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  1. #1
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    Default Drill Point Drill

    Any one here use the DeWalt Extreme 2 HSS-G Din 338 or can explain the Din338 part. I use them as a favourite drill for steel and wood? Peter
    Last edited by Penpal; 16th Jan 2007 at 07:29 PM. Reason: Forgot the pic

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    I think the DIN338 refers to the grade of HSS it is made of.


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    Quote Originally Posted by Penpal View Post
    Any one here use the DeWalt Extreme 2 HSS-G Din 338 or can explain the Din338 part. I use them as a favourite drill for steel and wood? Peter
    Steel or wood , mate I would like to see that drill up against a nornal 60 deg cutting angle drill through 1" steel plate , that type of drill granted will perform better through timber and other softer products but with steel the flatter cutting face has a problim with speed at the outer diam compared with the speed at the inner diam of the cutting face I have often used flat bottom drills with steel but only after first using 60 deg steel drills first , plus the sharpening of these drills makes them a throw away item for most people,
    use then if you will and be happy with the results but they are not a good drill to suggest to use to drill steel


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    Default Ashore

    Thanks mate the last awkward time on steel I was up a ladder clearance hole drilling for tapping 3/4inch holes in 6 inch round 3/8 inch pipe for my 8 by 8 metres car port,I had clamped the steel and found conventional drills grabbed chucking me everywhere,nearly broke my wrists so I used the drill point,a lot safer for me.Realise 1 inch steel is too fat for me and too heavy I tend to weld to it not drill and screw,I agree with you.
    One other thing never use the drill points with laminated anything it cuts the first layer that then spins madly no longer cutting only burning. Being produced in the first third of last century my fabrication is slowing to light materials now thank goodness.I enjoyed your comments,horses for courses. Peter

  5. #5
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    Food for thought; (As quoted from Machinery's Handbook 27th Ed.)

    ---

    Point Angle: Commonly 118deg, except for high-strength steels, where 118deg to 135deg are used, aluminum alloys 90deg to 140deg and magnesium alloys, 70deg to 118deg.

    Lip Relief Angle: Commonly 10 to 15deg, High strength or tough steels, 7 to 12deg. The lower values of these angle ranges are used for drills of larger diameter, whilst the higher are used for smaller diameters. For soft and free machining materials, 12 to 18deg except for diameteres less than 0.25", where 20 to 26deg are used.

    ---

    For tougher steels, a flatter point angle is commonly found. (For example, I can tell you that the majority of drills used in industrial operations, even for things as soft as cast iron, are of a 140deg point.)

    Din338 refers to the standard jobber drill dimensions and specs, not the material. (Shank size, point angle etc etc.)


    HSS obviously means High Speed Steel, while the -G designation is most probably the coating used.

    The design of the point looks like a similar idea to that of a candle point. -Which aren't just used for timber, either. (Makes a small pilot hole in the center to guide the outer cutting edges during drilling operation.)


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    Penpal, the pic in that post is what I call a brad-point drill.

    Personally I prefer for drilling wood, the step-point like you picture I find better for non-ferrous alloys. But that's just my opinion. [shrug]

    (My apologies for any seeming irrelevancy here, folks... this post is just a carry over from a discussion on another thread. )
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    Quote Originally Posted by Ashore View Post
    ...with steel the flatter cutting face has a problim with speed at the outer diam compared with the speed at the inner diam of the cutting face...
    Not sure if I understand. The speed at the outer edge of a given size drill (say 12mm), at 1000RPM, will be the same for a "normal" drill or the one pictured as well as any point less than the max diameter. Unless I've read your post wrong.
    Dan

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    The metal is cut along the whole length of the cutting surface, starting at the centre and progressing to the edge, forming a chip that is then discarded. The hole is cut by progressively shaving the unwanted metal away. If it is not cut in this manner, then I expect you have all sorts of issues occurring - chips not being discarded, overheating, clogging of the bit, rough finish etc. It is not like drilling wood, where you can slice the fibres at the other edge, then chip the waste away at the centre. Try that in metal, and it'd be more like trying to push a solid rod of metal through the material you are trying to drill.
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    Are you saying that the bit in Penpals post doesn't cut in the center? I thought that was the whole point of that design, the pilot point (with thin web) cuts the pilot hole then the rest of the drill follows and enlarges the hole. A bit like using a boring tool on a lathe.
    Dan

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    DIN is Deutsche Industrie Norm, similar to British Standard (BS) and American National Standards Institute (ANSI). According to my imperfect understanding, DIN338 is equivalent to BS328; addresses shank diameter, flute length, and overall length. I don't think they address point shape, as that can be ground to suit the task at hand.

    Brad point drills can drill metal, but they often leave a small donut of metal upon exit from the far side of a through hole. This must usually be removed from the bit by hand.

    Joe
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  11. #11
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    Quote Originally Posted by Dan View Post
    Are you saying that the bit in Penpals post doesn't cut in the center? I thought that was the whole point of that design, the pilot point (with thin web) cuts the pilot hole then the rest of the drill follows and enlarges the hole. A bit like using a boring tool on a lathe.
    No, I didn't say that at all. In fact, if you look closely at the central area of Penpal's bit, it is closer to conventional angles, so would bore quite well. The problem is with the rest of it, you have to scrape your way through the metal, rather than peeling swarf.

    Cutting wood and cutting metal are 2 completely different propositions. Yes, metal cutting drill bits will bore a hole in wood. Perhaps not as cleanly, but not bad. But wood boring bits are unlikely to cut metal.

    Think of a spade bit trying to drill a hole. Not dissimilar to the bit shown in action. The centre drills a small hole, providing a stable point for the rest of the bit to follow. If you have the speed bits, there is an outer point that severs the wood fibres to ensure a clean (er) hole. The body of the bit then follows, chipping out the rest of the material.

    In metal, the centre point might make a hole, the outer knives will blunt, scrape, and probably wear away, then the body will scrape and scrape (and probably scream while heating to red hot).

    Use the right tool for the job - keep the metal cutting drill bits for metal, and the wood cutting (/boring) ones for wood.
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  12. #12
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    Quote Originally Posted by Stuart. View Post
    The problem is with the rest of it, you have to scrape your way through the metal, rather than peeling swarf.
    It will still cut (peel swarf), the helix angle of a normal jobber drill is 27deg and these don't look too different so the cutting edge would have a cutting angle of 27deg which is a whole lot more than a lathe tool working happily with 5deg cutting angle. The Dewalt bit (to me) is just a miniature version of one of these (annular cutter) with a pilot.
    Dan

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