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Bosch GKS 190 Circular Saw

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  • Bosch GKS 190 Circular Saw

    The Bosch GKS 190 circular saw, for some reason, has an unusual arbor size, 20 mm. Does this mean that if you want to use blades with 5/8" holes, you are out of luck (a.k.a. S.O.L.) with the GKS 190.

    Up to now, I have had to find blades with 20 mm or larger holes, but now I want or need to use some blades with 5/8" holes (specifically Hitachi for fiber cement and Freud).

    Why Bosch would choose to have a nonstandard and unusually large 20 mm arbor on its saw is beyond me. (If you are a saw manufacturer, you want your arbor to be as small as possible. If you are a blade manufacturer, you want your hole to be as large as possible, no?) An e-mail to Bosch PH asking if there is an arbor/washer/bushing to fit 5/8" blades went unanswered.

    What is the arbor size on Makita circular saws? Makita website doesn't say. If 5/8", then that would seem to be a definite advantage of Makita over Bosch -- compatibility with a larger variety of blades.
    Last edited by guad; 10-13-2010, 05:25 PM.

  • #2
    Re: Bosch GKS 190 Circular Saw

    most if not all carbide blades have accessories includes especially arbor washers or spacers. I would actually be a disadvantage for the tool to adopt to the blade since the blade is the consumable (imho, it must be the other way around) the blade must have options to fit the tools or machines they want to be part of. So I don't think Makita or any manufacturer would have a distinct advantage in this case.
    I have blades like Makita, Bosch, Freud, Suzuki etc... all had spacers.

    click my signature and it will take you there........

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    • #3
      Re: Bosch GKS 190 Circular Saw

      I have an old bosch circular saw and it has a reversible spacer. Maybe yours has as well..

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      • #4
        Re: Bosch GKS 190 Circular Saw

        i bought a bosch optiline wood circular saw blade for my makita 5806 7 1/4 cs(the cheapest of the makita cs)and it comes supplied with 2 pcs of spacer to fit my cs.

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        • #5
          Re: Bosch GKS 190 Circular Saw

          HTML Code:
          Up to now, I have had to find blades with 20 mm or larger holes, but now I want or need to use some blades with 5/8" holes (specifically Hitachi for fiber cement and Freud).
          hey! where can i buy a fiber cement board circular saw blade?

          was looking for jigsaw blades for fiber cement board by bosch but is only available abroad.
          The devil will find work for idle hands to do.-Morrissey

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          • #6
            Re: Bosch GKS 190 Circular Saw

            Unfortunately, Bosch GKS 190 does not have a reversible spacer. It's a pity, because Bosch could have easily put one in to accomodate 5/8" blades, as the motor shaft is only 12 mm. By having a 20 mm spacer, they closed the door on 5/8" blades, restricting blade choice to 20 mm and larger, a much narrower market space ... that Bosch blades (e.g., Optiline) happen to occupy.

            Adapters will bridge the gap between small saw arbors and large blade holes, but will not allow a large arbor (like the 20 mm one on the Bosch) to fit a smaller blade hole (like the majority of 7.25" blades, which seem to have 5/8" holes).

            For fiber cement boards, these look good -- for 7.25" circular saw and jig saw. Might be worth asking the Hitachi distributor (supposedly Vic's Construction, mentioned in another thread) if they have them?

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            • #7
              Re: Bosch GKS 190 Circular Saw

              Originally posted by jonathanscruz68 View Post
              i bought a bosch optiline wood circular saw blade for my makita 5806 7 1/4 cs(the cheapest of the makita cs)and it comes supplied with 2 pcs of spacer to fit my cs.
              2? The Bosch Optiline 7.25" 40T and 60T that I have both came with 4 adapters, ID 5/8" 16 19 20 mm, OD 25.4 mm.

              Originally posted by violaine View Post
              [HTML]
              hey! where can i buy a fiber cement board circular saw blade?
              was looking for jigsaw blades for fiber cement board by bosch but is only available abroad.
              Unfortunately, Vic's Construction said that they do not have the Hitachi fiber cement blades, circular or jig saw.

              CORRECTION. Apparently, 20 mm arbor size is not unusual locally. In fact, it seems to be the 'standard' for 7.25" circular saws. I was told that Bosch, Skil, Makita, Maktec are all 20 mm.

              Unusual is AEG at 30 mm and Hitachi at 1/2" (with included adapter for 1"). No Metabo.

              Now if only I could find a 1/2" ID to 5/8" OD adapter, the Hitachi would be the answer for 5/8" blades.
              Last edited by guad; 11-12-2010, 08:42 AM.

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              • #8
                Re: Bosch GKS 190 Circular Saw

                i am currently refurbishing the ceiling of our kitchen t&b. at the beginning of the plan, a combination exhaust and lamp will be installed.my workmen was suggesting a hardiflex and was willing to make a hole for the circular lamp con exhaust using just a hacksaw blade which seems to be the norm elsewhere locally but then again there has to be a better way to make a hole out of the fibercement boards.

                i just want to voice this out so bosch can hear us.

                i ended up using a marine plywood.

                hole made by my bosch jigsaw.
                The devil will find work for idle hands to do.-Morrissey

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                • #9
                  Re: Bosch GKS 190 Circular Saw

                  Suggestion po lamang, nasubukan nyo po na ba ang magpatorno ng spacer/bush or ung mismong flange? Di ko alam kung mura, pero that is what I would be looking at as an option.
                  my 0.02$.

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                  • #10
                    Re: Bosch GKS 190 Circular Saw

                    magpatorno = to mill/machine?

                    Good suggestion, thanks for reminding. I'll look into it. Probably better than enlarging the holes on 5/8" blades.

                    For straight cuts on fiber cement boards, I understand that people use diamond blades on angle grinders, or do score and snap.
                    Last edited by guad; 11-13-2010, 07:13 AM.

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                    • #11
                      Re: Bosch GKS 190 Circular Saw

                      Finally, red blades, diamond blades, etc. -- in general 5/8" blades -- on a Philippine (20 mm) circular saw.

                      While this 20 mm disease is not limited to Bosch, on Bosch, it shows up on the previously mentioned 'spacer' (officially called 'Guide Bushing'). This is the part that determines the official arbor size. As suggested, I had the circular ridge/protrusion on the bushing cut down on a lathe from 20 mm to 5/8" diameter.

                      Bushing on the left is the original. On right is another bushing (cost P160) after cutting. There are scratches on the periphery because I had to file off the last fraction of millimeter by hand.





                      Below, the red blade is seated on the new bushing. Blade on right is Hitachi 7.25" diamond (PCD) for fiber cement.




                      Finally!



                      I wish we didn't have to go through contortions like this to use 5/8" blades. This is not a problem in miter saws, which are designed to accomodate 5/8" blades and larger (using adapters). Why the manufacturers set a high minimum of 20 mm for circular saws is beyond me. Is 20 mm the European or Asian standard that just got copied/imposed on PH?

                      Any manufacturer reps out there care to comment?

                      There is a risk, hopefully very small, that the smaller ridge on the modified Bosch bushing could shear under blade load. I don't think this will happen because the ridge is supported by the shaft. But if it did, the broken off ridge would have nowhere to go (would not dislodge and fly off) and the blade would remain firmly clamped, but possibly shift off center slightly, in the worst case.
                      Last edited by guad; 04-26-2011, 11:45 AM.

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                      • #12
                        Re: Bosch GKS 190 Circular Saw

                        BTW, for fiber cement, here are the Hitachi jig saw blades (carbide-tipped according to the label, not diamond) and Hitachi 10" diamond, obtained online (links given previously).

                        Last edited by guad; 04-26-2011, 11:57 AM.

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                        • #13
                          Re: Bosch GKS 190 Circular Saw

                          Ganito rin problem ko after purchasing Freud blade 7 1/4" with 5/8" dia. arbor.

                          Tomorrow I will be getting inner flange for my Bosch GKS 190 and bring it to machine shop for machining to accept the freud blade.

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                          • #14
                            Re: Bosch GKS 190 Circular Saw

                            Just try to keep the ridge concentric with the hole. Sounds obvious, but on the very old lathe that I used, this was tricky to do because the four jaws are independently (!) adjustable and not necessarily always centered. I assume that on modern lathes, the jaws are always centered?

                            I would be interested to know what the story is for other brands, e.g., Makita. Is there also a removable bushing that would have to be cut down, and can be cut down to 5/8"? Or do they have a better design, e.g., having a ring adapter (5/8" ID, 20 mm OD) and all you have to do is remove the ring?

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                            • #15
                              Re: Bosch GKS 190 Circular Saw

                              I already bring the inner flange to nearby machine shop cost me P250 for the machining. Know I have inner flange with 5/8" arbor. My Freud blade fit perfectly. I also bought a new inner flange cost me P180 so I can still use bosch saw blade with 20mm arbor.



                              Freud D0760X Diablo Ultra Finish Saw Blade cuts pretty well on MDF minimal chip-off. Already cut 2 sheets of 18mm MDF, 30 more sheets to go.
                              Last edited by bryant77; 05-07-2011, 06:58 PM.

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