Thread: MFT/3 for cutting accurately small plywood sheets with fine cuts

How small?

Originally Posted by Antoniomcs

Hi,

I need to cut quarters of plywood sheets (24"x49") into small pieces at 90 degree angles, accurately.
Ideally, it was not necessary to make any adjustments to the cuts and that the cut pieces came out perfect, with extreme precision, perfect right angles and with fine cuts.

Your definition of "extreme precision' would help.
I think you might mean "accuracy"

Precision means all the pieces come out the same size. but may all be smaller or bigger than required size..
Accuracy means they ll come out very close to the required size.

The correct way to state this sort of request is the size off the final pieces and the tolerance.
eg 20.4 x 31.6 +/- 0.1mm

Extreme precision and accuracy sizing is not really associated with wood (even plywood) as it will move. So you may cut it at one size today and a few hours later or next week it will be slightly different. If you want more precision then low expansion metal is required but even there temperature will affect the size.

Some Idea of your application of the pieces will help.

The inbuilt fence system would likely get you to within 0.5mm. I think a set of high/low dogs might get you <0.25 mm if you clamp the work and the track to the table. Maybe slightly better if the top is new and the dogs have a piston fit. It depends of on the (unstated) accuracy of the hole locations in the MFT top, any bow in the track and the saw+blade. Good dogs should be plenty accurate enough.

Of all the factors I think careful clamping is the most important.

The pieces to be cut are about 4"x13", 6"x12", for example.
There are smaller pieces, 3.5"x3.5" for example.
Just like there are bigger ones.

The thickness will always be the same, 5/8"

Originally Posted by BobL

Your definition of "extreme precision' would help.
I think you might mean "accuracy"

Precision means all the pieces come out the same size. but may all be smaller or bigger than required size..
Accuracy means they ll come out very close to the required size.

The correct way to state this sort of request is the size off the final pieces and the tolerance.
eg 20.4 x 31.6 +/- 0.1mm

Extreme precision and accuracy sizing is not really associated with wood (even plywood) as it will move. So you may cut it at one size today and a few hours later or next week it will be slightly different. If you want more precision then low expansion metal is required but even there temperature will affect the size.

Some Idea of your application of the pieces will help.

My main intention, to use the bandsaw for those cuts.
The blade that came with it is 1/2" 4 TPI, and I realised that it makes rough cuts, specially crosscuting 5/8" plywood.
I'me very new to this, so I'm searching for bandsaw blades that have a very fine cut. My intention is that the resulting cuts are 90º, very fine and clean, so that I could join the boards together right out of the bandsaw and make small boxes, without wasting to much time sanding the edges, removing the tear out, etc.

I don't know if that's possible, so, that's why I thought of the MFT/3, since I already have the TS55 for cutting a whole plywood into quarters.

The MFT3 and TS55 will get you right to the line.

It works best with a jig to automate the cuts.

Cleanup on very small pieces can be done with a jig and a belt sander laid on its side.

I assume you are making many pieces, not just a few.

Care to share something of the project?



Ill dredge up some pictures on the MFT jigs to do these kinds of cuts repeatedly, but its not complex.

These pictures show a few jigs that would be used to sand/trim any work very finely.


belt sander jig.JPG disk sander for box mitres.jpeg 259994789_610754320046608_4984666553442666354_n.jpg

This is the description of a jig thats useful for the MFT3 My Custom Adjustable Off-Cut Stop For MFT Repetitive Cuts - Now Modified Twice

maxresdefault-3964946827.jpg image-asset.jpeg 61086e362e432a2bc896fdc1a94219bc.jpg 1.jpg 2.jpg

Those pieces are too small for track saw use. Perhaps WoodPixel's jig might work. Typically pieces that size would be made on a table saw with a sled. Workholding and safety will be issues with pieces that small.

I have never seen a finished cut from a bandsaw in any material. That’s not what they do.

I thought I should mention, which is obvious, is we don't know what OP's project is.... so I was only offering how to do it generically with a jig.

It turns out while I was searching for a solution to assist, that I asked exactly this question on Festools forum many years back. I asked about doing "waste side" cuts, where the offcut is the desired piece. Being a leftie makes using the tracksaw a PITA.

The problem was the thickness of the blades kerf. I saved the pix above, this solution was designed by someone to replicate that kerf (the metal piece). It slides into place to get the measurements correct and subsequently taken out to subtract the kerf (or the opposite, depending on desired operation).

Obviously the knobs are for adjustment to get the distance right.

One takes this base IDEA and makes a jig to complete the desired cuts in a replicable manner. If this is only for 5 cuts, it's a TOTAL waste of time, but if one is to make hundreds of cuts, well, it pays for itself very quickly!

As for blades, the cleanest I've found for the Festool is the little diablo d0760x Freud blade ¹. Ill update the model number when I dig it out. It cuts a fine, smooth cut. Its not for nasty work, but near-finish.


I also thought these jigs for the belt sander and disk sander were clever. They are in my "Interesting Jig Photos" collection Depending on whether the OP wanted to do a Very Close cut then do a quick final tidy, might be a better option. Again, a jig that gets the size repeatably correct is made to fit onto the base idea of these el-cheapo sanding setups.



edit - tidied up my terrible English. Apologies, it is my native language.
¹ - link for example only. Shop local!

Wow,

The information shared here is very valuable, thank you!
Well, for now I'm going to need to make 4 boxes, so 16 small pieces plus the underside of the boxes. 20 pieces in total.
But if the project goes well, I might start needing to make 20 boxes a month, at least.

As I mentioned, the power tools and stationary machines that I have most suitable for this project are the bandsaw and the TS55.
I just bought them and I'm still learning how to tune them and use them in the best way.
My strong is using hand tools, but for this project I had to invest in power tools.

I understand that it's a perfect job for the table saw, but I don't know if I have the space for it.
I have a very limited workspace, so I didn't want to invest in a table saw just for this project, if I could manage with the bandsaw and TS55 (which I'll be using in another projects).
From what I understand, I will always have to refine the pieces cut by the bandsaw, even if the saw blade have a lot of TPIs.

The TS55 is a great saw and will be all you need for breaking down your sheets to the required width strips. Its the crosscutting to final size that you will have trouble using the guide rails on. Perhaps, as you originally asked, the MFT could work if you had long enough strips and resigned yourself to wasting the last 300mm or so from each.

If boxes are the thing being made, you are in luck!

We are all box makers here

There are plenty of options for "small workshops". A trellis to pre-cut, an upside-down circular saw mounted in a jig (a replica mini table saw) with a tiny blade ¹, using a portable worksite saw with a sled (incredibly accurate with a sled).... to a PARF table.

If "no space" defines your work and you need to break down sheets accurately, a Parf Dog Hole table top is the way to go. A Parf table will be perfect. It can be slid away like any sheet stock




and these extra ideas






¹ - its 165mm (6.5") and a 1.5mm kerf. CUTE!

Antoniomcs,

If you are limited for space a small table saw with a home-made sled is much faster at handling the size of pieces you are talking about and you can get glue-ready cuts.

I’ve made hundreds of boxes in a workshop 5 metres x 2.4 metres. I have a small table saw (Festool CS50), a full size router table, a veneer press, a drill press, a 300mm disc sander and all the usual hand tools and powered hand tools.

A good small table saw and sled will give you cuts accurate to 0.5mm or better if you are careful.

I think you will not need to worry about expansion/contraction given the very small sizes you are cutting.

If you need to fine tune any cuts a home made shooting board and a plane works wonders.

I agree with others here that it is very unlikely you will get the kind of cuts you need from a bandsaw.

Good luck with this project and please do send us pictures if you go into regular production.

Regards,

Brian

This seems to be very interesting, I didn't know this PARF table.
I'll have a closer look at this.
Maybe I don't need the MFT 3 after all...

Originally Posted by homey

Antoniomcs,

If you are limited for space a small table saw with a home-made sled is much faster at handling the size of pieces you are talking about and you can get glue-ready cuts.

I’ve made hundreds of boxes in a workshop 5 metres x 2.4 metres. I have a small table saw (Festool CS50), a full size router table, a veneer press, a drill press, a 300mm disc sander and all the usual hand tools and powered hand tools.

A good small table saw and sled will give you cuts accurate to 0.5mm or better if you are careful.

I think you will not need to worry about expansion/contraction given the very small sizes you are cutting.

If you need to fine tune any cuts a home made shooting board and a plane works wonders.

I agree with others here that it is very unlikely you will get the kind of cuts you need from a bandsaw.

Good luck with this project and please do send us pictures if you go into regular production.

Regards,

Brian

Thanks for the ideas.
I'm in a similar situation at the moment: a small room with the same area.
The CS50 is out my financial reach right now, too much expensive for my actual needs.
I was also looking at the small Dewalt table saws, they seem to be compact and more cheaper.
But as I mentioned, if I could just get away with these tools for this project, it would be the ideal.
Maybe using the bandsaw (using a blade with high TPI number), if it doesn't tear the plywood outside faces, and fine tune them with the shooting board


I never thought of the shooting board to fine tune the cuts. I have one and it might be useful.
Maybe I don't need a disc sander also.