Long flat on a round bar

[Archie]

Evenin' all. Would love to pick your collective brains on the best way to go about making a flat along the length of a round bar. I have an 18mm bright bar of 1.5-2m in length and I require a flat of 12.5mm width along the length of it. A back-of-fag-packet calculation (which I now can't find) says I need to remove just over or under (can't remember which!) 2.5mm from the bar. For a shorter piece I'd stick it in the mill and take a slice off but obviously with a piece this long I won't be able to do it in one go this way. So has anyone got any bright ideas as to either how I'd do it some other way (without the mill) or how I can do it section at a time on the mill without the bar turning when I move it along. Hope that makes sense? It does to me! Cheers chaps.

 

[malcolm]

How accurate does it need to be? The bodger in me came up with a method for doing that sort of thing with an angle grinder: http://www.mig-welding.co.uk/forum/album.php?albumid=28&pictureid=168

 

[Archie]

I've seen that pic before but had forgotten about it. I haven't a dividing head but since I only need the one flat that wouldn't matter. However, I don't quite see how you used the arrangement to get a length of flat?

 

[wyn]

Use the mill, but weld a bit of flat on the end so you can put some sort of level on it, to keep it orientated every time it's moved. Will it bend a bit when the material is removed ?

 

[Archie]

Genius plan Wyn! I think if I clamp it straight to the bed rather than putting it in the vice I should be OK. It doesn't need to be super accurate as it's only to be a measuring stick/end stop for the cold saw. Just accurate enough that I won't be annoyed to see a wavy edge along it's length!

 

[Paul.]

Use the mill, but weld a bit of flat on the end so you can put some sort of level on it, to keep it orientated every time it's moved. Will it bend a bit when the material is removed ?

Thats how I do it, Its a common job on some of the machinery repairs that i do, usually in stainless, A quick calc says you need to take off 2.52mm to leave 15.48mm that will give a chord of 12.5mm, they do bow, a nudge with the flypress will sort it.

 

[wyn]

A digital display type of level would be the best.

 

[Archie]

Good to know my maths isn't so wayward! Cheers Paul.

How much bowing are we talking about? I haven't a fly press...

 

[Paul.]

I use a moore and wright engineers level,
How much it bows depends on the material and how hard a cut you make, trick when straightening is a controlled push, not hit it, 2 blocks and a clamp on your nice bench will be fine.

 

[Hitch]

Id tack it to a bench and run the 9" up it a few times, holding it flat as possible if it need not be that accurate.
Suprising how accurate you can be with an angle grinder if your take your time. But seeing as you have a mill, leave the bar a few inches long, tack a reference on one end to use to level it up Then just cut to length.
Seems mightly long Archie, will it have another leg to the floor at the end?

 

[Hitch]

I haven't a fly press...

Two bits of hardwood 6" apart, copper/hide mallet on the back every 4" or so.

 

[Archie]

Another cunning plan Paul.

I'm not so keen on the angle grinder route Hitch but I might rough the top off and then pass it through the mill to tidy it up.

As for length, I think it's going to be OK. I stuck the full 3m length in the vice and there was only small amount of droop so with a bit less length.... fingers crossed! If it does then, yes, I'll probably stick a leg on the end.

 

[chunkolini]

Sorry to sound a bit thick here, but...
Why do you have to put the flat onto a round bar? cant you just use say a length of 12mm square bar? or something?
Doubtless I have missed something here.

Chunko',

 

[Archie]

It's for a measuring stick/end stop for the cold saw Chunko'. It has to be 18mm since that's the size of the hole in the machine into which the bar fits. There has to be a flat onto which to stick the scale which is 12mm wide and wouldn't bend around the bar. I got it done today so here's a crumby pic which I hope illustrates what I'm trying to explain.

 

[Hitch]

Weld a bit of 18mm round to something else....

 

[Archie]

As they say: "There's more than one way to skin a cat".