Router Bit resource ( another one:: plastic to CNC? )

I have access to a small CNC router and it has a Z travel range of abt 4", so I am wondering if any of you know where I can find a router bit(1/4" holding diameter) that has a cutting depth of 4"? I can’t really find something like that with 1/4" diameter so far.


I have used this company in the past to get long reach bits for our CNC router. Only catch is you have to order 6 at a time. But, in the two years since purchasing the machine I have yet to find any one else willing to make the 1/4 and 1/2 inch shanked bits. Maximum flute is usually 2 inches as well, but they did male me a 6" x 1/4" bit. Also if using Ren or 15lb or higher uethane go with the 4 flute, less chatter

I have sent a drawing of what I wanted as well, but I do not see the contact info, I think I had to call to get it. Micro-bits with 1/4" shank

Forgot about these guys if you want a standard 1/4" 4" bit. They were out of stock when I needed one, but that was 6 months ago.

Thanks for the info!

In the second link you have provided, there is a HSS 4 Flute Square & Ball End bit “Specially designed for Computerized Foam Milling Machines.” Under that section, there’s a 1/4" diameter bit with 6" cutting length. Do you think that will work for wood in general too? What about ren?

This is where I found my 1/4" diameter bit. The overall length is 4" but the cutting depth is about 3".


It should work for ren, when these companies say foam they are refering to ren and the 18lb or higher density signfoam. The wood should work just slow the feed rate down. One of those sites, I think, has an rpm and feed rate calculator on it.

Does the calculator tell me a recommended figure or is it telling me an estimate of the result?

I would think that most types of wood are less dense then ren.

Thanks for the websites again!

I checked the calculater. That is not the one I was thinking of, It must be on the renshape website.

Yes some woods are less dense than the foams, but are more resilient to cutting, unless using an MDF type particle board. The resiliance coupled with the tendancy to chip and splinter when cutting accross and against the grain require the slower feed rate. Some people use the same feed rate as they do with the ren, I just tend to slow it down to about 100 ipm feed rate at 16000 rpm, when using the 1/4 and 1/2 inch bits. I also only take off at most 1.5 inche cut depth per pass…less movement in the part. CNC routers tend to have +/- .005 to +/-.01 movement in the table depending on model.

Ok, this is my first time trying to mess with CNC routers so I am an absolute beginner. Yes I did check the calculator, but not sure if this is a recommended figure because I didn’t get to specify the type of material.

I am using Rhino CAM to do the set up, with the support of Visual Mill if I want more finishing passes.

The router I am using is Porter Cable 7310 at 30k rpm.

For roughing, I am using a 0.25" bit, with step over of 50% of the bit diameter, and step down of 25%. This is the setting recommended by another person who has been experimenting with this machine for the past year.

After which I will do parallel finishing and hill machining.

For the kind of wood I am experimenting with, I think this is the limit. The person suggests me to use 75% step over for the roughing to save more time, but I don’t want to break the bit(it’s already broken at the shank).

I would stick to the 50% step, and get a new bit. Most often when the bit is broken at the shank it was jamed into the table, or part while not rotating (or is as sharp as a butter knife). In other words the bit now is probably bent slightly, even a small barely noticable bend will effect the quality of the cut. Chatter, chips, oblong rounds, etc.

Another question. What kind of plastic is good for CNC routering(other than PU foam and ren)?

I haven’t tried routing with acrylic but I would think it will either melt on the bit or get chipped edges.

How about polystyrene? Is it available in blocks?

Plastics/resin that I can mix and dye by myself?

What about clear plastics?

Also, I am using Mach 2 to run the CNC machine. I don’t know what’s the moving speed. It has this speed bar which I can click + or - between 20% to 300%. How do I find out what is the moving speed so that I can get a more accurate time estimate?

Thanks again!

We do acrylic all day long over here.

Just experiment with speeds. You may need to slow it down a bit. But, even at 30K, you shouldn’t have a problem. Also, are you using any coolant? That tends to help extend the life of your bits.