Sled for Making a True Edge With a Table Saw

by Phil B

52K26419

Intro: Sled for Making a True Edge With a Table Saw

Even if your lumber has been planed for a true edge, changes over time can mean it is no longer true. I want to show a fixture for making a true edge with a table saw that is a little different from the traditional method, but leaves no marks on the lumber. My fixture is shown in the photo with this Introduction. But, in the next steps I will first show the more traditional method for getting a true edge with a table saw instead of with a joiner. The table saw is from a previous Instructable.

My sled clamps the workpiece to a surface covered with sandpaper. The friction of the sandpaper's surface keeps the workpiece firmly in place during sawing.

Materials
  • 1/2 inch plywood
  • 2 x 2 wood (or similar)
  • 3/4 inch and 1 1/2 inch stock for spacers
  • 1/4 inch threaded rod
  • "T" nuts
  • Wing nuts
  • Hex nuts
  • Washers
  • 60 grit sandpaper
  • Glue

Tools
  • Table saw
  • Framing square
  • Drill and bits
  • Screws
  • Wrench
  • Hacksaw
  • Measuring stick or tape


STEP 1: The Traditional Way

The usual way to get a true edge with a table saw means nailing or screwing a straight piece to the workpiece and using the straight piece as a guide against the saw's fence. The first few steps of this Instructable will illustrate that method, which I actually used to get a true edge on the plywood that became my sled. The downside of this traditional method is that it leaves marks, maybe even holes in a nice piece of wood. Later, those holes need to be sawed out or filled. That can waste expensive wood. See the text boxes to explain various parts of the photo. 

STEP 2: Details on the Traditional Method

Clamp the guide piece with the factory cut straight edge to the workpiece with an irregular edge. Check with a straightedge to be certain the factory cut guide will contact the fence, but the irregular edge on the workpiece does not.

STEP 3: Attach the Guide With Screws

Attach the guide with the factory edge to the irregular workpiece. I used screws because they make a firmer attachment than merely tacking the two together with brads or wire nails. The screwheads are countersunk so they do not catch on the table during ripping. I used three screws.  

STEP 4: Set the Rip Fence

If you followed the link to view my home made table saw, you know that I use a framing square and the saw's miter gauge to set the rip fence. First, I adjust the miter gauge with the framing square so it is at a right angle to the blade. Then I measure the distance I want between the blade and the fence. I move the framing square to that position and gently slide the fence up to the framing square. Then I lock down the fence with "C" clamps. As long as nothing gets bumped, this process is quite accurate.

STEP 5: Rip

Push the assembly into the saw's spinning blade while holding the guide firmly against the fence. The result will be a true edge on the irregular piece. Remove the screws that hold the guide with the factory edge to the irregular piece. Because my fence is quite long, I am able to true pieces of lumber a bit longer than my edge guide.

STEP 6: Special Attachment

This step begins the process for making my truing sled. Start with a piece of plywood 3/8 or 1/2 inch thick. It should be four or five feet long and about 12 inches wide. It should have one true factory cut edge. If it does not, use the traditional method described in the previous steps to get a piece with a true edge. Mark the true edge, or rip the piece again so both edges are parallel and true. Glue half sheets of  60 grit sandpaper to the plywood opposite your preferred true edge. I realize some pieces I need to true could be as short as 2 feet long. In those cases, I can lay the workpiece over two of the pieces of sandpaper. Workpieces 3 feet long or longer can be laid over all three pieces of sandpaper. 

STEP 7: Drill for 1/4 Inch "T" Nuts

I located the centers for three holes and drilled a small pilot hole for each through the entire thickness of the plywood. The holes are a little over 6 inches from the edge with the sandpaper. Countersink the flange side so they do not interfere with the smooth plywood surface when the sled is sliding over the saw table. Drill 5/16 inch holes for three "T" nuts. Drive the "T" nuts fully into their countersink holes.

STEP 8: Threaded Rod

Cut threaded rod. Round the ends. Use a washer and a nut above the "T" nuts to lock the threaded rod in place. 

STEP 9: Make Hold Down Clamps and Use

Make hold down clamps 10 inches long from something fairly sturdy. Drill holes in the hold down clamps. Use wing nuts and washers to attach the hold downs. Make 3/4 inch and 1 1/2 inch spacer blocks for lumber of both thicknesses.

The photo shows a piece of lumber 1 1/2 inches thick with spacers of the same size. 

Place the lumber with an irregular edge on the sandpaper portion of the special fixture. Clamp it down to the special fixture. Grasp the workpiece and try to pull it away from the sled. If the workpiece is firmly attached, set the rip fence for the required distance from the blade. Rip the untrue edge from the irregular piece using the sled. 

STEP 10: The Results

The photo shows the new straight edge on the workpiece. Also on the saw table is the irregular piece trimmed away. 

Remove the workpiece from the sled and put it away. Invert the workpiece. Adjust the distance between the blade and the rip fence. Rip the other edge so it is true, too.

This sled wastes less good wood than the traditional method that involves tacking or screwing the workpiece to a straightedge guide.

19 Comments

KellyCraig 8 years ago

Regarding patents, no matter how well they are written, the laws remain the same. As such, here in the states, merely creating the same thing with enough changes is enough to avoid patent infringements.

Consider the laser, as an example. The fellow who invented it only made about twenty-five thousand off it. HP, on the other hand, made a few changes and went with it and has made millions, as have many others producing the millions of things that rely on them.

KellyCraig 8 years ago

Regarding Saw Stop technology, now that company has to deal with Bosch, which designed their version and which does not destroy the blade in operation.

KellyCraig 8 years ago

To those saying negatively things about removing safety equipment, obviously, are not familiar with the operation of such equipment. For example, my equipment had to be removed or you could not perform rabbit, dado or grooving operations. Avoiding such operations would, of course, be ludicrous, since I could never make bookshelves using such joints.

KellyCraig 8 years ago

On the matter of riving knives, and splitters, such are a great investment in your future.

To be clear, circular saws do not have riving knives, which move up and down with the blade. They are relatively new, which Phil pointed out. For example, my commercial saw doesn't have one. Instead, I bought an after market splitter, which attaches and removes in seconds.

Since buying and using a splitter, which does the same thing as a riving knife, but without moving, kick backs caused by wood pinching the back of the blade and lifting off the table and throwing forward, have dropped to almost none in the nearly ten years I've been using it.

Couple a splitter or riving knife with a push shoe (a/k/a block) and your chances of controlling situations vastly improves.

KellyCraig 8 years ago

These do work great for, safely, cleaning up wood with a rough edge. Without it, the conversation about riving knives and splitters would take on an even more important meaning, since running rough wood would be equivalent to free handing it through the saw.

My saw is a cabinet saw with a three horse motor. Any thought of free-handing wood through is something best done by those with a wish for impalement or death.

Rather than fighting nuts, drop by your favorite hardware and pick up a couple knobs for 1/4-20 or your metric equivalent. They are relatively cheap and make using such jigs a breeze. I keep several in my jig building box for that reason. Of course, I, also, keep a variety of 1/4-20 bolts of various lengths for those purposes too.

Mindmapper1 10 years ago

using a circular saw without the riving knife fitted is extremely dangerous with or without your sledge/sled, timber can climb up the back of the saw. in a commercial situation in the uk it would be an offence under the health and safety at work act

Phil B 10 years ago

I did a fair amount of reading about riving knives and about the work lifting at the back end, etc. I tried adding a riving knife on another saw, but found it created more problems than it solved, including binding. I can assure you this sled will have plenty of downward pressure in use so that the back does not rise up.

klee27x 10 years ago

"it created more problems than it solved."

If a riving knife solves a problem just once, it will have been worth all the problems it created, no? And if a properly sized and installed riving knife is binding, isn't it solving a problem?

FTR, I would have few qualms about using your sled without a knife. As you said, it's pretty heavy, the stock is locked down, and you're only taking a little off the edge. But if the knife or splitter isn't installed by default, it makes it awful tempting to do just that one unsafe cut to finish a project.

Phil B 10 years ago

I did watch some videos on the need for a riving knife. In those, the piece cut was nearly square, no pressure was applied on the top surface of the piece to hold it down--only on the vertical surface pushed through the saw, the saw probably was heeling a little, and it was possible to get the saw to throw the piece. Yes, a riving knife would have prevented that, but so would a pusher that also holds the work down. Things like something thrown are also why I stand to one side of the blade and not directly in line with it.

I am probably older than you are. Most of the table saws I remember from every maker were made and sold for decades without riving knives. People used them safely for years and years. I am often a little bemused by safety features that came along during the last 30 or 40 years and no one remembers there was a time when people used these tools without those safety features and without anyone I know having a problem. I never even heard of others having a problem. Now, I did hear of a couple of incidents that involved a tooth coming off of a carbide tipped blade and embedding in the wall or the ceiling across the room like a bullet from a rifle. No one was hurt, but those events are frightening. No one is talking about that potential danger, either. A carbide tip flying across the room does scare me.

One article I read on riving knives acknowledged that many of them are eventually removed by owners because they created more problems than they solved.

Perhaps you have seen videos of the SawStop device that stops a spinning circular saw blade dead in a tiny fraction of a second. I think those are a wonderful piece of technology, but just one man has the patent on those and it is written so that anyone who makes any kind of safety device in the least way similar will be held guilty of patent infringement. He also tried to get its inclusion on all table saws mandatory on all saws by law. Would table saws be safer if he had succeeded? Probably. Are there selfish motives at work that have nothing to do with safety? Yes. Is that a good thing? No.

tim_n 10 years ago

SawStop shows both good and bad practices, yes excellent because it has protected a very clever idea and the guy that did it will be amply paid. Bad because you have to pay the price he asks for and no competition can muscle in and reduce prices (not to mention the one use cartridges). Until the patent monopoly comes to an end that is, then it'll be open season and I would expect many saw manufacturers will offer this on their premium range.

Choosing to remove and advocating there is no need are entirely different things. Kickback is a very serious thing (and damned scary).

Having had a riving knife stop an injury to myself, I can't say I would use one without one. It takes one moment of inattention to cause serious injury to you. I believe it's now illegal in the US for new tables not to be fitted with one. I'm in the UK and it's been law for a while as far as I know... even hand helds have them.

Just a note about 30-40 years of experience. I work in a safety critical area. Several times old hands have died through known unsafe practices because 'that's the way we've always done it and I'm OK' - it's a very difficult culture to overcome and the thing that frustrates accident investigators who see young people who've been taught by old hands and have died doing it because they're not as experienced.

Rather than fitting a riving knife, why not buy a new circular saw that's up to spec with the riving knife already fitted safely?

Saying that both instructables are very useful and informative and I look forward to making my own (with riving knife)

Phil B 10 years ago

Tim, Thank you for your comment. Back in 1969 Sears (Craftsman) came out with an electric circular handsaw that included a riving knife. I had never seen one before and have not seen one since on an electric circular handsaw by any maker in any price range. My electric circular handsaw is a better quality Porter-Cable only a couple of years old. Neither it nor any of the other choices offered when I bought it were factory fitted with a riving knife, nor do they have any factory fittings for adding a riving knife.

Apparently there is an alternative to SawStop named Whirlwind. It requires 1/8th second to stop a blade, which is longer than SawStop's 1/200th second (advertised as 5/1000ths of a second), but Whirlwind initiates the stopping process before flesh contacts the moving blade when hands and fingers are simply detected as being within a certain proximity. I am surprised Whirlwind is about to be marketed, given the way the patent on SawStop was written to regard any safety improvement to table saws as a patent infringement. 

bricabracwizard 10 years ago

Hi Phil, What you have created here is marvellous! I think the better option is to keep accident prone people away from this. Like you I have operated a bench saw for many years and like you always stand out of the line of fire and certainly never behind the saw, always to the side. Maybe your next instructable will be to create a guard over the blade (maybe an extension of your clamps and a back stop that is anchored to the table with a sliding guide) to inhibit flying pieces of wood. Or a body suit. Safety is always important, but it is also the responsibility of the person using the tool to make sure they are competent to use it. I would say common sense but there is no such thing today.

Mindmapper1 10 years ago

I attend many many accident investigations where saws have been incorrectly guarded and used. Removing something fitted to a machine to protect the operator is foolish to say the least. In 30 years I have never been to accident created by a knife being correctly fitted. A correctly fitted knife will prevent binding and kickback. A saw can throw a huge piece of lumber back if grabs the upside of the blade.

longwinters 10 years ago

Phil I love your project sorry you have to take so much heat from the safety SAMs anyone who has really worked with a table saw knows that when you get to stock that large it's mass provides a wonderful protection factor
There is a difference between respect and fear and if you are afraid no addition to a saw is going to make it safe

SherpaDoug 10 years ago

I often make small projects with interesting grain from wood from my firewood pile. I generally start by using hot glue to put a split log onto a piece of plywood to get the first true edge.

Phil B 10 years ago

Good idea. The hot glue fills in the gaps to conform to irregular shapes. Still, the hot glue breaks loose fairly easily. Thank you for sharing.

nyx702 10 years ago

Very interesting! I have been looking at various methods of milling raw logs on the table saw and might just be making something like this soon!

Have you tried this yet on round logs?

Phil B 10 years ago

Thank you for looking and for your comment. I have not milled logs, or otherwise tried to use them for anything other than cutting firewood, and those were not anything that would make good finished lumber. This sled is really for putting a true edge on lumber that has been finished, but no longer has a true edge. And, the purpose is to avoid wasting good wood because of nail or screw holes used to hold a guide onto the good wood during sawing. If you manage to adapt something from this for milling logs, please post some pictures and a brie description.