Thread: Good practice when using Compound Mitre Saw

Hi Clint, are you sure you got the right blade for the saw. I recently had my Makita blade sharpened and bought a spare to use while I was waiting. The clown sold me a blade for a compound saw, not a slide compound type. The difference is the slide model is square cut,or with opposing teeth the other has teeth all facing one way. I could not understand why my joints were not exact until I noticed burning on one piece which meant the blade was skewing thru the wood. After he reset the new blade to square, it has worked well. Try cutting a slice off the end of a 4x2 hardwood to test it out. Don't clamp both sides ever. That's why they come with only one clamp. Just hold the unclamped side and ease it away from the blade as the cut is finishing. Alternatively, place a piece of waste timber in front of your workpiece to avoid the guard snagging small pieces. Watch your fingers.

Good luck, Lionel.

Three other possible things to check are
1. Is the 45 degree mark actually exactly 45 degrees? It is worth some time fiddling with the saw to ensure that it so. You will get a better idea of this if you cut 2 mitres and compare the sum of the angles with a 90 degree square then that will help to tell you how close you are.
2. There is a tendency for the timber to want to creep either left or right when you cut mitres. That is because not all of the forces involved are directed at the fence at the back of the saw. A component of the force is directed along the table. You will have to watch carefully that there is no movement at all.
3. Is the timber straight and are both edges parallel along the entire length of the timber. If it is not then the mitres will not turn out 100%

I recall a recent thread on this problem so a search would be worthwhile.

Sorting out these problems is part of the game and you will succeed eventually.

Hi Clint,

Originally Posted by the big o

.... are you sure you got the right blade for the saw.

I had an 80 tooth blade originally on my Electra Beckum ... same results as you .. it was a fine blade but designed for avoiding chip-out on melamine, but no good for cross-cutting solid wood. I now use a 40 tooth ATB blade and it does a better job.

If you want to avoid break-out, then just put a bit of sacrifical wood fully under your workpiece.

Qw

P.S. Still do not be discouraged if results aren't perfect. In my humble experience, the 45 degree mitre cut, though deceptively simple, is about the hardest joint to get right. There have been books written about this problem.

I went off and did a search, found this link, but there are more!!!

I too have an interest in the perfect mitre as I ahve 20 kitchen doors to make, the first 2 look like ............ well I did them in 5 minutes and used my eye for the mitre!!

http://www.woodworkforums.ubeaut.com...ght=mitre+cuts

Can you say: shooting board & hand plane? Good, I thought so.

I have yet to get a perfect machine cut mitre joint, even using a 90 degree block on a sliding mitre gauge. Your power machine will get you very close, but for perfection you will have to use hand tools - or maybe one of those $300 mitre trimmer thingies, which I have no experience of. Most of the power cutters are 'close enough' for builders & rough carpenters, not furniture.

Lionel
I didnt realise that there were different blades as you say. My saw is a Makita LS1040 CMS and the blade I purchased from Carbatec is CMT p/n 273.250.80M which is decribed as Thin kerf ITK fine finish blade with a grind 40 degATB and 15 deg hook angle . The latter 2 bits of info mean nothing to me.

On the weekend I will put the original blade back on and see what difference it makes. My concern was tearout

Clint

Clint,

ATB means (from memory) 'Alternate Tooth Bevel' which means that each tooth is bevelled opposite to the tooth before it. The hook angle means how far forward (or back for negative rake) the tooth is pitched from centre. Your's being a fine cutoff blade is designed for fine finish cutting across the grain. I don't think it will be the cause of your problem. It will be slow to cut but shouldn't cause errors.

I think your most likely problem is that the 45 degree positive stops need adjusting. Other possibilities are that the workpiece is moving as you cut it, or maybe it's not straight. You can try clamping it.

Originally Posted by bsrlee

Can you say: shooting board & hand plane? Good, I thought so.

I have yet to get a perfect machine cut mitre joint, even using a 90 degree block on a sliding mitre gauge. Your power machine will get you very close, but for perfection you will have to use hand tools - or maybe one of those $300 mitre trimmer thingies, which I have no experience of. Most of the power cutters are 'close enough' for builders & rough carpenters, not furniture.

Ahh no not the hand plane... sounds like work!
I've got one of these LS1040 Mak's and have been make picture frames for about 18mths now, not one of my frames has a gap in the joints(now). It still has the original blade a 40t ATB I think.
The thing I have noticed about the LS1040 is apon start up the thing wants to jump off the table(no soft start), the wood can(and will)move away from the fence when it kicks no matter how tight the clamp is done up... bolt/screw/clamp it down because the alloy base plate is flexing!
It took me a while before I worked it out, it was killing my joint angles...

I have mucked up many a mitre recently and examined the problem minutely on my Ryobi:


1. The entire machine flexes, especially when nearing the bottom of the cut. A better quality machine should have less of a problem.

2. The blade sometimes goes into a vibrational mode, literally ringing, when nearing the final part of the cut; this causes the cut to be thicker when this happens. Being a novice on mitres, I suspect (but don't know) a different blade might solve the problem.
3. I have to get of my lazy butt and go through the effort to set all machine angles to match the marked ones.

4. I have to start using sacrificial pieces underneath. This will also ease problem #1.

As a result of all this and then some, I personally hate mitre joints.

Thanks Jur. And I thought I was the only one who hated mitre joints. I don't even think they look nice. All my frames (mirror / picture) are now "square" or butt joins with M&T or biscuits. Very strong and flush and I like the look better. And no angle hassles.

Hi to all.
Just a quick mention of what I have seen in the mitre saws while looking to maybe purchase one. I was at bunnings and noticed that all the cheaper models had a lot of flex in the whole arm (sideways that is). This must account for some inaccuracies. When having a test feel of the Bosch and DeWalt I noticed minimal sideways movement even when applying some sideways force.
Regards
Les

Hi

I have the $300 mitre guilltione from carba tec and it is Bloooooooooooooooody wonderful. Perfect 45 cuts everytime and because you can slice off paper thin pieces you end up with no feathering and a perfect joint.

If you are going to do a lot (20 cupboards :eek: ) then it is invaluable i reckon.


good luck

Originally Posted by jur

I have mucked up many a mitre recently and examined the problem minutely on my Ryobi:


1. The entire machine flexes, especially when nearing the bottom of the cut. A better quality machine should have less of a problem.

As a result of all this and then some, I personally hate mitre joints.

The LS1040 only flex's when its started, the jolt moves the wood before its cut other than that its impecable.
Yeah I dont like mitre joints either, IMO picture frames are the only place they belong. There's allways better joints that can be done on door frames and alike.

There are a few places that call for a mitre joint, like external joins in mouldings. I don't think there's anything particularly difficult about mitre joints, you just need to set your equipment (drop saw, mitre box, shooting board or whatever) up properly. It's worth getting it right. The point of the mitre joint is to hide end grain.