Hand grinding a 3" long 1/4" diameter straight flute, single flute, endmill for cutting styrofoam

[python50]

Hello everyone,

I make aluminum castings via the lost foam method. To make casting patterns I often have to mill blocks of Styrofoam that are 2" thick on the CNC router. The machine supports a maximum tool diameter of 1/4".

I can't (easily and economically) buy the exact endmill that I need to cut such thick material.

I am seeking guidance on making a 1/4" diameter single flute, straight flute, end mill for cutting Styrofoam. I typically cut at between 6000 and 24000 RPM. I expect it to produce some vibration.

I can't find many examples of such tools on the internet.

Suggested rake and clearance angle? Hand grinding methods? Examples of existing tools?

Thanks,
Jason

 

[Liljoebrshooter]

What about using a straight flute reamer?

 

[python50]

Thanks! I had never though of that. That sounds crazy enough that it could work. I will have to try it.

I would almost imagine that a reamer would require more clearance to be added for it to be effective. Styrofoam melts easily.

 

[whitmore]

I make aluminum castings via the lost foam method. To make casting patterns I often have to mill blocks of Styrofoam that are 2" thick on the CNC router. The machine supports a maximum tool diameter of 1/4".

Yow, think of all the dust clinging to everything.... Could your CNC thing move a hot wire? You'll want good ventilation (either
for dust abatement or fumes).

 

[python50]

Yow, think of all the dust clinging to everything.... Could your CNC thing move a hot wire? You'll want good ventilation (either
for dust abatement or fumes).

Personally, I greatly prefer dealing with stryrofoam dust over dealing with fumes. But yeah, it is really messy even with a vacuum.

 

[Liljoebrshooter]

Or a spiral cut router bit. Not sure about the length

 

[homebrewed]

Deep-cut router bits are available. I found one on Amazon -- Freud brand 1/4" diameter shank, 2-1/2" overall length for $14.

 

[Winegrower]

I have made a number of custom cutters for wood and aluminum. What I learned is that chip extraction is key to a good cutter. I wonder if the straight flutes would jam up too easily? I made an 18” long 1/2” diameter wood drill with straight flutes for the wood lathe, and though it worked, took a lot of pecking. A straight reamer works because it is not really moving that much material overall. Please post your experience if you proceed with the straight design.

 

[python50]

Deep-cut router bits are available. I found one on Amazon -- Freud brand 1/4" diameter shank, 2-1/2" overall length for $14.

While I couldn't find the exact part (that I imagined and hoped) that you had described, I think we may have a winner here.

Browsing the Freud Tools catalog shows a few 1/4" shank bits that should workable. It does look like I will have to sacrifice a little bit of cutting detail and use a 3/8" diameter cutter instead of an 1/4" one. But for most rough castings I think that will be acceptable.

 

[python50]

I have made a number of custom cutters for wood and aluminum. What I learned is that chip extraction is key to a good cutter. I wonder if the straight flutes would jam up too easily? I made an 18” long 1/2” diameter wood drill with straight flutes for the wood lathe, and though it worked, took a lot of pecking. A straight reamer works because it is not really moving that much material overall. Please post your experience if you proceed with the straight design.

I wish I could justify the effort because I am curious as well - but the premade router bits win this round. In the past I have successfully used a drill bit as an endmill to cut stryofoam without much ill effect. I found musing a drill in that manner produced stringy stryrofoam "burrs" and a rough surface finish - but that was perfectly acceptable for the sort of rough casting patterns I make.