful).

Using a chaser as described in earlier posts does improve the flanks and crests very effectively. My personal preference is to mount the chaser in a holder in the toolpost, for accuracy and fine control. It's too easy to lose the fine control of size, fit and finish when using a hand-held chaser (or at least that's my personal experience, so probably reflects my own tendencies). I use copious lubrication when chasing.

Marcus

I have had a few of those. I had one I used daily for a few years, then had to sell it. I still miss it.

Which model (250 Star; C15SS; C15T; or C15S - S was scrambles and T was trial version, so most were plain C15 - the 250 Star, although most folks didn't call it that - or the very nice C15SS Sport Star).

Marcus

Martyn,

This is probably no help, but I think you could produce all, or most, of that 3D shape using a small CNC vertical mill. Do you have dimensioned drawings (or even your own sketches with approximate sizes)?

You could certainly produce the curved section as you suggest, using an end mill and a rotary table, or using a boring head or boring bar, even though it is only a part-circle.

The bores should be no problem either.

The top curved sections might be possible using the bore holes as a pivot point, and the side of an end mill to get some or all of the curves. Then blend with files. Coarse files, well-chalked work best with aluminium, at least for removing bulk. As JasonB's post shows, you can get a really nice finish on aluminium.

Mind you; if you are not too fussed about the exact detail of the outside of the shape (i.e. you don't need an exact replica) it may be possible to simplify the shape and make machining easier. Anything that eliminates the filing would be a bonus.

To be honest, I enjoyed the article, and felt it gave a useful and interesting explanation of some aspects of the device. I've a friend who has already sent for the components, and I expect to do the same for the items I can't source from my electronic junk box. What interested me most was that I have a board which will substitute for the potentiometer to provide speed control from the computer.

I suppose its a variation on the "different strokes for different folks" theme; but this one certainly suited me.

Marcus

Excellent. I'm very interested in this.

Which model is this?

Can you comment on the experience of ordering and getting this shipped to the UK?

Did you have it shipped from Wisconsin or from Quingdao Port, China?

Are you running the new Path Pilot software, or the older software?

Lots of questions...

Marcus

Or what used to be called Cerrobend.

Marcus

The original bolt looks like brass or similar softish metal. It may be designed so that wear in this soft component prevents wear in the parts which pivot on the bolt. That would prevent a much more awkward (and potentially expensive) repair or replacement of those other parts. If it was me, I would replace the bolt with one of a similar material.

Marcus

How about a robot for exploring the sea bed? That's the sea bed and not the bottom of a paddling pool, so there would be considerable challenge in designing and making the vehicle, especially where it has to withstand reasonable pressure and go deep enough to get to the bottom of a typical harbour. It should have a steerable camera, and a way of sending video and/or telemetry back to the operator. That's a not inconsiderable challenge.

It should be steerable, of course, but it might have some intelligence of its own (it depends on the focus of your project, whether it is mechanical, electronic or computing-orientated).

Or you could assume a submersible and just focus on the command and control and telemetry and autonomous exploration, although that would miss out part of the challenge. You might need to simplify it in that way, though, for a project with a deadline.

It is easy to do this kind of thing on the land, and quite common now to do it from the air, but under water is not so easy.

Marcus

I don't much care if its a model or a real thing; it's about the engineering and the making. And the bikes have always hit the spot. But then so has almost anything else where someone has tackled the challenge of making something which appeals to them. It could be a custom car, or a toaster (petrol or steam), I don't discriminate.

That tank is a thing of beauty, with its folds and compound bend at the top rear corner. I'd like to see an article showing how that was done. Lovely.

Marcus

Well; it's a dog's life right enough...

Marcus

I have a copy of this book. In fact I've had it for a fortnight or more, so my pre-ordered copy must have been despatched quickly.

This is a beautiful book, and I am keeping it for my Christmas stocking.

There is a single chapter entitled "How its done" with photos from Cherry's workshop. The rest is a 'coffee table' book, with gorgeous photos of beautiful models. As a long time fan of the lady's work, I'm absolutely delighted with the book. The author has done a fine job; as has the publisher.

Yes; a blow-by-blow exposition, with some of the techniques and tools revealed would have been nice, but that's not really the aim of the book. So, after a heavy lunch with family and relatives, I will leave the others to the tv and chocolates, and slope off to a quiet corner on 25th December, for what I expect to be a joyous celebration of the very best in model engineering skill.

Did I say I like the look of this book...

Marcus

I endorse the "standing" comments. I stand at the lathe, drill and mill, but have a bar stool handy to relieve the pressure on the knees and feet occasionally, if required. I also have relatively high benches and use the same arrangement, with a modified telegraphist's chair (high central pole, and a ring near the bottom for feet to rest upon). The chair has been extensively modified so that it has a comfy cushioned seat and back, so that sitting is a pleasure. In fact I now have two of those chairs (second one came from a local building site) so I can entertain a friend in the workshop in relative comfort. That takes the pressure off the feet too.

The only problem with having stools or seats in the workshop is that they rapidly become handy places to put things down "just for a minute"...

Marcus

Jacques,

I have sent you a PM.

Marcus

I sometimes use a Laser Centre Finder in the tailstock chuck. It shines its beam right along the lathe axis, so you want to adjust the cutting edge to split the beam, so to speak. I use a Polarising filter to get a really small beam.

Marcus

I have two of these units, and would not be without them. They are in daily use. One of the advantages is that the wire can be routed vai pulleys so that the unit itself can be conveniently located while the wire is routed to a slightly different pickup point not directly aligned with the point at which the wire exits from the unit. On my drill, I have the unit clipped horizontally at the front of the head of the drill, and the wire is run around two pulleys to drop vertically down the right hand side of the spindle, to a projecting pin.

On the lathe, I have one permanently clipped to the bed so that it measures carriage displacement.

The units mount via large clips, so I can take the drilling machine unit and clip it onto the tailstock, measuring barrel travel.

I have a clip to allow a unit to be clipped on the carriage to measure cross-slide travel, but don't use it for that, as the resolution is not high enough. That's an issue often overlooked with the cheaper digital scales, so its not unique to this BW unit.

The features of the units are quite extensive, and they have 9 selectable travel measurement displays, so that for a mass production job I can turn to a shoulder, select the next position and turn another feature, etc.

The units I have are single axis free-standing units and they do not link to a central display.

Expensive - yes. Worthwhile - I wouldn't be without mine; to the extent that I have been considering buying a third unit (saving up, at the moment; and thinking about my Christmas List).

Marcus

I use brass or aluminium shims, but bent so they loosely grip the jaws to prevent them falling out as I try to juggle 1 workpiece and 4 shims and a chuck key with only 2 hands. I find it also helps to seat the work against two adjacent jaws before tightening the other two, so that the jaws sit square to the work and avoid constant sideways thrust.

In a 4 jaw, lots of damage occurs because as the jaws are finally tightened the work is sometimes moved sideways to finally line up on a mark, and the gripping jaws wipe across the work surface. Shims help prevent that.

Gripping against the reversed jaws sometimes helps too, although the corners of those curved faces can be fairly sharp too.

It's also a good idea to leave a little extra material on the work, to be removed or finished later, if possible.

Marcus

I have used EN24T recently for some stressed parts on bikes and on machines. It machines very nicely using carbide tools or HSS tools. I have cut threads, rather than use a die, mostly because of the nature of the thread I required, but a HSS die will work. The steel would need further heat treatment afterwards, to give it the hardness/strength characteristics to match a high tensile bolt, and while the machining is easy, getting the heat treatment done is a pain.

Stainless is not an appropriate material for a highly stressed job, as it is "softer" and less strong than most of the EN16/24/57 steels. Stainless sets up corrosion against steel and aluminium. I see lots of fasteners in stainless, now, including many small diameter fasteners, but I don't believe it's a good choice for every situation, especially small (M2) fasteners with an internal hex (like a grub screw). Some grades of stainless are not corrosion-proof.

Marcus