Accuracy of miter saws

[wptski]

I have a brand new Bosch CM10GD 10-Inch Dual Bevel Glide Miter Saw, my first.

I went through the setup checks and all checked right on the money but it cut off square at least 0.5 degree.  Most if not all procedures for checking the bevel setting is on the left side looking from the front.  Checked on the right and it's off square in the direction it's cutting off and by the same amount.

Adjusting the bevel is a PITA, first using a solid square(a Starrette #20 3" belonging to my father that is +80 years old) and finally a Wixey WR-400 3" which worked nice for that.  It cuts square now but where's the problem, blade or the base??

I had a Diablo 10" 80T finish blade coming so I put that on today and checked for squareness first, it showed the same error on the left side so it has to be something in the base on the left side.  This blade cuts super smooth and square as well.

I also installed a Oshlun laser washer.

Just what kind of accuracy at best can be expected from a miter saw?

 

[Birdhunter]

I just cut the ends on an 8" wide 1 1/4" thick Acacia board with my Kapex. The end cuts were perfectly square measured with a Woodpecker square. I did take the cuts slowly and by pushing with my arm in line with the cut.

This is the norm with my  three year old Kapex. I made no adjustments except for the lasers.

 

[magellan]

Some times it's not your setup.  It could be your fence is not machined accurately.  You may have to shim or build a supplemental fence.  Hope I'm getting my point across clearly    Some factory fences are not cast and machined perfectly and the saw itself is in perfect alignment but an error occurs.  Take a straightedge across your fence halves and look down on them to see if there is a gap

 

[wptski]

I have a hand-me-down 10-12 year old Makita LS1221. It's a 12" compound miter but no slide. It cuts square all around. Did require a little resetting but has stayed square for years. I've used it for rough construction and more exacting woodworking projects.

A Wixey WR300 digital angle block may also help in adjustments. Have you used a machined straightedge to check the base and the fence?

The Wixey WR400 is equivalent to the WR300 for that, I'd say.  I used a Brown&Sharpe 12" combination square which would be the closest I have to a machined straightedge.  Using its blade before I didn't see any problem with the flatness of the base but there has to be something off.  Since a longer board cuts square now on that side, it seems that there has to be a low spot toward the blade.  I do know that the base is slightly higher than the table.  The fence is square to the blade.

I've seen videos using a framing square to check the alignment of the fences from one side to the other.  Geez, the two I have look like they were stamped out and a mile off!

 

[wptski]

Some times it's not your setup.  It could be your fence is not machined accurately.  You may have to shim or build a supplemental fence.  Hope I'm getting my point across clearly    Some factory fences are not cast and machined perfectly and the saw itself is in perfect alignment but an error occurs.  Take a straightedge across your fence halves and look down on them to see if there is a gap

It's not off in that direction and if it was it can be adjusted by moving the angle scale.  It's the base to blade that's off.  I did check from fence to fence and added only .004" shim to one.

 

[Stone Message]

I have a brand new Bosch CM10GD 10-Inch Dual Bevel Glide Miter Saw, my first.

I went through the setup checks and all checked right on the money but it cut off square at least 0.5 degree.  Most if not all procedures for checking the bevel setting is on the left side looking from the front.  Checked on the right and it's off square in the direction it's cutting off and by the same amount.

Adjusting the bevel is a PITA, first using a solid square(a Starrette #20 3" belonging to my father that is +80 years old) and finally a Wixey WR-400 3" which worked nice for that.  It cuts square now but where's the problem, blade or the base??

I had a Diablo 10" 80T finish blade coming so I put that on today and checked for squareness first, it showed the same error on the left side so it has to be something in the base on the left side.  This blade cuts super smooth and square as well.

I also installed a Oshlun laser washer.

Just what kind of accuracy at best can be expected from a miter saw?

If you set up your saw accurately then it should produce results that you cannot fault with your square or, when doing mitre cuts, should not produce a gap in any part of the joint.

My old Dewalt RAS started off life being the bees knees but my woodwork improved and I began to see that it was not quite as good as I had thought. I managed to work around its idiosyncrasies but eventually decided to make a step change improvement. I went for the Kapex but did, for a while, consider the Bosch Glide. I cannot comment on the Bosch as I have never owned one but the Kapex is excellent.

Whatever saw you have you will need to find a way to keep it spot on and some saws will be easier than others. The Kapex has a reputation for accuracy which I have discovered for myself but you do need to do regular checks to make sure that it has not been knocked out of line.

If my Kapex produces a cut across a piece that is visibly out of square when looking to see any gap between it and my engineer's square then I go back to the saw to make an adjustment. I check it before every major project but rarely have to make adjustments.

Peter

 

[Holmz]

If it is repeatable and always cuts the same angle, then it can be also made to be accurate.

So is it repeatable?

 

[Lbob131]

This is why  I only use my scms  for rough cutting  and final sizing  and absolute  accuracy  is achieved  on the slider.

 

[JimD]

I use a CMS instead of a SCMS for multiple reasons (biggest is the workspace required on the bench) and one is the flexibility the SCMS has in the blade movement.  It is possible to make the cut inaccurately with poor technique.  It could be your saw but it could also be you.  If you hold the saw to apply a little pressure opposite of the error, does it cancel it?

 

[chris s]

Have  you tried cutting without the laser washer?

 

[wptski]

Have  you tried cutting without the laser washer?

No but that shouldn't have any affect as it just forces the blade against the inner washer.  Just to make sure I just tried the OEM washer, no change and it still shows off angle on the left side.

Using the blade from my B&S combination square shows the base to be dished in towards the center and/or high at the edges.  I should check with a feeler gauge to see if it’s more on the left side.

 

[justinh]

There is no fix for a warped base.  Return the saw and get a different one.  The only saw that I haven't been able to tune up to almost perfect was a Bosch.  I have heard of guys having to cut up the miter scale in order to true them up.

Using squares to true up a saw only gets you in the neighborhood of square.  Calipers and a 5 cut are more accurate.  I can true up my saw to .0005 of square on a 5 cut and dial out the blade runout to .002 in around 30 minutes.

 

[pixelated]

I have the 12 inch glide, haven't had any problems getting square cuts or squaring it. I've never had reason to check the bed or fence before, but just now went down and checked it with a precision straightedge and the bed and fence are flat.
If yours is off, I'd consider returning/exchanging it.

 

[wptski]

Despite reading of several reviews on Amazon about the 10" glide not cutting square, I gambled although the complaints were glide mode only.  One had returned one and had the same problem on the second one.  Some state no problem at all.

They don't sell the 12" on Amazon so can't say if it's only the 10" with issues.

I did check in glide mode with a indicator from the blade to a angle plate.  It wasn't perfect but not like one reviewer stated was off so much that it burn't the wood.  I cut 45 deg. miters on 1x6 and they looked good so I know this one ain't that bad.

Since I purchased on line from Acme Tools and the box is long gone, it would be a real PITA to return and I might be stuck here.  I'm retired from Ford Motor as a machine repairmen and have done hand scraping in the past, not much of it.  I do have a granite surface plate big enough if I wanted to make the base flat.  Since the base is proud from the table, maybe it can be scraped by just removing the fences as long as the surface plate doesn't touch the table.  Cast iron surface plates used like this have tapped holes on it's side for long bolts used as handles, a granite plate doesn't! 

 

 

[pixelated]

One option might be to take it to a local-to-you Bosch authorized repair center.

 

[Arvid]

what did our fathers and grandfathers do with just a handsaw and site made miter box to do some of the most ornate work you've ever seen. they would all laugh at us using this miter saw and calibrating with our 4-5 cut test.

 

[nickao]

No true at all, this cut test is similar to measuring checks that woodworkers and craftsman have used for hundreds, probably thousands of years.

Do you think they made stuff square by eye? The only difference is our tools are powered by electricity..

I remember my grandfather  who used a hand saw for miters using an almost identical system on his hand made miter saw to set it up! Thinking back I had no idea what he was doing, now  being grown  and into woodworking I realize what he was doing,  he was setting up his saw! The difference was he was adjusting a spring and lever. I actually have a hand saw miter box very similar to it today, and they need adjustment and this same type test could be used to test and even adjust it as well.

 

[Job and Knock]

No true at all, this cut test is similar to measuring checks that woodworkers and craftsman have used for hundreds, probably thousands of years.

Do you think they made stuff square by eye? The only difference is our tools are powered by electricity..

Well, the old boys I apprenticed under in the early 1970s would go only so far to make something right - the rest of the joint would be trued by eye, with a block plane or a mitre plane. Despite what you think no tradesman has ever had the time to be that "precious" when his livlihood is involved. When I go to site and pull out a chop saw I automatically do a series of test cuts and make any adjustments needed (bumping around in any vehicle puts even the best of saws out, eventually). After that I'll do a quick check every week or so that the saw remains in place - depending on usage. I always find it amusing to watch some of the new kids, fresh out of college, trying to get a skirting (baseboard) mitre to work - especially when the floor isn't level, the walls aren't straight, the walls aren't plumb and there are sundry other issues to deal with. They make adjustment cut, after adjustment cut, after adjustment cut but it really doesn't work for them and they don't seem to understand why. The greybeards tend to get so far with the mitre saw (i.e. one or possibly 2 cuts) then make some fine final adjustments with a sharp block plane because expediency is efficiency. But then again now I'm the old guy, with the grey beard.......  [wink]

 

[Arvid]

what did our fathers and grandfathers do with just a handsaw and site made miter box to do some of the most ornate work you've ever seen. they would all laugh at us using this miter saw and calibrating with our 4-5 cut test.

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