Sheet & plate edge straightening / grinding???

[astro_al]

Hi folks. Just wondering how people cut material from sheet or plate and then make the cut edges perfectly straight again. I have a guillotine but it only does 16 gauge. Most other stuff is cut with the plasma, but it usually requires a bit of post-plasma fettling, and then I find it very hard to get a ruler-straight edge on it - usually comes out slightly 'undulating' due to uneven grinding, or the odd 'nick' from the plasma cannon.

This weeks off-the-wall tool idea was to make a kind of vertical mill / spindle router thingy which would have an adjustable stop like a table saw and a milling cutter in a fixed position. You could 'feed' the plate past the cutter with the stop set at the correct width in order to get a perfectly straight edge on it.

Any thoughts??? Would be very simple to make.

Cheers, Al.

 

[snowcat]

The problem with using an end mill to true plate is the work will need to be fixtures to the table very well, I hate machining rouged work, it always causes vibration, and destroys tooling....

I personally guillotine, sheet and pug cut plate, At collage we had a gas torch mounted on a couple of linner rails this left fairly neat cuts, something similar could soon be maid to steady a plasma torch....

even clamping straight edges to act as a fence prior to cutting will leave a decent ish finish...

 

[David_W]

Slightly different way round the problem, but I've found that a metal cutting circular saw leaves really neat edges, got one of these and it'll go through 1/2" steel no problems
http://www.amazon.co.uk/185MM-METAL-CUTTING-SAW-1200W/dp/B000QB81BI/ref=sr_1_3?ie=UTF8&s=garden&qid=1247347328&sr=8-3.
Have seen the results from the guides for the gas-axes, pretty good results as well

 

[chunkolini]

Maybe try using a straight edge clamped on and running the plasma torch along it. With practice this leaves a beautiful edge with no oxide hanging off the bottom, looks almost sheared. Taking time setting it up is the most important thing, do several 'dry' runs to get the feel for the action, rotate from the hips if it is a long cut. You might like an extra from a kung fu film when you are rehearsing the cut, so keep the door closed. sounds a bit poncy, but visual the movement first.
Glasshoppahhh*.

Chunko'.
*apologies to David Carridine.

 

[^neo^]

depending how big the plate you're cutting is, use a linisher to get rid of wobbly edges.
Only real way to get a nice clean edge is guillotine though

 

[Hitch]

We are lucky to have the gear to be able to do it without a fuss, shear upto 13mm plate, profile cut everything else.

Although sometimes,disc, hand gas or hand plasma is the only way to do something.
Seen fixtures that use 2 small wheels, one each side of the torch, the torch fits centrally between them, in a fairly tight fitting bush. That stops any left to right movement, the wheels allow nice smooth movement, and keep it the optimum distance away.
Rest one wheel against a bit of flatbar, and your away.


Making a machine to mill after sounds unnecessary, a bit of thought on a cutting jig should solve your problems.

 

[astro_al]

Thanks guys. A solution would be a real time saver.

Snowy, I was envisaging using an old horizontal mill for the 'chassis', I know what you mean about rigidity. It could be used to bevel edges too - handy. What is pug cut?

David - my other idea was to make a wall-saw or panel saw like they use in B&Q to cut sheets of wood, but for metal. I just wonder how long blades would last cutting decent sized plate.

I think the problem with plasma is variations in travel speed lead to nicks in the cut surface. Sometimes the torch sticks slightly, especially if cutting rusty metal, which causes problems. I use a straight edge and 'flow' through the cut as a dry run first.

I'l keep thinking. The beauty of the saw or mill solution is that it can cope with almost any size of material. Guillotines are not so flexible and get heavy, expensive and large pretty quickly.

Cheers, Al

 

[wyn]

If you want to bevel the edges sometimes, use an edge beveling machine and it may be possible to turn it so the cutter works at 90* to the plate.

Or you could make up a machine utilising the cutters which should be ideal for that sort of thing.

 

[snowcat]

straight line cutter is the proper name PUG is the name of the original BOC machines so the names stuck..

 

[Paul.]

Heres a BOC pug, doing its thing