Bosch GCM12SD problem

[barry bortnick]

Hi,
I recently bought a Bosch GCM12SD glide mitre saw to replace my Dewalt. I got rid of the Dewalt as it was nearly impossible to push the blade straight through material (front to back) without deflection. I could not get an accurate 90 degree miter, and repeated cuts were all slightly different.
I am having a similar problem on the Bosch. The miter detent lever is plastic and when (properly) engaged, it (or the mechanism that it is part of) can wobble a bit, therefore you can lock the miter at slightly different angles. Therefore if it wobbles a bit to the left, I don’t get a nice 90 degree cut. It is about 1/32” off at the end of a 12” deep board. Am I being too critical? Does anyone else notice this? If you can’t count on the repeatability of most basic of cuts, than that would seem to be a problem.

[Jeff Roltgen]

Am I being too critical?
No!

Does anyone else notice this?
Absolutely! You are not alone.

I've paid very close attention to this on occasions when I can put my hands on the latest offerings in the showrooms. I have detected what you describe, and resisted "upgrading" for exactly the problems you've verified that they produce. A friend was recently raving about his Bosch, and how perfect the cuts were, but we tested it against my Makita and found, indeed, the Bosch displayed clear evidence of blade-wandering when chopping a 6" wide piece, yet the Makita's cut was super-straight when laid up against a straight edge.

I have a wonderful older Makita LS1013 from back in the heyday of sliding compound miter saws, before the sudden development of the space-savings crisis. This means 1 straight, solid set of SS rails, and deflection is not an issue under normal use. I know some other highly reputable carpenters that, for similar reasons, are still running 15-20 year old Hitachi's that they just keep rebuilding.

Milwaukee had one out a couple years ago that was built like my old reliable, and you could easily see with the deflection test that it was way more solid than it's multi-level and articulated arm contraptions that supposedly everyone needed so it fit against the wall in their shop. Not sure if it was the public or the manufacturers that decided it was problem, but the public is left to suffer with the performance you describe.

I have not found the holy-grail of modern day sliding compound miter saws yet, though if my Makita totally died tomorrow, I'd go looking for that Milwaukee, or even a Kapex, given the similarity in construction to my favored Makita.

I will say, since purchasing a sliding table saw recently, I almost don't use the miter saw in the shop any longer, as naturally, a 10' sliding wagon displays no deflection. So, while it's apples to oranges, I guess I have found the ultimate mitering machine for me.

Hopefully, someone can enlighten us here and show us the one we've been missing...

jeff

[barry bortnick]

Thanks Jeff! I haven't even measured the additional deflection one might get during an actual cut (although some test cuts did not seem to have any additional deflection.)
I think that a locked 90 degree miter should be perfect, without having to mess around with the mechanism, eyeball the gauge, and then check for a gap with a square. Even my old DeWalt did not have this particular issue - the miter stop locks were solid, but the dual tube sliders were always deflected one way or the other, or both during the same cut!

[Bobby Robbinett]

I would return that Bosch. I had the same issue when I tried one. The best non production miter saws are the Festool, Dewalt and Makita in that order. I actually find the Dewalt DW780 to be just as accurate as the Festool when properly tuned. Only downside is the additional time it takes to set the bevel on the Dewalt as you ideally need a digital gauge to make it perfect. If you are just cutting 90’s and the occasional angles on stiles and rails I would highly recommend the Japanese made 7.25” Metabo at around $1,200 as it is super nice and accurate. I have heard that Makita either has of is coming out with a saw to compete with the Metabo. These are not the Metabo or Makita saws you see in the box stores. These are Uber nice and quality that you would have to order. If you want ultimate accuracy and you can afford it then get an OMGA and be done. It is the most accurate miter saw on the market. They cost between $1,800 and $9,000 but they are cast iron and use an induction motor like a cabinet saw would use.

[barry bortnick]

Hi Bobby - I was unable to push my old Dewalt DW718 straight through a cut, front to back. It/I always wandered and I never got square cuts. Is the latest version any better? The slide construction looks identical on the newer DW779/DW780.

[barry bortnick]

I should point out that I am using this tool for furniture making, where 1/32" matters. If you are using this for general construction, then not so much.

[Andrew Hughes]

I have a Bosch glide with a 12 inch chop master blade. Mine cuts pretty darn good for a miter saw. I think it’s a excellent trim saw.
For wide cross cuts in thick material I would prefer a radial arm saw.
If your using the stock blade the saw came with ditch it and get something better.
Good Luck

[Bobby Robbinett]

If you are doing furniture then you need an OMGA. Their miter saws start at I believe $1,750 and go up to around $7,800. They are the most absolutely accurate miter saws ever made.

[Frederick Skelly]

If you are doing furniture then you need an OMGA. Their miter saws start at I believe $1,750 and go up to around $7,800. They are the most absolutely accurate miter saws ever made.

Agree 1/32" is too far off for furniture.

The OMGA is a great tool for what I've read. I'm not convinced you have to go that far (unless you just plain want to). I've found that once I set it up properly, my Makita gets it pretty dang close. And if that close is still not good enough for the furniture project, I can put the part on my shooting board to correct it.

[John Kananis]

$1750 for an OMGA? Sign me up haha. Maybe if it's used?

[barry bortnick]

$1750 for an OMGA? Sign me up haha. Maybe if it's used?
Hmm, the Festool is about the same price, only 2.5x the price of any other 'normal' saw, and using non-standard/proprietary blades, which annoys me.

[Richard Coers]

As far as I am concerned, a miter box has no place in making furniture. Not since I had a Hitachi 8 1/2" blade with a Forrest blade on it. That was in the 90s. Most of the saws today are more for building decks instead of holding tight tolerances. A sliding miter sled on a table saw is a necessity.

[Jonathan Jung]

Because of everything already noted, I have stuck with a non-sliding Dewalt 716. I use it solely for furniture joinery, always with a sharp 60t blade. Cutting slowly and with the stock held firmly, sometimes with a clamp, it does all my joint cutting and very well.

Sliding saws aren't for joinery. I've had the Kapex, Makita, Dewalt, and Metabo.

[barry bortnick]

No wonder it's unreliable. Bosch cheaped out here. Both the slotted plated and adjuster are plastic. I do need to be able to cut shelves accurately, and I don't have room for a sliding table. The Festool can't be counted on either?
479072

[Greg Quenneville]

Regarding the Festool, there are a couple of models wearing the Kapex name. The KS 120 is a very good saw. I built a large period house with mine…lots of frame and panel, lots of doors, stairs, shutters, casings and built-ins. Framing too. You can mostly*rely on that saw and its stops.

*Because my saw was an earlier model the fence eventually got knocked out of alignment so that it cut differently depending which side of the blade was used. After recognising the problem it was easy to adjust back to dead nuts. That happened after thousands of framing cuts being less than gentle on the equipment.

I made literally thousands of parts on that saw and they assembled gap-free.

[Darrell Bade]

I have the 10" version, use it to build furniture, cuts square, everthing fits together fine.

[barry bortnick]

I have the 10" version, use it to build furniture, cuts square, everthing fits together fine.
I considered the smaller glide saw, thinking it might be more precise. Are you saying there is no possible movement/mis-alignment when a fixed slot is selected? The additional design problem is that the slot mechanism, beside being plastic has the lever pivot point several inches from the slot and it is just badly engineered.

[Darrell Bade]

I considered the smaller glide saw, thinking it might be more precise. Are you saying there is no possible movement/mis-alignment when a fixed slot is selected? The additional design problem is that the slot mechanism, beside being plastic has the lever pivot point several inches from the slot and it is just badly engineered.

Nope, I'm saying that when I set my miter saw station up it cut square when checked with a square and in use it cuts square and furniture fits fine. Is there possible movement, never had reason to check. Is there a design problem, never had a reason to check in the 10 years I've owned it.