Routing MDF

[Jensmith]

Just for my own future knowledge I wonder if you can answer this for me:

I've just been routing MDF with a 3/4" straight cutter for fitting a bit of T-track and the MDF has been slightly burnt.

As far as I know I've followed the correct procedure -
I cut to the depth in 2 passes
Used the 1/4" dewalt router at speed 5 which burnt so tried full speed - 7 for what I think is a small cutter...
Used dust extraction - the most effective being through the column (it's a dw621k)
Took it slow and didn't feel like the router was struggling.

Does that sound ok?
I'm wondering if it's just the cutter as it's a cheap one that my Dad lent me out of a performance power router. It's basically new though having only used it to fit T track into pine a few weeks ago.

What do you think?

Thanks,
Jennifer

 

[gc]

I had similar problem running a 6mm rebate in mdf using a cheap cutter, when i tried it again with a better cutter there was no problem. With the cheap cutter i had tried making the cut over 3 passes and it was still causing problems.

 

[barkwindjammer]

Sounds like your 'rate of feed' is maybe a little slow and allowing the bit to scorch Jen.

 

[Eric The Viking]

I've never avoided scorching in MDF, but making a climb-cut pass last helped a lot.

Obviously this should only be done with the lightest of passes, but it did improve matters, especially on a chamfer bit, where the outer part of the cutter is going quite a bit faster than the inner bit by the bearing.

MDF: necessary evil.

 

[brianhabby]

Sounds like your 'rate of feed' is maybe a little slow and allowing the bit to scorch Jen.

Second that, try different feed rates,

regards

Brian

 

[Jensmith]

Sounds like your 'rate of feed' is maybe a little slow and allowing the bit to scorch Jen.

Second that, try different feed rates,

regards

Brian

I thought I was going fast enough without going bonkers but I can give it a try.

 

[moz]

Took it slow and didn't feel like the router was struggling.

Hi Jennifer. As others have said, the feed speed is too slow. It's something you can only get to know by experimenting but there should be some load on the motor when cutting, i.e. it will 'struggle' a little as compared to the free running sound. If you go too fast, the groove will clog up with chips and you are left with a rough finish. Also, cutters with a narrow shank can 'whip' or flex and you will recognize an unpleasant, rough squeeling sound when this happens Too slow and heat builds up too quickly in one place and burns the wood and can ruin the cutter very easily. Increasing the cutter speed as you did just makes it worse as you would have to move it even quicker to compensate. So the ideal is somewhere between. You can get burning also if the cutter isn't sharp enough so check this. If it is, I would say just push it quite a bit harder than you have been doing and look at the results critically. You quickly get used to how it should sound and feel but don't be afraid of making the thing work. Hope that helps.

John

 

[Jensmith]

Ok, thanks John, that's really helpful. I'll know what to do next time.

 

[MickCheese]

I have to say better quality cutters seem to burn less.

I don't know if it is the fact they allow a faster feed rate or they just create less heat as they cut cleaner. But in my experience a lot seems to be the cutter.

Mick

 

[cutting solutions]

Most industrial manufacturers cutting mdf use "top quality" "sharp" router cutters.
they use them (in many cases) until there is barely no carbide left on the tool body.

They dont have a problem with tools burning.(even at high feed speeds.....check the manufacturers catalogue for the max rpm and recommended feed speed for your cutter)
Titmans can be found here http://www.titman.co.uk/feed_rates.html

It may be that the feed speeds are incorrect but my experiences tell me that its cheap cutters that cause more problems.

 

[Berties]

Was using the router, was getting a bit of burning (plywood) so dialled down the rpm and just went slower.

 

[woodbloke]

Sounds like your 'rate of feed' is maybe a little slow and allowing the bit to scorch Jen.

Second that, try different feed rates,

regards

Brian

...and I'll third it. Sharp router cutters need to be moved fairly smartly through material...faster than you might imagine in order not to burn the material. I'd hesitate to recommend 'climb cutting' (going in the wrong direction) despite what EtheV has mentioned with the best of intentions, especially on material like MDF with no grain. It can be done on normal wood in certain circumstances but in normal practice it shouldn't need to be done in MDF - Rob