Cutting MDF window board ??

[Heatslave]

Hi ,

Confident and competent DIY’er here……Hope someone can help me with this one please ??

I’m using 25mm thick MDF window board for my internal window sills. I want a flush square edge level with the internal wall. My Jedi mind powers are telling me a circular saw will make a dogs dinner of the edge of MDF, and a hand saw would work better (even though it would be a pain in the @ss to do on a 2300mm sill) .

What do the pro’s think ??

 

[Why Not Indeed]

Not a pro but I've used a circular saw just fine with MDF. It's probably murder on blades and the dust won't be great for you either. But I got a nice clean cut.

 

[twillmo]

A circular saw with a reasonably sharp blade will be fine.

With MDF edges I put 2 part wood filler all along them, and then give them a sand when dry. It gives a pretty flawless finish once primed and painted with a couple of coats.

I've done a load of window boards in my house with 25mm MDF, feel free to ask anything.

You can't see it very well, but I did a chamfered edge instead of bullnose to match the original window boards in the house:

 

[Heatslave]

A circular saw with a reasonably sharp blade will be fine.

With MDF edges I put 2 part wood filler all along them, and then give them a sand when dry. It gives a pretty flawless finish once primed and painted with a couple of coats.

I've done a load of window boards in my house with 25mm MDF, feel free to ask anything.

You can't see it very well, but I did a chamfered edge instead of bullnose to match the original window boards in the house:

View attachment 344129

Nice job

 

[Heatslave]

I thought a circular saw might just “rip” the bottom of the MDF ??

 

[foxhole]

I thought a circular saw might just “rip” the bottom of the MDF ??

No, gives a good cut and rest of board is going to be sealed all round so even a poor cut won’t show .
You can get a decent bullnose with a router working from both sides and finished with sand paper .

 

[twillmo]

I thought a circular saw might just “rip” the bottom of the MDF ??

You want your circular saw to protrude about 2mm out the bottom of the board and you'll be fine. So your depth of cut would be 26/27mm

 

[opps]

Hi ,

Confident and competent DIY’er here……Hope someone can help me with this one please ??

I’m using 25mm thick MDF window board for my internal window sills. I want a flush square edge level with the internal wall. My Jedi mind powers are telling me a circular saw will make a dogs dinner of the edge of MDF, and a hand saw would work better (even though it would be a pain in the to do on a 2300mm sill) .

What do the pro’s think ??

You really need to consider having an overhang on the sill. It is very unlikely that the area under the sill will be perfectly flat. Regardless, the MDF will contract and expand at different rates.

If I misunderstand what you are asking, I apologise

 

[Heatslave]

No, gives a good cut and rest of board is going to be sealed all round so even a poor cut won’t show .
You can get a decent bullnose with a router working from both sides and finished with sand paper .

I’m after a straight cut on the outer edge, flush with the inner wall, so it’s got to be a really clean cut.

 

[foxhole]

I’m after a straight cut on the outer edge, flush with the inner wall, so it’s got to be a really clean cut.

Tiny cut for hand saw

 

[Heatslave]

You really need to consider having an overhang on the sill. It is very unlikely that the area under the sill will be perfectly flat. Regardless, the MDF will contract and expand at different rates.

If I misunderstand what you are asking, I apologise

You’ve got that correct. Here’s some pics of the one I did in the kitchen (hard work with a handsaw). The ones I’ve got to do are up to 2.3m, and will be a pain with a handsaw !! And I’ve seen plenty of examples of flush sills online, so it should be ok . And all the internal walls are freshly plastered with straight angle bead.

 

[twillmo]

You’ve got that correct. Here’s some pics of the one I did in the kitchen (hard work with a handsaw). The ones I’ve got to do are up to 2.3m, and will be a pain with a handsaw !! And I’ve seen plenty of examples of flush sills online, so it should be ok . And all the internal walls are freshly plastered with straight angle bead.View attachment 344143

Circular saw will produce and edge like that no problem.

You're much better with a hand saw than I am!

 

[matlob]

Can't you use the manufactured edge at the front and cut the back? Or if just using normal mdf the sheds will cut strips for you

 

[Heatslave]

Circular saw will produce and edge like that no problem.

You're much better with a hand saw than I am!

Ha, ha…..looks ok from a distance !! Thanks

 

[Heatslave]

Can't you use the manufactured edge at the front and cut the back? Or if just using normal mdf the sheds will cut strips for you

They come as bull nosed, with a slight cut-out at the back for how the windows are designed. So they need cutting square edged