Milling Steel Angle?

[VicParticipant @vic]

I’ve got some 75mm x 50mm steel angle that needs cleaning up. Angle is often pretty dire but the stuff I’ve got is particularly bad. Luckily the section is much thicker than needed so I hope to clean it up on the mill. I’m not sure of the best way to hold it though and the order of operations. Any suggestions? I have two pieces 150mm long to do. I should add that final squareness is not super critical and nor is the overall section. The biggest vice I have opens to just over 100mm and I have a 6” Angle plate. TIA.

[JasonBModerator @jasonb]

Pickle it firt in acid to get the black scale off rather than wear your tools doing it.

[JohnFParticipant @johnf59703]

I would hold it in the vice with a round bar against the moving jaw then use a fly cutter or shell end mill, do one outer face then reverse to do the other face.

Do you need to machine the inner faces as well ?

[Clive FosterParticipant @clivefoster55965]

$64,000 questions are whether the angle is flat or tapered on the inside and whether you wish to operate on the inside or outside.

Inside is theoretically easy. Whether flat or tapered.

Simply clamp down onto the mill table in several places and mill to size. Need to move the clamps for cutter clearance as you go and need a sufficiently long cutter to reach down past the upright. Which for most folk means a fly cutter. As you have two pieces to do you may prefer to clamp them together via the upright sides and operate on both at one setting. Probably reduces the chance of things moving during clamp shifting.

Working on the outside swops cutter difficulties for mounting ones.

If the angle is tapered you need to make the inside flat first before you can sensibly moon t it to deal with the outside. So might as well just do the inside and call it job done.

If it’s flat, whether as is made so, mount it on something to support the bottom side of the face you are milling and go for it. Last time I did such a job, not greatly dissimilar in size to yours, I clamped a bit of extruded alloy bar into the corner with toolmakers clamps, carefully mounted up in the vice with the usual tapping down precautions to make sure it was solid and had at it adjusting the clamp positions as needed.

If it had been longer I’d have gotten creative with a support bar on the table and several clamps.

Regrettably angle can have significant locked up stresses inside, largely depending how hot it was when rolled, and can distort after machining.

If its old bed iron angle bin it and get something decent, however many years you have been lovingly preserving it for that special job. No telling what got put in bed iron angle but it has a well deserved reputation for eating cutters, hacksaw blades and drills.

Johns round bar method can be OK on smaller sections of up to maybe 25 mm a side but on a larger section like yours it will almost certainly chatter. Especially likely with found material of indeterminate composition.

Although Jason is absolutely right about the effectiveness of acid pickle to remove mill scale I don’t care for acid in the workshop.  I would use a flap wheel in an angle grinder. Doing the job outside with the material strapped to my workmate ‘cos I also don’t care for loads of metal/rust dust in the workshop.

Clive

[VicParticipant @vic]

Both inside and outside need cleaning up.

[HopperParticipant @hopper]

I have milled steel angle with a fly cutter in the lathe with the angle clamped to the cross slide in order to make my own angle plates.

But the problem with holding it in a milling vice depends on whether it is taper-section angle or parallel section. The latter is easy enough to grip in the vice and mill the top face. The former not so. Even with a bit of packing on one jaw it can still move.

You could set your 6″ angle plate on the mill table and clamp your steel angle to that, with some packers/parallels to hold the job away from the angle plate so you can machine right up to the edge. That way, the machined surface will be truly square to the other outer surface. (Most angle iron is not truly square to any kind of precision standard.)

To machine the inside surfaces after the outers are done, it could be again clamped up against the angle plate and use a fly cutter that will get in underneath the clamps. Or it could be set in the vice on parallels if your vice is big enough.

[noel shelleyParticipant @noelshelley55608]

NEVER use bed angle ! often high tensile and hard to machine in any way,turned , milled, or drilling, also frequently cracks when welded.  Noel

[Clive FosterParticipant @clivefoster55965]

Reluctant though I am to cross pens (keyboards!) with the redoubtable Hopper I feel he is over sanguine in assessing the ease of machining angle sections of the size in question, 50 x 75 mm (2″ x 3″ in proper money) by holding in a vice.

At that size the material will have a strong tendency towards chatter unless supported beneath the area to be machined.

I’ve always found it a good rule of thumb to assess machining and work holding methods by component size and overall cross section. Basically up to an inch / 25 mm, inch to a foot / 25 mm to 300 mm and over a foot.

As this is a Model Engineering forum most discussions on methods focus around methods appropriate the inch / 25 mm class, albeit often long which is a slightly different aspect. At such sizes the simple grip in a vice should be just fine unless the part is very flimsy.

As Home Workshop guy working in 12 inch to the foot scale my natural home is inch to foot methods. Bigger parts often makes machining easier but supporting relatively thin overhung sections, like the angle being discussed, against chatter during machining can be very important.

Over a foot techniques being the easiest basically “Stuff that. I’m not lifting anything that heavy. Take it somewhere else.”.

One of the very few advantages of being almost 70 is having had plenty of time to make lots of mistakes whilst building up an impressive list of “shan’t do that again” things. Along with a pretty good feel for where the demarcation lines between  works-usually works-“are you feeling lucky”  for any given technique tend to lie.

Clive

[larry phelan 1Participant @larryphelan1]

Clive, you remind me of an old turner i knew years ago, who had a saying : “Any fool can take on a job, but the wise man knows the ones to walk away from”

I learned that the hard way ! These days, I am a little wiser and a bit more choosy.

[VicParticipant @vic]

There was a job that needed doing where I used to work. It was nothing to do with me and not even my department. The guys in the department though were somewhat reluctant to do it in case it went wrong – they were desperately worried about losing face and suffering the inevitable micky taking.  I offered to do the job and it worked out just fine. One guy watched me directly and several others watched surreptitiously. Pride it seems can prevent you attempting some jobs. 😆

Back to the angle. I don’t have anything stronger than citric acid so before I start work I’ll likely run an angle grinder (obviously the right tool!? 😆) over it before milling.

[HopperParticipant @hopper]

I have never found the scale on black steel bar or angle to dull cutters particularly. Cast iron, yes. Laser cut edges of steel plate, yes. But if you get the cut in deep enough to get under the scale on black bar or plate etc it does not seem to be terribly bad. Lot cleaner on the machine though if you remove it first. Yes, angle grinder is my weapon of choice for such.

[Howard LewisParticipant @howardlewis46836]

+1 for bed iron being horrible stuff!

FWIW, clamp the ouitside against bthe fixed jaw of the vice, and mill the top surface.

With that as a datum, you can now mill the other side at right angles to it.

But ensure the surfaces to be milled are on the same level, before starting the cut.

Then the macnied surfaces can be use as a datum to use an end mill on the inner surfaces, which are almopst certain to be tapered, so that D O C increases as you approach the inner end.

FWIW, I would feel inclined to use the side face (Flutes) of the end mill first, on the vertical face, before attacking the horizontal one with the end.

HTH

Howard

[VicParticipant @vic]

I originally decided to machine a pair of parts and then cut it in two for final shaping. After some more thought milling each component gives me more work holding options. I cut the angle roughly to length and cleaned up both ends. I then held it in the vice and fly cut the outer face of the long leg and without moving it cut the outer of the short leg with a long end mill. Next operation is to flip it over and cut the edges of both legs, again without moving it. After that I need to clean up the inner faces. I’m not sure whether to leave the fillet or not yet.

Edit: I didn’t bother touching the surface before milling and it cut just fine with both HSS and carbide tooling.

[VicParticipant @vic]

One down three to go. Once cleaned up I’ll size and shape them. Nothing fancy, I’ll probably just knock the corners off.

[Howard LewisParticipant @howardlewis46836]

You are well under way!

Probably fimished by the time that is typed.

Howard

[Howard Lewis]

On Howard Lewis Said:

+1 for bed iron being horrible stuff!

…
Howard

I read years ago that it’s because for many decades British bed-irons were made from recycled tramlines.    Tramlines were made from high wear resistant Manganese Steel,  hard, tough, with low ductility.  Having expensively dug up a road and buried rails in it, no-one wants to have to replace them in their lifetime!    That style of sprung platform for beds, no longer popular, coincided with the end of trams,  and some genius spotted a way to make money!

Manganese rail is easily converted into angle by heating and rolling it in a mill, and I imagine it being sheared and punched very cheaply into bed-irons at the same time.       Unfortunately, Manganese Steel is difficult to machine and weld, putting it on my Model Engineering avoid list.    Not impossible to machine but slow progress and a quick way of wearing out tools.

When a manufacturer chooses metal, he does so to suit his requirements, not those of a model engineer 50 years later!   As manufacturing has a much wider range of methods available than a small workshop, such as stamping, rolling, casting, grinding, moulding, extrusion, drawing, spinning, and explosive forming, no-one should be surprised if their nice bit of scrap is actually a present from Beelzebub!

Although Vic’s metal is emitting ‘I may be nasty’ warning signals, he reported later ‘ it cut just fine with both HSS and carbide tooling’.   But ‘it cut just fine’ is doesn’t tell us much because the measure is ‘how much metal was removed before the cutter went blunt’, not ‘cut OK for the short time I tried it’.

Only the man on the spot can decide if it’s worth persisting with awkward scrap;  it’s a balance between the cost of the material (cheap scrap), and the cost of cutting (time, cutters, and wear and tear on the machine.)    These days I usually buy known machinable metal, but my part of the UK has few scrapyards, none friendly, and not much local industry cutting metal.   Others seem much more fortunate.

As to holding long angle, I’d clamp it direct to the mill table – too bendy for a vice.

Dave

 

 

 

[derek hall 1Participant @derekhall1]

Will be interesting to see if once all machining has been done if this releases some stresses in the material causing it to bend

[HopperParticipant @hopper]

I’ve made a few small angle plates to use for milling on the lathe or drilling in the drill press, made out of 4″ steel angle cut down to about 1.5 or 2 inches each side, so the web is good and thick. Machined the outside faces but not the inside. No problems with either cutters blunting or the angle distorting after machining.

I got a bit carried away and scraped the surfaces in to a piece of plate glass so they were nice and flat. They seem to have stayed that way for years now.

[JasonBModerator @jasonb]

Good old JS used to pickle his blanks before drilling to mak the Myford indexing plates as the scale quickly blunted the drills. I also find it preserves the milled finish which can be advantagous when using black bar and section sto replicate castings which grinding would remove.

I’ve not noticed movement after machining, probably as it is hot rolled and in my case often tends to get heated again for silver soldering. Bright angle is a different matter. If this bit had moved then the crankshaft would no longer be at right angles to the cylinder, that was a bit of PFC

 

[duncan webster 1Participant @duncanwebster1]

As others have said, bed iron can be difficult stuff, but normal angles, channel etc tend to be made from S275, which is fine for welding (it is structural steel) and not too bad for machining, although getting a decent finish can be an issue

[VicParticipant @vic]

I’ve not noticed any movement so far on the first two pieces so fingers crossed.

[VicParticipant @vic]

Two done. I ended up shaping them just in case leaving too much bulk interfered with movement between top and bottom brackets. I was just going to sandblast and wax as usual but I think I’ll blacken these. As I’m not slavishly making a direct copy, the size is,within reason, anything convenient. They ended up around 70 x 70 x 36 with a 4mm section.

[Nigel Graham 2Participant @nigelgraham2]

I’ve sometimes used a soft-wood block between the inside of angle and the moving jaw of the vice, as it will distort enough to cope with the taper, gives lots of friction and dampens vibration.

This applies on the band-saw and bench-drill as well as milling-machine.

…….

No-one told us about bed-frames in the 1970s when my club used any number of them for all sorts of projects, including sleepers for a rebuilt 5″ & 7.25″ g  portable track! I do recall it being horrible to work though; not only tough but variably so.

We never did find a use for the dozens of tension-springs from some of those frames…

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