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I am fairly new to woodworking and I need to cut some hearts in 18 mm MDF - please see the design at the bottom of the post, including a revision inspired by @WhatRoughBeast. The radius of the curve is circa 30 mm and the default blade which came with my Bosch PST 650 is clearly unsuitable. I had a look at the manual - this website contains this direct link to the download, you may notice the link contains the extension .pdf twice but I checked and it works. I included a snippet below anyway, it says I need a "T 308 BOF" but these are only pricey and only available online.

My question is, what is the next best blade I can go for?

T 101 AO and T 101 AOF are both for clean curves but only up to 15 mm. I would imagine they can still produce decent results in a slightly thicker sheet - or am I better of with T 244 D, which are in stock in my local Selco, and OK for up to 50 mm but branded "fast" as opposed to "clean"?

My budget is limited and I don't use the jigsaw that much so I don't want to buy a full pack of the wrong blades. I don't mind branded/unbranded - any suggestions would be appreciated. Blade table Design preview design v2

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    Is there a reason that you're limiting yourself to Bosch brand blades? Jigsaw blades are generally interchangeable. (There are two shapes, "T" and "U", but most saws use the "T" shape.) – SaSSafraS1232 Apr 9 at 21:43
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    If you don't care what brand blade you're using I'd just go to the store and buy something. Honestly I would bet that the "15mm" blade will cut just fine through 18mm stock, just that it'll be slightly above the bottom of the material on the top of the stroke. 18mm is still less than 3/4" and pretty much every blade is going to cut through a 3/4" sheet. – SaSSafraS1232 Apr 9 at 22:08
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    Also, if you're having trouble making a curve cut just make a bunch of perpendicular relief cuts in the waste. – SaSSafraS1232 Apr 9 at 22:11
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    @SaSSafraS1232 Thanks for all your input, I really appreciate it. Please don't get me wrong, as I appreciate your rep score, but for the benefit of the woodwork stack exchange developing, shouldn't your last three comments be one answer? – pateksan Apr 9 at 22:24
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    Why not use two plunges of a forstner bit and then simply jigsaw with any old blade toward the bottom point? – Aloysius Defenestrate Apr 10 at 3:58
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Okay, (rubs hands together)... ready for an answer. I'll try to combine information from the comments (and will happily edit based on feedback if I've misconstrued anything).

To your question specifically. The T101 blades (or a similar generic) will turn tight curves because of its thin back and cut fairly cleanly. Don't worry about the supposed 15mm depth restriction -- the blade is long enough to go through 18mm. (It won't cut quite as cleanly as the fleam cut teeth of the 308, but not far off in MDF. The 308, by the way won't turn tight curves easily because of the thick back of the blade.) The T244 will be a rougher cut due to the nature of the teeth.

The bad thing about the T101 and T244 blades is that they won't track straight lines as nicely as a more typical (thicker) blade. One might want to cut curves with the thin blade and then switch.

You could also get away with using a normal 'clean for wood' blade with a thick back, and simply going back and forth to nibble up to the line. Just be sure to make enough room in the kerf that you can pivot the blade for a tight curve.

Depending on the jigsaw, blades can skew off vertical when cutting tight curves. Be sure to do a test piece and see that the front and back are lined up to your needs. If you find too much skew, then slow down and do more back and forth nibbling, rather than straight ahead cutting. (The downside to the nibbling is that it'll take more cleanup afterwards.)

Alternately, you could drill the round parts with a forstner bit (sometimes called sawtooth, though there are slight technical differences) or a holesaw.

A large forstner bit is non-cheap and ideally would be used in a drill press. Lacking a drill press, one would make a guide template with the same size hole and clamp it on your finish piece to constrain the forstner. (To make the first hole in the template, tack 3 strips of anything up against the sides of the forstner bit. The first template can be used to create an additional template that has two or four perfectly spaced holes.)

The holesaw is cheaper, though slower. Again, a drill press would be ideal, but because the holesaw has a pilot bit, it's a little easier to drill accurate holes handheld. A guide template would guarantee that you didn't skitter off and mess up your final product. Tip: clean the mdf dust off the holesaw teeth regularly... the dust clogs the gullets, which creates heat, which leads to premature dulling of the holesaw teeth. Tip 2: drill a hole in the rim of the holesaw's cutting path (inside the heart where it'll be waste) to help sawdust get knocked off the teeth.

To be very clear: using a handheld drill and either the forstner or holesaw isn't ideal. Take it slow and position yourself in a way that doesn't get your arm ripped off when the bit binds. You also need to be perfectly perpendicular.

If you go the round hole route, then cutting the straight lines down to the bottom point of the heart can be done with any old 'clean for wood' blade.

As a complete aside, if I had 20 of these to do, I'd readily justify the purchase of a router and a template setup, but I understand that not everyone is as addicted to power tools as me.

Thanks @Graphus and @SaSSafraS1232 for comments.

  • The project is on hold due to repairs cropping up at home etc. Great answer but surprised to see you say 308 won't turn tight curves. Do you think even the BOF variant (as opposed to BF, see snippet in OP) would be unsuitable? – pateksan May 10 at 0:04
  • Aaah, didn't distinguish between the BF/BOF variants. The wider blade of the 308bf will always resist turning more than a narrower blade. The 308bof is slightly narrower, so would turn better. – Aloysius Defenestrate May 10 at 3:09

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