Help me finish this...

[rcnewcomb]

The photos do help with the explanation. Thanks!

Regarding how fast you can cut as a function of the number of flutes, yes, the chip load calculator indicates the federate must be faster for more flutes.

[gsartor_1999]

Thanks for all the hard work! As a newbie the information is really helpful.

Some other questions I have had as a novice include:
Can all/any router bits be used in my CNC machine? What are the differences?
How far into the chuck should the bit go?
How tightly should the chuck be cranked down? (got mine stuck early on)
Can my bits be sharpened? Should they be?
What are some examples of "bad" cuts?

I am sure there are others. Hope you can use my feedback.
Gina

[beacon14]

Actually I was trying to point out that you spelled minute wrong.

While the chipload would indicate that the 3-flute bit should be run at a faster speed, one might not have the power in either their spindle or motors to push the 3-flute bit through the material as fast as it wants to be pushed. I use single-flute 1/4" compression bits instead of 2-flute bits for this reason. I can push the 1/4" bit faster than I can push the 2-flute bit, only because the 2-flute bit starts to bog down with my 2.2HP spindle if I try to push it too fast.

[steve_g]

Actually I was trying to point out that you spelled minute wrong.

Ha!... Now that's funny... or sad, a perfect example of the failure of the "look - see" reading method of the 50's! Spell check missed it because it's a word.

So the answer to your question... It appears that minuets range from 2-4 minutes long, average say 3... with a RPM of 10-20K average 15,000 that makes it 45,000 times...

All kidding aside... I appreciate feed back, even spelling error feedback. Since I hope this article can be used in many situations including classrooms, the perception of ignorance is not acceptable!

Thanks

Steve

[steve_g]

Gina:

Can all/any router bits be used in my CNC machine? What are the differences?

Some things I didn't go into in the BASIC information about router bits are Rake angle and Relief angles. These and other factors determine a bits suitability for a particular purpose. When you buy a generic router bit these sharpening angles are a compromise of what the manufacture thinks the bit might be used for. Sure... you can use any bit in your router but your results may be disappointing. When you buy from a trusted source you buy a bit for a particular type of job, Hardwoods, composites, plastics and the list goes on...

If others want to jump in here, I'll add a consensus paragraph to the article

How far into the chuck should the bit go?

Does page 6 of the current document answer this question for you?

How tightly should the chuck be cranked down?

I don't know if there is a Ft/lb answer here. My experience is if the bit slips it wasn't tight enough. I'm told that when people call SB tech support reporting missing steps on the Z axis... 90% of the time it's the bit slipping in the collet.

Can my bits be sharpened? Should they be?

At least one manufacture has stated that if a bit has .1" of carbide remaining, it's sharpen-able. Problems I see... Can you find a reliable service? by the time you pay for the service and shipping you have a lot of money invested in a bit that may not be its full design diameter. When a bit is under size you either have to define a new bit or program a path offset, you'll have to keep track of bits and actual sizes also. I know one company that amasses a large number of dull bits, has them all sharpened to the same CED and lives with two sizes of bits. Myself... I have my large V-bits sharpened after I have accumulated several. A sharpened V-bit that's Z-zeroed needs no compensation.

What are some examples of "bad" cuts?

A bad cut is one that you are unhappy with. If you are trying to do a glue up with no additional post cut work, you'll want a lot smoother cut than one that's going to be hid in a dado. In some future revision I hope to show poor cuts and what was done to make them better.

Steve

[steve_g]

Getting close to releasing version 3.2 , still two unresolved issues... One issue is that some sources say you can cut faster with a single flute but with poorer quality than say a 3 flute bit. No chip load charts support this, but people in the trenches say you have to slow down the feed speed of a three flute due to torque/Horse power issues. If that is true... you are actually changing the chip load for a three flute bit? Is this going to damage the bit if you don't have the HP to run at full chip load?

The second is similar to the first. As per the Onsrud chip load recommendations... I have suggested that when cutting 2X or 3X the bit diameter you need to reduce the feed speed by 25% and 50%. Other manufacturers make no mention of this, nor does the SB3 chip load calculator... As long as the router bit is maintaining RPM and not breaking, isn't chip load being meet without the reduction in speed?

Another interesting caveat I've come across is the statement by at least one manufacturer... "chip load calculations fail for bits 1/8" and less" WHAT? A lot of us do much of our cutting with 1/8" bits. Does that mean we're just on our own? Watch those bit temperatures... Let me know if your experience is that chip loads fail for smaller bits!

Steve

[geneb]

Steve, another pointer I've found in the forum is on how the bit sounds when it's cutting.
The quote went something along the lines of, "If the bit is screaming, it's hungry! Feed it more! (increase the movement speed a bit) It's as if the bit is yelling for more food. I know, silly, but it made perfect sense to me.

g.

[steve_g]

another pointer I've found in the forum is on how the bit sounds when it's cutting

Page 20 current document


Just like a baby… Feed a screaming bit. Usually a bit that’s “screaming” wants a greater chip load.

[geneb]

*sheepish grin*

Nevermind.


g.

[steve_g]

An update is available but I decided to make a new thread as apparently some people are unaware of how to go deeper into a thread. I am still seeing some folks downloading the first version of this document...

Steve

http://www.talkshopbot.com/forum/showthread.php?t=15176