# Adding soft start to mitre saw



## bobblezard (28 Feb 2022)

Hi,
I've got a Bosch GCM10s mitre saw. It's a good saw with one significant hassle.
It trips my circuit breakers every second or third use.
I've looked on line and see some have fitted a soft start module into the switch /motor of the saw itself. That looks a less than neat option with this saw model though someone has done it. I've seen some 'in line' versions that you can plug the saw into but can't find anything for sale in UK. This would be ideal if not too expensive.
Has anybody any experience of dealing with this effectively? Ultimately I may end up moving the saw on but would prefer not to. The only thing that seems to help, a bit, is putting a lot of cable (25m extension lead unfurled) between the saw and socket.


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## Rich C (28 Feb 2022)

I changed to a C type breaker to avoid this. Not sure if that's a viable option for you.


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## robgul (28 Feb 2022)

Casual DIY on YT retro-fitted a soft start to one of his saws - worth a look


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## Spectric (28 Feb 2022)

I have a 12 inch Bosch mitre saw and it has never given any issues with tripping, they have soft start built in which you can just feel and so there is no need for a third party softstarter. I would suggest you get an electrician to check your instalation and maybe have the saw checked over by a service centre as that could be at fault. Never change a type B protective device for a type C unless you can measure your circuit impedances, it is also not permitted under the regs because it is a change in design, without testing can you say that the circuit could withstand the extra fault current required to trip.

Worst case a 32 amp type B requires 160 amps, a type C requires 320 amps and your circuit impedance needs to be low enough to allow this level of fault current without melting, this can be a bigger issue with T&E because the CPC is a smaller CSA than the main conductors.


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## bobblezard (28 Feb 2022)

Thanks Spectric, but this saw, as far as I am aware has no soft start, it's always started with a kick. This seems to be a common problem based on a Google search.
There are no known faults with the installation, professionally installed and checked over recently, I run a range of different machines and devices with no problems, this is the only device that trips the circuit. It's rated 8a but obviously drawing much more on start up.
I won't be changing the breaker myself, but will explore options with my electrician when I can. I'm hoping for a 20amp supply in due course but wanted something in the meantime.


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## bobblezard (28 Feb 2022)

robgul said:


> Casual DIY on YT retro-fitted a soft start to one of his saws - worth a look


Thanks,
Yes I've seen a few if these retrofits, I was hoping to have something that didn't involve opening up and modifying the saw case.but that might not be possible.


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## bobblezard (28 Feb 2022)

Raymond Innovations | Soft Starter | A10 | Power Tools | Woodworker's Journal 

I was hoping to find something like this but no luck beyond this search, I guess it was either ineffective or not commercially viable.


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## baldkev (28 Feb 2022)

Schneider Altistart 01 Soft Starter for Three Phase Motor 1.5kW-3kW - Soft Starters


Part No: ATS01N206QN, Brand: Schneider, Model: Altistart 01 Soft Starter for Three Phase Motor 1.5kW-3kW




inverterdrive.com





Probably a bit above budget..... i havent used one but have considered it for my new extractor. Its now on a 20amp breaker and hasnt tripped.


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## Spectric (28 Feb 2022)

Would this help









Buy A Bosch GCM 10 J SOFT START-UP MODULE 1609B00909 Spare Part


Bosch GCM 10 J SOFT START-UP MODULE 1609B00909 Spare Part. Fix Your Bosch Circular Saw Today, All Spares are Ready For Quick Cheap Delivery Our Spares are Genuine Bosch Parts and Come with a Full Bosch Guarantee.




www.sparetoolparts.co.uk


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## bobblezard (28 Feb 2022)

Spectric said:


> Would this help
> 
> 
> 
> ...


Thanks, yes I saw these, I think this is very similar to the modules some of the YouTubers are fitting, the Makita compatible ones are cheaper on fleabay and seem to be very similar. I will open up the saw and have a look, if I'm lucky there will be space to squeeze one in and I'll be able to fit it but was hoping to avoid having to get into the internal electrics.
The switch gear seems quite tightly packed so I'm worried it wouldn't fit inside and end up with it taped to the casing somehow. 
But as you say the later saws/different models do have them.That GCM 10J looks like exactly the same casing etc. So maybe there is room.
Its got soft start and improved extraction too, maybe I should upgrade


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## the great waldo (1 Mar 2022)

Something like this
Electrical Soft Start Controller, Aluminum Bottom Single 2-Phase Soft Starter for Motor(Module) : Amazon.co.uk: Business, Industry & Science
should do the trick. They are usually thermistor based and easily available in Europe although don't seem so easy to find in Blighty.
Cheers
Andrew


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## bobblezard (1 Mar 2022)

the great waldo said:


> Something like this
> Electrical Soft Start Controller, Aluminum Bottom Single 2-Phase Soft Starter for Motor(Module) : Amazon.co.uk: Business, Industry & Science
> should do the trick. They are usually thermistor based and easily available in Europe although don't seem so easy to find in Blighty.
> Cheers
> Andrew


Hi Andrew, yes that looks very much like what I am looking for. That one is rated to 1kw whereas the saw is 1800w but if I could find one that matched then I would definitely give it a go
Thanks

Edit: just found the 2kw version, I'll order one and give it a go


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