Kick back

[Rknott2007]

Has anybody experienced kicked back on a table saw with a full length fence? I've always used a pull back type fence, but am considering a change to full length.

 

[Philly]

When I first got my saw I used to occasionally get kickback - I re-adjusted the fence with about 3 thou of toe-out away from the blade. Never happened since.
Hope this helps,
Philly

 

[Jeff Gorman]

The half-length fence is intended to allow for any tendency of the work to spread.

Pressure can develop between the riving knife and a full length fence. This encourages the up-running teeth to lift the work and cause kick back.

There's more about fences at: http://tinyurl.com/yadxz79

...... and general circular sawbench safety at: http://tinyurl.com/cujmde

Very didactic and not exactly holiday reading, but might be worthwhile!

Jeff
www.amgron.clara.net

 

[Ironballs]

At our yearly machine shop induction at college we're always shown how to set the fence on the table saw, the fence should only go as far as the first gulley on your blade, ie just past the cut.

This is how I set mine at home, haven't had kickback this way but I have with a full length fence and it was most unpleasant. I also now have a blade with anti kickback teeth

 

[seaco]

I have a Delta Unisaw and never have!

 

[Richard Findley]

Like Ironballs, when I was at college we were taught to set the fence to the depth of the hook of the blade. The only time I get kick back of this sort is if someone has adjusted the fence and I didn't spot it before using the saw!! I guess there is a time and a place for a full lengh fences which is....... :-k :-k :-k :duno: :duno: :duno:

HTH

Richard

 

[ondablade]

I've never experienced kickback, but have always used a short rip fence. That said it does mean there's very little support for the last part of a rip cut, and if the piece wanders away from the blade (e.g. if you use a push stick) the last bit of the cut may not be straight. It gets even harder if your infeed table is short.

Has anybody got a smart fix for this?

Those articles make for sobering reading Jeff. It's tempting to not take say a 3hp saw too seriously when e.g. you experience it bogging in a heavy cut, but what's a bit scary is just how much energy/inertia there is tied up in the blade, shaft and motor when it's up to speed. If you are unlucky enough that a piece of wood gets properly hooked up with it it can have a lot of speed and energy.

There can be advantages to a full length rip fence, at least in terms of the ability to secure and/or support both ends, but a short sub fence gives an effectively short fence anyway.

There doesn't seem to be much concern about using a full length rip fence in the US. Incra's demo video for example shows repeated cuts made with one.

I wonder what the legislation is on the subject both here and in the US...

ian

 

[woodbloke]

On the K419 that I used it's fitted with a short fence as described by Damian...I've never experienced any kick back - Rob

 

[Doug B]

I`ve used a full width fence for the 15 years i`ve had my present Wadkin table saw, it`s what came with it.

In all that time i`ve never had kick back when using the saw as it was designed to be used.

I have had it when doing things that is wasn`t designed for, but as with a lot of things like kick back, it is more often than not user error or machine misuse that causes incidents, not the design of the machine.

 

[ondablade]

That's why i asked the question about US practice Doug. You'd imagine that if it was a huge problem that they would have responded over there.

Thinking it through:

A saw spindle mounted riving knife is possibly the first line of defence.

If you are working without one though, and the wood springs when cut so that it nips on to the blade then unless you are using a suitable top guard it's coming your way short fence or no short fence.

If it springs towards the rip fence then its likely also to get flipped up over the top - but if you have an effective top guard then it should likewise protect you.

The other possibility is that the workpiece gets projected straight back at you, but unless i'm missing something that is not likely unless it ends up in (tangential) contact towards the top of the blade. A decent top guard should surely protect against that too, especially if its one like on this Felder K 975 panel saw that is mounted on an overhead arm and can slide right down on to the workpiece: http://www.ukfelder.co.uk/gb-en/product ... &zoom=true

That saw is supplied with a full length rip fence too, and while it is retractable you have to wonder why.

Blades with the obvious possibility to really kick back (like rip blades) seem to generally have cut limiters, but not finer blades. So maybe blade type is a factor too. As are the state of the blade, and the nature of the cut.

Blade height is another factor - you effectively get to trade reduced risk of tear out for increased risk of kickback.

Another question - despite what i said about the momentum tied up in even a smallish saw - is it perhaps just on larger more powerful saws that kickback becomes truly life threatening? i.e. you are obviously going to get hurt if you try to push a push stick into a blade with the palm of your hand and it catches a tooth, but how often is that going to happen? My sense by the way is that even quite a small saw is a significant risk.

It sounds to me like a close fitting riving knife (that doesn't have to be removed) and top guard is the really important defence against kickback.

Another possibility. A bit of digging brought this up - US made Grip Tite magnetic mounting rollers and featherboards: http://grip-tite.com/ A longer demo http://www.youtube.com/watch?v=zR0TkOds ... re=related

Another: Board Buddies - probably not a lot different to feather boards http://www.rockler.com/product.cfm?page=11262

Another: MagSwitch http://www.rockler.com/product.cfm?page=17217

The ability of rollers to keep the workpiece down tight and against a rip fence (almost like a power feeder - which is another safety option) is the pretty impressive on the Grip Tite video, especially the second one.

Reading between the lines it sounds like the really tight guidance given by e.g. the Grip Tite may eliminate much of the possibility of kickback (except when the wood springs after cutting) by keeping the workpiece precisely located - they say you can usually stop feeding mid stroke and get no burning...

A short rip fence is not going to be very usable with this sort of solution though....

Rules aside i wonder what the reality/experience is?

ian

 

[PAC1]

Like most I was taught to set the fence to the teeth of the blade and did so religiously! In 2004 I bought a Felder which has a full length fence. It is set a couple of thousanths out. I have never experienced kickback on the Felder.

If you have a sliding table the other way of dealing with difficult wood (bowed, twisted etc) is to clamp the wood to the sliding table and cut it so that the waste is to the right of the blade. I use this technique a lot as I do not have to push the wood through the saw I simply lightly guide the carriage. The wood is more stable as it is fully supported in the same place all the time.

 

[Digit]

Most of the US systems that I have seen Ian use kick back limiters attached to the riving knife. Freud Pro cross cut blades do have cut limiters.

Roy.

 

[Jase]

I've experienced some second hand kickback when a friend was using the saw and he managed to send a piece of 400x400(ish) 15mm mdf spinning off the saw which then bounced off his stomach and then travelled across the workshop hitting me in the back. Pretty painful for both of us especially when you're not expecting it. :?

 

[FatFreddysCat]

There doesn't seem to be much concern about using a full length rip fence in the US.

I wonder what the legislation is on the subject both here and in the US...

Really? Then why is it such a recurring topic of conversation on almost every US forum you read (do a search for Richard Jones and Barb Siddiqui and you'll even find a published article or two by member SgainDubh on the subject, like this one). In Europe it's not so much legislation, but TEACHING which means that almost every properly trained wood machinist automatically uses a short position rip fence as described by others. But then we've also had riving knives or splitters since before I was a lad, so kickback isn't such a topic amongst trained woodworkers here. Interesting how the USA is now bringing its' legislation in line with ours :roll:

That saw [Felder] is supplied with a full length rip fence too, and while it is retractable you have to wonder why

The answer is very simple - for jobs such as trimming man-made boards to continuous width (e.g. when removing glued-on lippings), facing a few millimetres off an already sized board (including solid wood) where there is no possibility of movement to affect the cut, etc. In those sorts of jobs support is required but where there is little danger of the board opening out into a Y-shape and jamming twixt fence and blade - something you can experience in spades when breaking down hardwood boards on a long rip fence. Solid wood can be stressed, especially the more exotic hardwoods, so for ripping a short position rip fence really is a necessity - unless you want to experience kick back at some point. Fiddling around with Grippers and the like is really just a sticking plaster approach when there exists a better, safer solution

Those people who say they've never had a kickback are lucky. I'd hazard a guess that most if not all are amateur woodworkers who in reality do very little sawing. As soon as you start to rip hardwoods in volume then binding and movement become much more common and it's worth avoiding kickbacks. After all nobody like blood blisters, or worse

 

[Ironballs]

Even using a properly set up saw at the college I had a 55mm thick piece of oak bind up and refuse to go any further and the saw was determined to send it back my way. That saw is a big Sedgewick mother and it was all I could do to hold it whilst trying to kick the emergency stop

 

[ondablade]

Thanks FFC, that gets a fact based view on the table, which is great. That article by Scian Dubh and Barbara is good solid factual stuff too.

I was being a little provocative, because sometimes it's hard to tell what's just lore, and what's for real. I'm most certainly no expert though.

To try to summarise. It sounds like as ever it's a lot about the specifics of the situation - that the ripping of long pieces of hardwood is much more likely to result in problems than man made boards - although these too can spring it seems.

Safe(r) practice is clearly situation dependent, there's no one size fits all rule.

There are situations where rip cutting with the fence extended is necessary - specifically the case you mention where a relatively short and wide piece may otherwise tip out of the line of the blade when it runs out of support.

Hold downs, rollers and featherboards, riving knives and top guards plus good infeed and outfeed support can meanwhile do a very nice job of keeping things safe with materials of regular thickness on a long fence.

Ripping rough natural timber does not on the other hand favour guides and hold downs, and is best handled with correct manual technique, and with the fence retracted.

For sure there's lots of debate about kickback on US sites, but on the other hand it's not at all common to see somebody over there using a short fence (except on a European saw), or for that matter the varieties of hold down.

Something is definitely different between here and there though when you see demo videos from a company like Incra using a long fence and zero safeguards - the litigious scene over there suggests that it's not seen as bad practice not to do so, as i doubt they would be leaving themselves liable. Perhaps it's simply that in the US that safety is often seen as more a matter of personal responsibility than of rules and procedures....

 

[Doug B]

Those people who say they've never had a kickback are lucky. I'd hazard a guess that most if not all are amateur woodworkers who in reality do very little sawing. As soon as you start to rip hardwoods in volume then binding and movement become much more common and it's worth avoiding kickbacks. After all nobody like blood blisters, or worse

I presume this comment was aimed at me, as i stated (& stand by) the fact i`ve never had kick back on a saw with a full width fence, when using the machine for the job it was designed to do.

I was taught that a saw with a full width fence was for use with components that had at least 1 face side & 1 faced edge. It was not for ripping large sawn sections of timber, that was done on a dedicate rip saw. A much larger machine with a thick short steel fence, (& the one i worked on), a power feed.

I have ripped large sawn sections on my table & have encountered kick back, but as stated in my previous post, this in my opinion is a misuse of this type of saw & not what it was designed for.

Using a machine for its designed purpose, in a way that avoids encountering a problem is neither lucky or amateur. :roll: :roll:

 

[FatFreddysCat]

Those people who say they've never had a kickback are lucky. I'd hazard a guess that most if not all are amateur woodworkers who in reality do very little sawing. As soon as you start to rip hardwoods in volume then binding and movement become much more common and it's worth avoiding kickbacks. After all nobody like blood blisters, or worse

I presume this comment was aimed at me, as i stated (& stand by) the fact i`ve never had kick back on a saw with a full width fence, when using the machine for the job it was designed to do.

Not specifically, no. At the risk of starting something it was made because there appears to be a widely circulated myth in woodworking fora that if it hasn't happened to me (yet) then it can't/won't happen, etc. when logic often dictates otherwise.

I was taught that a saw with a full width fence was for use with components that had at least 1 face side & 1 faced edge. It was not for ripping large sawn sections of timber, that was done on a dedicate rip saw. A much larger machine with a thick short steel fence, (& the one i worked on), a power feed.

But what do you call a large section? If your piece of material happens to be an 8 x 4in piece of partly machined elm or walnut which you were converting to a 4 x 4in section then you could still come unstuck using a long rip fence were there to be enough tension in the timber for it to allow the timber to warp and pinch between fence and blade. In part it depends on the size/power of the saw you're using with, at least in my own experience, kickback and stalling being much more likely on smaller/lower powered table saws. I've even seen experienced site chippies get kickback on portable table saws ripping down mild 3 x 2in CLS (quite a few times) and that's hardly large section or even a particularly heavy cut, so I think I'll stand by what I wrote (and which was what I was taught as an apprentice)

 

[Doug B]

At the risk of starting something it was made because there appears to be a widely circulated myth in woodworking fora that if it hasn't happened to me (yet) then it can't/won't happen, etc. when logic often dictates otherwise.

So you don`t like statements that in your view are inaccurate & contradict your experience, that`s fair enough.

Those people who say they've never had a kickback are lucky. I'd hazard a guess that most if not all are amateur woodworkers who in reality do very little sawing.

But you are happy to make a statement that is inaccurate & condesending when putting your views across to other posters, when all they have done is post their experience.


I`m off to bask in my new found status :shock:

:idea: I wonder if the tax man will give me a couple of grand back from what i`ve just paid him, :?:

 

[awkwood]

I bought a lot of reclaimed timber from a firm that cut up beams etc
I was there one day when they had been cutting a 15' length of 12"xi 4" of douglas fir. it nipped and kicked back, flew across the saw mill and knocked the boards out of the tounge and grove doors as it passed through
This taught me a lesson, as these guys used the saws all day everyday,it could happen with any piece of wood as you can never tell what stress there is in any piece of wood.
I have had a few pieces ride up off the table and kick, but very few that gave you no warning signs at all