Hole cutter for plastic tank - cheap?

Looking through the various ball valves, bits etc, it looks like I need to cut 22mm, 27mm and 35mm holes to install a couple of plastic water tanks. Can anyone suggest a suitable cutter(s) for this?. I've seen various expensive holesaws and the like in Screwfix. Problem is, once used this tool will end up adding to my relentlessly expanding 'bought for one job and will never get used again collection"**, so if possible I'd like to buy 1 usable cheap item and throw away, hopefully!.

Thanks, Egremont

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** One of the most frustrating things about DIY, perhaps eclipsed only tbis syndrome... You need a small amount, 'x', of something. However you have to buy (ie pay for) a pack of 10'x'. This leaves you lumbered with 9'x' of said something, probably bulky, which hangs around for years until you eventually lose hope of finding a use for it/them and so the 9'x' (you paid good money for) ends up in the bin. And if you're really unlucky, you find a use for it soon afterwards!.
Reply to
Egremont
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I've always just heated up an appropriately sized piece of copper pipe and pushed it through the tank. Works a treat though you sometime have to trim a bit of flash away with a craft knife.

AWEM

Reply to
Andrew Mawson

any piece of junk will cut sheet plastic. I'd go to poundland and get one of those holesaws made from a cast metal plate plus a selection of bits of bent hacksaw blade that you push into the right groove to get the size wanted. Not too sure if they go as small as that, but if they do, =A31 will do it. Go easy with them though, theyre very weak.

Failing that, even a candle and pin would do it.

NT

Reply to
bigcat

Screwfix part 12620 does almost ever hole size you'll ever need and for £15 I have found is well worth the money.

Reply to
Mike

Well I hadn't even dared to think of shoving hot copper pipe through the plastic!. Even if I had the courage to try this, then the next problem is I don't have any 27mm or 35mm copper pipe.. Maybe not a goer for me but someone else might find this tip useful one day...

Screwfix 12620 may do every hole size you'll ever need, but with a minimum cutting radius of 40mm it won't do _any_ of the holes I need. Just as well, I've just done a Screwfix delivery so this would cost me £21 inc delivery to get this week.

This leave the pound-shop concentric cutters. Probably the best bet, depending one the hole sizes, sharpness of the cut and the accuracy needed (eg would 30mm do for a 27" hole?). I want cheap but I don't want leaking tanks in the loft!.

One other thing might help - chuck some/all the fittings I've got and get different sized ones.

Egremont

Reply to
Egremont

You'll certainly have leaking tanks if you cut a 27" hole!!

Reply to
Set Square

... e.g. would 30mm do for a 27mm hole... etc etc

Reply to
Egremont

Hmm. Either they've changed the design or the 40mm min is a misprint. I've done all the holes on several water tanks with mine. I'll have a look at it tomorrow to see what the smallest diameter I can get is but I would estimate in the 10 to 15mm sort of region.

Reply to
Mike

I've done that a few times (before buying a holesaw set - incidentally on offer from screwfix though currently out of stock) and none of the tanks has suffered. However the tank manufacturers inevitably warn not to do this. I wonder why. Maybe they think we're too thick to trim the burr off and it'll leak?

Reply to
John Stumbles

Or this one is a third of the price and will do the same job:

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Reply to
John Rumm

I had a look at mine today and it goes down to 20mm. As the Screwfix catalogue says part 12620 starts at 40mm it would appear mine, which came from Screwfix a long time ago, is a different thing so please scrap that suggestion.

Reply to
Mike

Perhaps you have something like Screwfix 17377 (£19.99), aka Toolstation

72369 (£9.94!)?. The smaller cutter range is 22-40, definite possibility for me. The big cutter is superfluous though this tool looks like it might be generaly useful. All I need to do now is find another £30-06 to spend to get the free delivery!. Then again there's always the Pound-shop holesaws.

On paper Toolstation seem to do a good range of stuff, seemingly very cheap - I just sent off for a catalogue to put next to the Screwfix one.

Egremont

Reply to
Egremont

No. MIne is definitely like the 12620 but looking again at the photo I think the boss in the centre may have got bigger, hence the larger min diameter.

Yeah. Unfortunately in practice some of their products leave a little to be desired in quality, their technical support is almost non-existant and they don't want to replace unsuitable items. On my last order TRVs, expanding foam and adhesive were all of poor to unusable quality.

Although Screwfix went through an appalling patch a while back they appear to be back to rights and I've never had a problem with them - if something proves to be not up to the job they've usually refunded without hesitation.

Reply to
Mike

little to be

expanding

hesitation.

With some companies you expect a few failures, little help, and minimal prices. Thats toolstation. A lot of their kit is silverline, which is at the lower end of seriously usable building tools. If moneys tight, its just right. If you want the best, shop elsewhere. (Dont buy the rubber grouter, it leaves black marks.)

For more budget stuff, try

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the cheapest of all is generally poundland. Surprisingly some of their stuff is quite ok - much of course isnt. But when you pay =A31 a go you just budget for a percentage of duds. You can be paying =A31 for stuff that would cost over =A310 from any serious supplier, so if youve not got every tool known to man, theyre a good source of stuff thats better than not having the tool. And their hammers seem just as good as any other, despite the joke price.

NT

Reply to
bigcat

The green SX foam I ordered seems to do what it claims on the tin...

Reply to
John Rumm

The outcome...

I got the ajustable cutter from Toolstation. This worked fine on the small open-top tank, where I was able to get something solid behind the plastic being cut. I was a bit doubtful of the auger-type action but I'd practiced first on some surplus material from this tank (which I'd cut-down to get into the back of the loft - half empty so will be fine). Good job I did - the hole size was a bit larger than indicated by the cutter gauge.

But no such luck with the big enclosed (Screwfix 50G, £60)) tank - I think the plastic was different (softer?) and I couldn't get much behind the material. Made a horrible gashed mess for smallest hole. By now holecutters arrived in local Poundshop. The concentric one, with finer teeth, looked most promising and recovered failed 22mm ball-valve hole (as 27mm overflow hole) brilliantly.

But, 35mm hole attempt failed horribly again - bounced all over the place and made a horrible mess, thereafter the cutter wouldn't hold in it's arbour. Finally tried other Poundhop holecutter - solid but big teeth. Made another horrible mess - didn't bite but bounced around and end result looked like a car tyre gashed into tank. I suspect all holecutters would have been OK with first tank with something behind.

In the end I recovered the situation by marking holes with respective washers, drilling out and filing!. A bit long winded but simple, cheap, zero-risk and very good result - I was lucky not to ruin the big tank with the cutters. There may have been a better way (and hot pipe was an option for the smaller holes), but all in all I never found out what is was!.

Egremont.

Reply to
Egremont

There is a solution. Buy a cutter of the type that consists of a drill on an arbor and screw on cutters in stout metal e.g. Screwfix

72870 or even 11002. You can buy either the set or individual cutters. B&Q have them as well, as do trade plumbing places.

The concentric type cutters with springy steel blades are about as much use as a chocolate teapot as are the adjustable types.

If you drill slowly, the arbor type drill the pilot hole accurately and the stout cutter behind completes the job. You don't need to support the tank from behind.

It is simply not worth writing off a large plastic tank for the sake of saving a few pounds and buying from the pound shop.

Reply to
Andy Hall

Andy Hall wrote in news: snipped-for-privacy@4ax.com:

Couldn't agree more. £10 (for six cutters and the arbors) is not a fortune

- not much more than £1 each. That is exactly what I did when doing the same job three years ago. The number of times I have used them since would have justified the set. With that experience I think that I would push the boat out and get a decent brand!

Reply to
Rod

OK thanks for the extra info. Knew I must be going wrong somewhere.

I should have mentioned that I tried to make do with my good but single-speed HSS drill, tried the 14V cordless first but not enough 'puff''. Obviously if I'd had variable speed HSS or even fully recharged my 14V I

*might* have had better results even with some of the £1 cutters.

I'd thought about Screwfix 11002, but the holes of 22, 29 & 38mm didn't match my requirements of 22, 27 and 35. Most holesaws I've seen seem to have rather coarse teeth, which made me unsure that most would cut into a plastic tank OK (though I'll believe it now if you say they do). I suspect that, for just drilling plastic, the cheaper ones aren't much different from the new holesaw mini-set (fairly robust arbor + screw-on cutter type) I'd got from the local Pound shop?, and from memory the exact hole sizes were again elusive. So I went with £1 cutters and in fairness don't know if I can blame them for the result at high speed.

To do this particular job again as a one-off, I would still mark out the exact hole using the fitting washers, drill a ring of small holes just inside this line, cut out and then file (with small half-round file) to the ring mark - totally safe, accurate and zero cost, and no extra unwanted tools about the place. Obviously takes 20 mins per hole instead of 2 mins, but for a single job I can live with that.

In some other circumstances, I might fork out on a holesaw set, try it at slow speed and hope for the best!.

Egremont.

Reply to
Egremont

I think that the key with a plastic tank is to use a slowish speed and not to press too hard. The other aspect of this is to avoid the plastic getting too hot and melting. You don't want that either.

Reply to
Andy Hall

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