Jigsaw Blades for cutting Straight 90degree Lines?

[MrDavidRoberts]

I have this problem that I'm not able to cut straight 90degree lines in wood If I have attached a straight edge guide and run it along it.
It starts cutting fine, but than as it goes the blade seems to bend more and more and if the cut is more than 10cm long your line comes to probably about 80!!!! degrees all wonky and you basically destroy your workpiece.

I believe the problem is because it's a thin jigsaw blade and when you wedge it against a guide you probably create some pressure points once you get some differently structured timber/knot and it just bends as the jigsaw doesn't have anywhere where to move as its wedged against the straight edge. I have tried this with 3 jigsaws and all of them have been as hi-end as they come so probably not a jigsaw fault, but blade or operator fault.
Cutting in mdf and other thin man-made stuff is just fine, and also its fine if I don't run it against a straight edge for thicker solid wood.
But when it comes to cutting some 5cm thick solid-wood with a Straight edge guide, oh boy...

I have some regular thicker all-purpose bosch/dewalt/makita blades and they produce the same results, So I'm just wondering if there are any blades that can cope with such task or I'm doing something wrong or this simply can't be done with a jigsaw?

 

[MikeJhn]

You should be using a table saw to rip 50mm thick timber a jig saw was never designed for that task.

Mike

 

[Phil Pascoe]

They will cross cut accurately more easily than rip - but don't even think about a straight edge, it just doesn't work as you cannot correct a slight drift and it will become worse.

 

[Nelsun]

If you have to use a jigsaw you can help reduce deflection by cutting in short ”pulses" for want of a better word. Rather than pushing through the cut in one long motion, cut a few inches, pause, retreat an inch then cut another few inches. This lets the blade try and straighten up slightly. If it's going wonky wonky it'll still be wonky but it helps slightly some of the time.

I'm by far no expert on blade choice so I'll keep my gob shut other than to say there's plenty in Google that attempts to explain what all the numbers and letter mean.

 

[Homers double]

As others have said it's hard not to drift, I use nelsons approach of do a little, reverse a bit and a little forward again.
Regarding blades I prefer makita ones, I was also given a few festool jigsaw blades by the rep during a on site demo they were the most rigid jigsaw blades I'd encountered, but the finished cuts were rough as a dogs buttocks although there was no drift.
I'll put some blade info up when I get to work

 

[pcb1962]

Festool blades cut truer than any others I've ever used in thick timber

 

[transatlantic]

If it's a straight edge, use a circular saw. Much more accurate, and also much quicker! (and possiby a cleaner cut)

If it's a curved edge, then it might be worth making up a template from thinner material which you can then use to clean up with a bearing bit in your router.

 

[skipdiver]

Caused by friction isn't it? As the blade gets hotter, it starts to deflect. Jigsaws are ok if used within their limitations but accuracy isn't their strong point.

 

[transatlantic]

Caused by friction isn't it? As the blade gets hotter, it starts to deflect. Jigsaws are ok if used within their limitations but accuracy isn't their strong point.

Probably also to do with path of least resistance, so I'd expect it to be worse with soild wood over MDF

 

[bugbear]

Caused by friction isn't it? As the blade gets hotter, it starts to deflect.

If it gets hot enough it might get soft (but, oh boy, it would need to be very hot).

But I can't see any directional effect caused by heating that would cause deflection?

BugBear

 

[mbartlett99]

As has been said - 50mm thick is just too much to ask of a little blade. Even a good circular saw will struggle to do that in one pass; with a new blade in my TS55 I can just manage 40mm.

I'd suggest hacking it out with your jigsaw as a rough cut and then taking a bearing guided router bit down a straight edge to clean up. Even then you'll probably need to rout in several passes for safetys sake.

 

[Phil Pascoe]

Caused by friction isn't it? As the blade gets hotter, it starts to deflect.

If it gets hot enough it might get soft (but, oh boy, it would need to be very hot).

But I can't see any directional effect caused by heating that would cause deflection?

BugBear

That's what I thought. I suspect the blade just tracks into the summer growth of the wood when ripping.

 

[Farmer Giles]

I've had the same problem in the past, the only way I know to solve it is the mafell P1CC jigsaw. Check out the youtube videos.

Their secret sauce is no guide roller behind the blade plus a laminated blade design.

If your cutting a straight line then a jigsaw is probably not the best tool however if you are cutting curves and still want the cut to be perpendicular then the mafell is the way to go, but eyewateringly expensive. I have tried metabo and bosch jigsaws with a whole raft of blades. You cannot use a rail guide or cut curves and get a perfectly perpendicular cut with any of them and even going slow and inching forward and back is not a complete cure and you get a very rough cut.

I recently bought the mafell but haven't put it though its paces much, however as an indication the blade doesn't wonder off like a conventinal jigsaw. I cut some oak using a guide rail with it as I couldn't find my circular saw and my table saw was covered in junk and it worked a treat. I have tried that with a conventional jigsaw and decent blades and it bends or breaks the blade, normally you compensate for the wandering cut by turning the jigsaw a little, you don't need to with the mafell.

The oak was only 20mm but it was perfectly square and smooth, there is a youtube video of a mafell v a festool jigsaw cutting very deep softwood and they do sell a long balde for this so I'm guessing that will work fine too.

 

[MrDavidRoberts]

Back to a handsaw I guess, a bit of a workout but I can easily cut to a 1mm accuracy with one even over 1m+ lengths
I'm kinda scared to have a tablesaw because of watching too many videos about kickbacks and due to the fact that my best friend doesn't have full set of fingers anymore due to one #-o

I'm aware of the mafell however the pricetag+cord puts me off+ I have just bought a new cordless makita one which is as sweet as they ever get.

 

[Bodgers]

The Mafell is probably a more expensive version of the wrong tool for the job...

A Bandsaw is probably the best choice for a long rip.

Failing that a circ/track saw with a retracting riving knife, possibly done in a couple of passes.

 

[Paddy Roxburgh]

I'm kinda scared to have a tablesaw because of watching too many videos about kickbacks and due to the fact that my best friend doesn't have full set of fingers anymore due to one #-o

.

Hi David, if you always use 2 push sticks and always stand to the side of the work and always use a riving knife and crown guard there is absolutely no way that a table saw can bite you. All table saw accidents are caused by incorrect usage, ignore America videos on table saw use, those guys just don't want to keep their fingers. Table saws are fast and accurate at ripping and cross cutting (with a suitable sliding table or sled) and with a sharp blade can leave a pretty clean surface.
That said if you were to have one stationary saw it should (in my opinion) be a bandsaw as they offer much more versatility as they can cut much deeper and also do curved work, some even cut their joinery on them (not me). The main disadvantage is that the cut needs planing/scrapping/sanding to get rid of saw marks (on most work). I have a pretty decent festool jigsaw but very rarely use it as the bandsaw is far more accurate. If I was only allowed one powered saw it would definitely be a bandsaw (although I would really miss the track saw).
Paddy