Cutting corrugated sheets

"Steve B" fired this volley in news:jq2pnu$i56$ snipped-for-privacy@speranza.aioe.org:

Although the Galvalume guys will tell you that using anything but a shear voids the warantee, almost all the professional pole barn constructors in this neck of the woods use a diamond saw to cut 5-vee, and standing-rib barn metal. It works pretty well, if very noisily.

The reason the manufacturers say it's bad to saw is because a shear tends to wipe the plated layers across the cut, while a saw (supposedly) leaves the end clean and bare.

I use a power shear (Malco "Turbo-Shear" drill attachment). It's a tiny bit of a chore moving up and down ribs, but not as bad as you might think. The nose of the cutter has a geometry that allows you to follow the ribbing without much distortion.

LLoyd

Is it a universal brush motor? If so you can reduce speed with a router speed control rated for the current of the saw. If it's an AC induction motor then no.

I tried some experiments with "light dimmers" and felt they didn't work very well for motor speed control, but then I didn't know that AC induction motors don't like to be speed controlled that way.

Roller stands and roller tables are awesome tools to have. I use mine for all kinds of things. I wish I had a couple more.... and a better place to store them. LOL.

"Bob La Londe" fired this volley in news:6I8xr.41749$ snipped-for-privacy@newsfe01.iad:

DON'T store them, Bob. Dedicate a couple to every tool, and leave them up!

LLoyd

Universal motors normally spark inside. Induction motors normally don't.

jsw

Looks nasty to cut.

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I think that most radial arm saws, and hand held circular saws as well, are brush equipped universal motors. Those should do pretty well with a dimmer -- or even better with a speed controller which senses back EMF between the pulses to determine speed and adjusts the power to try to maintain that speed.

But this won't do much for the needed torque. A saw *made* for this would have a mechanical way to slow down the motor -- such as perhaps a worm gear. That boosts torque while cutting speed.

However, if you have no brushes (consult the diagram in your manual if you can't find external brush caps), it will not work well at all.

Frankly, I have no idea. I can imagine the makers have a custom shear which follows the contours -- but that would be good for just a

90 degree cut -- or they might have another for 45 degree and maybe even 30 and 60 degree cuts -- depends on what the demand is.

Do they offer suggestions as to how to cut it?

I, personally, would be very worried about that. The only thing which might make it somewhat safer is the loss of torque because of your speed control. :-)

Good Luck, DoN.

[ ... ]

Probably not well at all. Sewing machine motors are very low horsepower, compared to circular saws. (Something like 1/10th vs 1 HP or so -- more for larger blade diameters.)

1) Look for insulated screw-in caps on the outside which allow you to inspect and change the brushes. (They wear out over time.) They should be about in line with the end of the rotor where the commutator would be, if you know what those are. 2) If you can't find screw-in caps (probably a cheaper saw), look in the manual (download it from the maker's site if you can't find the one which came with it) and look at the diagram. If you know what motor brushes look like, you should be able to recognize them in the drawing. If you don't, spend time reading through the parts list which accompanies the manual looking for the word "brush" or "brushes".

And you've never had a power tool quite working because the brushes are worn out, either? If all your tools are new, maybe not. If you get old ones, and they start acting flakey, they probably need new brushes (very cheap repair items), and the commutator may need to be turned and (perhaps) the mica in the grooves undercut.

But I really don't think that this will be very satisfactory even with a speed control. If you want to cut at slow speeds, you need to gear the speed down and the torque up -- e.g. use a motor designed to run that kind of saw blade.

Good Luck, DoN.

I was told it's the heat harms the coating, so only cold cutting should be done. You could rough cut say one inch out from the desired line, then cut to line with manual snips.

Jordan

Definitely not stupid, Steve, you know that you don't know, so you are intelligently asking for help. A real dummy would go ahead without asking.

For cutting corrugated, I use a metal cut off disc in a 9 1/4 saw or for smaller stuff a 1 mm disc in an angle grinder. Lotsa noise & sparks, watch for grass or other combustibles. I has a grass fire start from 6 metres away, all around where I was working was bare soil.

Alan

I bought an old Sears table saw with the blade arbor pulley safely outside the base housing to use for sawing sheet metal with abrasive cutoff disks. The table tilts rather than the blade, making it very inconvenient for sheets of plywood.

The motor is under the plate the saw mounts on, protected from the stream of sparks. It's weight tensions the belt so it lifts when the blade jams. The fine adjustment is a rubber hockey puck wedged under the hinged motor plate. I raised the saw base on blocks so I can blow out all the sawdust before cutting sheetmetal.

If the cut edge is up, under another sheet or the ridge cap, the LPS3 I spray on it is enough to minimize rusting where the zinc has been burned. Otherwise I cut the sheets with an air shear like this.

lotsa hand pressure.

If you or storms mess up the corrugations you can reshape them over 2" pipe with a plastic hammer:

jsw

I have a blade I purchased years ago for my 7 1/4 Skill. It looks like a diamond blade,but isn't. It has approx 5/8" deep slots every 30 deg.or so. It works great for all types of sheet metal products. It's not around now or I would try and see the mfg. CP

Pilgrim fired this volley in news:pilgrim- snipped-for-privacy@70-3-168-216.pools.spcsdns.net:

It's a "ferrous metal cutting blade". It's nothing more than a circle of High Speed Steel with some notches. I have a couple.

They cut by friction, alone, and work fine, so long as you're not trying to preserve a finish, or avoid burrs on the cut line (which they leave in abundance).

LLoyd

I put them on my CNC plasma machine and just do up's and downs as I cut the sheet.

Mart> >

"Steve B" fired this volley in news:jq87cv$fm1$ snipped-for-privacy@speranza.aioe.org:

No, just a disk of HSS. The notches simply provide room so as the edge expands, the blade doesn't cup or warp when it gets hot. It cuts purely by friction heating getting the work metal hot enough to scrape away. They count on the red-heat hardness of high-speed steel to make it survive the red-heat softness of the sheet metal you're cutting.

You have to run them fast (rotation rate), and apply pretty good pressure to get them to cut... no diddling in the work.

The Borg would normally stock them. Sometimes even my local ACE does. Sears always did, too.

LLoyd

Plus, the heat of friction introduced into the disk is distributed

*around* the entire disk, while the roughly equivalent heat of friction in the work is concentrated at the spot you're cutting.

Not having done it, I don't know how much damage it does to the coating. Keep in mind, though, that the zinc on galvanized steel melts at a significantly lower temperature than aluminum -- several hundred degrees F lower.

If you get steel hot enough to melt, any zinc on it is hot enough to vaporize. That's not true with aluminum.

I suspect that any damage is confined to an area pretty close to the cut. But that steel is now somewhat oxidized, and the coating is, too. So any rust-proofing repair -- with zinc chromate paint, or zinc-loaded epoxy -- isn't going to stick unless you clean it well.

Jordan fired this volley in news:jq8t3g$cmo$1 @speranza.aioe.org:

Only that last preserves the plating. Even the backwards carbide blade both heats and completely bares the cut end.

Lloyd

Ed Huntress fired this volley in news: snipped-for-privacy@4ax.com:

Power shears are really the way to go. Those I picked up at the siding supplier work a treat, and are only a tiny chore to get over ribs.

Lloyd

Well.... back when I had money I put up a 3000sqft warehouse next to my house. Figured it would have room for a small office, storage for my communications contracting business, room for my 3 trucks and 2 boats and a little space in the back for wrenching on trucks and boats if times got tough and I had to do my own work again.

Now that I don't have money I wish I had put up 6000 sq ft back when I did have money. I never in my wildest dreams would have thought I would be setting up a small shop much less a small machine shop and doing as much work in the warehouse as I do in the field.

I am using every bit of it, and I only manage to keep one boat and one truck inside now. My new service truck sits outside.

If I ever get around to finishing the office that will help some. I'll get a stack of drywall out of the way, and move a lot of the shiny purty parts out of the warehouse into the front office.

I'm also considering putting in some mezzanines to move some storage to a second level. I have a 16' eve height so a 7' or 8' mezzanine in 1/2 the shop would work out ok.... if I only had the money. LOL.