Advice Please - Wavy cut from Miter saw

[David Ewing]

All

I didn't see a post on this relative to a mites saw based on a quick search....

I have the new Bosch GCM12SD Glide miter saw. I wanted the 12" chop that Fine Homebuilding rated #1 but this is now phased out.

When I make a cut - either as a basic chop OR in slide mode I get a wavy cut. By that I mean that the remaining face when held to a straight edge has a wave in it. So If I were to make a cut and glue the freshly cut board to a straight board (butt joint) there would be a gap.

The gap is small but I paid $700 for furniture quality - as was given on the previous model.

I get this quality off my Sawstop -- so I want it off my miter for when I need to have multiple setups going at once.


I tried changing blades - I went to my 96t Freud that I had on my junk miter saw - smaller wave but still there.

Im thinking runout in the arbor is causing a wobble. Or for that matter anything in the rotor that would allow wobble (bearings, etc).

Any other thoughts?

Other than this issue - the saw is great!

[Prashun Patel]

Can you post a pic of what you mean by wavy?

I know that my miter saw tends to push the piece away from itself, which results in a non-parallel cut. The solution is to make sure the piece is clamped or butted against a stop during the cut. If you do either of these things, does the waviness persist?

[Tom Ewell]

Sawstop with 10" blade, Bosch with 12" blade.

Is the blade on the Bosch a full kerf or thin kerf?
If thin, try a full kerf.

Check for run-out and establish with Bosch that it is within spec, if not, let them deal with it.

[Martin Wasner]

Most saws you're going to have to nibble into a big cut unless the saw has a ton of mass and is very stiff. I do agree you need to check for run out as well.

[glenn bradley]

Good advice here. It is disappointing when a well reviewed tool goes the way of the dodo due to factors beyond the quality of the tool. First step, clamp your work; that eliminates your grip as the problem. Second step, improve your blade; the factory blade will be OK for construction work (I never expect to get a finished cut from a miter saw) but, to get to your expected/acceptable level you may want a task-specific full kerf blade.

[Bill White]

Your miter saw has some slop in a bearing or two creating the irregular kerf. Check out the flex at the end of travel.
Bill

[Eric Schmid]

If there is runout in the blade it is likely that the problem is in the flanges that secure the blade to the arbor; inner and/or outer. The arbor could be out of spec, but that is less likely.

[David Gutierrez]

I have the same saw and have not experienced this problem. I did set mine up with a upgraded blade from infinity and it is a full kerf.

[Justin Ludwig]

I'd check the arbor for burrs and any inconsistencies, then test it for run out. My 4 yr old dewalt SCMS will cut as true as I want (with high quality blades).

Wavy lines sounds like like there is something minute, yet prevalent in the arbor/flange.

[Art Mann]

You really need a negative hook angle trim blade made specifically for miter saws.

[Jim Dwight]

I get good cuts with no waviness from my Hitachi 12 inch non-slider. I think it has a Hitachi blade - which isn't great. I'd consider taking the saw back for replacement or repair. It shouldn't cut like that. I also have a Pro-Tech (inexpensive) 10 inch single bevel and it cuts fine too with a decent blade.

[Bob Reda]

Have the same saw and the same problem, had the bearing replaces and is as good as new

Bob

[Paul Mattaliano]

Have the same saw and the same problem, had the bearing replaces and is as good as new

Bob

the arbor bearing?

[Marvin Davidson]

Hi David. I know that your post is old, but I'm curious to know if you were able to solve the problem. I too have the exact same problem. I love everything about the saw, except for the wavy cut that you describe. I have sent mine back to Bosch for repair. Was your problem the bearings, or something else. Thanks for any info you can give me.

[Mark e Kessler]

I had trouble with that saw too, sold it and bought the makita 10” that will yield a 12” cut capacity. Also you will not get a “Furniture” quality cut from a mitre saw....

[George Makra]

You might want to try one of these.

https://www.forrestblades.com/dampeners-stiffeners/

[Frederick Skelly]

Hi David. I know that your post is old, but I'm curious to know if you were able to solve the problem. I too have the exact same problem. I love everything about the saw, except for the wavy cut that you describe. I have sent mine back to Bosch for repair. Was your problem the bearings, or something else. Thanks for any info you can give me.

Marvin,
Welcome to the Creek!
Hey, I hope David checks in to answer, but don't be disappointed if he doesn't. It looks like he hasn't logged on here in just over a year.

I hope Bosch gets your saw sorted out.
Fred

[Mark e Kessler]

I didn’t read all of the other replys so maybe this has been mentioned

1. Are you taking a fullcut, your issue can magnify when the blade is not fully supported on both sides of the board.

2. At what width does this occur? 3”, 6”, 12”?

3. Try a 3”-4”, board tight against the fence, straight down cut (cut off 3/4”, do not slide out) after cutting through do not raise the blade back through the material let the blade stop first - check it, any better?

4. 3”-4” again this time pull the slide out like as if you were cutting a wider board, cut 3/4” off let the blade stop, don’t bring the spinning blade back through the cut material, is this cut worse?

5. Repeat #4 with a “6 and 12” ( or close to it)

if #4 and #5 are wavy
1. could be excessive run out in the arbor (least likely of the bunch)
2. the washers clamping the blade are not flat
3. The blade is not flat
4. the travel of the slide is not coplaner, even if this isn’t the 100% cause i can almost guarantee you that it is not coplaner and needs adjustment.

Even if the arbor, washers and blade are within spec you would probably have a total runout of ~0.003-0.005 at the arbor and best case the blade has maybe has ~0.0015. Translate all of that at the tip of the blade and it is even worse.

For perspective My sliding panel saw has a little less than 0.0005 runout at the arbor and my blades typically have ~0.001-0.002, the centrifugal force probably eliminates most of the blade runout

The miter saw is a construction tool and not a furniture tool, it can be close But not out of the box without adjustments, if you want a furniture quality mitre saw buy an Omga mitre saw. (I am going to get blow back on that...lol)

Or use a ts with a sled and better yet buy a slider, my miter box just collects dust...

I also tested a ton of mitre saw blades (not a Forrest though, but $120 freud industrial blades and others) and to my surprise found that the stock Makita blade. ( on amazon) left the best cut out of all of them, what was the runout you may ask? Doesn’t matter, its the finished cut, so don’t get to rapped up in the numbers but they are a good way to gauge why way things are going.

My advice is to first check for coplaner and adjust, if it is not coplaner (it won’t be) you will be recutting with the back of the blade.

To adjust for coplaner grab a board (i use 1/2” ply) that is the full cut capacity of the saw, clamp the material down so it won’t move and do a straight down cut (plunge down then bring the blade back up) then don’t move the wood pull the slide all the way out make the cut but don’t side back - bring the blade back up.

If the end of the board is smooth with no step then it is coplaner (surprise! Even I can be wrong...) if it is stepped the slide is not coplaner and needs adjustment. I don’t know how to adjust the Bosch but on the end of the rails of the Makita there are cap screws, you loosen them slightly and take a scrap between the 2 rails and tweek them one way or the other to get them coplaner.


mk