Information on straight-line ripsaws' capabilities, characteristics, and performance. April 21, 2011
Question I am shopping for my first straight line rip saw. I have never had any experience with them and I would like to know what to look for. Some of them have the blade on the top and some have the blade on the bottom. Is there any advantage to one system over the other? All of them rely on some kind of pinch point between rollers and a chain.
Are there any limitations regarding material thickness from this system? Can I switch between 3/4 and 1 1/4 inch thick stock without having to adjust anything? What is the shortest length of material that can be safely fed through this machine? Safety is the number one goal for me. I don't want any kickbacks. What should I look for in safe designs? Are the import saws worthwhile or should I shop for used American iron?
Below is a video of a guy running a straightline rip saw. At 2:09 minutes in he lifts the board to inspect for something.
Forum Responses (Solid Wood Machining Forum)
From contributor G: My guess is he's looking to see how straight the edge is to start with. I do it all the time.
From the original questioner: So this has nothing to do with crowning the board?
From contributor Z: He is double checking that he is putting the desired side of the plank against the fence. Perhaps there is some crook in some of the planks and he is favoring the crook direction always to the same side.
From contributor G: It has everything to do with "crowning" the board. I find it easier and less wasteful to put the crown towards the fence side of the saw (even though the fence is not used) when straight line ripping. To do so I need to sight down the edge of the board to put the correct side towards the fence.
From contributor M: I have owned several SLR saws, and far and away the safer version is the blade on the bottom. These machines are however a little more expensive and require larger diameter blades to reach through the chain. I have never had a kick back with this type of configuration. I did own a top blade model that cut beautifully but several kickbacks and a 12' hickory edging through the operators leg got me to switch.
Our current machine is an import and has been excellent, but there are good buys on old iron out there right now. Obviously the key to a saw that cuts straight is the chain, and an old machine that is worn out can be expensive to replace these components, if there even available. Adjusting from different sizes is a quick crank of the handle to raise or lower the head.
From contributor O: My experience is with Diehl SL-55's and the like. All bottom cutting machines, with a 20hp direct drive saw arbor. Height is easily adjustable. They will still kick back, so the operator needs to learn to stand off to the side and you do not want shop visitors to access the area near the infeed area. The machines will rip continuously all day and never break a sweat. They are capable of glue line rips up to 16' where you can glue directly off the rip line.
From contributor A: We like the grizzly, works good, but did have a kickback when the operator was butting short boards end to end. 1 1/2" material should not be a problem, but you definitely have to adjust for different thicknesses. Shortest board may be around 8", but that is cutting it close, probably getting into the danger zone. There should be two or three rows of kickback fingers, not just one. I’m not sure why the blade under the table would kick back less (tablesaws kickback all the time), but that piece of info is useful.
From contributor B: Can a SLR cut to width accurately?
From contributor M: Yes a straightline can cut to width accurately.
From contributor Y: I can understand how the first cut on the saw is very straight. Is it very hard to keep the stick against the short fence for subsequent parallel rip cuts? Does the second rip produce a tapered board or a parallel board?
From contributor M: The beauty of the first cut being so straight is the second one tracks real well along the fence, even being short. Of course take it all with a grain of salt, a piece of material that is bound up is going to spring no matter what and can cause tapered cuts. A long piece of stock is less likely to stay real straight and may need some coaxing to stay against the fence. The general purpose of a straight line is to prep material for a second operation, whether moulding, or to chop saw and jointer for edge preparation, or even further ripping at a table saw. We do use ours for glue line operations, but it is not necessarily blow and go, a piece may need to be re run for straightness and ripped a little narrower to get a good glueable edge.
From contributor R: It may not be obvious by the video or if you are not familiar with the machine, but a key part of the operation is a laser or shadow line. The shadow line light is now almost 100% replaced by lasers.
The laser line represents the cut line of the blade in the machine. Line up a crooked or wany edge on the laser line and push the material forward into the feedworks with the line where you want the rip to be. As soon as the feed grabs the board it is sent thru the saw and cut right on the line defined by the laser.
A properly set up and maintained Diehl can cut 16' of glueline quality cut on nearly every board. The used saws may need a little or lot of work to get to that point, but you may just want the auto feed and smooth accuracy. Excellent for prepping molder blanks. Rough mils are often described as rip first or cross cut first to differentiate as to what type of yield is expected. But the straightline ripsaw is an integral part of nearly every shop processing lumber of any quantity.
From contributor U:
The last reply is correct with using the laser line or guide of some kind. The first cut should be made using the laser line and not the fence. Pretty much an eyeball cut to get a straight. The machine should hold it. Not sure you need one unless you are milling a lot of lumber.
From contributor H: If you cut solid wood a SLR is something you shouldn't be without. Aside from the possibility of kickback your fingers aren't anywhere near the blade. Speed, accuracy, and safety go up from using a table saw. There are plenty of good used import top mount blade saws in the 5k range. I am a small shop wit one employee and don't understand why a SLR isn't in every shop. I use mine for glue joint rip and sizing as well.
From contributor B: Can you rip to width as accurately as a standard table saw?
From contributor H: Yes and no. If you are ripping with a table saw by hand then yes, much more accurate using a SLR. If the T-saw has a power feeder then maybe not. It depends on the material as the T-saw will follow a warped board, the SLR doesn't. That is a hardcore reality. In practical use the SLR exceeds anything else outside of a moulder.
