Router Bit Questions

[spalm]

I have never tried spiral up-cut bits and want to take the plunge. I want to route MDF, hardwoods and ply. Any suggestions?

Seems like solid carbide is what is available. Is a two flute 1/4” a good choice for profiling? Would a 1/2” allow faster profiling at a loss of inside radius availability? Three flute? Do they perform OK for smooth bottom functions as well (mortising, pocketing or leveling)? How about plunging? Can it leave a rough edge at the top on ply? Is a $15 to $20 bit good enough?

I have never really thought about feed rates when routing by hand. It was always just “steady and smooth”. I now have a fairly strong CNC with a fairly good feed rate with a fairly powerful variable speed router. How do I go about maximizing my cuts? Should I basically just go by ear and look at the results? I can deal with that, but I have heard about chip load and such, and I don’t see specs for standard Freud or Amana type bits.

I have always wanted a set of metric mortising bits for use on Baltic Birch for my router table. Any sources, or should I just continue to use multiple cuts with inch sized bits?

Thanks,
Steve

[ger21]

You can probably cut as fast as your machine will go with a 1/4" spiral. A 1/2" can excert a lot of force, but may give better cuts because it's more rigid. Three flutes will usually cut smoother, but you might not notice the difference. An upcut spiral will leave at minimum a fuzzy edge on ply, to severe chips if not sharp. Differrent woods will give different results. Spirals will give perfectly flat bottoms. You should always ramp into a cut as opposed to plunging straight down. Plunging will shorten tool life. Look in the Onsrud catalogs for feed rates. You'll have to register to download the catalogs. http://www.onsrud.com

These are the ones we use at work. http://www.vortextool.com/standard/p...fm?groupID=264
If you buy 5 you get a 30% discount. Just enter 5 for the quantity to see the price. $22 each or $15.40 if you buy 5. Excellent bits.

Also, the price for 1/2" bits is about 4 times what 1/4" are. If you can get 3/8" colets for your router, you might want to look at the chipbreaker bits at Vortex. Although more money, they cut quieter and require less power from the router.

[Chris D]

I have been using end mills in my router for some time now - they are often cheaper than router bits and work really good in most applications. Pick up a couple of cheapo, solid carbide end mills from www.use-enco.com or a similar discount industrial supply.

The upside to using end mills, they are inexpensive - especially 1/4" and 1/2".

The downside to using end mills, shank sizes pretty much follow the tool's cutting diameter. However, with CNC, you can pretty much plan for and use any size tool that will fit so it isn't much of an issue.

Chris

[spalm]

Thanks Guys,

Gerry, I have never seen a professional machine, much less one in action. I would really like to do that sometime. What feed rates and depth of cut do you use there? I am set up to do 120 ipm rapids, but that seems like mighty fast to route with. It is real smooth so I guess I will try it (the whole machine may destroy itself). Should I run the router flat out also at 25K rpm?

How often do you change a bit?

Steve

[ViperTX]

Generally, if you're running carbide bits on wood you run at the highest RPM. Personally I experiment on the material I'm cutting and keep a history for the future.

[ger21]

With 1/2" bits, I cut at 400ipm and 15K rpm. Both hardwoods and plywood and mdf. You need at least a 5HP spindle to do this. (ours is 10HP)

For 1/4" bits at 100ipm, try around 18K. Then slowly back off the rpm a little at a time. If you go too slow, you'll get rougher cuts. Don't run at the highest rpm. Heat causes bits to get dull, and the faster they spin, the hotter they get.

It's sort of a juggling act between highest possible feeds at lowest possible rpm, while maintaining acceptable cut quality.

[ger21]

I misread your post, Steve. I thought you could cut at 120. How fast do you think you can cut at? Maybe try a 1/4" spiral at 60-80ipm and 12-15K.

[spalm]

I have no idea what speed I can cut at with the new router attached. I can rapid at 120ipm, that is all I know. I doubt I will be able to route at that speed, but I don’t know why I think that. I guess you kind of answered an underlying question with the fact that it can be done at 400ipm on a pro machine with lots of horsepower. I ordered some bits, so I will try to report back.

What depth to try cutting at? Is 1/8" step too conservative?

Steve

[ger21]

With 1/4" bits, try 1/4" to 3/8" to start. One problem with 1/4" bits is that the dust and chips can get packed into the slot pretty good. When you make multiple passes you end up recutting the chips and dust. I plan to add some air nozzles on my router to try to help alleviate this. With a 1/2" tool we cut 3/4" and sometimes up to 1-1/4" in a single pass. Your machine probably won't be rigid enough for this. With a sharp (new) bit, you should be able to cut 3/4" in MDF, though. MDF cuts very easily with sharp tools. ONe thing you may notice is that the deeper you cut in one pass, thee poorer the quality of the cut may be. Usually if I'm cutting hardwoods, they'll be sanded anyway so it doesn't matter. And for MDF and ply, it's mostly just visual.

I've read on another site some where about guys cutting 3/4" panels of nested parts with 1/4" compression spiral bits (I think from Onsrud) in a single pass. I think they were getting 60-80 full sheets of parts in with 1 tool before it was too dull to use. I've never tried this because I usually use 1/2" tools for everything, and we don't nest our parts, they're cut on a saw.

Most good quality commercial routers can cut at 1500ipm to 2000ipm. Ours is 7 years old, so it's kinda slow. These can cut at 3150ipm!! http://www.komo.com/CNC%20Routers/Ma...r_mach_iii.htm