On 30/03/2018 11:02, Dave Plowman (News) wrote:
In article ,
John Rumm wrote:
On 29/03/2018 23:50, Dave Plowman (News) wrote:
As a supplementary, I used an angle grinder with a metal cutting disc
in a bench stand to cut the tube last time. OK, but not perfect.

I've got an old B&Q chop saw. No longer used as I have a very nice
Makita compound mitre sliding one. Would it be possible to find a mild
steel cutting blade for that? Being so much larger than the angle
grinder stand, easier to set the tube lengths and clamp in place, etc.

Look at the evolution range of blades - they do ones for steel (and
other stuff).

Looking on Ebay, discovered I can buy a steel cutting blade for the 305 x
30 Makita. But don't want to risk any damage to that.

IIRC, the B&Q had an odd centre size, so would probably need to find an
adaptor too.

Plenty on eBay, as I found when re-blading my 35 year old Bosch. In your
case I would probably re-blade the B&Q.

On 30/03/2018 16:53, Dave Plowman (News) wrote:
In article ,
newshound wrote:
On 30/03/2018 10:47, dennis@home wrote:
On 29/03/2018 23:50, Dave Plowman (News) wrote:
As a supplementary, I used an angle grinder with a metal cutting disc
in a
bench stand to cut the tube last time. OK, but not perfect.

I've got an old B&Q chop saw. No longer used as I have a very nice Makita
compound mitre sliding one. Would it be possible to find a mild steel
cutting blade for that? Being so much larger than the angle grinder
stand,
easier to set the tube lengths and clamp in place, etc.


Tungsten tipped blades cut mild steel with ease.
I have an evolution mitre saw (£25 second off ebay).
You need a fine toothed blade for something with thin walls.
Also be gentle.

I used it for alu 20x20 extrusions for a bit of 3d printer I was
modifying a few weeks ago and the result was perfect.

I have also used it to "plane" down metal after giving up with a file.


+1, I have an evolution chop saw, and it is fine for speedfit type tube,
also ordinary old fashioned dexion.

Do they run at a different speed from that likely with my B&Q one?

Not obviously different. What you have to watch is that the steel chips
coming off sting a bit if they hit bare skin. I usually stick a face
mask on when using it.

You need to hold square tube down firmly into the guide, preferrably use
a clamp for small / irregular stuff. And don't ram the blade hard in,
try to feed it gently. (I'm sure you have good mechanical "feel", this
comment is for less experienced users).

Decided to just go ahead with what I have, for cutting. Angle grinder in a
stand with steel cutting discs. And wondered if I'm using the wrong
technique?

A new disc cuts well, but soon seems to get blunt (or clogged) without
looking badly worn. Thinking it might be my Chinese Bosch ones, bought
some Rhodius (made in Germany) from ToolStation, which were more
expensive. And if anything they are worse.

It's cutting through the top of the square that is the problem. Once
through that it rips down the sides. And I can rotate it to cut the bottom
vertically.

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On Friday, 6 April 2018 19:08:21 UTC+1, Dave Plowman (News) wrote:

Decided to just go ahead with what I have, for cutting. Angle grinder in a
stand with steel cutting discs. And wondered if I'm using the wrong
technique?

A new disc cuts well, but soon seems to get blunt (or clogged) without
looking badly worn. Thinking it might be my Chinese Bosch ones, bought
some Rhodius (made in Germany) from ToolStation, which were more
expensive. And if anything they are worse.

It's cutting through the top of the square that is the problem. Once
through that it rips down the sides. And I can rotate it to cut the bottom
vertically.

Grinding discs depend on pressure, which drops as teh disc sinks into the work. I rotate workpiece or keep altering grinder position to keep cut rate up.


NT

On 06/04/2018 19:01, Dave Plowman (News) wrote:
Decided to just go ahead with what I have, for cutting. Angle grinder in a
stand with steel cutting discs. And wondered if I'm using the wrong
technique?

A new disc cuts well, but soon seems to get blunt (or clogged) without
looking badly worn. Thinking it might be my Chinese Bosch ones, bought
some Rhodius (made in Germany) from ToolStation, which were more
expensive. And if anything they are worse.

It's cutting through the top of the square that is the problem. Once
through that it rips down the sides. And I can rotate it to cut the bottom
vertically.


Have you tried starting with it rotated by 45 degrees, then in 90 degree
steps - so that you are always cutting into a corner?
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In article ,
Roger Mills wrote:
On 06/04/2018 19:01, Dave Plowman (News) wrote:
Decided to just go ahead with what I have, for cutting. Angle grinder
in a stand with steel cutting discs. And wondered if I'm using the
wrong technique?

A new disc cuts well, but soon seems to get blunt (or clogged) without
looking badly worn. Thinking it might be my Chinese Bosch ones, bought
some Rhodius (made in Germany) from ToolStation, which were more
expensive. And if anything they are worse.

It's cutting through the top of the square that is the problem. Once
through that it rips down the sides. And I can rotate it to cut the
bottom vertically.


Have you tried starting with it rotated by 45 degrees, then in 90 degree
steps - so that you are always cutting into a corner?

Did wonder about that. Sadly the vice on the stand isn't big enough to
allow mounting the tube at 45 degrees.

--
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Dave Plowman London SW
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In article ,
Roger Mills wrote:
On 06/04/2018 19:01, Dave Plowman (News) wrote:
Decided to just go ahead with what I have, for cutting. Angle grinder in a
stand with steel cutting discs. And wondered if I'm using the wrong
technique?

A new disc cuts well, but soon seems to get blunt (or clogged) without
looking badly worn. Thinking it might be my Chinese Bosch ones, bought
some Rhodius (made in Germany) from ToolStation, which were more
expensive. And if anything they are worse.

It's cutting through the top of the square that is the problem. Once
through that it rips down the sides. And I can rotate it to cut the bottom
vertically.


Have you tried starting with it rotated by 45 degrees, then in 90 degree
steps - so that you are always cutting into a corner?

Looking at the grinder stand, I can adjust the position of the vice
relative to the blade. At the moment it is set so the blade hits the
centre of the tube face. I'll try altering it so it hits a corner first.
The vice isn't big enough to hold the tube at 45 degrees.

--
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Dave Plowman London SW
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In article ,
Dave Plowman (News) wrote:
Have you tried starting with it rotated by 45 degrees, then in 90 degree
steps - so that you are always cutting into a corner?

Looking at the grinder stand, I can adjust the position of the vice
relative to the blade. At the moment it is set so the blade hits the
centre of the tube face. I'll try altering it so it hits a corner first.
The vice isn't big enough to hold the tube at 45 degrees.

After some experimenting found a decent place for the vice so the disc
starts the cut on a corner. Needed a packing piece for the movable part as
the thread wasn't long enough. But have now managed a clean cut with only
one rotation of the work. About half way through now so having a coffee
and cake. ;-)

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Dave Plowman London SW
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Got a tip out of all this. For those who don't regularly cut steel with
and angle grinder. Ie, like me.

Reverse the disc once in a while. They seem to go 'blunt' quite quickly.
Reversing it reverses the effect. I assume it gets sort of clogged up.

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Dave Plowman London SW
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On Sun, 08 Apr 2018 23:10:16 +0100, Dave Plowman (News) wrote:


Reverse the disc once in a while. They seem to go 'blunt' quite quickly.
Reversing it reverses the effect. I assume it gets sort of clogged up.

Shouldn't really happen with steel. Aluminium, yes, but not steel.



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In article ,
Cursitor Doom wrote:
On Sun, 08 Apr 2018 23:10:16 +0100, Dave Plowman (News) wrote:


Reverse the disc once in a while. They seem to go 'blunt' quite
quickly. Reversing it reverses the effect. I assume it gets sort of
clogged up.

Shouldn't really happen with steel. Aluminium, yes, but not steel.

Err, I've just said it does. I'd suggest you try it before commenting.

I cut ally with my circular saw. Gives a perfect cut. Hence me asking
earlier about similar for steel.

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Dave Plowman London SW
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On Mon, 09 Apr 2018 11:03:35 +0100
"Dave Plowman (News)" wrote:

In article ,
Cursitor Doom wrote:

Shouldn't really happen with steel. Aluminium, yes, but not steel.

Err, I've just said it does. I'd suggest you try it before
commenting.

I cut ally with my circular saw. Gives a perfect cut. Hence me asking
earlier about similar for steel.

You're possibly not pressing hard enough - the wheel needs to lose the
blunted/clogged grit to expose fresh abrasive. The resin that bonds
the abrasive particles is designed to wear away at a rate suitable for
whatever material the disc is designed to cut, so it will be pretty
tough for steel.
Try taking multiple nibbles (press and release, press and release ...)
rather than applying steady pressure in one go.

In article 20180411030240.7846a679@Mars,
Rob Morley wrote:
On Mon, 09 Apr 2018 11:03:35 +0100
"Dave Plowman (News)" wrote:

In article ,
Cursitor Doom wrote:

Shouldn't really happen with steel. Aluminium, yes, but not steel.

Err, I've just said it does. I'd suggest you try it before
commenting.

I cut ally with my circular saw. Gives a perfect cut. Hence me asking
earlier about similar for steel.

You're possibly not pressing hard enough - the wheel needs to lose the
blunted/clogged grit to expose fresh abrasive.

Here, that seemed to produce the very worst results. Best way was short
sharp bursts allowing things to cool in between. But I didn't try massive
pressure.


The resin that bonds
the abrasive particles is designed to wear away at a rate suitable for
whatever material the disc is designed to cut, so it will be pretty
tough for steel.
Try taking multiple nibbles (press and release, press and release ...)
rather than applying steady pressure in one go.

That's what I did. But the thing still stopped cutting.

Best results on this square tube would likely have been with a corner
square to the disc. But the vice on the stand not big enough to allow
this. Once it had sort of broken through, it cut just fine.

Other thing was with the maximum depth of cut with this setup, anything
other than starting with the tube flat and square in the vice required
more than one pass.

But job's finished now and OK. Perhaps I should just have bought the
aluminium version of the tube, as that cuts perfectly using my circular
saw. But it is over twice the price. Probably strong enough for the job,
though.

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Dave Plowman London SW
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