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[4]

Why my Cuts are rough?

[3]
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oskar

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#1
As per attached pictures the first groove I did went nice and the finish is acceptable to me as a first try in milling. However the first 2 pictures shows another groove I tried and that did not go well and even I broke the endmill which was a 3/8” shank, 1/8” OD 4 flute. All cuts are with passes of 1/32" deep and I can see / hear the endmill has a hard time doing the job.

I also have 2 videos which shows what happened


I like to know what I did wrong, perhaps the endmill is too small for the job, my speed / feed rate are too slow/fast or something else?
 

Attachments

JimDawson

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#2
Your videos are broken. Maybe you need to set them to public?
 

oskar

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#3
Sorry about that Jim, went back and I published them and here are the links. Hope this works now


 

benmychree

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#4
You don't say what was the RPM and feed settings, but feed looks too fast, and a 4 flute cutter was not the best choice for clearing chips, best 2 flute, and I do not see any lubricant used, and there is way too much tool overhang. For cutting deep narrow slots, a slitting saw would be a much better choice, you could likely cut the slot in one pass.
 

T Bredehoft

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#5
Yeah, your feed rate is 'way too fast. baby the cutter, Too much sticking out from the (is that a drill chuck?) holder, too.
 

Cadillac

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#6
From the videos this is what I'd say first is planning your project step by step. I would have did the ends or sides first then would have slot the center out. With how you are holding the part any vibration is gonna make that part sing. Second is how it's being held. There's a lot of overhang in every direction. It needs to be rigid. Third you have,had a lot of overhang on your tool. Looked like a 3" tool. If your slotting shallow you use the shortest endmill. Even deep slots start with a shorty and work to a longer one to cut down on chatter and deflection. Fourth your feed rate looked alittle fast. I usually start slower see how things are acting and speed up as necessary. Using a stream of air at the endmill will help with chip removal along with some lube.
 

JimDawson

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#7
Yup, what was said by all above :)
 

P. Waller

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#8
Milling Aluminum Dry

This rarely works well, also a 1/8" diameter end mill needs at least 4000 Rpms
 

oskar

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#9
The endmill is attached to an ER16 collet and next time I will try not to have so much overhang

Sorry guys I think I know what’s happened. I misread the belt location between the Sherline motor pulley and the Taig headstock Pulley.

Using my handheld tach the way the belt is set now I get a max speed of 2400 RPM and I did all my cuts at that speed. I don’t know why the first slot I did turned out ok, perhaps because the 1/8” OD endmill was brand new and by the time I went to do the sides slot the end mill was worn out?

Changing the belt to the other slot on the pulleys my tack reads 5800 RPM when I have the speed control knob at about 40% of its range
 

oskar

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#11
From the videos this is what I'd say first is planning your project step by step. I would have did the ends or sides first then would have slot the center out. With how you are holding the part any vibration is gonna make that part sing. Second is how it's being held. There's a lot of overhang in every direction. It needs to be rigid. Third you have,had a lot of overhang on your tool. Looked like a 3" tool. If your slotting shallow you use the shortest endmill. Even deep slots start with a shorty and work to a longer one to cut down on chatter and deflection. Fourth your feed rate looked alittle fast. I usually start slower see how things are acting and speed up as necessary. Using a stream of air at the endmill will help with chip removal along with some lube.
Nicely said, thanks for your time

Looks like my problem was too slow RPM and kind of fast feed. Next time I will know better
 

benmychree

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#12
What likely broke the cutter was chips balling up in the flutes, chips then cannot escape and the cutter breaks; lubricant such as WD40 or just plain kerosene or diesel fuel will help to prevent the chips from "welding" into the flutes, and as another wrote, an air blast would help clear the chips out.
 

oskar

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#13
I do use WD40 but maybe not enough and I prefer to use a shop vacuum to clear the chips instead of an air blast which splatter the chips.

With the good tips here hopefully next time I will have a better luck
 
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