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Thread: Speeds/Feeds for Drilling in Annealed A2 tool steel

  1. #1
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    Default Speeds/Feeds for Drilling in Annealed A2 tool steel

    Hi guys,

    What are the appropriate feeds and speeds for drilling in annealed A2 tool steel? I've been drilling 17/64 holes in A2 1 1/2 deep for body clearance on 1/4 20 cap screws in a mold I've been making for epoxy granite test samples. Drill bits have been breaking or burning up left and right at 1400 RPM (figuratively, I'm not running the mill backwards).

    I looked in the chart in the Morse catalog for tool steel and they say 100sfm which amounts to 1400 RPM on a 17/64 bit. The hardest tools steel they give in the chart is supposed to be 50sfm which would amount to 700 RPM.

    I'm having better luck at closer to 500 RPM. I've also been using Cool Tool Cutting fluid from monroe fluid technologies.

    I've noticed drilling too slow causes the material to work harden while too fast causes drills to dull or burn up. I also managed to break a 13/64 bit off in another hole so I've acquired an MA Ford Hi-Roc bit to drill out the broken drill bit and will report on how this works.

    Regards all,

    Cameron

  2. #2
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    Cant tell you the exact feed and speed .but from experience get around 450 rpm and play around up are down a little from their . That is the way I do things . Start slow and work up . You don`t burn tools up that way.

  3. #3
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    Lane thanks. That's what I was looking for. I'll tweak my VFD knob down a bit further and see if things start going better. I had destroyed a few 1/8 carbide endmills by going too slow in the same material and I incorrectly applied that lesson to drilling. . .

  4. #4
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    Cameron,

    My Machinery's Handbook gives the typical drilling speed and feed for A2 with a HSS drill to be .007" feed/rev and 85 sfm, which works out to very nearly 650 RPM. Optimal speed and feed are given as .015" feed/rev and 45 sfm (~350 RPM).

    I have a feeling that any work hardening you are experiencing might be due to insufficient feed. Keep using plenty of cutting fluid. You may also be having problems if you are using cheap/dull drills - I would recommend a cobalt HSS (M42) drill for longer edge life if you have lots of holes, and a 135* split point for the harder material. Name brand drills (Precision Twist Drill, Cleveland, Morse, etc.) will work better for this sort of thing due to better geometry.

    Let us know how it turns out, that epoxy granite is some interesting stuff.
    -Brian
    In theory, there is no difference between theory and practice... but in practice, there is.

  5. #5
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    Brian,

    Thanks for the detailed response. The drills in question have been brand new Morse drills 135 degree but not cobalt and a few Triumph 118 drills that are easily sourced locally. Most of the problems have been caused by using too high a speed and too low a feed out of ignorance. There are also possible issues from drilling into the edge of a Heat affected Zone from some small welds although the issues seem too far from the welds.

    Mainly however, this is the most complicated project I have ever done and I have no experience cutting steel on the Bridgeport (only aluminum), much less tool steel.

    The project so far involves 2 end plates, 4 side plates, 8 dowel pins and 30 tapped screw holes counterbored for the heads of 30 allen head cap screws. I've been practicing what I learned from reading 1910 and 1970 circa books on die making doweling parts together for alignment etc. All I need to do now is tig the side plates together and then use a carbide burr to clean up the curves in 48 inches total of o-ring grooves. The big pain in the grooves is the 8 round corners that I lacked a rotary table for and made by a combination of chain drilling and using a boring head and a custom tool by hand as a primitive shaper with a 1/4 circular stroke. If I can get them from looking like they were hacked out by a rabid ground squirrel to chewed out by a slightly annoyed weasel, I'll consider it a success I'll see if I can get the antique digital camera running and take some pics when I get through. The complexity comes from the fact that this mold was designed to hold either vacuum or pressure while staying relatively high tolerance.

    As for epoxy granite, my work and that of others is chronicaled in the epoxy granite thread over on CNCZONE in the general mechanical engineering forum. I've been at it a bit over a year personally and I expect to have a good formula before I've worked on it for two years.

    Regards all,

    Cameron

  6. #6
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    Default A2 Drilling Speed

    Ive drilled a few Miles of A2 in my Life. My simple formulae is Take the Number 160 and into it divide the diameter of the drill. Use Coolant, if you work harden A2 it gets Tough. If youre drills dull stop drilling and SHARPEN IT. Good Luck.

  7. #7
    airsmith282 Guest

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    i dont drill alot of tool steel but i do drill and tunr a ton of Stainless steel 316 316l 303 and some stuf that i got thats alot harder to turn never mind drilling it dont know the number on it got it formt he slavage yard any how i leanrd to not go past 330 on my lathe for driling it and i use lots of cutting fluid and it does not seem to hurt my drills to often and i get nice hoels drilled as well , i tried 550 which is my next speed up and i have snapped and burned up drill bits and blew the tips all kinds of problems ..

    i have to agreee some of the speeds and feeds stuff is right on but , in personal experence i find some to be off the wall as well..

    one thing thoes charts fail to mention is the type and quailty greade of cutter or drill to be used for such hi speeds and i have also found the last whil eafter doing alot fo research that over 90% of all the charts i have found and bookmarked etc.

    refer to machine CNC operaions which tend be right off the top...

    manule machines are not to be used at such speeds and if you do you are going to need some really super hi end cutters and drills to pull it off the same way a CNC is doing it..

    other wise take is slow use lots of cuttiong fluid or flood coolent etc something to keep it cool clean out the swarf as often as you can etc..

    over the next few days ill be turnning and drilling some drill rod for a gun part iam building for a guy so ill let you know how that goes.

    my 2 cents and some of my own findings of trial and error to reach and answer ..

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    Thanks madman et. al.,

    I appreciate the advice. My engineering skills are substantially greater than my rusty manufacturing skills
    so I need all the help I can get. Fortunately, I've drilled and counterbored all of my 17/64 holes on this project now except for one that has a 13/64 drill broken off in it flush with the surface. Wouldn't have made it this far if not for taking madman's advice and figuring out how to sharpen drills offhand on a bench grinder. My hi-roc drill bit should arrive today to drill the stuck bit out of the part.

    I also learned during the course of this project that the pilot of a counterbore is not a cutting portion of the tool and that if you get it really hot that it will squish and deform causing the pilot to become too big even for the correct screw body clearance holes. Fortunately, the now oversized pilot will get stuck in a hole and break off leaving a once again functional counterbore while a quick few whacks with a pin punch will knock the broken pilot out of the hole. I'd prefer not repeating this lesson. . .

    Thanks for the help,

    Cameron

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    Quote Originally Posted by ckelloug
    I also learned during the course of this project that the pilot of a counterbore is not a cutting portion of the tool and that if you get it really hot that it will squish and deform causing the pilot to become too big even for the correct screw body clearance holes.
    I haven't gone that far, but I have run into a similar problem when I was counterboring Metric screw holes with the next size Imperial counterbore -- the counterbore pilot is slightly too big, and it doesn't like it if you push it too hard. I got to opening up the pilot hole a bit with an endmill so I could get the Imperial counterbore in there. Kind of a goofy way of doing it, but I don't want to invest in Metric counterbores.

    Cameron, I need to sit back with a cold-one and read the latest 400 pages of the epoxy granite thread. The last result I saw (a couple months back) was stunning -- the cast EG looked like poured black granite. You guys are amazing!

    Last edited by lazlo; 11-12-2008 at 02:30 PM.

  10. #10
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    Machining A-2 with HSS tooling I take the speeds and feeds I normally use for cold rolled 1018 and reduce by 1/3. 1/4" drill in 1018 runs about 1200,I drop down to 900 for example.

    Peck drill or shower down on it,don't dwell it will work harden as you found out already.
    I just need one more tool,just one!

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