Experience with a wall chaser

[Lobster]

Just tried using one of these for the first time this morning with less than satisfactory results!

First off, I discovered that the *maximum* separation for the cutting discs is 29mm; since the *narrowest* size of channelling available is

30mm - and I normally use wider stuff myself - this is a bit useless IMHO.

Secondly, the instructions point out that for safety you need to move the machine in the opposite direction to that of the disc rotation. That means in practice that you start at the ceiling and 'pull' the machine towards you, working down the wall; ie the opposite direction to which you'd use a portable circular saw. This means that you can't follow your pencil line to cut straight; mine kept wandering off all over the shop. Laughably there's a laser guide on top which projects a pretty red line UP the wall, nicely aligned with the cut you've just made - ie does nothing to keep you on track. Lower down the wall, ie below the machine, the cutting line is completely concealed by the dust extraction pipe.

Is this experience similar to others? Or am I doing something daft? I find this machine worse than useless at present.

Incidentally this is the 45-quid Aldi machine, but before I get a chorus of "well what do you expect!" in its defence I'm not sure whether 'proper' machines are any different in the above respects?

David

[ben]

I used a petrol driven stone cutter once gave me a chase down the wall and a bloody doorway where I didn't want one. lol

[Grunff]

Most of the ones I've seen are 30mm max.

??

[soup]

Do you have the chaser upside down have tried several times to visualise holding it upside down seems that would give you the lazer on the "right" side but I could be very wrong only you can tell if you are holding it the wrong way round.

[Rob Morley]

If that's the maximum separation then won't the width of the cut will be

29mm plus two disk thicknesses?

Surely if you keep the laser pointed at a mark on the ceiling as you pull the tool down it will end up with a straight cut? I must admit I've never used one of these myself, but my experience of cutting with various circular saws and grinders is that if you don't worry too much about getting it straight it will tend to be fairly straight anyway, but if you try to correct every slight deviation you end up wobbling all over the place.

[Lobster]

That's what I also found from checking a few other models just now. But why, though??!

Oh, OK... I buy mine from a local electrical wholesaler, and their narrowest type is 30mm - which has a channel only wide enough for a single cable. Maybe the 'flats' on this brand are exceptionally wide or something?

David

[Lobster]

Sorry no; what I meant was 29mm was the width of the cut.

Well firstly the line wouldn't reach the ceiling from all the way down the wall, it's only intended to illuminate a short way; but secondly, surely even if you could, there would be nothing to stop you from veering off at an angle, and ending up 12" away from the intended socket position but with the laser still glued to the ceiling mark?!

David

[Grunff]

My gut feeling is that chasing is such a crappy, dusty job, you really want to remove as little material as you can get away with.

It must have some pretty wide flats.

[Andrew Gabriel]

Some of them can be operated with one blade removed, and then you can do two runs and get whatever width slot you want.

Um, 30mm is the widest oval trunking normally used.

12mm is the narrowest. Are you trying to use capping in a chase by any chance?

IME, you don't want a perfectly straight slot. I did that once, and then the trunking wouldn't stay in the slot without using nails to grip the sides. A freehand slot as you get from following a line by eye will have just enough deviation from straight to grip the oval trunking without using any extra fixings.

[Andrew Gabriel]

You are using capping, which is the wrong stuff for a chase. Use oval trunking, for which 30mm is the maximum (and that is significantly bigger than is required for 2 x 2.5mm² T&E).

[Lobster]

That does make some sense. When DO you use capping then?

David

[ben]

When I was on house rewires the only time trunking was used is when we couldn't chase the wall. I've never heard of trunking being used in a chase and then plastered over,too expensive so capping was used when a wall was chased.

[Andrew Gabriel]

On the initial install/first-fix when building is being constructed -- before the walls are plastered. Capping is shallower and can be lost in the plaster scratch coat depth. Oval trunking is thicker which could result in the chase needing to cut slightly deeper than just the plaster.

You don't actually need to use capping or trunking at all -- you can just bury the wires (or at least in cases where that's not permitted, neither is plastic capping or trunking). Having said that, I do always use oval trunking in a chase so new wires can be pulled through if necessary.

[Rob Morley]

I said it would be straight - I didn't say it would go where you wanted it to :-)

[Lobster]

Thanks Andrew, that's resolved my first issue with the tool, that of the chases being too narrow. What was your experience versus mine of cutting in a straight line and making the beast cut where you want? Does yours cut in the direction of ceiling -> floor too?

(And by the way - anybody got any top tips for stopping your goggles steaming up!?)

David

[Lobster]

No he means oval-section stuff, which is specifically intended to be plastered in; you are talking about the expensive rectangular stuff with removable cover, designed for surface mounting.

I've always used capping myself as it just seemed easier to cover over cables in a chase rather than thread them through trunking; I'd never appreciated they actually had different uses.

David

[Brian Sharrock]

As a spectacle-wearer I have trouble with goggles steaming up - and I've tried most of the safety glasses, cum 'divers' mask style with and without holes, vents etc. etc. The only thing which I've found 'work's for me is a Trend Airsheild mask/helmet. One looks somewhat like 'Dan Dare' - [for those who read The Eagle); but at least the thing works and its down-blowing air flow across the forehead seems to keep one much cooler and comfortable when doing things such as chasing walls.

[Rob Morley]

Try wiping a tiny amount of washing-up liquid inside the lens.

[Andrew Gabriel]

I think they all do. I just draw a line down the wall and follow it. Make the line line-up with some feature on the chaser such as a corner of the dust cover, rather than being a centreline for the chase which may not have any marking on the casing. Once, I nailed a batton to the wall and ran the chaser down against the edge of that. As I said in an earlier posting, that generated a chase which was too straight and the trunking would fall out.