Squaring up MDF sheets

[Estoril-5]

So im a novice when it comes to woodwork but enjoy making things.

I don't have the space or all the tools in my garage.

Previously when buying MDF sheets I would use a spirit level and clamps to make a straight edge and then cut with my circular saw which was ok but a hassle.

I then realised Selco cut the sheet for you, so I headed over with a cut diagram and they did the job it's Just that their accuracy isn't great (appreciate that's not what the service is for).

I then found out online there's a place called cultist.co.uk but the sheet is expensive and delivery is £35+vat, not cost effective when you just want a single 8x4 cut.

So gentleman, what would you suggest for my dilemma?

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[Myfordman]

Get a track saw or look on you tube for a sawboard video or three
If you can't lay an 8x4 down in your garage to cut it yourself, get selco to cut it oversize and trim to final size yourself with either of the above.

 

[custard]

You need a plunge saw with a track, plus an arrangement to support the workpiece above your garage floor on sacrificial bearers. Get a decent track saw, learn to set it all up properly, and the accuracy is all you'll ever need.

Good luck!

 

[Phil1975]

Tracksaw & either a large MFT table , if you have the space, or a bit of maths (Pythagoras), if you don't.

Then you can make/buy paralell guides to make the setup useful for rip cuts or a smaller MFT table which can be setup to allow smaller but repeatable cuts.

Don't ever assume a sheet of ply or MDF is either square or accurately dimensioned. In my experience not many are!

 

[Estoril-5]

Thanks for the reply guys, daft question, what's an MFT table?

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[murrmac]

Thanks for the reply guys, daft question, what's an MFT table?

http://www.axminster.co.uk/festool-mft- ... ies-702780

 

[transatlantic]

Many people put some kind of cheap foam/insulation under the sheet to be cut so you can work directly on the floor, say outside your workshop. Then set your saw to cut just a little deeper than the sheet thickness so as to not damage the foam more than you need to.

It might also be worth while making yourself some giant T squares for your saw to follow (of different sizes, from something very stable like plywood or MDF). Spend the time to get those accurate and they'll be there for many years to come. You don't need anything fancy to make them, just follow the 3|4|5 rule with a tape measure. The bigger the multiplier the more accurate it'll be (assuming you have a good tape measure)

The important thing is that you have a straight edge to begin with.

 

[MusicMan]

The bigger the multiplier the more accurate it'll be (assuming you have a good tape measure)

The important thing is that you have a straight edge to begin with.

Don't assume your tape measure is accurate, though. Most are Class II or worse, which is 1 mm per m. Axminster and TheTapeStore (but not Stanley) sell Class i, but even this is 0.5 mm per m. If you own two or more tape measures, try comparing them sometime.

Of course you are fine if you use a 1-unit story stick for setting out your 3, 4 and 5 units, though similar errors can creep in if not careful.

A 1 m steel rule is normally very much better than a tape measure.

Keith

 

[transatlantic]

The bigger the multiplier the more accurate it'll be (assuming you have a good tape measure)

The important thing is that you have a straight edge to begin with.

Don't assume your tape measure is accurate, though. Most are Class II or worse, which is 1 mm per m. Axminster and TheTapeStore (but not Stanley) sell Class i, but even this is 0.5 mm per m. If you own two or more tape measures, try comparing them sometime.

Of course you are fine if you use a 1-unit story stick for setting out your 3, 4 and 5 units, though similar errors can creep in if not careful.

A 1 m steel rule is normally very much better than a tape measure.

Keith

Yes, I did say assuming you have a good tape measure

I wonder if there is anyone here who could work out what that discrepancy of 1mm over 1m would have on the 3|4|5 rule?

So lets say I used 60cm, 80cm, 100cm, and my tape measure was out by 1mm? what effect on the accuracy would that have on the 90 angle? ...I'm curious.

I want to say that assuming the error is the same thought out, so +/-0.001mm per mm, for this case it shouldn't affect it.

If however the error occurs part way through, then of course it would be an issue.

 

[owsnap]

I think the problem more is in the fact If you can even mark that half a mm accurately with a pencil? and after that can you line up your saw/ and judge accurately how much the saw blade will take off.. I know that I can't do all of that with a 0.5mm precission myself. -1mm is possible however- that is most of the time.
also I have found that the pitagor isn't really possible (precise) in practice if you don't have a huuuge long metal ruler to mark everything

 

[Claud1]

The bigger the multiplier the more accurate it'll be (assuming you have a good tape measure)

The important thing is that you have a straight edge to begin with.

Don't assume your tape measure is accurate, though. Most are Class II or worse, which is 1 mm per m. Axminster and TheTapeStore (but not Stanley) sell Class i, but even this is 0.5 mm per m. If you own two or more tape measures, try comparing them sometime.

Of course you are fine if you use a 1-unit story stick for setting out your 3, 4 and 5 units, though similar errors can creep in if not careful.

A 1 m steel rule is normally very much better than a tape measure.

Keith

 

[Stanleymonkey]

I'd go with the tracksaw or homemade version as well.

Worth thinking about what you normally make before you buy any gear.

Do you ever use full size 8'x4' sheets or are you always cutting them down into much smaller pieces to make boxes, speakers, trays etc?

If so - get them cut to half size at the shop and then work in the warm and dry of your garage and buy things the right size for that.

If you need to cut the full 8x4 down at home - then can you work outside on sawhorses? (before taking the smaller pieces in to the nice warm garage!) Buy the right sort of tracksaw for that scale of work.

 

[ComfortablyNumb]

Get a rail saw, ukj jig and some part dogs. You'll be able to cut square to tolerance of less than 0.001mm

 

[owsnap]

Get a rail saw, ukj jig and some part dogs. You'll be able to cut square to tolerance of less than 0.001mm

can I have a link on what is the ukj jig and some part dogs ?

 

[MattRoberts]

http://www.axminster.co.uk/ujk-technolo ... tem-102278

http://www.axminster.co.uk/veritas-70mm ... air-504543

 

[owsnap]

http://www.axminster.co.uk/ujk-technology-parf-guide-system-102278

http://www.axminster.co.uk/veritas-70mm ... air-504543

 

[transatlantic]

Get a rail saw, ukj jig and some part dogs. You'll be able to cut square to tolerance of less than 0.001mm

yeah yeah yeah

 

[YorkshireMartin]

I think the problem more is in the fact If you can even mark that half a mm accurately with a pencil? and after that can you line up your saw/ and judge accurately how much the saw blade will take off.. I know that I can't do all of that with a 0.5mm precission myself. -1mm is possible however- that is most of the time.
also I have found that the pitagor isn't really possible (precise) in practice if you don't have a huuuge long metal ruler to mark everything

Thats why for very accurate marking out, you use a knife. +/-0.5mm is probably fine for initial dimensioning of sheet goods, but the tall cabinet I built recently would have looked awful if the margin of error was potentially 1mm at the joints.

Obviously you do have to account for kerf and many other things to achieve high levels of accuracy.

 

[Estoril-5]

Thanks for all the replies guys, going to look at making my own t square using this 3 4 5 method (although I don't know how it works).

I can't get a full MDF board in the car so will need Selco to cut it down so I can transport it.

Think I'm going to stick with using a clamp and straight edge with the circular saw till I can afford a track saw.



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[transatlantic]

Thanks for all the replies guys, going to look at making my own t square using this 3 4 5 method (although I don't know how it works).

You remember Pythagoras's theorem from school?

5^2 = 3^2 + 4^2
5x5 = 3x3 + 4x4
25 = 9 + 16
25 = 25


Lets say we want to use ar larger triangle, we just scale both sides.

e.g scale by 2

2(5^2) = 2(3^2 + 4^2)
2(5x5) = 2(3x3 + 4x4)
2x5x5 = 2x3x3 + 2x4x4
50 = 18 + 32
50 = 50

or double the figures

10^2 = 6^2 + 8^2
10x10 = 6x6 + 8x8
100 = 36 + 64
100 = 100