Another thread about feeds and speeds

I know this question comes up a lot on this board, but I couldn't find an answer to my question on any other threads. I am running a CNC router for a cabinet shop, and I've been learning the machine as I've been going (I'm 3 weeks into this job now), so pardon my ignorance on any issues that might seem obvious.

The machine we have is a brand new Biesse Skill. No-one else in my shop knows computers, so running the machine is all on me. The most commonly used bits are a 3/8" compression bit (60-123MW) for trimming and a 1/2" downcutting bit (57-360) for dadoing. I've noticed that my tool life is pretty short, I'm usually changing my compression bit once a week (running anywhere from a couple 4x8 sheets over the day if we're slow to near constant use over my 8-10 hr days). From reviewing other threads, I've noticed that tool life should be much greater than that, so I looked over my feed-rates and compared them with Onsrud's charts. My default feed-rate was around 350 in/min, and when I calculated the feed-rate from Onsrud the minimum rate should be 432 in/min. Chipload with the previous settings were .009, and onsrud's numbers say it should be .012 minimum for the 5/8 and 3/4 sheets we cut the most. I used the 60-100 profile for these equations.

Link to the chart i'm referencing: http://www.onsrud.com/files/pdf/2012...0Chipboard.pdf

Most of the reason why I'm sharing all that data is to make sure i'm doing it right. The bit feels cool after running my test parts (6x6x3/4 square with dadoes in it), so based on what i've read here, that setting is good. Obviously, I'll be able to stress-test the new settings and see if i've actually prolonged tool life.

Now, when I went to do the same math for the my 1/2" bit, I couldn't find the bit at all on the chart. I found it on the mdf chart, but it's softer than chipboard, so the chip-load it's specifying isn't going to be correct. Is there a tool that's close to what i'm using on the laminate chart?

Sorry for the wall of text.

-LaserGuided

I run 3/8" compression bits at 700ipm and 16,000 rpm.

1/2" downcuts at 750ipm and I think 15,000 rpm. Just turned the machine off, so I can't double check.

You should get between 50-100 sheets from one compression bit, depending on the material.

Gerry,

Thanks for the reply. I would have gotten back to you sooner had I time, but we've been pretty busy these last few days. Got a chance to plug in your numbers, tool seems to still be in good shape so far. I have run about 30 sheets on the bit already without noticing any wear on the bit. The majority of what we run is mdf and chipboard, so I don't know how quickly those material wear out bits. The only thing i noticed is how large the chip load was on your settings (.021+), are you running a different bit than I am?

Thanks again,
-LaserGuided

Not the exact same bits, but I'll run those chiploads with any manufacturers tools.
I know my 3/8" compressions are standard 2 flute from Onsrud and Vortex.

I probably have about 5 different 1/2" downcuts that I swap between when they get dull. It really should matter if they're good quality bits.

When I visited a chipboard factory a few weeks ago they stressed at various points how their factory is set up to guarantee a long bit life: Their big customers kind of demand this.
They had a concreted yard for the chip delivery, did various preprocessing and I think magnet stuff. The glue recipe was also part of the "bit-friendlyness".

What I want to say is that not just the machine but also the piece that affects bit life.

Thanks for the replies.

Changed out the 3/8 bit around 40 sheets into it's life because it ran over a staple left in the side of one of the sheets :( Aside from a chip in the upcutting flutes, the bit looks pretty okay (Has some discoloration from use) and still feels relatively sharp. I hadn't found any issues with cut quality while I ran it, so I think it could have kept going into the range Gerry mentioned. I hadn't realized how many sheets we run in a week.

What cpr is saying about chipboard manufacture makes sense. I think that if they are primarily selling to shops like ours, then reduced tool wear is a selling point for them. Pity we haven't figured out a glue for it that sharpens bits.

I got a kitchen that I'm starting on now that's coming out of prefinished maple ply. Since the density of the wood is different, I have to change speeds, yes? I figure I can set-up a separate tool in my machine with the different settings. I checked Osrud's site for hardwood ply's and got a broken link. Anyone know what the change in chipload/feedrate/rpm should be?

Thanks again,
- LaserGuided

I cut prefinished plywood at the same 700ipm with a 3/8" spiral. The way our software works, the feedrate is tied to the tool, and it's too much trouble to change it.
Prefinished plywood isn't really much harder than MDF or particle board, as the core is usually a softer wood.

Yeah, ours is pretty similar. I was planning on adding another compression bit for plywood use (since generally plywood means a residential job, and residential means highest quality possible), and I could give that different settings. The Shop manager here is a real stickler about edge quality so I'm trying to get the best results possible from my machine.

I actually use the 3/8" mostly for plywood, and use a 1/2" compression for melamine and laminate sheets, as I can cut faster and they last longer.

If you want a tool that lasts a lot longer, try the Onsrud Marathon coated compression spirals. Not sure how much more expensive they are, though. I got a great deal on the ones I've been using.

I noticed that series when I was browsing their website not too long ago. We run the MW's, which is only 20 dollars cheaper. Biggest problem now would be that I doubt the boss is going to buy new ones if we already have 6 that we have on rotation with a sharpening company. I'll keep it in mind for when we need to order more bits.