Beat bits (or technique) for cutting MDF

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Beat bits (or technique) for cutting MDF

Postby Mikehell » Sun Jul 28, 2019 4:38 pm

I cut craploads of MDF at work. Can't find a bit that doesn't leave sawdust packed into the groove. Upcut still leaves lots of dust. Much of the MDF I cut is 1" thick. Can't seem to cut this without leaving mountains of dust.
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Re: Beat bits (or technique) for cutting MDF

Postby Adrian » Sun Jul 28, 2019 4:54 pm

Getting the feed rate right is crucial as is the quality of the MDF. With the right feed rates you should be getting about an equal amount of fine dust and spiral chips. With the cheaper MDF you'll get nothing but dust no matter what you do.

Best way to cut it if you don't want it packing down into the cut is a single pass with an upcut bit. As long as your extraction system is up to the job (hugely important with MDF, I have a dedicated 2.2hp extractor for it) there shouldn't be that much dust on the board that way.
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Re: Beat bits (or technique) for cutting MDF

Postby sharkcutup » Sun Jul 28, 2019 7:00 pm

I second and totally agree with Adrian.

MDF does create a tremendous amount of dust/chips so be sure to have a good extraction/collection system.

Getting the feed/speed rates correct is crucial too because if it is too slow (burning/smoking) it not only smells bad but does not do the router bit much good either because it is getting to hot which can dull it by changing its temper strength due to that excessive heat. Too Fast causes chatter and rough edges.

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Re: Beat bits (or technique) for cutting MDF

Postby Samson » Sun Jul 28, 2019 7:16 pm

sharkcutup wrote:I second and totally agree with Adrian.

MDF does create a tremendous amount of dust/chips so be sure to have a good extraction/collection system.

Getting the feed/speed rates correct is crucial too because if it is too slow (burning/smoking) it not only smells bad but does not do the router bit much good either because it is getting to hot which can dull it by changing its temper strength due to that excessive heat. Too Fast causes chatter and rough edges.

Sharkcutup


Not to mention a fire hazard. I've heard about and witnessed several fires on the cnc. All of them involved MDF. The dust is so fine, and filled with resins, that it is easily combusted.
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Re: Beat bits (or technique) for cutting MDF

Postby sharkcutup » Sun Jul 28, 2019 7:22 pm

Thank You Samson! I failed to mention that aspect, Thanks Again!

I have never had a fire but it can very easily happen! I have had: Smoking, yes; ruined a couple of good bits, yes; chatter, yes! It does take some experimental time to achieve the optimum feed/speed rate for a particular machine.

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Re: Beat bits (or technique) for cutting MDF

Postby rscrawford » Mon Jul 29, 2019 6:26 pm

What kind of hold down do you have? Cutting full depth on 1" MDF creates a lot of pull upwards on your workpiece, and you could end up losing hold down if you rely on a vacuum spoilboard system.

Using a 3/8" compression bit seems to work the best with MDF. Single pass, and the chips packing in the kerf helps with vacuum hold down. I just cut 8 sheets of 3/4" and used 16000rpm and 600ipm single pass with a 3/8" compression.
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Re: Beat bits (or technique) for cutting MDF

Postby rscrawford » Mon Jul 29, 2019 6:26 pm

What kind of hold down do you have? Cutting full depth on 1" MDF creates a lot of pull upwards on your workpiece, and you could end up losing hold down if you rely on a vacuum spoilboard system.

Using a 3/8" compression bit seems to work the best with MDF. Single pass, and the chips packing in the kerf helps with vacuum hold down. I just cut 8 sheets of 3/4" and used 16000rpm and 600ipm single pass with a 3/8" compression.
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Re: Beat bits (or technique) for cutting MDF

Postby tomgardiner » Mon Jul 29, 2019 9:13 pm

A few tool manufacturers make vortex collet nuts or integrated mini fans into the tool holders to specifically address the problem. One is FS Tool's Aerotech system
Www.dustfreenesting.com
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Re: Beat bits (or technique) for cutting MDF

Postby Mikehell » Wed Jul 31, 2019 11:50 pm

rscrawford wrote:What kind of hold down do you have? Cutting full depth on 1" MDF creates a lot of pull upwards on your workpiece, and you could end up losing hold down if you rely on a vacuum spoilboard system.

Using a 3/8" compression bit seems to work the best with MDF. Single pass, and the chips packing in the kerf helps with vacuum hold down. I just cut 8 sheets of 3/4" and used 16000rpm and 600ipm single pass with a 3/8" compression.


I typically use a 1/2" compression, one pass. I guess it's a toss-up. I can either spend time cleaning the table of sawdust, or get less dust and spend the time sanding off tabs.

I made me a dustboot out of some flexible PVC freezer room door material I found. Made me a tool path that zig-zags across the entire table. Problem solved.
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Re: Beat bits (or technique) for cutting MDF

Postby ger21 » Thu Aug 01, 2019 12:20 pm

The only way to get the dust out of the grooves, is this:
Do a rough cut about 1/8"-3/16" oversize, about 7/8" deep.
Then go back and make your finish cuts, and the extra room will allow the bit to pull the dust out of the kerf.
You do still need very good dust collection, though.
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