Makita angle grinder switch - Page 1
Forum section: electronics / beginners

author: ME
author_rank: Frequent Contributor
timestamp: July 15, 2025, 12:12:24 pm
content: I brought a non working 240v 4 inch makita angle grinder non working , On checking it out the switch was bad , the live side of the ac input went to one side of the switch that had normal contacts , The neutral side ac input went to a small pc board and was open , I just ran a jumper from the neautral ac input over to the output and it now works ok,what is the pcb for on the neautral side of the switch input and why have it?.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 15, 2025, 03:00:32 pm
content: It's probably a thyristor speed control. Now with that bypassed, it will run at full power only. Probably not an issue if that's OK for you.BTW, no such thing as "live and neutral". They are both live.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 15, 2025, 03:02:17 pm
content: What parts are on that PCB? First guess would be that it's a mains EMC filter, but that would require both mains wires. It may be a current limiting or slow start up to prevent the "jerks" when power is applied. Angle grinders also tend to have a circuit that keeps them off when the power is temporarily interrupted (for example a blown fuse), but the switch is locked in the "on" position.Here in the EU there are 115 and 125mm grinders and disks. I find this quite silly and supid even. I can't think of a reason to use 115mm over 125. 125mm disks are slightly more expensive, but that is well compensated by the extra amount of material on the disks.For the rest, It's barely worth messing with second hand angle grinders. Cheap ones cost around EUR 30, and a decent one costs around EUR 50 and EUR 80. There are high quality versions, but those cost > EUR 300, and I very much doubt they are that much better.

author: themadhippy
author_rank: Super Contributor
timestamp: July 15, 2025, 03:43:41 pm
content: Quotefrom hazy memory it used to be 115mm / 41/2inch was standard for grinders whilst 125mm /5 inch was for sanders and any ways real men wont be happy with anything less than a 9incher

author: armandine2
author_rank: Frequent Contributor
timestamp: July 15, 2025, 05:52:54 pm
content: 4-inch was small at the timemine was purchased IIRC in the early 80s, possibly in Hong Kong, corded , still working fine.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 15, 2025, 06:01:10 pm
content: 180mm is also very common, available in every toolshop (toolshop as in a shop where you can buy tools). But I rarely use the 180mm anymore. The 180mm grinders have a much bigger gearhead so the extra depth is relatively small. And you have more control over the 125mm grinders (I don't even buy them in the higher power ranges, these things go from 500W tot over 1200W), but especially the thinner disks of the 125mm grinders make them nice to use. Most of the thin disks are 0.9 or 1mm. There are 0.6mm disks, but these are much more expensive and quite fragile too, (Especially when storing, or when a something drops on them while they're laying down). They do have a significant advantage in some cases because they put very little heat into the object you are grinding. I do have a 190mm Hikoki circular saw. I am planning to make an adapter for it for 180mm grinding disks. I'm guessing that the extra stability produces straighter cuts, and reduces problems with disk wear though excessive vibration.230mm is the next size up, but it does not have much advantages. I only use it when the big disk is really mandatory to reach through a piece of material. And if the material is movable, ist's really time for a plasma cutter or bandsaw.100mm? Yes apparently it exists, but I have never seen one in real life.80mm is the next step down. You can buy small handheld circular saws in that range, (Circular sawblades in all sorts of diameters seem to be more common.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 15, 2025, 09:07:02 pm
content: With more modern angle grinders (usually from some 800 W und up for the small (115 or 125 mm) ones) they may have a relatively complicated electronic speed regulation with actual speed feedback. This allows more power from the same motor size by and a more stable speed. These motors don't like it very much when the electronic is bridged, as they would run too fast with no load.

author: ME
author_rank: Frequent Contributor
timestamp: July 16, 2025, 03:19:27 pm
content: FWIW this has no speeed control just an on off switch actuated by a plastic slider.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 16, 2025, 09:04:03 pm
content: Apart from the angle grinder size comparisons, there are about 5 different circuit suggestions for what it could be. The information you are looking for should have been freely available in the service manual of your grinder, but alas, it's not a perfect world.So apart from guessing, we need more info here. Posting a picture of the PCB would help. You probably need to clean the PCB to make parts numbers and such visible, because angle grinders tend to get pretty dirty inside.