Getting ready to drill lots of holes - speeds/feeds check

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stioc

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I'm getting ready to drill approx 60 or so 1/4-20 tap holes in a 0.775" thick 6061 AL fixture plate. My sharpest 13/64 drill bit I have is from this set: https://www.amazon.com/gp/product/B001EYU5N8

I don't have a VFD so I really don't like changing speeds, so I almost always leave my belt config at 1800 RPM (good for AL or plastics which is all I machine). Using a few of the free speeds and feeds calculators I'm arriving at 5-7IPM. However, I also saw one calculator suggest that if the depth of the cut will be more than 3 times the diameter (which is true in this case) to reduce the speeds&feeds by 50%.

I don't mind how long it takes to drill, my goal is to not burn up the bit and break it in one of the holes. I have one of those cheap mister/coolers but I generally only use it for air, but I can use WD40 too.

Any thoughts, advice?
PS. I plan to do the tapping by hand since I don't have a spindle reverse or a tapping head.
 
probably want to countersink those holes after you drill them. Slow is better than too fast when drilling holes IMO. Knock the speed down and play it safe is what I would do. Kerosene, TapMagic or WD40 are your friend for aluminum. Number 7 drill is the preferred drill for 75% threads and in aluminum I go with that, for steel I go 60% threads usually. That said if 13/64 is all you have go with that.
 
Thanks, I'll dig through my drill stock to find a #7 drill but I doubt it'll be as sharp as the new set. I'm good with going slow as long as I don't go too slow for the RPM and burn up the drill bit from excessive friction.
 
7IPM will be fine at 1800RPM. May even be on the slow side.

HSMadvisor is saying 13.5IPM and peck drill them at around .54" per peck.
 
Thanks cs900! I'll start at 7 to 9 and see how it goes...I think I generated the gcode for .4" chip breaking drilling so two pecks per hole. . Oh does HSM assume HSS drill bits because mine aren't HSS, they're cheaper metal with fancy coating.
 
btw, GWizard for .2031 HSS at 1800 rpm recommends from 2 to 8.5 depending on the Conservative to Aggressive slider with no Peck. for Cobalt it is 1.8 to 7.7 ipm with a .2 peck.
 
stioc said:
Thanks cs900! I'll start at 7 to 9 and see how it goes...I think I generated the gcode for .4" chip breaking drilling so two pecks per hole. . Oh does HSM assume HSS drill bits because mine aren't HSS, they're cheaper metal with fancy coating.
Click to expand...
Sorry that was for carbide!!

1800 RPM @ 11IPM with a peck of .54" for coated HSS.
 
Thanks again guys! I got it done, the 7ipm @1800 rpm worked perfectly! After 60 holes the drill bit was luke warm and still sharp (I really like this set of drill bits btw). I mostly just used air for coolant and a random spritz of wd40 here and there. I'll post the details in my RF30 build thread but here's a quick pic:

40721760445_6c350b0fc3_z.jpg
 
Looks Great! Did you use any PECK and if so, how deep for each peck?
 
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