Spotting for hardmetal drills
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  1. #1
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    Default Spotting for hardmetal drills

    Hello.

    A rule of thumb is not to spot for full carbide drills and use pilot drills instead (for 7xD and up). However, half of the tool magazine are drills so it's not possible to have a pilot drill for every one. There are 140 degrees pilot drills and for example Guhring has one. Does anyone use them? I have learnt by experience that as short as 7xD drills (we use Sandvik R840 and R860.1 mostly) make a "bzzz" sound upon entering the material and the hole is tapered about 1xD length. Sometimes less and sometimes more, depending on how dull the drill is. I was hoping that a spot drill would eliminate this problem.

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    Try adjusting your programs so that the initial drill entry speed and feed are reduced for a short distance, then increased to the target S/F. That should cut down on the buzzing sound.

    Do some experimenting to find values for slow S/F and depth, then adopt them where needed. It's a bit of a pain, but could save you from damaged drills.

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    Quote Originally Posted by hhtw View Post
    A rule of thumb is not to spot for full carbide drills and use pilot drills instead (for 7xD and up).
    Generally yes, I agree with you. But "rules" are made to be broken.

    Your Solid Carbide Drills should not be wandering that much. I am guessing with no real information that there are other factors---Mechanical, Programming, Set-up. I would do an investigation into that first, and if everything were sound as a whistle, I would Spot everything with a 140º Spotting Drill. I would not try to use a Pilot Drill for every Finish Drill I needed. I would do an Inventory on which Drills are wandering and which ones are not.

    There are literal hundreds of ways to generate holes, Drilling is ideal, but it isn't the only way to make a hole. Prioritize your holes.

    R

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    I use Guhring 5514/5515 and 6400 for almost all of my drills. I do not pilot any of them. They are terrifyingly fast, give GOOD hole sizes (some vary depending on my programming) excellent finish, and it is all plug and play in my opinion, pop the drill in, set the S&F according to the book, and go to town.

    I have one job with a 10x Cobalt drill, that I predrill with a 5515. It ends in a interrupted cut, Guhring recommended it. It has the same 140* geometry as the 5514/5515.

    Anything over 1/2" I tend to drill with a .404 drill, it just happened to be in the drawer, and then open up with a 3/8" rougher.

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    go slower feeds and speeds and most carbide drills get much quieter and tool life gets much longer
    .
    like rather than 45 minute tool life 90 to 200 minutes is possible. remember salesman wants to sell you more drills

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    Quote Originally Posted by DMF_TomB View Post
    .
    like rather than 45 minute tool life 90 to 200 minutes is possible. remember salesman wants to sell you more drills


    Go faster and harder and MAKE MONEY. My tooling rep certainly wants me to buy more tooling, but more than that he wants me to MAKE MONEY, so that I buy MORE TOOLING.

    90 to 200 minutes are possible... ? That should be NORMAL.

    I was up at the shop I used to work at, lets see, 3 years ago? They have the SAME DAMN Guhring drills in the tool holders as when I left. Do they use them every day, NO, do they do production, NO. But I will bet one of your $100k a year paychecks that they have more than 200 min on them!

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    1) cast iron and ductile iron vary widely in hardness. slag or hard spots when bigger than a grain of sand effect tool life and when grain of rice size can dull a tool in 10 seconds. depends on metal being drilled. tool life of 45 to 60 minutes is normal expectations. usually go faster if getting over 120 minutes tool life
    .
    2) i look at total yearly costs especially scrap and rework. often sudden tool failure causing 20 hours of rework a year was not unusual and taking 5 hours yearly longer drilling slower and saving 20 hours of rework ends up being faster
    .
    3) i record total time to make a part including rework or delays from sudden tool failures

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    Quote Originally Posted by Fal Grunt View Post


    Go faster and harder and MAKE MONEY. My tooling rep certainly wants me to buy more tooling, but more than that he wants me to MAKE MONEY, so that I buy MORE TOOLING.

    90 to 200 minutes are possible... ? That should be NORMAL.

    I was up at the shop I used to work at, lets see, 3 years ago? They have the SAME DAMN Guhring drills in the tool holders as when I left. Do they use them every day, NO, do they do production, NO. But I will bet one of your $100k a year paychecks that they have more than 200 min on them!
    His boss is tightwad of the year. A Thousand examples of "tripping over Dollars to pick up Pennies".

    R

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    I usually spot holes for any carbide drills that are longer than 5xD. Typically I will use a 2xD version of the same drill (or at least the same brand and series) to spot. That way the point angle and geometry are the same, so that you are not blowing the corners off of your drills or causing chatter.

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    One thing I've done in similar situations is to interpolate a shallow pilot (maybe 1xD) with an endmill. One endmill can pilot a practically infinite number of drill sizes.

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    I guess I should ask, what are you considering "hardmetal" drills?

    What Rc is the metal that you are drilling?


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