Small saw. Proxxon or something else

Like Michael, I'm confused by some of John's terminology. I suggest it's best not to use engineering specific terms in an ordinary way because it might confuse engineering savvy readers. For example, 'EXACTLY 45°' strongly implies high-precision, which is achievable in a home workshop, making the clarification 'as one can reasonably hope to obtain in a home workshop without undue time, effort and pain' unhelpful too. Especially when we find the actual requirement is 'within 1 to 1.5°', which isn't particularly exact at all.

Worth trying to express problems accurately, even though it's so difficult to do. Pays to be precise, numbers preferably, because the requirement can have a big impact on the tools and techniques needed to meet it. Really bad to be advised to buy the most expensive kit on the market when something ordinary would have done, and equally bad to be told a basic tool will do the job when it won't!

Considering mirror-like surfaces, it's the difference between:

• The foot of a camera tripod left in shiny 'as machined' condition. Not much work, nothing special needed. Bog standard job.
• Handles on the same tripod not needing to be accurate but brightly polished for cosmetic effect. Again, fairly painless, but extra effort needed to do the polishing, perhaps a linisher, belt-sander, and powered mop, though all these can be extemporised on a mill or lathe. For best effect the 'extra effort' will be considerable, and lots of people cheerfully do it.
• The internal moving parts of a camera might be lapped flat. Lapping is a notch or two more advanced but not impossible in a home-workshop. However, the choices made might be the difference between success and failure, particularly if the operator is semi-skilled. And if a lot of this sort of work is to be done, a skilled operator will save much valuable time by using suitable tools.
• A camera's mirror will be highly polished close to optically flat, the real McCoy. Again, do-able at home, but much quicker and easier with the right gear. Optically flat is a tough target and I'd prefer to buy a mirror rather than make one myself.

John's redefinition of optically flat still leaves me in the dark. I'm not sure if he's after an optically good mirror for imaging or a straight edged reflector for cosmetic reasons. Depending on how good the edge needs to be sawing with sacrificial support underneath might be good enough. However, I'd probably make the plate by cutting it oversize with a saw or nibbler and then milling, filing or grinding the edge to size. Two processes, one fast and crude, the other slow and delicate to remove cutting damage and get dimensional accuracy.

Excellent work can be done with simple tools. It requires skill and patience, and maybe one has to ignore an overflowing giant scrap box! When time is of the essence it pays to cough up for the best tools available and make jigs etc. Otherwise, most of us use the best tools we can afford, which are rarely top-end. My machines are relatively crude, underpowered and lack rigidity. But they mostly do what I need eventually, provided I drive them carefully, practice, take advice and think! In my world Model Engineering is one compromise after another.

Dave

To slow for grinding appears to be a case of “internet knowledge”

My surface grinder is supposed to run 71/2” wheels iirc, so I didn’t look at that.

However:

Bog standard bench grinder from B&Q. Takes 150mm wheels, runs at just under 3000 rpm.

Homebrew cutter grinder:

Has a 4” cup in it currently, also runs a 4” saucer.

Speed:

Also just under 3000 rpm.

I have never needed to run a slitting disk on either, but I don’t doubt that with a thin wheel at that speed both would still work. Of course it would need to be the right wheel. Abrasive wheels are cutting tools, and much like different types of carbide or HSS there are different types of wheel. A wheel designed to run at 10000 rpm is built differently to one with a slower maximum speed.

I do wonder if John S is trolling or just indecisive.

Dave

Sorry I forget to add, 18v shear for roughing out, bench shear for trimming edges to finished size, incase it might have caused some confusion.

John, regarding drilling, in the other thread I said they do a sensative drill attachment which is ideal for small holes and allow the drill to be raised and lowered quickly to clear swarf etc. You can buy similar over here that will fit for a lot less.

As I have said from the start a mill with slitting saw will do the job I just stuck a bit of manky 0.8mm, 110mm long mild still in my mill and mounted a fine tooth HSS saw blade. First cut is leveling off the top second is cutting a 1.5mm wide strip. Any bend you see is due to the parent metal being from the scrap bin and not flat to start with. If cleaned up it would Look flat which is what I expect you mean as you don't want deformed edges like a shear can gibe or curled parts like tin snips.

Could not get the phone to focus well but once the small burr was knocked off it would clean up well with a quick rub. A more concentric blade would probably help too!

@SillyOldDuffer
I'm sorry, it is clear that I am still being clear enough. I am up against tight deadlines and just want to do cutting the doesn't very obviously bend the steel near where it has been cut. Like I say high speed cutting discs don't have this problem, once you have deburred the cut itself.

I am working with magnets and need to transfer the maximum possible magnetic flux between surfaces. As you may know, much like electrical current, magnet flux doesn't like jumping big gaps.

Yes as noted, sacrificial support would help. If strong enough it would help perfectly but would slow down the cutting speed, and generate a lot of cuttings.

Like I say using a nibbler was an absolute disaster, with the bending of the 1mm steel extending for a good mm or so, even on 1mm mild steel plate. A hacksack does not bend the plate but I find it painfully hard to cut long distances very straight - I just want a machine to help me.

Can I just say it needs to be flat to within 1 thou and move on?

@Pete - Your shears looked like a mechanised version of a nibbler that's all. I they can cut steel sheet reliabily with no visibly obvious sign of any bending near the cut them I might buy some myself! Yes most of my requirement is for 1mm steel, but I will need to various sizes cut down to 0.1mm steel from time to time as well.

Also - to get clear a "Bench Shear" is basically a guillotine with a long arm for leverage, yes? [I am a newbie, please remember]
If so, presumably you will get at least a bit of rounding /deformed edges. In 1mm steel the question arises how far this extends.

Here is a quick diagram of what I mean:

@Dave S -
Interesting to know that 3000 RPM at 4inch diametre makes for good grinding. Whether that makes for good CUTTING on a 1mm abrasive disc I don't know.

But given those numbers, can you explain why are all the circular table saw manufactures are all so adamant that their machines can't cut steel? If just don't make sense...

> I do wonder if John S is trolling or just indecisive.
Back off. Absolutely not trolling.

I am a newbie but learning fast. However it seems that every time I am about to make a decision I get new information that renders what I was about to do a poor decision.

@Jason B - awesome video! I agree a good quality mini milling machine would solve a lot of problems. What would you say is the thinnest thickness of mild/stainless steel you could do that treatment with?

I would not want to go much below 0.5mm without additional support, with it sandwiched then I don't think your 0.1mm would be a problem. Will see what I have to try it on tomorrow.

John, I wasn't suggesting you buy one, I just said that's what I would use to rough it to shape without distortion before using the bench shear, it's used freehand so won't produce you precision straight edges.

A small mill is the ideal tool.

> Cutting with a grinding disk is grinding

I would have thought that during grinding it may be important not to change any heat treatment of the metal... e.g. when sharpening a knife say. Whereas cutting - e.g. with a angle-grinder - seems like a more brutal process. From what I can see 4.5" (115mm) and 9inch (230mm) angle grinders seem to run unbelievably fast even the large ones seem to run at 6000RPM, smaller ones more like 8000RPM. I would have guessed that if you want precision a slow speed would help. But if you want precision and the ability to cut fast, then an extremely high speed would also help. ...But what do I know?

@Dave S
Your ad hominem attacks are noted.

I thought we were here to discuss 'workshop tools & tooling'... but since you ask, yes, various deadlines have now passed... with more to follow.

So far I have been making do with fine-toothed hacksaws, good quality course file and a fine file, and various grades wet & dry, sometime mounted on flat blocks of MDF. Once cut I have 'sanding' them down using customised small stick-like piece of wood (or sometimes finger) with double-sided sellotape (which works BRILLIANTLY, btw).

The problem is that it's extremely time-consuming as well as demanding great skill & concentration... and all trying to do manually what a machine could do much more accurately.

At some point soon we will need to move to small-scale production of our products and that will definitely necessitate better tools. But we are poorly resourced and without a permanent workspace and I need to be extremely careful with finances and use of space.

Yes, some stuff I have outsourced - some machining and some laser-cutting - but it as you can imagine it always has a relatively slow turnaround time and a large cost, particularly the setup cost. And before you can blink you soon find that what you've ordered isn't quite what you actually want!

I have flagged from the top, and repeatedly, that I am a newbie to all this. It is precisely because I am listening - intently - to all new information and opinions that making making decisions has proved hard. "Any damned fool can make poor decisions" and make them as fast as you like!

If you want the truth, I have felt honoured and delighted with all the high quality contributions from model-making experts in this community tolerating my various dumb questions, not that their opinions always match each other - we all have our individual biases & preferred ways.

However until now, I have been assuming that if any contributors to this thread no longer find this thread interesting... that nobody is "forcing" them to read any of this stuff. If this is not the case please do let me know.

Edited By John Smith 47 on 24/04/2021 01:57:52

I'm not sure, John's toughest requirement in my eyes were the seemingly ridiculous weight/space restrictions for metal working equipment, the space restriction being absolutely none, I got the impression he was willing to spend good money for the piece of equipment that would meet his requirements.

In this thread John, everyone has suggested things that could be made to work, to make parts of what you want, a shear could work, but it wouldn't grind you 45° edges, a table saw type machine like the proxon with an abrasive cut off disc could cut your metal, but it wouldn't grind your 45° edges accurately.

A small milling machine is the obvious thing that could achieve your goals, a hss slitting disc, a small abrasive disc for cutting your parts, you could mount small grinding wheels combined with a tilting vice to finish your edges at desired angles, it would do pretty much everything you need.

The new model sieg x1 sold by Arc euro advertising at the top of this page, has a fixed column, 4 screws, as I said to you in another thread, this machine weighs 50kg, if you remove these 4 screws you could meet your requirement of being able to move two 25kg parts from the dining room table to the side cabinet when not in use, I believe this was your requirement, it costs about £600, is in stock from a UK supplier.

Cutting sheet metal accurately is such a fundamental component of model engineering that I've enjoyed this instructional debate. If only some enterprising manufacturer would pay heed and design something that works - I'm sure many of us would buy it.

John and myself to start with.

Now the (long retired) corporate/financial analysts in me comes out. Jim Byrnes in Florida and Sherline in Australia were modellers who decided that the machines they wanted were not being made...the rest is history. Anyone out there with a business plan?

Just dreaming, as I do of owning a real lathe and mill. Alas, my /Sherlines are all I have room for.

Stuart

I am guilty! Though in mitigation the forum does tend to wander off the subject! I thought we'd moved away from the magnet problem (which I also misunderstood at the get go), and where discussing the properties of Proxxon type tools in general.

I don't believe any of the Proxxon tools will do the magnet job in a single operation. Worse, I can't think of an affordable general-purpose machine that would do it either! Expensive machines yes.

All is not lost. The job can be done in steps, in this case two:

1. Make oversized blanks so the flaws can be removed later. Doesn't matter much how the blanks are made. Saws, Laser, shears, grinding wheels etc all deform the work to some degree or other, and the magnet requirement is too tough for any of them.
2. Finish the blanks with a tool that trims them to size, removing the damaged section in the process, and leaving a good finish. Could be done in a lathe, but a milling machine is the obvious candidate.

Making parts in several stages is the usual way things are done. Here, the workflow might be:

1. For speed, magnet-blanks could be churned out by a shear. (Saws are slower and less accurate, but can be used for other purposes. If speed doesn't matter, and other cutting work is on the card, saws are more general purpose.)
2. Clamp the blank in a milling machine and remove the edges to size. It will probably be necessary to trim off the delicate burr left by the milling cutter, but this is an easy job - swipe with a fine file or grinding block.

If many blanks are to be finished, it's worth making jigs to hold them. Rather than carefully positioning each blank in the vice, instead drop them into a fixed jig that guarantees position and accuracy. Making jigs is a lot of trouble, usually not worth doing unless tens of identical parts are needed.

I think it's do-able with a Proxxon saw AND a Proxxon Mill, even though neither are entirely happy cutting steel.

Worth repeating: John's price and space constraints make this a difficult challenge. Industry could produce these for a fraction of a penny, but their method, probably involving grinding, is expensive to set up. They might charge £10000 to make one, and then knock out the next thousand for a quid!

Dave

Dave

Hi, it seems to me that not many people want a table saw to cut steel with such precision, being there doesn't seem to be any budget machines about, and I doubt one would be very cheap. Cutting any metal by mechanical means, will introduce a certain amount of distortion and the thinner it is, the easier it is prone to distortion. Industry probably has machines, but of course they will be used for mass production and therefore the cost of them would be viable.

I don't know exactly how flat the OP wants his thin steel or what width and length he is after. I've cut this piece of 0.004" (0.1016mm) from a rolled up shim steel stock, with a decent pair of scissors and have only wiped a smooth file over the edges to remove any sharps. It is 30mm wide and 115mm long and both sides have been cut. I'm not claiming that the sides are absolutely straight or that it is absolutely flat and the distortions that can be seen is where it has been straightened between my figure and thumb, even at this thinness, you can distort it just by handling. I think JasonB's idea of clamping between two pieces of wood and cutting with a slitting saw on a milling machine would be the best bet, even if the cut was slightly wider and then clamped between two pieces of wood in a vice, so that just a small amount is sticking out, to enable it to be filed to size. So without expensive machinery, there is not really a mass production method.

Regards Nick.

Edited By Nicholas Farr on 26/04/2021 17:18:47

Nicolas,

I think that I already mentioned that I cut aluminium and brass sheet with sheers then file to a smooth straight edge - like your example above. My one refinement is testament to my lack of skill, as my cuts are rough I cut 1mm outside of my score and place the sheet in a vice with a length of angle iron each side, then file down to the score. Pretty good finish.

But I would prefer a machine to do this; my wood table saw (Proxxon FET) cuts very accurately, straight and smooth but imho only works with wood. If there were a table saw that did to non ferrous metals what the FET does to wood...

I guess its machine up or skill up and as a retiree who has never dirtied his hands with engineering before, skilling up seems the greater challenge.

Stuart

@Nicholas Farr - I wonder what would a 10x5 mm square look like in close-up?

Yes, 0.1mm mild steel is exceedingly thin and is very easily bent between fingers. For my purposes right now I have been needing to cut 10mm x 5mm little rectangles of it. And the resulting steels need to lie "absolutely" flat (i.e. flat to within 1 thou - call it 0.02mm).

I can see that a really good pair of scissors or guillotine/"bench shears" could do the job, however by the very nature of the process one side or the other always gets BENT out away from the rest of the sheet. Once bent it is almost impossible to bend it flat again. To be fair, I've not yet tried an enormously large pair of very shallow sheers with blades that are very nearly parallel to each other - maybe the steel sheet might only be bent within elastic limits [??], but I don't have space for a really large device in my domestic setup.

Further more when you zoom right in, there will be at least a little rounding.
See my post above (@ 23/04/2021 18:47)

The only thing that I have found that doesn't bend thin steel at all is a high speed abrasive cutting disk. Obviously it leaves a bur but ones that is removed by light sanding the sheet as a whole remains dead-flat.

@Stuart Munro - have you ever tried putting an abrasive cutting disk into your Proxxon FET?
From memory your circular saw has a diameter of 80mm and a RPM of 7000, so that would create a cutting speed of I make it about 1,700 m/min which should work pretty well, particularly if you have a very think cutting disk.

i.e. That's really I've got to: Cutting mild steel by high speed cutting disk. HOWEVER the problem seems to be that nobody seems to have manufactured a small circular saw that is designed to cut (what would in effect be any metal) using an abrasive cutting disk.

There are lots of hand held cutting disks (AKA Angle Grinders), but so far I have yet to find any embedded into a table so as to create a "circular saw table".

e.g. This Proxxon "MICRO cutter MIC"

**LINK**
[Spec: 230V. 40W. 20,000rpm. Maximum cutting depth 4mm. Cutting width 0.5mm. Weight approx. 300g]

It's rather under-powered at just 40w, and I'm sure faster would be better, but from experience 20,000 rpm can cut 0.1mm mild steel quite nicely without bending it near the cut.

J

P.S. This will no doubt cause howls of abuse & derision but there is a high speed (20,000 rpm) low cost (c. £250) , compact, highly portable (7Kg) milling machine available... the MICRO Miller MF70, complete with its build quality and crappy run-out.



Yes, IF I could find something better quality of similar spec then I would buy it, but such a thing doesn't seem to exist. And NO I can't afford the much heavier, vastly more expensive Sherline just yet. (c. 16Kg c.£1250 - £1500 all in)

PS
New line of thinking - ever tried a "Guillotine Sheer"?



e.g. 4in Guillotine Shear by Pepe Products ($479.00 in sale in USA)
https://pepetools.com/products/4-guillotine-shear-made-in-usa
Seems to cut without bending!

That looks a nice little tool but [here we go again] ...

• Cuts up to 20 gauge for gold, silver and copper only.

MichaelG.

.

They even offer GBP pricing:

https://pepetools.com/products/4-guillotine-shear-made-in-usa

Edited By Michael Gilligan on 27/04/2021 13:18:06

Stuart,

Proxxon offer blades for the FET for non ferrous materials including the fine tooth 28730:

**LINK**

Hi, John, well these three pieces are approximately 10mm x 5mm, didn't get too fussy with the size, but I'm still not claiming they are absolutely flat and you might be able to make out the 0.015mm thick piece of kitchen foil in front front of them. Best I can do I'm afraid.

They are sitting on the back of my 6" Moore & Wright straight edge.

Regards Nick.