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Harbor freight bench top mill

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okiemike

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#1
Hi. I am new to milling. I just purchased the harbor freight unit and I have had terrible luck buying decent end mills. I will mainly be milling 1/4 thick 6061 aluminum. I want to mill using a 1/4 end mill a slot 3" to 4" in length all the way through so a 1/4-20 bolt can slide. I see where you can get center cut end mills and make one pass cleanly. I don't want to spend a bank full of cash for a good set. But so far I am not having any luck.

Any help I would greatly appreciate. Thank you

also I may even try and use 1/4" and 1/2" lexan
 

westsailpat

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#2
I don't understand , what do you mean by no luck ? Also if your finished slot is 1/4 you may want a smaller dia. e'mill , so can make finish passes . Here is a good source for e'mills . https://www.mcmaster.com/#end-mills/=1cnkexm
 
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okiemike

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I am wanting to go all the way through 1/4" thickness piece of aluminum flat bar. I can't get through the 1/4 aluminum with the end mill I have purchased without making several passes. And once I have completed the slot I have some burs.. I am not expecting a totally clean slot. And even thought I didn't purchased this unit not only on this video below.. But for the price I figured it would be a decent entry unit and I have a Harbor fright 5 minutes from my house. But I went with this unit because I wanted to duplicate what this gentlemen was doing in the video below. I do see he made 1 cut pass and 2 clean up passes.. I am assuming I am just buying the wrong end mills.

I just want to find end mills to do what this video does from 8:45 through 10:00
 

Eddyde

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#4
For that cut use a ¼" 2 flute end mill. You will need it to be center cutting if you want it to drill the starting hole, or you can drill the hole separately. Don't use a 4 flute, you'll get a lot of chatter.
 

westsailpat

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I would start with a new e'mill sounds like yours is wore out , if you are getting a lot of table movement when plunging just lock the XY and then plunge with Z . Another thing you could do is drill a hole first so you don't have to plunge .
 

okiemike

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For that cut use a ¼" 2 flute end mill. You will need it to be center cutting if you want it to drill the starting hole, or you can drill the hole separately. Don't use a 4 flute, you'll get a lot of chatter.
That is what I purchased 4 flute and not center cutting. I can make 3 passes but these 4 flute have been a head ache. I read somewhere about only using 2 flutes cuts better.. but I wanted to ask for help. I appreciate your input. I will look now.
 

Eddyde

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Yes, use 2 flutes for slot cutting, 4 flutes for side milling. For cutting aluminum and mild steel use high speed steel (HSS) end mills. For a ¼" end mill in aluminum you can probably run the mill as fast as it will go, use some WD-40 as a lube to help give a smoother finish. While center cutting end mills will drill the starter hole, it will cut much better if you pre drill a pilot hole, say 3/16", for a ¼" slot. If you do go for it in one shot, peck drill.
 

okiemike

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Yes, use 2 flutes for slot cutting, 4 flutes for side milling. For cutting aluminum and mild steel use high speed steel (HSS) end mills. For a ¼" end mill in aluminum you can probably run the mill as fast as it will go, use some WD-40 as a lube to help give a smoother finish. While center cutting end mills will drill the starter hole, it will cut much better if you pre drill a pilot hole, say 3/16", for a ¼" slot. If you do go for it in one shot, peck drill.

I will do a pilot first and then run the end mill and use wd40... thank you again
 

Silverbullet

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#11
Use wd40 or kerosene to lube your cutters , spray misters work well also . Aluminum builds up on the cutter edges causing many of your problems. Two or three flute endmills will do great buy the best you can afford , remember high speed and cobalt cutters have worked for fifty plus years.
 

benmychree

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#12
There are also special end mills for milling aluminum.
 

petertha

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#13
End mills that do a nice job in aluminum look like this. You can get them in most machinery supply places, even Ebay & AliExpress. (With the usual offshore caveats) I've found prices better on Ali, especially carbide which are razor sharp. Unfortunately Asian are mostly metric shanked so I have an ER collet system which has paid for itself very quickly.

Nobody has mentioned climb vs conventional milling direction yet so I'll throw that out. Simply plunging & traversing in one direction means you have the cutting edges going in opposite direction relative to either slot side. If one surface of your slot looks ok but the other is raggy, this is why. For something as simple as a bolt clearance slot, make the roughing slot, then step over a couple thou & finish in climb direction only. In this mode I find 3 or 4 flute cut very well. Maybe this is part of the confusion. Now your slot end radii will be ever so slightly out of round because of this slight step over, but again for a clearance slot it wont be seen or felt. Sometimes people drill a slightly oversize hole on the ends for this reason, it has a bit of dog bone appearance but cosmetically better.

For more precision work, if you need to hit exactly 0.250" slot and with an excellent finish, then its better to step down to an EM diameter beneath 0.250 & mill as above.

BTW if you haven't discovered roughing end mills, you really should. They are not just for industrial hogging, they are excellent on hobby machines because they cut chips so efficiently & actually work better with lighter less rigid machines. I typically have a matching pair like 0.250" roughing & 0.250 finishing. Hog off the bulk material & then swap to the finer EM for finishing. Because the EM diameters are the same (nominally) you dont have to change your dial setup.
 

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petertha

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#14
This may not be appropriate for your project but hopefully a picture makes things clearer. Here I require exactly .250" width AND the best finish. But I don't necessarily care about the end diameters matching up exactly. Drill (oversize) 9/32 ends, slot & finish with under size 3/16" EM. Now you can use the appropriate milling direction to achieve the finish.
 

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