How Accurate Are Parallel Guides, Really?

[darita]

I've been looking a lot at different parallel guides and I've watched plenty of YTs of guys saying, "Dead On".  I'm just wondering if they really are as dead on as a table saw when it comes to cutting parallel?

 

[Crazyraceguy]

It relies 100% on your actions in calibrating them. They very much can be perfect, but it's not automatic out of the box.

 

[Michael Kellough]

Like CRG said, it’s up to you to dial them in but after that the results will be extremely repeatable as long as you take the basic precautions in setting them to the stock. Like make sure the stops are snug and that the stops aren’t sitting on splinters etc.

I bought the Festool version over a decade ago and like most everyone was dissatisfied. That’s why there are so many choices now. The curser is kinda crude so I made a vernier scale to add to it that allows me to read .1mm directly. But it’s also annoying that the chunky extrusions have to be beyond the workpiece so the support under the work has to be longer, very inconvenient when the work is 8 feet long already.

The sit on top versions are much more user friendly. I bought the TSO stuff and am very satisfied with it.

 

[GregorHochschild]

For ripping a full sheet with two rails that are joined together, I was always struggling to get perfect results and constantly checking whether the rails are well aligned. Probably the precision was good enough over 2.4m but I wasn’t happy. I would want a single rail and I think that would have solved my issues with breaking down full sheets with tracksaw and parallel guides. Now I have access to a sawstop ICS and I am getting excellent results.

In short, your results with parallel guide will depend on the whole setup. A good and flat work surface is important as well.

 

[Crazyraceguy]

Like CRG said, it’s up to you to dial them in but after that the results will be extremely repeatable as long as you take the basic precautions in setting them to the stock. Like make sure the stops are snug and that the stops aren’t sitting on splinters etc.

The sit on top versions are much more user friendly. I bought the TSO stuff and am very satisfied with it.

I'm about to do the same thing, since there's a Systainer version now. I couldn't possibly be happier with the MTRX triangle in the Systainer. It is very well thought out and incredibly accurate.
Just last week, I cut 45 degree miters on two countertop ends, that are 32" wide. Those corner triangles are so dead-on right from the saw that they fit each other, making a perfect square. You can flip either one, either way and they make a perfect square, and the track cuts so cleanly that they are nearly seamless (out of particleboard)

 

[Crazyraceguy]

For ripping a full sheet with two rails that are joined together, I was always struggling to get perfect results and constantly checking whether the rails are well aligned. Probably the precision was good enough over 2.4m but I wasn’t happy. I would want a single rail and I think that would have solved my issues with breaking down full sheets with tracksaw and parallel guides. Now I have access to a sawstop ICS and I am getting excellent results.

In short, your results with parallel guide will depend on the whole setup. A good and flat work surface is important as well.

Good points. It would be rather awkward to deal with that whole apparatus, especially including a joined pair of tracks. The 3000 rail is fantastic, but not everyone has the ability to store one. That's the only drawback to them.
Supporting the sheet through the entire cut on a tablesaw is important too though. Ripping full-length strips from a full sheet is just not in the cards for a lot of people's tablesaw either.
The struggle of the track and guides is only an accuracy issue, not a safety one. Without a good infeed-outfeed support system, the opposite is the case on a tablesaw.

 

[ChuckM]

Snip. Ripping full-length strips from a full sheet is just not in the cards for a lot of people's tablesaw either.
Snip.

Norm Abram did it on his older and later newer tablesaws, using the workbench (built to the new table saw's height) as a support at the front.

Anyone who wants to rip sheets on their cabinet saw should consider mounting a JessEm stock guides to their fence. That guides not only prevents kickback but also holds the large sheet tight to the fence making feeding the 4x8 a lot easier. Still, it takes a mastery of the basic feeding skill to do the task with perfect results. Practice it on a 1/8" or 1/4" sheet if you want to develop the skill before attempting it on a 3/4" - 4x8 piece.

 

[GregorHochschild]

Completely agree. Ripping a full sheet on a cabinet saw requires skill and setup. I ask the lumber yard to do one rip on full sheets whenever I can. That makes it so much easier to handle the pieces. Still a full length rip afterwards but lifting and controlling the pieces is much easier.

Overall, I still think it is easier and faster to get accurate results on a good table saw setup compared to parallel guides in most situations. Not saying it can't be done but it just requires more attention, careful alignment of the cursors on both guides etc.

Snip. Ripping full-length strips from a full sheet is just not in the cards for a lot of people's tablesaw either.
Snip.

Norm Abram did it on his older and later newer tablesaws, using the workbench (built to the new table saw's height) as a support at the front.

Anyone who wants to rip sheets on their cabinet saw should consider mounting a JessEm stock guides to their fence. That guides not only prevents kickback but also holds the large sheet tight to the fence making feeding the 4x8 a lot easier. Still, it takes a mastery of the basic feeding skill to do the task with perfect results. Practice it on a 1/8" or 1/4" sheet if you want to develop the skill before attempting it on a 3/4" - 4x8 piece.

 

[woodferret]

One other knock against parallel guides and tracks is cupped boards.  Ive fumbled some cuts when the rail was unknowingly pivoting on a high spot.  The hooks on the guide did decently well at holding deflection to a mm or two, but still.  That might be a situation where a STM might have been handy to allow full clamping (I did it on the ground with foam).

 

[simonh]

Always ensure your parallel guides are attached square to the track (check often). It's easy to knock the long parallel guide arms out of square, which alters the distance from your stop to the cutting edge. Then, the boards end up not parallel along the length (I know this through experience with perfectly calibrated arms!).

 

[Crazyraceguy]

Completely agree. Ripping a full sheet on a cabinet saw requires skill and setup. I ask the lumber yard to do one rip on full sheets whenever I can. That makes it so much easier to handle the pieces. Still a full length rip afterwards but lifting and controlling the pieces is much easier.

Overall, I still think it is easier and faster to get accurate results on a good table saw setup compared to parallel guides in most situations. Not saying it can't be done but it just requires more attention, careful alignment of the cursors on both guides etc.

Snip. Ripping full-length strips from a full sheet is just not in the cards for a lot of people's tablesaw either.
Snip.

Norm Abram did it on his older and later newer tablesaws, using the workbench (built to the new table saw's height) as a support at the front.

Anyone who wants to rip sheets on their cabinet saw should consider mounting a JessEm stock guides to their fence. That guides not only prevents kickback but also holds the large sheet tight to the fence making feeding the 4x8 a lot easier. Still, it takes a mastery of the basic feeding skill to do the task with perfect results. Practice it on a 1/8" or 1/4" sheet if you want to develop the skill before attempting it on a 3/4" - 4x8 piece.

It can definitely be done on a full-sized cabinet saw, with adequate infeed and outfeed support. I have done it for years, but we have tons of space and huge tables.
I can't imagine doing it solo with a contractor saw though.
We used to use cutting 4" toe kick strips as an "informal test" for new hires. Give a guy a 4' x 8' sheet of 3/4" ply, point them to the saw and ask them to cut it into 4" strips, with no instruction.  We don't do it manually anymore, so that kind of went away, but in all that time, I only ever saw one guy cut the sheet in half lengthwise first.
As I have said, I don't currently have a tablesaw at home, so I'm going to give it a go without one. initially at least. Then when I do, it will likely be the new Festool one, which is not really the thing for this task.

 

[Alanbach]

To me the trick is to buy really good parallel guides known to be very accurate if calibrated properly and then use them often enough to become proficient. I have a 450 square foot home shop, a 52” PCS with outfeed table and three plus decades of accumulated decent technique. For me, making a full length rip on an eight foot sheet of ply is relatively easy and accurate and my Jessem guides allowed me to stop asking my wife for occasional help. The challenge came in with big cross-cuts in ply. Those can be dicey so I bought the TSO rail squares and eventually the parallel guides. They are great and can be spot on accurate but like most precision tools in the shop they can be fiddly and if you don’t use them regularly you can struggle a bit. The parallel guides are great if you need to repeat a bunch of cuts of a certain size. If you are making one or two of each size just get both TSO rail guides and just mark your cut lines.

 

[ChuckM]

Snip.The challenge came in with big cross-cuts in ply. Snip.

Spot-on. Rip cuts are not the problem.

The track saw/ circular saw is the tool of choice for crosscutting. I sure wouldn't do it in the way these folks suggested in their video, given the risk of kickback (depending on the cutting width):

 

[Crazyraceguy]

Yeah ChuckS, that is sketchy at best.
It is showing two absolutely wrong techniques at the same time.
1)The piece between the fence and the blade should never be wider than it is long.
2)Two people should not even attempt to control the same piece. If something goes wrong, they will not react in the same way. The potential for wrong already exists as point number 1.

Spot-on. Rip cuts are not the problem.

The track saw/ circular saw is the tool of choice for crosscutting. I sure wouldn't do it in the way these folks suggested in their video, given the risk of kickback (depending on the cutting width):

They are if you don't have adequate infeed and outfeed support, and as I alluded to before, technique is important too. Say you need a single 4" strip from the width of a 4' x 8' sheet. That really requires support to the side of the saw too, if you are taking the 4" against the fence. Many people, in home shops, don't have the capacity to do it the other way around. Plus, this started out to be about parallelism. Leaving your desired piece as the off cut is not the way to get that. You are cutting oversize and re-cutting again at best.

Cross-cuts are definitely an issue too. Very few hobby woodworkers are going to have a panel saw (in either form vertically or horizontally) Track saw win again.

This whole thing follows the general concept of either taking the part to the tool or bringing the tool to the part. It all usually depends on which one is bigger/heavier.

 

[sancho57]

When I owed the Festool parallel guides I was able to get consistent cuts.

It was out 1.5 mm over 8 ft which really is pretty good.

They were just sort of a hassle to use so Now I use the TSO PGs which are easier to set up and I get just as good or better cuts

 

[eschumac]

I bought the TSO Drop on connectors. This tipped me to the TSO parallel guides. That and I already had the TSO sourced Festool square.

 

[darita]

Does someone offer a gauge to set the guide stops?  Rather than depending on my old eyes, it would be easier for me to set a gauge, then set both stops to that.

 

[Michael Kellough]

I don’t know which system you have but once the rail is secured to the guide rail you can simply place a squared up piece wood or a rule between the guide rail and the adjustable stop. With each stop curser set to the same increment on the rail you then adjust the stop to make strong contact with the block of wood (or rule).

Then make a test cut. Most likely the test piece will be slightly longer than it should. If so you then place a feeler gauge the thickness of the discrepancy between the stop and a small block of wood that you can clamp to the rail. Then remove the shim and adjust the stop to reach the block of wood.

Should add that the rail/stop can be individually adjusted. You don’t need a long piece of wood to try and do both rails at the same time.

 

[Imemiter]

Does someone offer a gauge to set the guide stops?  Rather than depending on my old eyes, it would be easier for me to set a gauge, then set both stops to that.

Incra-style parallel guides would be a good idea for eyes like ours. 

 

[guybo]

Does someone offer a gauge to set the guide stops?  Rather than depending on my old eyes, it would be easier for me to set a gauge, then set both stops to that.

these work great for that,so do the newer rule stops, align to splinter guard and check both. Maybe woodpecker tool will make them again