Table Saw Safety

[Speaker]

Hi All,

Has anyone had any experience of fitting a braking system to a Record TS250 Table Saw?

Or better still, does anyone know of an after-market system that could be fitted?

Thanks,
Tony

 

[Spectric]

You would need some big modifications, look up regenerative braking where you are turning the motor into a generator and putting a load across it so it slows down, something more industrial than a home workshop.

 

[MF1000]

The bandsaws used in the meat industry have heavy duty brake systems linked to an optical sensor array that detects if a blue glove gets close to the blade. Works really well but creates a hell of a bang when it’s tripped.

 

[ajs]

What's the motivation here? If it's some DIY SawStop style thing forget it now. If you're talking about accelerating spin down rather than an instant stop in theory two options come to mind. To be honest I don't really like either.

First is electromagnetic braking, you'll need a couple of strong electromagnets either side of the blade. The magnets and motion of the blade will create eddy currents that convert the speed of the blade to heat. That slows down, but won't bring to a complete rest. HGVs, trains etc use that for high speed braking. It's established technology but as a retrofit I'd consider it experimental at best.

The other option that crosses my mind would be some form of caliper brake - think push bikes. Speed of the blade is likely higher than intended but mass is lower so it may be a goer. Still don't like it mind.

Ultimately I really don't like the idea on even a conceptual level. I'm quite happy to consider this as a thought experiment but if you do this in practice don't sue me when it goes pear shaped.

 

[deema]

Braking systems to comply with the regs were in introduced to avoid the accidents that occurred due to operators popping their fingers in to make changes to blades before the blade had fully stopped turning. In some instances large saws could take minutes to slow down and when time was money, or the supervisor was breathing down your neck for productivity short cuts can be tempting. So, unlike the myth that some how a braked saw will save your fingers if it starts to chew in them due to it stopping before 10 seconds has elapsed, it will have finished lunch and your fingers will be gone before your brain has actually assimilated what had happened.

 

[Sideways]

Again - we need to know why you want to brake it and how quickly.

(UK) Woodworking machines used commercially in (more or less) anything bigger than an owner operator shop have to meet a health and safety requirement of stopping within 10 seconds.
Most small saws like the Record and even many mid sized ones stop within 10 sec without modification so that is not a reason.

As mentioned nothing that you can retrofit will act as a poor man's DIY "saw stop".

The two real options for 3 phase machines but not for your TS250 are

1. A DC injection brake. A £300+ electrical add on that injects a controlled amount of pure DC electricity into a motor while it is stopping, which creates an electromagnetic braking effect within the motor itself
2. For 3 phase motors powered from a variable frequency drive, some VFDs can be fitted with a braking resistor that decelerates the mòtor rapidly and dissipates the energy as heat.

Both of these are very common but not for single phase / DIY machines, the electronics cost a few to several £00s. They are used to ensure commercial machinery with (e.g.) heavy cutter blocks and 14" plus sawblades stop within the mandatory 10 sec.

 

[Johnwa]

I've never thought about this topic but we used to fit dc injection braking systems to 3ph drillers, lathes etc. Would this work on a 1ph motor in this application. Input is needed from smarter minds than mine I dont have a clue!

 

[Sideways]

The injection brakes I've handled have always been made for 3 phase, but we wire 3 phase DOL starters for use with single phase motors, and the dc module injects dc only between two phases, so it might work between Live and Neutral.
Single phase motors invariably have a capacitor that a 3 phase doesn't, but that won't pass DC, and the DC voltage is less than the mains itself so no hazard to the capacitor.
So, I've never done it, but maybe yes.

The point remains. Why bother ? It will only stop the saw a few seconds faster and the brake might cost more than the machine ....

 

[Spectric]

Lets provide the sensable solution here, rather than looking at technology to deliver or improve safety why not accept it as being completely within your control.

The saw is only a hazzard if you don't follow a safe working practice and being a stationary machine it relies on you presenting your fingers to the blade for removal so don't put your fingers near the blade, be patient and wait for it to stop and learn that in any incident the best manoeuvre is to step back and raise your hands in the air, think and then hit the stop button. Many incidents are down to stupidity and lack of concentration, working in an untidy place where there are trip hazzards and poor lighting. The table saw is probably the most dangerous machine any of us have in our workshops and it deserves respect, keep away from that blade and don't blindly follow how some people use them when watching youtube video's and you will keep your digits.

 

[Speaker]

What's the motivation here? If it's some DIY SawStop style thing forget it now. If you're talking about accelerating spin down rather than an instant stop in theory two options come to mind. To be honest I don't really like either.

First is electromagnetic braking, you'll need a couple of strong electromagnets either side of the blade. The magnets and motion of the blade will create eddy currents that convert the speed of the blade to heat. That slows down, but won't bring to a complete rest. HGVs, trains etc use that for high speed braking. It's established technology but as a retrofit I'd consider it experimental at best.

The other option that crosses my mind would be some form of caliper brake - think push bikes. Speed of the blade is likely higher than intended but mass is lower so it may be a goer. Still don't like it mind.

Ultimately I really don't like the idea on even a conceptual level. I'm quite happy to consider this as a thought experiment but if you do this in practice don't sue me when it goes pear shaped.

Hi, the motivation is that there have been a couple of near misses caused by people not realising the blade is still spinning - fortunately no serious damage has been done.
I realise that short of something like the Sawstop any braking system will take time to be effective and any damage is likely to have already occurred.

I had done some research and found the regenerative braking option but realising it is out of my comfort zone wanted to see if anyone had any knowledge/experience they might be prepared to share.

However, I now realise what a minefield it would be in terms of liability.

We will just have to keep reminding users (again and again and again and….) to follow the guidance they have been given on safe usage of such a dangerous machine.

Thanks to all who have responded…

Tony

 

[Spectric]

Hi, the motivation is that there have been a couple of near misses caused by people not realising the blade is still spinning

Then these people need to be kept away from the machinery, if they are stupid enough not to wait till the blade stops then they are going to have an accident, just a case of when and how but it will happen and you cannot wrap everything up trying to prevent it.

If these people are employee's then remember that safety is not all down to you, as an employee you also have a part to play and the right to refuse to use any machine that you feel is unsafe or you are not confident in using providing the employer has followed the machinery directives such as PUWER and has ensured all maintenance and inspections have been done to ensure it is as safe as practically possible.

The way we were taught safety is that you comply with all the rules and regulations but you cannot be held accountable for someones stupidity.

 

[user 35906]

I have an old Electra Bekum table saw with a 300mm blade that took almost 2 minutes to stop after being turned off, on another forum I was told about dc braking so I fitted a 3 position switch- on-off and DC so I couldn't supply the AC and DC at the same time. For the DC supply I fitted a 19v DC laptop charger and now the blade stops in around 10 seconds. If I come across a higher voltage DC supply I will try that to see if it works even better.

 

[aet1]

I go along with Spectric, as you have others using the saw I assume this is a commercial concern, so every person who uses the saw must have been trained and I think tested to cope with the regulations, so their fingers should never be near the blade.

 

[Sideways]

However, I now realise what a minefield it would be in terms of liability.

We will just have to keep reminding users (again and again and again and….) to follow the guidance they have been given on safe usage of such a dangerous machine.

Thanks to all who have responded…

Tony

It sounds like you are involved with a club, men's shed or makerspace.
Be careful.
Joe public is an i-d-i-o-t.
Adopt and reiterate the attitude that access to tools is a privilege, not an right of membership.
It must be earned by users constantly demonstrating good working practice and revoke it automatically when people have an incident.

I just signed up at a "new to me" turning club and was amused to notice that they mentioned several times to different people "we don't provide training".
You need to be very clear about your liabilities and you must control your members firmly, you do not let them control you or you open your committee up to world of pain.

 

[Spectric]

I just signed up at a "new to me" turning club and was amused to notice that they mentionwd several times to different people "we don't provide training".

I always thought that these sort of clubs were there to help people who were new to the subject, if you are new to turning then you would expect the more experienced members to help you by passing down their knowledge and showing you the ropes. I wonder if they mean official training !

 

[Sideways]

I wonder if they mean official training !

I'm sure they do.
Members are friendly and helpful but there is obviously a subtext that everyone is aware of.
The club does not provide training. You are expected to be competent, you are responsible for your own actions and using their equipment at your own risk....

The guy who likes to turn bigger pieces and has a reputation for catches has a regular place on the back row. He faces the opposite way from everyone else so when he throws something out of the chuck, it bounces off the back wall and not the skull of the person in front of him )

 

[Doug71]

When the 10 second braking rule came in we had electric brakes fitted to a few of our machines, it wasn't cheap and they didn't all work that well.

We had one fitted to the Wadkin BRA cross cut, that worked well and made sense as it normally kept spinning nearly all day after you turned it off.

One was fitted to the Wadkin BSW rip saw, we could never get that one dialled in properly. It was either too brutal stopping it too quickly or the blade was still spinning after the brake had stopped, it seemed to depend on how long the saw had been running.

We had one fitted to the Multico tenoner which never worked that well plus had to spend more than the machine was worth on limited projection tooling to bring it up to regs.

Wasn't the old fashioned way to make things stop quicker to just tighten the belts?

 

[baldkev]

Wether a business setting or club, i would seriously consider paying a private health and safety advisor for a one off visit to look at any machinery and give an opinion on legality ( needing brakes / guards etc ) and to provide guidance on who could potentially use it. This means, for instance, anyone with basic training could use a morticer, but the same cant be said of a spindle moulder.

By doing so, you have shown that you took this threat seriously..... plus your advisor will have been a very good investment if it prevents just one accident

 

[Sideways]

paying a private health and safety advisor for a one off visit to look at any machinery and give an opinion on legality ( needing brakes / guards etc ) and to provide guidance...

There is a lot of sense in this, but
It's more complex than one visit to look at some machines.
If you are a club, the HSE rules that apply to businesses won't apply to you per se.
But I believe that you will still have a legal duty of care to members, so it makes little difference in practice.
This means a simple but robust management system, risk assessments, yada yada.
One visit is unlikely to cut it.

Our men's shed, before it closed, employed people to do risk assessments, train the trainer, and annual LEV (extraction etc) checks. None of them were competent. How do you find a trustworthy one if you don't have the background to assess them yourself.

 

[Bristol_Rob]

For that kind of information and guidance I recommend reaching out to you local FE College that teaches joinery.
They will have qualified teachers and technicians that are poorly paid and would probably love the opportunity to earn some money outside of work hours.

The College will also have a H&S officer/manager that could also add value. Between those two you will get everything you need.

Good luck