Odd mitre saw cuts

[rafezetter]

I bought a compound sliding mitre saw a few years ago and used it well enough although it was admittedly a cheaper branded one - Challenge Pro - but it seemed to do for me for making my bed frame.

A short while back I wanted to make some very accurate cuts for some condiment caddies for the local pub, you know the kind for sauces and whatnot, but for the life of me I couldn't get the box edges to come together right off the saw.

After quite a lot of faffing, buying a good atkinson walker blade, and truing up the fence / base to within 0.01mm it was better but still off.

I am of course assuming the blade is flat and true - which is why I bought the Atkinson to remove that doubt.

What is happening is the cuts are concave - if I make a full length cut of 300mm or so on two bits of scrap and butt them up, cut face to cut face - there is a gap in the middle akin to a spring joint. It's about 1mm.

Has anyone ever come across similar?

Also if you have a lower end mitre saw can you state how accurate they have been? I've used a really expensive one at my old work which was super accurate, (I know, I checked) but I'm not forking out hundreds for something I only use rarely.

Edit - the one at work was an Electra Beckum 301 - apparently one of the best CSMS in the world so maybe I'll find it hard to get one as accurate as that?

 

[flat n smooth]

I think this is in the wrong section mate


Mod edit:-- Moved.

 

[Bluekingfisher]

It could be several things eg

1. The blade could be flexing as you make the cut.
2. There may be run out on the saw blade arbor.
3. You have slop in the bearings on the glide bar
4. A combination of all three.

Investment in an inexpensive dial gauge could prove useful to check for run out on all three areas.

Failing that, a process of elimination may identify the issue.

First, make a cut just on the chop motion (not using the slide bars) then check the cuts. If that is ok, unplug the saw and apply side ways pressure to the blade with the blade lock on, any slop in the bearing or the arbour will be obvious.

Similarly next, extend the motor and blade to full extension and apply sideways pressure to the motor and blade housing to check for slop in the bearings of the glide bars.

You have to remember, sliding cross cut saws were designed for rough carpentry work. Even high end saws do not always produce top class cuts when cross cuting wide boards.

You could also take the cut vey slowly and not force it through the timber to see how that effects the results.

If all else fails, just make the rough cut and trim to final dimension with a block plane. You may be expecting too much from a cheap saw? No offence.
David

 

[rafezetter]

Thanks for that reply David - I know I probably am looking for too much from this, for what I paid for it, but your reply was exactly the sort of advice I was looking for which will either help me reduce the problem or at least know what I'm looking for again in the future.

 

[Bluekingfisher]

No problem mate, I too have owned several "economy" SCMS in the past, fine for framing and rough work, for which they cannot be faulted. However, when making exact cuts their shortfalls are evident.

I now have a Bosch 12" chop saw ( Not the sliding type) it allows for a 200+mm cross cut at 90 degrees which is more than enough to cater for skirtings etc. Anything wider is done at the TS

Why there is not a range of quality 305mm chops saw available here in the UK I don't know, perhaps the manufacturer only wants us to buy the more expensive and fickle sliders.

Ultimately, the more moving parts then the more opportunity for error.

I hope you overcome your issues with it.

Cheers

David

 

[SteveF]

I have had the 301 for nearly 20 years now

abused and used
even dropped it off the stand one day
still cuts true
motor is sweet as new

highly recommend you find a used one imho

Steve