# Help with bending cast aluminium



## inkyblue (15 Oct 2015)

Discovered today that my favourite circular saw must have taken a fall or something, and the sole plate which is cast aluminium, has bent. This means that it's no longer running square to the blade. Has anyone got any tips, for example should I heat it before attemting to straighten it back? I was thinking of placing between two of sheets of steel and gently hammering?? Tips appreciated as I got the saw in the States nearly 20 years ago, and it fits my hand like an old friend. Thanks


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## adidat (15 Oct 2015)

Cant help thinking it would probably break very easily like most cast materials. Would it be possible to file away the damage and polish with sand paper.


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## inkyblue (15 Oct 2015)

No, it's more like a buckle. Wish it was as simple as a file and sandpaper job


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## dickm (15 Oct 2015)

I'm with Adidat on this - if it's really cast ali, hiding to nothing it will break if you try to bend it back, whatever you do. BUT, does the fact that it bent anyway, rather than broke, suggest it may not just be cast?


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## inkyblue (15 Oct 2015)

Thats why I was hoping it would bend back, given that it's bent in the first place. It may not be cast, but certainly looks it


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## timber (16 Oct 2015)

inkyblue":cmn16yve said:


> Thats why I was hoping it would bend back, given that it's bent in the first place. It may not be cast, but certainly looks it


I have a Motorway sigh board from the M1 that was taken down by contractors , it is covered in plastic coating of some sort .
It is quite hard and stiff However when I put the propane torch to burn the plastic off to make some small brackets it just went all soft and floppy ,like a piece of rubber. The sign I suppose when made is rolled under extreme pressure , easily cut with a jig saw though.
You may finish up with a floppy saw if you heat it!!!??


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## AndyT (16 Oct 2015)

Maybe an alternative approach to rescuing the saw without bending... find a suitable piece of thin flat steel (old throwaway saw?) and glue it on to the bent baseplate. Use a gap filling construction adhesive like Gripfill so as to bridge the gaps between the new flat base and the old bent one.


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## adidat (16 Oct 2015)

Timber i thought motorway signs where made of a worthless material so there woukd be no point in nicking them for scrap


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## AES (16 Oct 2015)

@inkyblue:

I agree with all the above - if it really is cast ali (or even worse, pressure die cast "monkey metal" - looks a bit like cast ali but has a high zinc content and can be overall a bit of a duller grey than ali) then in my experience you're on a hiding to nothing trying to straighten it out.

The idea of replacing that plate altogether (with a piece of sheet steel) is a good one, but depending on how complex that base plate is (holes, slots, etc, etc) it could be quite a bit of work making a new one (but by no means impossible).

IF there is a small piece of the base plate that you can safely cut off with a hacksaw without damaging it any more than it is already, it's worth while having a look at the cut off piece - if you break it in 2 has the break line got a dull grey granular structure? And how difficult was it to break, easy, or pretty tough?

An approach to trying the repair is to take a broken piece from the off cut and apply a normal plumbers blow lamp to it, but be warned, most aluminiums melt at around 700 deg C (cast monkey metal a lot less) and the hottest part of the flame on a standard propane plumbers torch is at least 1000 deg C, so go easy. A trick here is to see the temperature change happening on the metal by coating the part with a bit of damp toilet soap - when the soap coating turns a dull brown then stop heating! Is the piece now a molten blob or is it still intact? If intact you can try a repair by heating the complete bent plate in the same way, again coating it in soap so that when the soap turns brown you stop heating and try bending it straight - GENTLY!

The chances are it will snap at the point, leaving you with 2 choices (apart from making a new one from steel).

Choice 1: - Google for aluminium welding/soldering rods (there are several on the market), get some scrap ali for practising on, follow the instructions (and there's at least one video on Youtube showing it being done) and when you're comfortable with the procedure, try welding the 2 bits of plate back together. It CAN produce quite acceptable and strong results sometimes (but NOT always)! And you need to work out in advance some sort of (heatproof) "jig" to hold it still during the repair.

Choice 2: - If your broken sample piece melted in the test above, or if you're not happy with the above aluminium soldering/welding idea, then just try bending the plate back straight without any heating. It may or may not straighten without heat - probably not, so if not, it'll again leave you with 2 pieces to join. There are various cold metal epoxy "welding" glues on the market but I've never tried any although I've heard good reports. My own fall back in that situation is to use the old original Araldite (needs at least 24 hours to harden, NOT the newer 5 minute stuff). Make sure the joints are VERY clean (acetone is good), work out some "jig" arrangement with ply or something to hold the parts together for the 24 hour+ hardening time, mix the adhesive EXACTLY as per the instructions, apply to both parts, and cross yer fingers. You can decrease the hardening time by heating overall, gently in the oven (IF domestic authorities allow - but make sure you take steps to catch any overspill in the oven - NO, don't ask!). 80 degrees C needs about 3 to 4 hours in the oven, depending on size/mass of the part. Araldite does produce some very good results provided the joint is VERY clean before applying adhesive, provided the mix is exactly as per the instructions, and provided the parts are held perfectly still and straight throughout the hardening period.

The only other thing I can think of is to find a professional ali welder with a TIG set up (because trying to straighten it will almost certainly break it, or if not then at least badly weaken it - ali does something horrible called work hardening when you bend it, making it tend towards being brittle). But TIG is likely to be costly, so only really worthwhile if it's a valuable/expensive tool.

Sorry if any of the above is teaching granny, good luck, hope it helps

AES


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## inkyblue (16 Oct 2015)

Thanks for all the suggestions, much appreciated. Am wondering if it's best left as is, and gluing a piece of 6mm phenolic to the base. From what I've learned and heard, the chances of it snapping are too great to risk I think Cheers


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## AES (16 Oct 2015)

@inkyblue:

Yup, your idea about using a phenolic piece on the plate may be a good alternative - it depends what the plate and the bend looks like. How about posting a pic?

And I'm not so sure that gluing phenolic to ali is a good idea, it may work or it may not, but phenolic is a bit difficult to glue well to something like ali - I don't know what glue to recommend. If you can do it, riveting would be a better solution, but although it's not too difficult it does need a bit of know-how, and a practice beforehand if you've not done it before (I'm talking about "proper" countersunk ali rivets here, not the DIY stand-by of pop rivets applied with lazy tongs (which will not give you a flush surface on either side of the rivet).

If you do fancy a go at riveting send me a PM and I'll send you a bit out of one of my old text books from my apprenticeship which makes it pretty clear. I can even send you a hand full of ali rivets in the post if you want to try!

Best of luck with it - annoying when something like that happens on a favourite tool.

Cheers
AES


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## dickm (16 Oct 2015)

+1 for actually breaking it, then getting the parts properly aligned and find a really skilled Tig welder to put it back together. BUT, it'll probably cost you more than a really good replacement saw, unless you know someone who will Tig for mate's rates.

Have tried welding/"brazing" ali myself with disastrous results - either end up with lots of melted metal or what looks like a tidy joint but falls apart a few days later


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## AES (16 Oct 2015)

Mel,

Dickm is quite right about ali welding/soldering/brazing (whatever you want to call it), it is very easy to produce disastrous lumps of molten junk, but it CAN be done, and I've done so myself - it "just" needs lots of patience and practice before you try the real repair. That's why I wrote something about watching Youtube and practising if you do decide to go that route.

But overall, I think the general consensus here is that you've got a major problem on your hands, and unless the tool is of significant value you'll just end up spending a lot of time and effort practising whatever method you choose and still most likely end up frustrated with a broken tool.

Dickm's suggestion about a TIG welder at mates rates is probably the only realistic way out for you - personally, whatever method you choose, and however much you practice, I shouldn't think your chances of coming out with a workable tool is better than 50-50 at the very best. Sorry.

Good luck anyway

AES


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## inkyblue (16 Oct 2015)

Thanks for the kind offer AES. Was thinking of taking the sole plate off the saw and making a sub plate from the phenolic, and drill through exactly where the screws hold the plate to the saw frame, and re-attach both with slightly longer screws. Kind of like a router sub-base. I'll try to shim out under the deflected part, and give it a thin coat of stixall. I'll try to get to it next week......that's the plan. Cheers once again for the kind offer


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## Beau (16 Oct 2015)

AES":2kfhsrom said:


> @inkyblue:
> 
> Yup, your idea about using a phenolic piece on the plate may be a good alternative - it depends what the plate and the bend looks like. How about posting a pic?
> 
> ...



If you want to have a go at bonding phenolic to the base West system epoxy should be up to the job.


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## Racers (16 Oct 2015)

I straightened my Makita biscuit joiner after dropping it. it took a few careful taps with a hammer to bend the casing back, it wasn't bent much just enough for the base not to shut properly.
Try a few taps to see it it will move you will need to find where it is bent and support it at the bend and tap the bent bit back in to line.
I did fix a bent Hitachi router base by epoxying on some 6mm plastic, I used thicker layer of epoxy on the bent bits and clamped it to a flat surface.
It worked out well.

Pete


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