Small saw. Proxxon or something else

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Russell Eberhardt on 22/04/2021 10:15:03:

.

… 32 teeth per cm. …

.

Jason, for info ^^^

MichaelG.

[John Smith 47Participant @johnsmith47]

Yes, I tried sawing with the finest saw that a jewellers could provide (32 teeth per cm) but the 0.1mm mild steel just bent. A small high speed spinning disk (c 20,000 rpm) was MUCH easier.

Like I say, all snips always seem to bend one side. I require a deed-flat finish (a little deburring is acceptable).

If I have to build some specialist tooling, then maybe. But I am a relative novice and it will take time, I will get it wrong and fail to including critical features etc… to yes, possibly but only after I have exhausted all other options.

[HollowpointParticipant @hollowpoint]

Sandwich the metal sheet between 2 pieces of wood and then you can just cut through the whole lot with a scroll saw. 😉

[JasonBModerator @jasonb]

Thanks for the 32 tooth correction. but that is still three thicknesses of metal to one tooth so you won't get 2 teeth in contact or even 1 on the 0.1mm material.

As Hollowpoint says often when cutting thin sheet the work needs fully supporting by laying on a board and cutting both or even sandwiching.

Back to my point of doing it on a mill with a slitting saw this shows some 0.5mm brass being cut into thin strips, you can just see a bit of brass sticking out on the left and the saw marks in the back board where I have stepped down and made several cuts. The saw has cut right through the front board

Not a good photo of the brass as its covered with flux and solder but all exactly the same width and with a good finished edge

 

Edited By JasonB on 22/04/2021 11:55:36

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by JasonB on 22/04/2021 11:54:05:

Thanks for the 32 tooth correction. but that is still three thicknesses of metal to one tooth so you won't get 2 teeth in contact or even 1 on the 0.1mm material.

Yes you are right of course I must have shifted the decimal point. I claim old age

Russell

[Roger BParticipant @rogerb61624]

I checked last night which saw blade I was using and it is actually the HSS version rather than the carbide one.

If you choose the Proxxon FET you will have the possibility to use an abrasive disc or one of these small saw blades. 50mm diameter rather than 80mm will give a useful reduction in cutting speed for the saw blade.

[John Smith 47Participant @johnsmith47]

**LINK**
"The 28020 is a Tungsten tipped Saw Blade with high-alloy special steel"

Given that it is tipped with Tungsten, how come it can't cut mild steel? I get that it can't but I am curious to know why it can't. I was thinking that if we could slow down the RPM, and increase the torque of the motor (e.g. by having a higher wattage motor running more slowly) maybe that would help

Likewise I am also curious that solid carbide discs are no better.

Either way for thin metal sheet (e.g. 0.1mm) the easiest way to cut it and maintain flatness still seems to be a very high speed disk.

OK, just how mad is this suggestion?
Go for something mass-product & much more powerful and find a way to do precise grinding cuts.

e.g. Bosch GTS635-216

**LINK**

Cost: £335.99
Power: 1600watts – a surplus of power
Speed: 5,500 RPM – pretty very fast for 21cm
Weight: 22Kg – not impossible
Incline: 0 to 45degrees
Saw blade diam: 216 mm
Bore: 30 mm

I just need to find some very thin (1mm? 2mm?) abrasive cutting disks that are 216x30mm.
[I ran out of time googling but surely they exist!]

But even if I have to settle for quite wide cuts, at least I would get my straight cuts… through steel.

J

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Smith 47 on 22/04/2021 16:50:29:

**LINK**
"The 28020 is a Tungsten tipped Saw Blade with high-alloy special steel"

Given that it is tipped with Tungsten, how come it can't cut mild steel? I get that it can't but I am curious to know why it can't. I was thinking that if we could slow down the RPM, and increase the torque of the motor (e.g. by having a higher wattage motor running more slowly) maybe that would help

Likewise I am also curious that solid carbide discs are no better.

.

.

The blade is intended for an underpowered machine with an inadequate spindle

Please see Peter’s post and my response, on page 1

The blades could almost certainly do your job: if suitably supported and adequately powered at an appropriate speed.

… but Proxxon needs to inform you in the context of its machines.

MichaelG.

[Roger BParticipant @rogerb61624]

In John Smith's milling machine thread I drilled a 3mm hole in steel with my MF70. 636 people looked at that video over 5 days. No one commented. I could make a spindle nose adaptor for my FD150 and make a sawing trial at 5000rpm with a 100w motor (I might anyway because it might be useful for me) but will it change anyone's opinions, probably not.

I am a happy Proxxon user and I understand the limitations of their machines, I have in the past discussed price/performance balance with their technical department as I have with Sherline. That is why my FD150 has Sherline chucks.

[Pete.Participant @pete-2]

Posted by John Smith 47 on 21/04/2021 12:15:56:

@Pete – I need the metal to stay absolutely flat after it has been cut.
In my experience sheers never seem to achieve this.

Rather than endless what ifs, I thought I'd demonstrate what I said.

A simple table on my bench shear before I had machine tools at home, it would be made with dowels at various angles now.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Roger B on 22/04/2021 18:49:42:

[…]

I am a happy Proxxon user and I understand the limitations of their machines, I have in the past discussed price/performance balance with their technical department as I have with Sherline. That is why my FD150 has Sherline chucks.

.

Roger,

Please forgive me if my comment came across as ‘generally’ negative to Proxxon … that was not my intention.

I was simply trying to honestly answer John’s specific question relating to the use of that saw and/or its listed blades to cut steel.

MichaelG.

.

Edit: ___ upon re-reading my earlier post: The statement

… but Proxxon needs to inform you in the context of its machines.

Might better read:

Proxxon has a general duty to inform purchasers of the ‘design envelope’ of its machines, and has done so:  It has evidently determined that cutting ferrous material on that saw, with those blades would be outside that envelope.

Edited By Michael Gilligan on 22/04/2021 20:47:24

[Martin KyteParticipant @martinkyte99762]

Posted by John Smith 47 on 22/04/2021 16:50:29:

**LINK**
"The 28020 is a Tungsten tipped Saw Blade with high-alloy special steel"

Given that it is tipped with Tungsten, how come it can't cut mild steel? I get that it can't but I am curious to know why it can't. I was thinking that if we could slow down the RPM, and increase the torque of the motor (e.g. by having a higher wattage motor running more slowly) maybe that would help

Likewise I am also curious that solid carbide discs are no better.

Either way for thin metal sheet (e.g. 0.1mm) the easiest way to cut it and maintain flatness still seems to be a very high speed disk.

OK, just how mad is this suggestion?
Go for something mass-product & much more powerful and find a way to do precise grinding cuts.

e.g. Bosch GTS635-216

**LINK**

Cost: £335.99
Power: 1600watts – a surplus of power
Speed: 5,500 RPM – pretty very fast for 21cm
Weight: 22Kg – not impossible
Incline: 0 to 45degrees
Saw blade diam: 216 mm
Bore: 30 mm

I just need to find some very thin (1mm? 2mm?) abrasive cutting disks that are 216x30mm.
[I ran out of time googling but surely they exist!]

But even if I have to settle for quite wide cuts, at least I would get my straight cuts… through steel.

J

The gullets on the TCT circular blade are huge. I would suggest that the least worst case would be that the material stalls the saw and the worst case that it throws the material back at the operator. If you look at an Evolution Chop saw blade which is designed to cut metals the gullets have an anti kickback profile which limits the depth of cut.

regards Martin

[John Smith 47Participant @johnsmith47]

Posted by Michael Gilligan on 22/04/2021 17:27:32:

Posted by John Smith 47 on 22/04/2021 16:50:29:

**LINK**
"The 28020 is a Tungsten tipped Saw Blade with high-alloy special steel"

Given that it is tipped with Tungsten, how come it can't cut mild steel? I get that it can't but I am curious to know why it can't. I was thinking that if we could slow down the RPM, and increase the torque of the motor (e.g. by having a higher wattage motor running more slowly) maybe that would help

Likewise I am also curious that solid carbide discs are no better.

.

.

The blade is intended for an underpowered machine with an inadequate spindle

Please see Peter’s post and my response, on page 1

The blades could almost certainly do your job: if suitably supported and adequately powered at an appropriate speed.

… but Proxxon needs to inform you in the context of its machines.

 

MichaelG.

CUTTING WITH BLADES
OK please can you help me out here. Use of blades means calculating the cutting speed (i.e. "Vc" ).

1) What is the correct range of cutting speeds for mild steel? A what would be a reasonable margin for error on this?

I looked it up on Wikipedia and found the suggested cutting speeds range from "3 to 38 metres/minute" for mild steel – but I believe some people are challenging this(?)
Aluminium is: "122 to 305 m/min" cutting speed.
Wood is: "183 to 305"

2) And how can I calculate the correct RPM vs diametre in order to get this cutting speed?

I believe that the correct equation is:

Cutting Speed (called "Vc", in metres per minute) = (Pi x Diam (in mm) x RPM) /1000 … yes?
i.e. Vc = (3.141592 x Diam x RPM)/1000

Example A.
In round numbers, supposing we had a disk of 100mm diametre running at 5,000RPM, plugging the numbers in we get:
Vc = (3.14 x 100 x 5,000 )/1000 ==> 1,571 ==> call it 1,500 m/min – which is more like 100 times what we want for steel, no?

Example B.
My little 22mm abrasive cutting disk cuts well at 20,000 rmp, but I notice that it doesn't seem to cut well at c. half that speed
Vc = (3.14 x 22mm x 20,000rpm)/1000 ==> 1,382 ==> call it 1,300 m/min

Example C.
Proxxon FET Table saw – large 80mm disc:
Vc = (3.141592 x 80mm x 7000rpm)/1000 ==> 1,759 ==> call it 1,700 m/min

Example D.
Proxxon FET Table saw – small 50mm disc:
Vc = (3.141592 x 50mm x 7000rpm)/1000 ==> call it 1,100 m/min

Example E.
Rutland Mini Saw
80mm disc, 6800 rpm ==> c. 1,700 m/min
80mm disc, 4400 rpm ==> c. 1,100 m/min

Example F.
Bosch GTS635-216
216mm disk, 5,500 rpm ==> c. 4,600m/min
(but can I find a 1mm thick disk? If not could I tolerate an unnecessarily wide cut?)

Conclusion:
These disks are all spinning FAR too fast, even for Aluminium and wood they are way too fast!
For mild steel presumably what is needed is much slower, but also more torque

CUTTING WITH ABRASIVE DISC
A 1mm wide cut would be a reasonable target. Yes things can get very hot but at least thin plates don't get bent where the don't get hot.

J

PS What about a reciprocating 'jigsaw' built into a table-top?
e.g. Rockwell BladeRunner X2 – is dirt cheap c. £170 (and does at least claim to cut steel!)

**LINK**

Let's be honest it's way too cheap to be of good build quality (sounded noisy in a youtube review) and it's USA voltage so I would need to get a voltage converter too. But it got good reviews on eBay (4.6* from 278 reviews).

 

Edited By John Smith 47 on 22/04/2021 20:45:24

Edited By John Smith 47 on 22/04/2021 20:45:47

Edited By John Smith 47 on 22/04/2021 20:46:07

[JasonBModerator @jasonb]

You don't say what you are cutting with HSS, carbide and Abrasive discs will all have different cutting speeds and you have been considering them all in this thread.

[Ian PParticipant @ianp]

As I understand it the OP want to cut 0.1mm/0.004" sheet steel (into narrow strips?)

How narrow? how long? what kind of steel is this? how good does the cut edge need to be? lots of questions come to my mind but if I had to cut (what sounds like shimstock) I would never had thought of sawing.

Sawing such thin material is in watchmaking territory, it certainly can be done but the work has to be very well supported and doing this on a circular saw type machine where the blade comes through a slot in the table the edge of the slot is going to be further from the side of the blade than the material thickness.

For one-off or small quantity it might be best to bond the steel to a sacrificial plate (brass, steel or even a sheet of Formica) and use a mill or router to create the outline before separating the parts.

Other possible methods of making parts out of thin material include, laser or water-jet cutting or etching.

Ian P

[John Smith 47Participant @johnsmith47]

Posted by Pete. on 22/04/2021 18:54:18:

Posted by John Smith 47 on 21/04/2021 12:15:56:

@Pete – I need the metal to stay absolutely flat after it has been cut.
In my experience sheers never seem to achieve this.

Rather than endless what ifs, I thought I'd demonstrate what I said.

A simple table on my bench shear before I had machine tools at home, it would be made with dowels at various angles now.

@Pete to get clear you are saying that even a huge guillotine puts a curve into ONE side of 1mm thick mild steel sheet, but the other side stays dead flat, yes?

To my mind that is just a nightmare, because you end up will loads of bent mild steel that you cant use for anything else unless you find a way to bend if flat again. And that means huge bulky rollers as well as a high bulky guillotine.

I think all my problem would be solved by:

A) a small abrasion-type cutting disk that is 1mm thick, that is buried into a table in a circular saw table
type of configuration.

B) for slightly thicker steels, a slow turning circular saw (or band saw?) that has a very high torque should do the job.

Regarding Proxxon as a brand, I find myself deeply conflicted. I have some of their stuff and in general it is reasonably good, but i) the prices are extremely high and ii) the build quality is sometimes very good but the next minute it is absolutely woeful, for no good reason. I mean certain things rattle badly that damned well shouldn't rattle at all.

Bottom line: Proxxon stuff is all pretty expensive and although much of their stuff is great, but you can't RELY on the brand to be great.

This make them sometimes feel like toys for amateurs even though some of their stuff IS pretty darned good. Frankly they just need a big new management shake-up and proper quality control… and a few spindles that run true and they would be absolutely brilliant.

[John Smith 47Participant @johnsmith47]

 

JasonB
In my defence, see 3rd paragraph of my intial post:
"But will it be able to cut/grind mild steel and stainless steel?"

And most of it will be c. 1mm thick sheet. Recently I had to cut some that was 0.1mm thick too, so it would be nice to combine both. 

Wait, do abrasive discs care about cutting speed? It seems to me that the faster the spin the better the sparks, fly off taking the heated material with them. Am I missing something?

@Ian P – Regarding length of cut, it varies – ideally at least 10cm.
Yes, using a sacrificial material is an option, but it is time consuming and messy, so I was broadly hoping to avoid doing much of that.

Recap: I was very struck by just how well a thin abrasive cutting disk (38mm x1mm @ 10,000 to 20,000 rpm) cut through both my 1mm thick steel AND my 0.1mm thick steel. It was fast and it left the sheets absolutely flat (once de-burred). Also, FWIW, at larger scale (according to various youtube videos) it seems huge cutting disks are the way to cut though steel FAST with angle-grinders etc. 

My problem is that they can't do LONG, accurate cuts – but 'obviously' (to me at least!) you could if the blade was buried within a table in a circular saw table type of configuration.

Unfortunately (as far as I can see) the world doesn't seem to have made any circular saw tables that have 1mm thick abrasive cutting disks!

Edited By John Smith 47 on 22/04/2021 21:34:13

Edited By John Smith 47 on 22/04/2021 21:36:15

[speelwerkParticipant @speelwerk]

Perhaps not possible with stainless (never tried) but 0.1 mm brass cuts easily with a Stanley knife along a ruler. Niko.

[John Smith 47Participant @johnsmith47]

Posted by speelwerk on 22/04/2021 21:46:35:

Perhaps not possible with stainless (never tried) but 0.1 mm brass cuts easily with a Stanley knife along a ruler. Niko.

I tried with a knife on a cutting matt but what resoluted was not longer flat and got bent near the edges. The problem is that 0.1mm is quite easily bent.

To get clear, I need a result that its more or less "optically flat"! i.e. It is not bent around the edges, and when I sand it down with super-fine wet & dry the sanding goes right to the edges of the cut.

Fwiw, I was cutting a 10 x 5mm piece of 0.1mm mild steel. I suppose if you cut it against something that was very rigid, but not quite rigid-enough to blunten your blade – maybe a very rigid cutting mat that you don't mind damaging, then you might get away with it (??)

[Pete.Participant @pete-2]

As I said before, cut it oversize using a method that doesn't bend it, angle grinder slitting disc, Bandsaw, anyway that pleases you, personally I'd use my makita 18v sheet metal shear as it doesn't distort the sheet on either side.

Then with the fence set to exactly 90° on my bench shear, trim one edge, place trimmed edge against rear fence, trim second edge, repeat, you now have a square with straight cuts and 90° corners as accurately as you set the fence.

[speelwerkParticipant @speelwerk]

I just cut it on the workbench which is made out of melamine board and changed every year or so when it has to many (cut) marks. With a sharp knife it stays straigth and leaves almost no bur. Niko.

[JasonBModerator @jasonb]

John I did read what you wanted to cut and have mentioned yoyr 16 x 13 plates to give people an idea of sizes.

You asked "what is the cutting speed range for steel" and I asked with what you were going to be cutting with as each cutter will have a different cutting speed.

I gave a speed in your other thread and queried those you got from Wiki

As a rule of thumb if using HSS then 30m/min, Carbide tipped or solid tooling 100m/min and abrasive discs 3-4000m/min all could be +/-20

From this and your example calculations it's easy to see that all these saws are really designed for wood as the speeds are optimised for that and too fast for optimal cutting of metal with HSS or TCT blades or a bit too slow for optimal cutting with Abrasive discs

As a simple example that saw blade I show in the mill when cutting steel would be going at about 100rpm if cutting steel. A similar size 1mm cutting disc in my small angle grinder would be running at 11,000rpm. Now maybe you can see why I asked what cutting materials was being used as it affects the cutting speed

[Stuart Munro 1Participant @stuartmunro1]

Posted by John Smith 47 on 22/04/2021 21:13:04:

Regarding Proxxon as a brand, I find myself deeply conflicted. I have some of their stuff and in general it is reasonably good, but i) the prices are extremely high and ii) the build quality is sometimes very good but the next minute it is absolutely woeful, for no good reason. I mean certain things rattle badly that damned well shouldn't rattle at all.

Bottom line: Proxxon stuff is all pretty expensive and although much of their stuff is great, but you can't RELY on the brand to be great.

This make them sometimes feel like toys for amateurs even though some of their stuff IS pretty darned good. Frankly they just need a big new management shake-up and proper quality control… and a few spindles that run true and they would be absolutely brilliant.

Joihn, I have to agree re Proxxon. I have one of the FET table saws discussed in this thread; its generally very good and can be adjusted to about 0.1mm BUT the fence appears to be about 0.5mm out along its length but the BLADE is what is not at 90 degrees to the table. I make do by setting the fence parallel to the blade but for a tool of this price this should not happen.

Stuart

[Stuart Munro 1Participant @stuartmunro1]

p.s This is why I'm attracted to the Byrnes Table Saw – by all accounts the Rolls Royce of wood modellers table saws but coming in a £550 – £600 landed in the UK…..

[Stuart Munro 1Participant @stuartmunro1]

pps – now that I know that it has blades to cut Brass sheet and aluminium sheet it may become a realistic option as a multi material saw. Off to se the minister of home finance.

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