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Wood cutting

Discussion in 'Home Cinema Building DIY' started by slingshot, Mar 25, 2003.

  1. slingshot

    slingshot
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    Decided to build yet another sub, and I'm sick of cutting wobbly edges in MDF, so does anyone know of anywhere that will accuratley cut MDF if you give them the sizes (and how much am I likely to end up paying)

    Cheers

    Slingshot
     
  2. deckard

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    Whenever I've needed MDF cutting I've had it cut where I've bought the MDF - B&Q usually. They have a large industrial saw that will cut straight and clean, just tell them the dimensions. I think the first 3 cuts are free and 50p thereafter, but I could be a bit out on that.
     
  3. dnrc

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    you sound about right with the prices in B+Q there.

    last time I got a sheet of 18mm MDF cut into enough pieces for 2 subs for £17.

    One point though, check how accurate the machine is before you have the whole lot cut as these things do lose accuracy after a while.
     
  4. Gary Lightfoot

    Gary Lightfoot
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    If I want to cut straight edges, I mark out the line, then use some G clamps and a straight bit of wood to make a guide for my jigsaw. It worked really well for me too.

    Probably cheaper to get B&Q to cut them for you if you have to buy the clamps though.

    Gary.
     
  5. jpwhaley

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    I used the same method as Gary, clamping down 2 pieces of wood to act as a guide for my Jigsaw. Requires careful measuring but works.
     
  6. Mike Swannick

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    I would recommend the clamps and wood option for DIY straight lines but use a circular saw if you can. There isn't enough power in your average jigsaw to prevent the wood itself causing minor deviations. Its even harder if the blade isn't brand new and super sharp. Even a cheap circ. saw will give you more control & therefore a straighter cut against a clamped fence.
     
  7. slingshot

    slingshot
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    Thanks guys, last one I cut by hand, it wasn't to bad, I gave up with a jigsaw, but I didn't try clamping.

    Think I'll try B and Q first (saves me breathing in all that MDF dust).
     
  8. hornydragon

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    GUys what blades do you reconmed for 18mm MDF will be borrowing a mates dads jig saw so need to know before i poick it up so i can pop straight to B&Q get the big cuts done and a new blade while i am there
     
  9. Mike Swannick

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    There are 2 types of jigsaw blade fitting. Black & Decker style which are held in place by Allen Key locking nuts & Bosch which fit into place with a 90' 'bayonet' style twist and then locked by whatever mechanism is on the saw. Hopefully you will be using the Bosch type blade as they tend to stay straighter then the B&D fitting.

    The Bosch blades each have a number and the packet will show a basic icon type graphic to depict what material the blade is designed for. The blades with the small teeth close together are for metal/polycarbonate generally, so you want to be looking for a blade with big teeth alternately offset (like a handsaw). The broader (ie from front to back, not side to side) the blade the better as this will stop it twisting during the cut.

    Despite the temptation to cut quickley with a sharp new blade, go slowly and uniformly otherwise your lenthways cut may look straight but the depthways (18mm) cut will be way off.

    Still recommend using a circular saw if you can get one.
     
  10. buns

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    well guys....... im still using a hand saw and a bit of sandpaper! Though given the choice id go for a small circular affair

    ad
     
  11. hornydragon

    hornydragon
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    I know i can borrow a jigsaw! Dont think my mates dad has a circular saw. My uncle has everypower tool under the sun but won't let me borrow them!!!!
    I will find out what sort of fitting i need tonight then.
    PS what grain of sand paper should one use on MDF???? do start with wet and dry or something a little coarser???
     
  12. Mike Swannick

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    If you buy new MDF that hasn't been exposed to the elements for too long and cut it squarely in all planes you should only need the finest of sandpaper to finish off minor blemishes. It's been my experience that the exposed face of MDF doesn't sand down well since it's a really smooth finish to start with. In its untreated state MDF absorbs moisture from the air and 'fluffs out' slightly and loses that nice sheen that it had when you first bought it, hence the note about it being new & well stored at the point of purchase. Once you've cut & assembled it, get it treated with paint or varnish or whatever in order to retain that smoothness.

    Another tip about using a saw with a clamped piece of wood as a guide (a fence). In order to accurately measure the distance from fence to cut, do it a couple of times into some waste wood. Depending on what type of saw you use will affect the width of cut. It's only a couple of millimetres but will make the difference between a flush joint and a nearly flush joint. Remember to add or subtract the width of cut from the distance of the fence from the cutting mark. If you cut bang on the cutting mark your cut size will be out by exactly half of the cutting width. The wider the blade, the bigger the error.

    eg: (ASSUMING THE FENCE IS FIXED ON THE WASTE SIDE!!)
    If the blade (2mm wide cut) to fence distance is 30mm and you want to cut on the outside of your mark the the fence needs to sit 30mm + cut width (2mm) = 32mm away from the cutting mark. To cut on the inside of the mark subtract the width of cut.

    Hope this makes sense. Practice on some waste sheet wood first and see if your cuts come out accurately.
     
  13. wandgrudd

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    you dont want to be useing a jig saw you need to get a circular saw (screwfix 32.99 item no 15770-24 ) i gives a beeter cut and a lot faster than a jig saw.
     
  14. hornydragon

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    Argh this is supposed to save me money!!!!!
    I will get B&Q to do the major cutting for me i think!!!
    Then cut to length with the jigsaw.
     
  15. Taz

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    :lesson: This is called the Kerf of the saw :lesson:


    :D
     
  16. Mike Swannick

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    >> This is called the Kerf of the saw <<

    I knew it had a name but not what it was. You learn something new everyday.
     
  17. enablerbro1

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    As this thread is about woodcutting ..... what is the best way to cut a 'U' shape with all straight edges? I'm sure it has a proper woodworking name. I was thinking jigsaw because they are supposed to be able to cut "tight angles", according to Argos, but I can't see how the blade could cut the right angles I need. Do I need to cut the two lines in and then drill a hole for the blade to cut the third line or can the jigsaw just be turned and cut the right angle?
     
  18. wolfboy79

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    A jigsaw blade cannot be turned directly through ninety degrees. If you try to turn in this was at best it will probably snap, at worst you might injure yourself.:eek:

    It can however cut a pretty tight curve. Approach the bottom of the 'U' on the first side and then cut a curve so the blade ends up straight on the bottom of the 'U'. Do the same on the next corner and remove the waste. You will be left with a curvy 'U'. Carefully run the jigsaw down the first straight edge stopping right in the corner. Remove the saw and approach the corner from the bottom of the 'U' back into the same corner. Repeat for the other corner.

    This can take a bit of practice for a clean finish but is not do difficult to achieve. Securely clamp the wood first, hope it helps:thumbsup:
     
  19. KelvinS1965

    KelvinS1965
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    For this you would need a 'router'. They have interchangable bits that make straight, curved or chamfered cuts. You can cut slots in wood or even make your own profiled skirting/architave. I bought mine in B&Q years ago but hardly use it, but when I do it is so useful....I built my own staircase handrail and baserail from solid beech using it, including the slots to put the 'spindles' in. I'll admit that in my current house I bought the ready made items from Wickes though as it was a damn sight easier.:D
     
  20. enablerbro1

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    That's what I thought, it was argos that nearly had my eye out with their "tight angles" claims. I can see what you mean with cutting the U with curves and then going back along the straight lines to cut the right angle. Very clever (and obvious :oops:). :smashin:
     
  21. enablerbro1

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    A router would be very nice (and another obvious :oops: solution) but I don't think I'd use it nearly as much as a jigsaw.
     
  22. Dave_Gregory

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    It also depends on how big your radius is as well, as if its is a tight curve then I ssume its only a small slot so if you havent got a router then I suggest you use either a big enough drill bit, or a hole saw to give you the tidy cut and then use your jigsaw to cut the straight edges.

    I agree though that I dont use my router that much but when I do it certainly gives great results. I made about 5 radiator covers with it including a large radius cut on each of about 1.5m by attaching the router to a piece of wood as a pivot and very satisfying.

    Dave
     
  23. enablerbro1

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    I opted for cutting a partial straight and then curve it towards the bottom straight, finished off the bottom straight (so had an L shape but with a curve instead of a right angle) and then removed the jigsaw and cut the third straight edge to meet the bottom of the L. Then I went back and finished cutting the first straight and then the second straights. Job done. Sounds like a lot more hassle than it actually was.
     
  24. wolfboy79

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    Glad it worked for you.:smashin:
     
  25. enablerbro1

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    I had to make use of a small plane to tidy up but not too bad a job at all. :thumbsup:
     

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