Anyone with experience (or opinions) on machining MDF?

[Electrojim]

Greetings all!

I've got a project coming up in which I am replacing an aluminum casting with MDF (yes, fiberboard, probably from Home Depot!). The stuff's pretty flat and would be just fine in this application, but I'm wondering if I dare approach local shops (or hobbyists) to work with the stuff. Doubtless the tools and speeds would be different between aluminum and glue+sawdust (the MDF), but is it practical to seek someone to do this?

The job is to turn a one-inch-thick, 13-inch OD MDF 'platter' with a crowned OD edge. It will become a flat-belt-driven turntable for a phonograph-record recording lathe, and will need a metal hub, spindle and bearing assembly as well... but out of metal, of course. It would require a lathe with ample swing to accommodate a 13" piece; any ideas on how to get something like this started will be most welcome.

 

[ChazzC]

Greetings all!

I've got a project coming up in which I am replacing an aluminum casting with MDF (yes, fiberboard, probably from Home Depot!). The stuff's pretty flat and would be just fine in this application, but I'm wondering if I dare approach local shops (or hobbyists) to work with the stuff. Doubtless the tools and speeds would be different between aluminum and glue+sawdust (the MDF), but is it practical to seek someone to do this?

The job is to turn a one-inch-thick, 13-inch OD MDF 'platter' with a crowned OD edge. It will become a flat-belt-driven turntable for a phonograph-record recording lathe, and will need a metal hub, spindle and bearing assembly as well... but out of metal, of course. It would require a lathe with ample swing to accommodate a 13" piece; any ideas on how to get something like this started will be most welcome.

I’ve used MDF as a support when milling slots in Lexan (Polycarbonate) sheet and in the process have milled shallow slots in the MDF. Can’t remember the f&s, but it cuts cleanly but does leave a fluffy burr. A shop vac is a necessity to remove the dust while milling, as is a very sharp end mill.

A one-machinist shop may be willing to take the project on, but if it were me I would need the lathe clean before starting and immediately cleaned afterwards: sawdust attracts oil and can get everywhere - if care isn’t taken the dust will get into places it shouldn’t be and where swarf wouldn’t normally be an issue.

All of that said, this is a project for a wood shop.

 

[DavidR8]

I have used a lot of MDF on my CNC router but always with a dust collection boot which is very good at collecting dust at source. Based on that experience I would not want to turn it on a lathe, either metal or wood. It makes just awful dust which gets everywhere.

 

[ChazzC]

Forgot about CNC Routers: could machine the 13” disk with a raised edge easily!

 

[Martin W]

Find a local cabinet shop. They could easily cut this on a CNC router. Usually a company that produces MDF cabinet doors would be your best bet. There are probably hundreds in California
In the good old days before CNC, I wold use the existing turntable as a template to router a new one with a plunge router and pattern bit. If I couldn’t use the existing I would mount a piece of MDF on a faceplate on a wood lathe and turn to dimensions.
or put a router on a jig to cut a circle like drawing one with a compass.
MDF cuts like butter but you need high speeds and carbide tools. And a respirator or 3M dust mask
Buy MDF that is 100% softwood, not the cheap stuff with hardwoods mixed in. Use Arauco or Egger that are quality American producers.
Martin

 

[francist]

Buy MDF that is 100% softwood, not the cheap stuff with hardwoods mixed in

What is it about being all softwood that makes it better, or conversely, why does hardwood content make it less desirable? Just curious.

 

[Martin W]

The 100% softwood cuts better, sands better, finishes better, The ones with hardwood don’t leave as nice a finish are heavier and not as stable.
. Most door manufacturers use only the best MDF as it cuts easier and leaves a finish that can easily be thermofoiled or painted with minimal sanding or prep.
It even works better for spoil boards on the CNC as the vacuum sucks down better for work holding.
Martin

What is it about being all softwood that makes it better, or conversely, why does hardwood content make it less desirable? Just curious.

 

[woodchucker]

The 100% softwood cuts better, sands better, finishes better, The ones with hardwood don’t leave as nice a finish are heavier and not as stable.
. Most door manufacturers use only the best MDF as it cuts easier and leaves a finish that can easily be thermofoiled or painted with minimal sanding or prep.
It even works better for spoil boards on the CNC as the vacuum sucks down better for work holding.
Martin

LDF.. Light weight, density board..
BTW there's also water resistant mdf.. I've never used it or the LDF..

 

[Martin W]

LDF.. Light weight, density board..
BTW there's also water resistant mdf.. I've never used it or the LDF..

Extira, is one brand of exterior MDF. I put a piece in a bucket of water over the weekend. It was as good as new on the following Monday. I have never used the lightweight stuff either.
Some of the sheets we get from Europe now are 9' x 21'. Our supplier cuts them into manageable sheets of 9' x 7' They still don't fit on my CNC. We have to optimize the G code for best yield. (Well, the computer does.)
Martin