Posting just in case any newbies feel bad about throwing away one endmill they have been using for a while, or a brand new one that just broke after 30 seconds of use
Things I have learned over time:
buy a loupe (or USB microscope). Sure way to know when an endmill is dull (that and the horrible cutting sounds). A bad way is running your fingers along the flute’s cutting edge
don’t cut multiple types of materials with the same endmill. Especially endmills that cut plastics or metal
deflection kills (endmills)
runout kills (micro-machining endmills)
if the endmills changes color, it’s fried (due to wrong feeds and speeds)
MDF wears out endmills fast. Using a brand new endmill to make profile cuts MDF is a pity
the tip of a 15° vbit breaks if you so much as look at it the wrong way
tapered bits are rock solid. I have yet to break one.
I should have bought a surfacing bit (e.g. McFly or similar) much earlier than I did, I’m never getting back the time I lost surfacing things with 1/4" endmill over the years.
lye is a great way to get melted aluminum off an endmill’s flutes.
acetone is a good way to clean-up gummy residue one endmills from cutting through tape.
using calipers to “check” the diameter of an endmill is a good way to break the cutting edges. Don’t.
super long endmills with super long length of cut are handy but require very (very) conservative feeds and speeds
I bought a 1/2" endmill once (just because I could), used it a few times for fun and CNC mayhem / to test my dust collection at max capacity, but it’s pretty much useless for real projects I do.
I re-use the containers at need for tooling which when purchased doesn’t come in suitable package.
I will note that the “change color” dictum should be considered in light of how thin coatings are, and that a coated endmill may still be usable and cut well after the coating has been worn away.
Also, I try to keep track of which materials a tool has cut, and after a while a tool which was used for plastic will be relegated to cutting aluminum.
Ah, good point, the color change I mentioned only applies to uncoated endmills indeed!
And instead of color change I could have written “going dark brown”
MDF’s ability to dull endmills is impressive. It took me ruining a project several times with the endmill going off-track to realize what was happening. Now I just use inexpensive endmills for MDF, because they die fast either way.
We did that a lot at a machine shop I worked at. It is good for expensive cutters at larger scale. But man, unless you have a box of nice endmills, it’s more expensive. And I hate to toss a piece of carbide, but it seems to be cheaper to get a new one in 90% of use cases of the people here.
At this depth in the hardwood running full width at 1,400mm/min the pucker factor is a little less with the 1/2" cutter, it sounds much happier than 1/4" or 8mm does. These are cheap as chips so I’m not upset if I wear them out roughing, they come in a 3 pack which is a hint…
The finish passes were with an 8mm to reduce how much I have to chisel out of the corners of those mortices. 8mm is a really nice cutter size to use if your collet will hold them, especially at this longer flute length (52mm) which makes for a somewhat weak 1/4" bit.
If an endmill is sharpened the outside diameter will change as they clean it up. A small to medium size machine shop might do it if you had enough. It would require them to setup for cutting the bit. Each size would require a setup by the shop. The cost of setup at, lets throw a figure out that I was quoted a few years ago 100.00 an hour for machine work. Maybe he didn’t want my job, but I don’t have enough end mills to validate that kind of cost. And if the diameter is going to change I don’t want to reprogram Create for the new tools.
I learned from buying cheap bit off Amazon. Yes some were crud. But I learned from breaking them. It is when you break a 65.00 bit because of my mistake that you want to cry. Don’t be afraid about breaking a few. That is how we learn, investigating why as well as not doing it again and again and…
I take mine to a local cutter grinder, he charges about half the cost of a new one to resharpen.
Part of the deal is the timeline in which I get them back, I do believe I ride on the coat tails of the area
machine/job shops. So when he has a set up to do similar size endmills for them, that’s when
he’ll do mine. This can take weeks sometimes to get them back.
The guy I go to is also very cool, (sole proprietor) and I can’t say that every business is willing to work this way.
They might not be the highest quality, BUT:
Speed and feed for chip load
Listening to my machine and bit while cutting
Paying attention to when a bit gets dull
I would rather break a $2.00 bit instead of a $20.00.
Now that I am more confident, quality is what I try to buy. You are still going to have issues, much less though.
