Thread: Which End Mill & Feed rate for MDF?

Spindle speed available?

My default speed for MDF with a 6mm single flute downcut carbide bit is 4 metres/minute at around 18,000 rpm from memory

The Onsrud catalogue (pretty much the best resource out there for feed rates if you don't mind lots of charts) recommends:

1/8" single flute straight bit: 7m/min
1/4" single flute straight bit: 8.5m/min
1/8" or 1/4" 2 flute down spiral: 8.5m/min
All @ 18k rpm

Downcut is the best to stop furry edges on the top.

Really, you can move as fast as you like in 3mm. At work I run 3mm ply/MDF with a 2 flute 6mm downcut bit at 18m/min, but I'm guessing your machine can't quite move that fast...

Originally Posted by pippin88

Spindle speed available?

My default speed for MDF with a 6mm single flute downcut carbide bit is 4 metres/minute at around 18,000 rpm from memory

Sorry pippin88, Yep max spindle speed 4000mm/min. Is the 6mm single flute downcut the same as single flute spiral??

Originally Posted by Mulgabill

Sorry pippin88, Yep max spindle speed 4000mm/min. Is the 6mm single flute downcut the same as single flute spiral??

Spindle speed should be in rpm, not mm/min...

Downcut is a type of spiral that's shaped to cut down instead of up to reduce surface tearing at the expense of slightly worse dust extraction. It should be assumed that all spirals are upcut unless specifically labelled otherwise.

Solid carbide spirals are the way to go. If they're designated upcut or downcut they are spiral bits. In MDF I doubt if it matters whether it's single or two flute, just make sure you get something of quality made from virgin material. Single flute is particularly good in materials that tend to melt, plastics for example. Don't get conned in to buying anything harder than HRC45, for timber, or even the softer metals, you'll just be wasting your money. As others have said downcut leaves a beautiful finish on the top surface.

Originally Posted by aldav

Solid carbide spirals are the way to go. If they're designated upcut or downcut they are spiral bits. In MDF I doubt if it matters whether it's single or two flute, just make sure you get something of quality made from virgin material. Single flute is particularly good in materials that tend to melt, plastics for example. Don't get conned in to buying anything harder than HRC45, for timber, or even the softer metals, you'll just be wasting your money. As others have said downcut leaves a beautiful finish on the top surface.

Thanks for the added info aldav! Can you recommend a supplier of the cutters?? Thanks

Originally Posted by aldav

Don't get conned in to buying anything harder than HRC45

Huh??
You can get steel into the 60s HRC, surely solid carbide would be well into the 80s?

Originally Posted by Mulgabill

Thanks for the added info aldav! Can you recommend a supplier of the cutters?? Thanks

Not without getting in to trouble with the Mod's for 'advertising'. I'll send you a PM.

Different scales Elan - steel is Rockwell while carbide is Vickers.

Then I'm still confused as to why you wrote HRC, which is Rockwell. Or am I missing something completely here?

Carbide comes in HRC 45, 50, 55, 60 and 65. The Americans use the 'C' classification system and there's also the ISO classification system. There isn't a universal standard, individual manufacturers use their own grading systems. Have a look at this chart - https://www.federalcarbide.com/tungs...son_chart.html. How could anyone possibly get confused?
The Chinese have another classification system again!! HRC 45 is the broad equivalent of C2 (American), K10 (ISO) and YG6 (Chinese). Composition is 90-92% tungsten carbide and 8-10% cobalt with hardness of 90.5 to 92 HRA. I find that there is no point in having coatings for wood. Make of it what you will, I'm no expert.

Wow that's fast. If I were using a table mounted router with a carbide spiral, running the same rpm, should I move it this quickly too? (My material, that is)

Does moving it slowly cause more wear?

Reminds me Aldav, I need to order a few spares for a big job.

Moving too slowly will cause your bits to go blunt faster than they should because they end up scraping instead of cutting. They also retain a lot of excess heat (the number one enemy of cutting tools after abrasive materials) that would normally be carried away by decent size chips.

While it's best to try to stick to the recommended speed, based on the ideal chipload for the tool, rpm and depth of cut, you should never compromise your own safety to do so; if you can't hand-feed that fast, don't try to.

There are also other factors like motor power and required surface finish that might slow you down.

Originally Posted by elanjacobs

Then I'm still confused as to why you wrote HRC, which is Rockwell. Or am I missing something completely here?

This has been niggling away at me for some time and I've finally come up with the answer. When they quote HRC rates for solid carbide bits it's a statement of the maximum hardness of the material they should be used on, not a statement as to the hardness of the bit. So a carbide bit designated HRC45 is more than hard enough to handle any timber you can throw at it. Bits to handle material up to HRC65 are available as are various coatings to improve bit performance, but for wood they're just a waste of money IMHO.