MDf

[simuk]

Hello Folks

I machined some 18mm mdf with a router in my workshop today,and i am far from happy with the finish of the mdf .

Problem is the deeper i rout into the mdf the fluffier the finish .

Is there grades for mdf?

Has anyone any suggestions as to how i can improve on this?



Thanks Inadvance

Simon

[dom]

Hello Simon and welcome.

Yes there are grades of MDF. I find the best finish is achieved with MRMDF (moisture resistant and green) The stuff you get from the sheds, B&Q etc. is a cheap grade
Could also be that your MDF has been kept somewhere damp or your router bit is blunt or you're trying to take off too much at once

[simuk]

Hello Dom thanks for the reply & welcome,

The mdf that you see in the pic is the cheap sh*te from a shed, so gonna try the green stuff tomorow. The cutter was brand new & i did machine it in several passes.

Simon

[jfc]

There are different grades in normal MDF aswell . I think it's caberwood and medite that are the main suppliers with medite being the better grade . I'm sure i'll be corrected if i'm wrong .

[nickw]

You will find that all grades of MDF are fluffy on the inside, though some are better than others - that's just the way it is. Wood hardener, or Super Glue for smaller jobs, can be used to stiffen it up again, but you're never going to get a good finish straight from the cutter.

[dom]

Agreed Jason. Caberwood and Medite are good
Sorry Nick disagree not all are fluffy.

[nickw]

Dom,

So why do you need to treat edges? Or are you saying that you don't need to?

[jfc]

Treating the edges is not the same as furring up . There is one grade that has serious furryness ;D You can see it on the edge of the sheet sticking out about 0.5mm .

[dom]

wot he said ;D

[nickw]

So are you really saying that Simon can expect to get the same quality of surface on machined faces as is found on the outside of a board?

[jfc]

Yeah c'mon Dom , what are you saying ? ;D

I would say no not straight from the cutter but you have more of a chance with a better grade MDF or MR MDF . I never use MR MDF for normal work but then again i dont normally get involved in the finishing so i hardly ever come up against the problem .

[Scrit]

Nick

Medite and Caber are better quality than the cheap imported brands. Personally I dislike Caber as it is darker and seems to generate a lot more dust than Medite, however I'd agree that even Medite can generate a fluffy edges. For that reason I used to specify either "deep-rout" or sometimes moisture resistant grade for CNC machining. Deep-rout is a denser grade specially produced for CNC machining - in fact it is somewhere between MDF and HDF in density and it produces much sharper moulded edges. Almost as good is the more readily available MR-MDF, although that has the disadvantage (in some circumstances) of being tinted green

See, it's not just Dom who's being a smart ar*e ;D

Scrit

[dom]

wot he said ;D

[simuk]

Thanks for the replies, like i said earlier gonna try the green stuff tomorrow, any ideas how much i should expect to pay for a sheet of 18mm

Simon

[cnc paul]

Simon,

The best material is DeepRoute from Silvermans but it comes in limited thicknesses and more expensive, then Medite V313 MR....the green stuff.

I use the V313 mostly, as Scrit said the rest are a bit fluffy.



CNC Paul

[bjm]

All MDF will get 'fluffy' as you get near the centre of the board (some less than others) due to the manufacturing process. It has a density profile across the thickness - the surface faces are always very dense with a reduction in density as you approach the centre. If you machine deep you are getting into softer material hence the fluffiness.

Brian

[dirtydeeds]

mdf has poor routed edges because the density of the inside of mdf is not as high as the surface

my method of achieving a good finish is nothing every body who uses a router doesnt already know.

rout close to final depth then cut a final shim of depth at a fairly low feed rate


having done this, paint with zinsser bin (expensive but it dries VERY quickly)

it fills the pores and hardens the fluff

now take 180 grit paper to the mdf, the paint stiffened fluff just sands off and 180 grit doesnt round off the arrises too much

result good sharp looking mdf edges and quickly

[simuk]

well i machined the V313 and yep definitely better , apart from the price £25.11 a sheet .



Showed my customer & they wanted to know if i could paint the edges & the groove green on all of them. ;D.

With the Deep - Rout mdf, in percentage terms how much better is the finish compared to the v313?

Dirty Deeds thanks for the heads up on the zinsser bin, is there anyway of asking for it at the trade counter, without sounding German?

Simon

[dirtydeeds]

say it in american

its american paint

its the only paint a carpenter needs, it is white knotting primer

costs about £16 for just under a litre, it dries in under 5 minuites in summer

dulux decorator centre, johnsons, brewers and a whole host of others

keep your brush in meths and you never have to clean the brush





clearly i own the firm and have shares in it to be this enthusiastic.....................

so why do i have to go to the dulux decorator centre to get it.........................

why do i have to buy it if i own the firm.....................

[tim]

dirtydeeds said:

costs about £16 for just under a litre

or £11 in my Crown decorator centre ;D

Cheers

Tim