Standard Router bits or end mills for cutting sheet goods?

[PortlandGTS]

I'll soon be building a FLA300. I plan to use it primarily for cutting, dadoing, and rabetting cabinet panels from sheet goods. Can I use standard straight router bits for this application, or do I need the end mills used in other CNC work?

Also, are the custom, low-runout collets available for routers important for this type of work?

Finally, what kind of feed rates should I be using?

Thanks,
Tom

[brtech]

Router bits are designed to do that, end mills are designed to cut metals. Lots of people have used end mills with satisfactory results, but the router bit is made for the task. A spiral bit is probably what you want for most of your tasks. For larger cuts, you probably want an up spiral. Smaller pieces may need a down spiral to keep from lifting the part.

It's easy to check run out with a dial indicator and a base for it. You should have that for other alignment tasks anyway. If your run out is small enough for your job, why spend more money? If your stock collet can't do what you need it to do, the precision collets are not very expensive. Don't forget to clean the collet.

There is a great chart on the Onsrud site that lists speeds and feeds for various materials:
Chiploads | Feeds and Speeds | Metal | Plastic | Composite | | LMT Onsrud

[ger21]

I'll soon be building a FLA300. I plan to use it primarily for cutting, dadoing, and rabetting cabinet panels from sheet goods. Can I use standard straight router bits for this application, or do I need the end mills used in other CNC work?

"End Mill" usually refers to tools for metal cutting. For cutting wood, you'd use spiral router bits. They tend to be much more expensive than end mills of the same size.

Yes, you can use carbide tipped straight bits. But, they won't last as long as spiral bits do, and aren't capable of cutting as fast as spiral bits can. But for a homebuilt machine, they should be fine. And they're much cheaper than solid carbide spirals. You can also get carbide tipped tools that are specifically for CNC use, which are more aggressive cutting.

Also, are the custom, low-runout collets available for routers important for this type of work?

Depends on the router you're using. With my Porter Cable, I use the standard collets for 1/4" and 1/2" bits, and precision collets for tools with 1/8" shanks.

Finally, what kind of feed rates should I be using?

The simple answer, is "as fast as possible". The faster you cut, the longer your tools will last. But several factors come into play. Spindle power and rigidity are the two main factors. You want to cut as fast as you can, while still achieving good cut quality. Tooling and material also factor in. You can cut dado's much faster with a downcut spiral than with a straight bit, and a downcut should almost always give you better quality cuts, even at much higher speeds.

It'll take some trial and error to determine what works best for you.

What type of router do you plan on using?

[PortlandGTS]

Thanks - both replies are helpful. The Onsrud link has a lot of good information, and looks like a good source for router bits.

I have a Bosch 1617 that I'm planning on using with the CNC router. It seems like it's common to use this router in CNC applications.

One other question I've been pondering:

I get the impression that more Z travel than necessary is bad, because it allows the spindle to move around too much. The FLA300 provides 6" of Z travel, and the plans show 9.75" from the bottom of the gantry rail to the top of the bed (I assume this is the key dimension determining the leverage on the Z axis).

I can reduce the distance somewhat by adding a top and spoilboard, and raising the entire bed, but am constrained because I want to use a common outfeed table for the router and my tablesaw.

Since I will primarily be cutting sheet goods, my question is: should I consider lowering the gantry by cutting the legs that support it? I hate to do this because it lowers the Z axis travel, and limits the potential for future uses of the router. But if there's going to be a problem, I can cut the legs now and worry about extending them in the future if I do need more travel.

Thanks,
Tom

[ger21]

I'm not familiar with the design, but it makes no sense to me to have 9.75" clear under the gantry, with only 6" of travel. When the router is at the top of it's travel, there's no reason for the gantry to be any higher than the tip of the tool, except maybe extra clearance for hold down clamps?
Basically, the taller the gantry, the higher the forces acting on it become. So the lower the gantry, and shorter the Z axis, the more rigid it should be.

Other than cutting large foam blocks, it's pretty rare to see anyone cutting anything much thicker than 2-3". Mainly, because you won't find tools that long, and even if you did, you run into clearance issues with the body of the router.

I design enough Z travel so that I can reach the table with a 1" bit, and clear the bottom of the gantry with a 3" bit (3" below the collet).

5"-6" clearance under the gantry should be more than enough. Just allow yourself room for spoilboards and fixtures, which can decrease the usable clearance.

Again, I'm not familiar with the design, so modify at your own risk. Just adding my 2¢.