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Edge sanding MDF

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fuster

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I do a lot of this. Must have done something bad in a past life.
I've developed my method of getting the edges smooth in as fast a time as possible as because of this (I make a lot of frame and panel MDF doors for one thing, so there are a lot of edges), and was just wondering if anyone else does the same as me or if there are any great ideas I haven't thought of.
I also don't have much equipment, which will become obvious....
I only use MR MDF as it needs so much less sanding and sands to a far better finish.
First if there is a run of sanding to do, I clamp my belt sander to the bench with a fence running either side of it to give me a 2.4 metre run. I run all edges along this using 120 grit paper twice, with opposite faces down to ensure keeping it square.
Then I use my random orbital sander with 125, 180 and sometimes 240 grit depending on level needed. Holding this by hand and trying not to round over the edges, which is something I've become quite good at.
Works very well except for the occasional slip with the ros.
And if I'm making carcases to paint I'll make them up first then run the ros all around the front edges.
Just interested in other ideas.........
 

jasonB

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I lay all the rails & styles on the bench edge up, clamp them together then run the ROS over them, no risk of rounding over the edges as you are working on a flat surface not an edge
 

Chrispy

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FWIW I cut rails 1mm over size and pass them through the spindle moulder with a TCT rebating block fitted to "plane" the cut edges, I find that the planed edge sands much easier than a sawn edge. I think it's to do with the way fibres are cut / layed over.
 

Lord Kitchener

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I sand a lot of MDF doors, I lie them on the bench and go round them with my recently purchased Mirka 125mm 22V ROS. This thing is brilliant, and so light I can do lots of doors without my arm getting tired. I only sand to 80 grit as the doors are all painted and smoothing them is takien care of during the painting process.
 

fuster

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Thanks for the replies. Mostly I want the Mirka sander as that looks great! I've got the Makita ROS and never liked it much, especially since I dropped it and now it's a bit wild and difficult to control. Because it takes so long to come to a stop I put it down too early and it flew off the bench onto the floor. Was thinking of one of the festool sanders but Mirka looks like the one to go for when I get the funds.
Haven't tried planing so may give that a go to see if it speeds things up at all and definitely going to give Jason's method another go - I've tried it in the past and found that slight differences in width mean more work sanding them all down to meet before they all get sanded smooth.
I use the festool to cut all stock as I don't have a table saw. On larger pieces I always measure to the back of the rail as it gives a more accurate measurement than using the edge of the splinter guard which becomes uneven quite quickly. For the thinner cuts (under 185 mm, the width of the rail) I measure up to the splinter guard and subtract 3mm for the saw kerf, but this results in less accurate cuts of course. One fine day I'll get a table saw and life will get easier, but there is a long list of wanted items competing there.....
 

jasonB

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Mine are cut on the tabel saw so there is not the problem of odd widths.

J
 

Hudson Carpentry

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Nab a tea towel while shes not looking. Put it on you bench but screwed up. Place the slowing down sander on the towel and it dampens the movement and stops the sander from moving, enabling you to put the sander down without having to wait for it to stop.
 

mailee

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I also sand them all clamped together on edge with my ROS too. I may give the planer a try after reading this though. :wink:
 

tony100

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What about bobbin sanders? Anyone any experience of industrial one,I appreciate small ones are for curved work.
 

RobinBHM

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I find using a rebate block on a spindle moulder the easiest way to finish mdf edges. Taking about a 1mm cut removes all saw marks and leaves an edge ready for fine sanding. I sand down to 320 grit so the edge is somewhat burnished and seems to soak up much less polish.
 

mahomo59

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Fuster where you located? On the ripping down side of things, Stiles and Rails etc. Have you got a cutting service near you? I use Avonplywood and get lots of Rails/Stiles cut in a job lot. For example I have a run of 22mm cabinet doors etc so I got two sheets worth of mrmdf cut @ 70mm and it's perfect, edges are cut very well and takes little sanding. I then clamp together like Jasonb etc.
 

Bluekingfisher

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If you need to paint or seal, don't you have to seal the sanded edge as well? I have found that sanding alone does not provide an edge good enough for painting.
 

Bradshaw Joinery

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I was told if you use a 1500+ grit in a ROS, It melts the glue in the mdf edge with the surface heat and almost polishes it without sanding.... however only use this technique with a/c paints as waterbased will not stick to the glue.... they need a mechanical adhesion.
 

petertheeater

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Hi all. I too find myself sanding stacks of MDF on occasion (a lot). Wherever possible I will stack them on edge of the bench . All lined up and clamped, I use a random orbital. Usually only to 120 grit which is good enough for the sprayers to work with. This method ensures that the pieces are all flat and not rounded and a little care is taken towards the ends.
The downside to this method is it can be a bit hard on the arm holding the sander sideways. For this reason I have just invested in one of those new brushless green and black sanders from Germany. For draw sides and rails etc I clamp them together edge upwards and sand that way. I've often thought about a big stationary belt sander with the belt sideways and passing the work past the sanding belt but wardrobe carcasses and long items would need a lot of room in front and past the belt requiring support. I'm becoming more and more convinced that it's often easier to take the tool to the work rather than the other way around.
 
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