Why are my slots stupid?

[stupoty]

I always use a 3 flute for slotting . Only one flute is in contact with the work at any time reducing overcut .

I like the two and three flute cutters for slotting , I never have good luck with a four flute.

Stu

 

[RaisedByWolves]

Agreed, the only way to cut an accurate slot is in two passes with a smaller diameter end mill. However, if you don't need high accuracy, slots for bolts etc, I find that a straight cutting, 2 flute end mill or router bit will give the best one pass results I'm not sure why but I heard it long ago and it seems to work.

The key to it is overlapping plunge cuts and then taking out the leftover protrusions, and finally offsetting .005-.010 per side to finish up the cleanup.

That is what I did here and took 1/2 the diameter of the endmill per plunge as it was soft aluminum. For steel I would go more like .100 or less depending on the rigidity of the machine and the depth of cut.


On this cut I was doing little "Exploratory machining" just wanting to break through and not touch (Read gouge) the inner walls of the tube under the plate. For this slot it didn't matter the size it cleaned up at, but using that .500 mill, I could have easily made a .510-.515 slot with clean sides.

If however I wanted to get an on size .500 slot, I would use a 7/16" endmill and math.

 

[RaisedByWolves]

Wow, this forum never disappoints! Thank you guys for the super informative responses.

So even in steel I should use a two flute cutter for slotting and to cut the slot undersize first...now I know.

Machining is wonderful. I love learning all this stuff. I wish i got into this as a profession.

The problem you would find in this timeframe is there are not a lot of entry level "Manual machining" jobs out there.

I was trained in it when everything was going NC, and would love to train someone in it before I retire.

I had a chance to train a really smart guy for 9 months last year, but my company screwed him and he left.

 

[Threadkiller]

I like the two and three flute cutters for slotting , I never have good luck with a four flute.

Stu

Ill keep that in mind. Thank you!

The key to it is overlapping plunge cuts and then taking out the leftover protrusions, and finally offsetting .005-.010 per side to finish up the cleanup.

That is what I did here and took 1/2 the diameter of the endmill per plunge as it was soft aluminum. For steel I would go more like .100 or less depending on the rigidity of the machine and the depth of cut.


On this cut I was doing little "Exploratory machining" just wanting to break through and not touch (Read gouge) the inner walls of the tube under the plate. For this slot it didn't matter the size it cleaned up at, but using that .500 mill, I could have easily made a .510-.515 slot with clean sides.

If however I wanted to get an on size .500 slot, I would use a 7/16" endmill and math.



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Thats good to know man. I was thinking of trying plunge cutting but like i said before my endmill wasnt the best. However if I thought to go undersized I could have used a sharper carbide endmill.

I know, sadly, manual machining seems just about dead in terms of industry applications. I was looking into taking a manual machining class at a local boces a couple years back but missed the registration deadline and I thought to myself "that sucks but no biggie ill take it the next semester" next semester it was gone and it was introduction to CNC. CNC is cool but i love the art of manual machining and would love to learn and develop my skills better than just trial and error...mostly error lol

 

[RaisedByWolves]

Ill keep that in mind. Thank you!


Thats good to know man. I was thinking of trying plunge cutting but like i said before my endmill wasnt the best. However if I thought to go undersized I could have used a sharper carbide endmill.

I know, sadly, manual machining seems just about dead in terms of industry applications. I was looking into taking a manual machining class at a local boces a couple years back but missed the registration deadline and I thought to myself "that sucks but no biggie ill take it the next semester" next semester it was gone and it was introduction to CNC. CNC is cool but i love the art of manual machining and would love to learn and develop my skills better than just trial and error...mostly error lol

Sounds like you have your head straight. Most guys now want to jump right into CNC whether it be at home, which I just don't get, or for work. As far as work goes the only ones making decent money are programmers, and that can be outsourced either within the conus or outside. Programming literally went the way of IT.

Jumping into CNC for home use in my opinion will be expensive and frustrating. The up front cost will be expensive and without having manual experience you're going to burn up a lot of tooling before getting proficient in knowing what your machine will do and listening to what the machine and tooling is telling you.

Not that its impossible, but I see people equating it to 3D printing and from a cost standpoint its anything but.

Now, as far as that dull endmill goes, and plunge cutting, you can touch up an endmill in a pinch just like you can touch up a drill. Sharpening the flutes? No.

Touching up the tips/end so you can plunge? That is certainly doable.

As far as skills go, I have been in Tool&die for 35yrs and I'm still learning every day.

 

[Threadkiller]

Sounds like you have your head straight. Most guys now want to jump right into CNC whether it be at home, which I just don't get, or for work. As far as work goes the only ones making decent money are programmers, and that can be outsourced either within the conus or outside. Programming literally went the way of IT.

Jumping into CNC for home use in my opinion will be expensive and frustrating. The up front cost will be expensive and without having manual experience you're going to burn up a lot of tooling before getting proficient in knowing what your machine will do and listening to what the machine and tooling is telling you.

Not that its impossible, but I see people equating it to 3D printing and from a cost standpoint its anything but.

Now, as far as that dull endmill goes, and plunge cutting, you can touch up an endmill in a pinch just like you can touch up a drill. Sharpening the flutes? No.

Touching up the tips/end so you can plunge? That is certainly doable.

As far as skills go, I have been in Tool&die for 35yrs and I'm still learning every day.

Yeah there's definitely a disconnect with CNC that's what I don't like about it. Even if I wanted to get into it, like you said, you have to walk before you could run. I know manual machining is a super complicated and in depth profession/art. I dont even consider myself a novice at this point, I dont have the seat time. That being said its crazy that you've been doing it for 35 years and there's still more to learn. Thats another thing I love about machining.

Touching up an endmill? Lol I still have trouble getting a decent grind on drill bits I don't know if I would attempt an endmill at this point it's tough being self-taught with everything. Youtube has helped immensely, although there's only so much you can learn without doing. At least for me.

 

[RaisedByWolves]

That being said its crazy that you've been doing it for 35 years and there's still more to learn. Thats another thing I love about machining.

Touching up an endmill? Lol I still have trouble getting a decent grind on drill bits I don't know if I would attempt an endmill at this point it's tough being self-taught with everything. Youtube has helped immensely, although there's only so much you can learn without doing. At least for me.

I’m lucky that I had the unfortunate fortune to be religiously beat about the head and shoulders by some really good old heads coming up.

I hated some of those guys with a passion at the time, but I get it now, and they taught me a lot even if I didn’t understand it at the time.

FF to today, I love to teach people what I know and challenge them. Unfortunately societal norms have shifted so much for the most part that even when a guy like me tries to help people and tones it way down, people still get their feelings hurt.

This is basically why we got locked into a 4 year apprenticeship. You just hunkered down and did it, because feelings don’t feed your kids.

As far as learning, I don’t care what the discipline is, anyone who thinks they know everything simply does not know what they don’t know.

Or their just a pompous a-whole.

As to being self taught, just do it.

Fail, break thinks, but each time step back and analyze what you did, what worked or didn’t and you will learn.

If you can do it without going broke all the better.

 

[woodchucker]

Let me ask all you non 4 flute guys something.

How is a 4 flute crap while a 2 flute is good?

A 4 flute is just a 2 flute doubled up. There are always 2 flutes engaged. when the 2 flutes disengage another set of 2 flutes comes in and equalizes the cuts.

A 3 flute would be more prone to push off one side.

The more flutes you have the less vibration, less hysteresis.

You have a lower feed rate with more cutters because you are taking less off with each cut. A 2 flute can hog off more and has deeper flutes to clear chips with...

I think it's like a tablesaw with an 80 tooth blade, it cuts unbelievably slow, but with a glass like finish..
A 24 tooth blade is a fast cutting ripping saw, and will push through quickly but with a rough finish.

Same with metal removal.. more flutes smoother finish and slower feed, less flutes rougher finish and faster feed.

All bets are off with DULL cutters. I don't think a dull cutter will give you a clean even cut. There will be vibration and it will play havoc on the slot size.

 

[mattthemuppet2]

chip clearance is much better for 2-3 flutes, so you're less likely to get chips packing the flutes or recutting the chips. One reason why 3 flutes cut slots better is that there is only one flute cutting at a time (in theory). With 2 or 4 flutes, two flutes are cutting at the same time so if one flute rubs instead of cuts it pushes the other flute deeper into the material. To be honest I've never managed to get a good finish with 2 flutes unless it's carbide and I'm running it as fast as I can.

 

[woodchucker]

chip clearance is much better for 2-3 flutes, so you're less likely to get chips packing the flutes or recutting the chips. One reason why 3 flutes cut slots better is that there is only one flute cutting at a time (in theory). With 2 or 4 flutes, two flutes are cutting at the same time so if one flute rubs instead of cuts it pushes the other flute deeper into the material. To be honest I've never managed to get a good finish with 2 flutes unless it's carbide and I'm running it as fast as I can.

so then, slow the feed down, and 4 flutes will unload the chip .. same with band saws blades, and tablesaw blades, and metal cutting slot cutters. less teeth = more space for chips, more teeth slow the feed down to clear the chips.