Rip Fence Advice

[Iwf]

I need a bit of advice regarding rip fences.

I've built my own table saw, using the Makita Site Saw as a base. The rip fence that came with the saw was rubbish so i bought the Axminster Rip Fence upgrade. All is basically well except for three aspects. Firstly the fence only reaches half way along the saw blade; secondly because of the base of the saw the fence doesn't slip easily across the table. Finally when cutting narrow < 20mm and thin (say 4mm) edging I'm finding the timber flaps as it passes the upward moving part of the blade, because there's nothing to hold it down. My old Triton had device built into the riving knife to prevent such behaviour.

I'd been thinking of extending the fence by adding ply or plastic to each side and using the t tracks on the fence to hold them in place. That would allow me to add a finger board after the blade to hold down the timber In principle I could add plastic to the underside too. On the other hand having a short fence means the timber has somewhere to go after first contact with the blade.

Any advice gratefully received.

 

[PAC1]

The fence on a table saw for ripping wood should only extent to the gullet of the tooth (not even half way). If cutting sheet materials etc a long fence is often used but it needs to be very carefully set up so that it is at worst perfectly parallel to the saw blade but preferably running out very slightly. As for the thing to stop wood riding up the back of the blade, if the saw has not got a crown guard it is very dangerous and despite every US video on you tube should not be used.

 

[custard]

The fence on a table saw for ripping wood should only extent to the gullet of the tooth (not even half way).

I've got a different take on that. I was once working at a workshop when they were having a long exchange with the HSE on just this matter, the HSE's advice was that for timber ripping the fence should not extend past the centre of the saw blade. That makes sense to me, it's enough to accurately guide the board through the cut but there's no sideways pressure or restriction from the fence once the workpiece is in the "lifting" quadrant of the blade.

 

[Steve Maskery]

TS fences are a bit of a conundrum really, in that we have two competing requirements. We want the fence to be as long as possible for maximum support, but we want to avoid the end of the cut board from pressing on the fence and thus forcing the rest of the board into the blade and being kicked back.
So actually both PAC and Custard are both right, in that FOR RIPPING the fence should extend past the gullet of the first cutting tooth but not a far as TDC of the blade. Anywhere in that 2" or so of tolerance should be fine. Once the wood has passed that tooth, it is severed and the cut is done, it's just a case of getting it past the rest of the blade without incident.

However.

As the workpiece gets wider, that short fence provides less and less support. If, say, I had 18" to the right of the blade, which I might well have if I am cutting MDF, a short fence like that is pretty useless for the last part of the cut, I'd virtually be cutting freehand! But MDF does not spring like timber can, so it doesn't need that space to spring into. This kind of cut is not ripping per se, even though we might use the term to denote cutting it down its length. So for stable material like MDF a full length fence can be used for maximum support, without the risk of contributing to kickback.

So on my saw I have a full length fence, on which is mounted an adjustable short fence. It is actually a lidded box which straddles the long fence and it is somewhere to keep spanners and Allen keys etc. for the saw. I'll take a picture when I go down to the workshop.

 

[PAC1]

The fence on a table saw for ripping wood should only extent to the gullet of the tooth (not even half way).

I've got a different take on that. I was once working at a workshop when they were having a long exchange with the HSE on just this matter, the HSE's advice was that for timber ripping the fence should not extend past the centre of the saw blade. That makes sense to me, it's enough to accurately guide the board through the cut but there's no sideways pressure or restriction from the fence once the workpiece is in the "lifting" quadrant of the blade.

Interesting, as I tend to set it between the gullet and the centre. However the HSE written advice is still no further than first gullet. The further along the blade you go the greater the need for the fence to be very precisely parallel to the blade or running out slightly.
If you have a full length fence it is worth making a short rip fence that can be clamped to the full length fence. I made one for my Felder full length fence and find it very useful.

 

[JonnyW]

A really interesting post.

I was always taught never have the fence past the centre of the blade when ripping battens of wood.

Then as Steve states, place the fence past the blade when cutting sheet material to keep your cut travelling straight when you get to the last bit of the sheet.

Jonny

 

[custard]

However the HSE written advice is still no further than first gullet.

You're right, this is what the HSE says here,

http://www.hse.gov.uk/pubns/wis16.pdf

However, as I say I was working at a workshop who took issue with this, saying having the fence this short meant the workpiece could swerve out of line towards the end of the cut. After a bit of back and forth the HSE relented and accepted a rip fence position that was longer, I think from memory what they actually said was no further than the arbour. That seems pretty sensible to me and is how I set up my saw.

 

[skipdiver]

I usually set mine 'in the zone' between the gullet and the centre of the blade. I think it's something that you learn as you get more experienced and becomes second nature depending on the material being cut. I also learned very early in my woodworking career not to stand in the flight path of your tablesaw. When working in the machine shop of a caravan company, my immediate boss was ripping a piece of Ramin, a particularly brittle and splintery wood, when he got a kick back. The wood split and a piece like a javelin shot back and speared him in the stomach. A hospital visit and a couple of stitches sorted it out but it taught me a lesson early on. It was also at that same machine shop that one of the cabinet makers lost his right index finger as a result of carelessness, so i learned respect for sharp spinning stuff early.

 

[siggy_7]

I've always followed this advice - think it was from my saw's manual, or possibly a Taunton's book: Draw a line from the centre of the blade at a 45 degree angle towards the back of the saw. The rip fence should not extend backwards beyond this line. Thus, as your fence position gets wider you can extend the fence further to give support towards the end of the cut for wider rips/sheet good work. I've never had a kickback problem following this method.

 

[transatlantic]

From what I understand, we're talking about these 3 cases.

I think the second case still doesn't provide enough support. The more board that passes that arbour point, the less mechinal advantage you have of controling that board, and so without the support of the full fence, I feel like it would wander and affect accuracy. But I'm very surprised that the third case is considered the 'correct' way, .. looks dangerous to me.

 

[MattRoberts]

Indeed - there's a reason why riving knives exist. If they're installed and effective, there shouldn't be any reason why not to use a full length fence for rip cuts

 

[custard]

Indeed - there's a reason why riving knives exist. If they're installed and effective, there shouldn't be any reason why not to use a full length fence for rip cuts

I disagree there Matt. A riving knife stops the kerf closing up, it doesn't stop a solid timber board warping and pressing in from the side if trapped by the fence. If you apply lateral pressure to a riving knife you can see how easily they flex.

 

[Adam9453]

+1 for what custard said above.
I always have the riving knife and crown guard in place but once when I was ripping a piece of timber and it snagged slightly on the full length fence, it pushed into the back of the riving knife which flexed and therefore the timber hit the blade and was thrown off the saw (fortunately relatively gently) but it reminded me that for solid wood you really must not use a full length fence when ripping.
As others have said, if your cutting MDF, ply or other stable sheet materials then a full length fence is no issue and I always use a full length fence with those sheet materials.
The thing which some don't realise about a riving knife is that the timber can push into the back of the blade before it gets to the riving knife which is one of the ways kickback can still occur even with a riving knife fitted.
Like others have said, I always stand to the side so as to be out of the firing line if something does go awry

 

[PAC1]

From what I understand, we're talking about these 3 cases.



I think the second case still doesn't provide enough support. The more board that passes that arbour point, the less mechinal advantage you have of controling that board, and so without the support of the full fence, I feel like it would wander and affect accuracy. But I'm very surprised that the third case is considered the 'correct' way, .. looks dangerous to me.

The third applies to ripping timber only. The logic is that when cutting timber the tension in the wood is released and so the timber might bend banana style and bind on the fence or blade causing kickback. So if the fence does not restrict the wood the chance of binding decreases (not eliminated).
For cutting sheet materials plywood mdf etc then a full length fence is fine as long as properly set up as the sheet will not bend.

 

[MattRoberts]

I disagree there Matt. A riving knife stops the kerf closing up, it doesn't stop a solid timber board warping and pressing in from the side if trapped by the fence. If you apply lateral pressure to a riving knife you can see how easily they flex.

An interesting point - I guess I was basing my statement off my own knife - it's pretty rigid 2mm steel and doesn't flex much at all.

 

[PAC1]

I disagree there Matt. A riving knife stops the kerf closing up, it doesn't stop a solid timber board warping and pressing in from the side if trapped by the fence. If you apply lateral pressure to a riving knife you can see how easily they flex.

An interesting point - I guess I was basing my statement off my own knife - it's pretty rigid 2mm steel and doesn't flex much at all.

Matt
The problem arises with a long fence if the timber wants to bend away from the blade. The riving knife will not save the day. If the fence restricts the timber movement the timber will still bow so it presses against the riving knife and saw blade, binds on the back of the blade (the riving knife being thinner) and will take flight. This happens when the timber has not been kiln dried well and is wetter in the middle than the outside. With some wood Iroko or Afromosia it happens because of the horrible grain.

 

[JonnyW]

I've had battens of wood bind between the blade and the fence due to the movement of the wood when ripped. This was sorted by moving the fence nearer the front of the blade.

If you look at the graphic within the HSE's link that Custard posted, it's pretty obvious why the wood would rise up and be thrown towards you, should the wood become wedged between the fence and the back of the blade. At the front of the blade, the teeth are traveling down to the saw and not upwards.

I've had pieces of wood hurled across the workshop that Fatima Whitbread couldn't have thrown better, and have had lumps of wood rise up the blade - all brown underwear material.

We used to hammer wedges into the cut, if the batten started to tighten over the riving knife.

However I do agree that shortening the fence can affect the accuracy of the last little bit - especially if you have an overzealous apprentice (or a partner) with no concept of pulling something out in a straight bl**dy line.

Jonny

 

[Sawyer]

Full length fences seem to be the norm nowadays, perhaps because it's imagined that most of us work chiefly with sheet materials. My Axi TSCE-12R, in all other respects a very satisfactory machine came this equipped. I however, do not often use sheet materials, so made up my own rip-fence attachment, which is in place 95% of the time. A slide fit, I can remove or replace it in a couple of seconds. I normally set it so that the fence extends just beyond the gullet of the tooth at the point where the blade enters the top surface of the stock.

 

[Steve Maskery]

This is mine. It looks a bit scruffy these days, but so would you if you'd spent 2 years in a barn.

As I say, it also doubles as a toolbox:

The low lip is so that I can get it under the guard if I need to rip anything very narrow.

 

[Iwf]

Gentlemen

Thank you all for all the insightful information. I've learnt a lot, and avoided some dangerous situations, just by reading these replies. In particular about how best to set blade in reference to the mitre slot and fence. It makes perfect sense that the blade shouldn't be exactly parallel to the fence, but only after I'd read it several times.

I don't actually have much room for ripping sheets, so I think I'll settle for the big sled and a short fence. I also have the bits for a sliding table attachment.

Lots of food for thought, but great advice.

Thanks very much