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Metal cutting jigsaw

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David Brown 906/12/2015 17:17:02
75 forum posts
4 photos

I have bought a Bosch GST 25 metal cutting jigsaw. I wanted to cut 6mm thick 6082 aluminium.

The jigsaw comes with special blades for cutting alumium. I have managed to destroy 3 aluminium cutting blades and 3 ordinary metal blades. I only managed to cut the aluminium with extreme difficulty and the cut is not straight. I can probably clean it up on my mini mill.

Does anyone have this jigsaw and have any idea what I am doing wrong?

At first I thought I was not fitting the jig saw blade properly, but having changed blades a number of times I am pretty sure I am doing this right. The instructions are useless.

David

JasonB06/12/2015 17:23:56
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21467 forum posts
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A handheld jig saw will never give a totally straight cut no matter how good your eye, they rarely work when run against a straight edge either as the blades don't track true to the side of the base, infact you can strain teh blade more trying to use a straightedge than freehanding it.

Not got the bosch but my DeWalt DW331 cuts OK on the odd occasion that I have used it on metal

Edited By JasonB on 06/12/2015 17:29:20

paul 195006/12/2015 17:30:54
143 forum posts
32 photos

I use a cheap Bosch jigsaw that I bought for a few pounds from a car boot sale but i buy the best blades i can, if a blade is blunt it will not cut straight often cheap blades will nor cut from new. if you push hard it will not cut straight also look at the blade and not the machine

Keith Long06/12/2015 17:39:24
866 forum posts
11 photos

My experience of jigsaws is using them to cut wood rather than metal, but in thick material you won't get a straight cut accurate to a line through the thickness of the material. My guess would be try different speed (cutting strokes / min), use a coarse blade so the gullets don't get clogged, using the pendulum action will help with that as well. Not sure whether coolant/lubricant would help or just get very messy, might be worth trying using a small amount as an experiment.

On the odd occasion I have used a jigsaw on metal it's been on thin steel sheet for car repairs. Works OK but NOISY.

Edited By Keith Long on 06/12/2015 17:39:48

frank brown06/12/2015 17:58:50
436 forum posts
5 photos

You are using some cutting oil/3 in 1 /WD40? Just find the optimum blade speed/ feed pressure and it might come right. In theory the blade should be doing 200 Ft/min (milling cutters). So at .5"/rev this works out to 4800 RPM, seems too high. On the other hand manual hacksawing is 50 strokes per min of a 10" blade , is 500 ins/min or 40 Ft/min, which would be 4800/5 = 1000RPM.

Frank

Neil Wyatt06/12/2015 18:13:45
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My ancient B&D jiggy cuts 3mm steel OK, I'm sure it would happily cut 6mm aluminium with a nice coarse blade.

But it isn't a precision tool in metal.

Ajohnw06/12/2015 18:18:56
3631 forum posts
160 photos

One of Myfordboys video's shows him cutting 1/4 steel neatly with one of these, building a furnace series.

**LINK**

I would have thought it would handle a good deal more on aluminium with the correct blade.

John

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David Brown 906/12/2015 18:48:42
75 forum posts
4 photos

I have not been using cutting oil I will try this next. The blades seem to be jamming, maybe cutting oil will help?

What cutter is best for aluminium on a mini mill (I have the Sieg SX2)? I need to remove around 2-3mm from the edge to get it straight, the sheet is around 70cm long and 17cm wide. Also, what is the best way to hold this on the milling machine?

David

Ian P06/12/2015 20:10:16
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2529 forum posts
102 photos

I use an ancient Bosch jigsaw (their first pendulum model) and have used it on 6 and 10mm thick ali plate. I get the best results using freshly made wood powder (sawdust) as a lubricant.

To clarify, when cutting metal I mark out where I want to cut on a thin piece of plywood or hardboard and clamp or tape it to the metal. The jigsaw blade cuts through the meat and the wood creating the 'fresh' sawdust (at the right time and at the right point) and seems to act as a lubricant. It certainly stops aluminium 'sticking' to the blade.

I used to frequently cut apertures in already painted or anodised enclosures and regardless of how much masking up or surface protection I applied the sole plate of the jigsaw always marked the finished surface because trapped swarf particles got hammered into the surface. Masking tape or any liquid lubricant just made this worse by holding the swarf in (the wrong) place. A layer of hardboard totally eliminates this problem.

The only way to cut a dead straight or accurately with a jigsaw is to proceed very slowly. Let the saw do the work and only use light pressure in the cutting direction.

Ian P

Clive Hartland06/12/2015 20:19:06
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2729 forum posts
40 photos

One thing is that the blade is sticking, this creates a, 'Jerking' effect which will buckle the blade. Use any lube, perhaps even candle grease rubbed over the cutting path. This is much like a bandsaw and you have to hold the jig saw firmly.

Clive

Robert Dodds06/12/2015 21:02:35
294 forum posts
46 photos

David,

Have you got this Bosch "pendulum motion" set right. Iv'e never experienced it but the claim is that it eases cutting forces on thick sections. According to the Bosch spec your'e good for 25mm alum or 15 mm steel so you are well inside the limit
Speed wise you are on a 25mm stroke up and down so 1 rev = 50mm 2" or 1ft in 6 reolutions. Therefore to get 200ft/min youwould be looking at 1200rpm not counting the fact that its a sinusoidal motion so the average velocity is probably half that.
Read more about pendulum motion at <http://www.toolstop.co.uk/the-importance-of-pendulum-action-what-it-is-and-why-you-should-have-it-a1119>

Bob D

David Colwill06/12/2015 22:01:44
767 forum posts
40 photos

I've always struggled with the pendulum action on jigsaws on the odd occasion I've used one on metal. I found it best to switch it off. If cutting aluminium I think I'd be inclined to try a medium wood blade on a slowish speed. As for cutting steel I too found the blade life almost nonexistent, probably due to rushing.

Regards.

David.

Ian P07/12/2015 15:27:25
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2529 forum posts
102 photos
Posted by David Colwill on 06/12/2015 22:01:44:

I've always struggled with the pendulum action on jigsaws on the odd occasion I've used one on metal. I found it best to switch it off. If cutting aluminium I think I'd be inclined to try a medium wood blade on a slowish speed. As for cutting steel I too found the blade life almost nonexistent, probably due to rushing.

Regards.

David.

Not using the pendulum when cutting metal is something I would agree with, I should have mentioned it earlier.

Using Bosch blades I have always found their life quite acceptable although in steel I have only cut 3mm thick (plus wood thickness)

Ian P

Dave Powell 207/12/2015 17:01:35
33 forum posts
11 photos

I recently had to resort to using a jigsaw for cutting 3mm steel, I had some fairly steep radii to work round as well as some long straights. I purchased a pack of very high quality blades and the whole job went rather well. I did find that the blades blunted fairly quickly but can't see that being a problem in ally, although pinning (like with files) could possibly be an issue. As others have said make sure the pendulum action is turned off. Don't try and run the blade too fast and be careful if cutting tight radii. My curves were approx. 2 1/2 inch radius and I just about got round them ok.

David Brown 907/12/2015 19:46:07
75 forum posts
4 photos

So I tried again with some cutting oil and turned off the pendulum action and it worked fine! Thanks for all the advice.

It cuts straighter now. It still isn't cutting totally straight but I have understood that this is probably not possible with a jigsaw. It is straight enough that I can easily use my mini mill to get it really straight if I need to. I cut it free hand.

I will try sometime using a thick length of bar as a guide, Using a straight edge does not work well as it is not thick enough, or I guess I could just try a straight piece of wood.

I would have got a metal cutting band saw but don't have enough space. Unless I have a really thick peice of metal this jigsaw will do fine.

David

Dave Powell 207/12/2015 20:40:30
33 forum posts
11 photos

One tool that I get on really well with is an angle grinder equipped with one of those 1mm thick cutting discs. It's great for cutting straight lines in a wide range of thicknesses, I have only used on steel though so don't know if they are any good for ally. I find it much easier to get a good straight line than when using a jigsaw.

Peter Neill07/12/2015 21:05:51
12 forum posts

Ok, I’ll hold my hands up and take the shame. Some years ago I bought a JML Exact Saw, a small handheld 2” circular saw that’s more like a Jigsaw really.

Quite a clever little design except for the spring loaded trigger switch and the spring loaded blade guard, which are both really s%*t pieces of design. Any way, I use this to cut up to ¼” thick Aluminium plate which won’t fit in my Bandsaw, and it breezes through this like butter. However, if you don’t modify the sprung switch and guard, you would be cursing the awkwardness of that bit of design to high heaven.

norman valentine07/12/2015 21:12:57
280 forum posts
40 photos

I have used a jigsaw to cut 1/4" brass. As long as you keep the pressure light it is possible to cut straight but certainly not quickly.

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