How to cut a hob extractor "chimney"?

dunroving

Thank you for all of the helpful suggestions. In response:

It's a costly error to make if a DIY approach results in a burr, discoloration, a crimp, etc.

I called several metal fabrication companies and all but one said they only do large-scale industrial jobs.

I called several laser-cutting companies who mostly said they can only cut 2-D (flat panels), and the other (3-D) company would charge £70.

After further research, I have come to the conclusion that the part is an incorrect length (wrong part).

Adding together 90cm countertop height + 65cm gap to bottom of the canopy + 45cm depth of canopy + 52cm duct length + 6cm minimum length of tejescopic bit = 258cm (or 2.58cm) – this is 30cm higher than a typical modern ceiling.

I have been in touch with Bosch and they couldn't get their heads around it, so have had to send photos and an explanation.

It also struck me that if I modified the duct, the warranty would become void.

nofoollikeold

Be a bit careful with the measurements. Some hob manufacturers require the minimum height above the hob to be measure from the top of the pan stands. Could add a centimetre or two to your figures.

ianto11

Which model..? because this one as an example (link ) has an adjustment of 294mm from full extension to retraction and at it's minimum it's 660mm

So you would have 900mm to worktop, 650mm min to bottom of hood and 660mm to top of chimney
Total of 2210mm and you 2300mm ?

robotrobo

Will2208 wrote: »

I used an angle grinder with a thin blade. I clamped chimney to a workbench, marked up where I wanted to cut and then very carefully and slowly cut with an angle grinder.

I had exactly the same problem.
so i made a wood frame for the inside to hold the thing in shape , top and bottom,i used a few small wood screws and then a thin blade in the angle grinder , take your time

dunroving

nofoollikeold wrote: »

Be a bit careful with the measurements. Some hob manufacturers require the minimum height above the hob to be measure from the top of the pan stands. Could add a centimetre or two to your figures.

The measurements have been pretty accurate. I have an induction hob. The Bosch manual says the gap to the bottom of the canopy should be greater than/equal to 550mm.

900mm (to hob top) + 550mm gap = 1450mm to bottom of the hood canopy. With a 2.30m ceiling height, that allows 2300 - 1450 = 850mm of space for the extractor canopy + duct piece #1 + duct piece #2 (extender, set at lowest setting). However, these 3 pieces are a total of over 850.

I have been doing a load of research online and now realise that the instruction manual is incorrect. It says the 3 pieces above can range from 642mm - 954mm (depending on whether the 3 extender is at its shortest or longest). I found a Q&A on their customer site where the height of the product can rage from 799mm to 975mm - which is (a) different from the manual, and (b) incorrect!

The bottom line is that for this to work, you have to have the canopy set at its lowest permissible height from the hob (550mm for electric, 650mm for gas), the extender set at its lowest, and have a ceiling height of 2.30m (electric hob), or 2.4m (gas hob).

I could have fitted this in, just about, with these lowest settings, but the instruction manual indicates you have a lot more leeway than you really have. And set at these heights, you can't have a standard splashback between the hob and chimney canopy (because the space is not tall enough).

It looks like my options are (a) pay to get the chimney shortened, and void the warranty, (b) remove the canopy and re-attach it at a lower height (requiring removal of my glass splashback, and redecorating), or (c) hope that Bosch recognises the major error in the instruction manual and somehow provides me with a shorter chimney that will fit.

ianto11

apologies if I'm misunderstanding...but do you need the extender could you not use the canopy and on duct ?

Oop s just looked at the drawing I sent and I see 3 parts there also :o

dunroving

ianto11 wrote: »

Which model..? because this one as an example (link ) has an adjustment of 294mm from full extension to retraction and at it's minimum it's 660mm

So you would have 900mm to worktop, 650mm min to bottom of hood and 660mm to top of chimney
Total of 2210mm and you 2300mm ?

It's a DWP64BC50B (manual here).

Similar to the manual you posted, the diagram on p. 10 indicates a minimum height of 642mm, but this number is grossly incorrect - it's actually more like 850mm.

I found a technical sheet also, here. On p.2 it gives the height of the canopy as 246mm (so, close to my measurement of 250mm), and for the chimney of 573mm minimum. That adds to 819mm, which is a different number yet again(!), but again far greater than the 642mm in the manual.

We were working on the 642mm in the manual, so thought the 700mm we left would be more than enough room.

dunroving

ianto11 wrote: »

apologies if I'm misunderstanding...but do you need the extender could you not use the canopy and on duct ?

Yes, you could*, but even without the additional duct, the lower duct is still too long by over 10cm. So, with it flush to the ceiling, the bottom of the duct is below the top of the canopy.

* If you did this, you'd have a gap at the top, which although not functionally problematic, would look odd. Fitting involves attaching the upper duct to the wall, flush with the ceiling, pushing the lower duct over it, and dropping it about 5cm onto the attachment point at the top of the canopy(it's a drop-down fitting, not a push-on fitting).

ianto11

Bizarre....keep us updated with the feedback from,Bosch

dunroving

Interestingly, in a Q&Q section on the Bosch site, the following question is asked:

"My ceiling is low at 210cm. I want to fit this over a gas hob, so there is a minimum clearance required. Will it fit?"

The answer is:

"Hello, thank you for contacting Bosch Q&A.

The height of this product is a minimum of 799mm(chimney at a minimum) and a maximum of 975mm(chimney at a maximum).

There also needs to be a minimum distance of 650mm from the top of the gas hob."

(Note the Italics - every piece of information on the dimensions of this device is different, and all incorrect!)