pre drilling for holes

Discussion in 'Tools' started by Luiz Fernando Pinto, Sep 30, 2019.

Help Support HMEM by donating:

Tags:
  1. Sep 30, 2019 #1

    Luiz Fernando Pinto

    Luiz Fernando Pinto

    Luiz Fernando Pinto

    Member

    Joined:
    Jun 21, 2019
    Messages:
    7
    Likes Received:
    0
    Gender:
    Male
    Location:
    São Paulo - Brazil
    Hello, i made a hole with 10 mm diameter them the final diameter 11mm, my tool became like this and i didnt made the final hole, obviously. Is that because the relation of the diameters was too small?

    upload_2019-9-30_16-24-14.png
     
  2. Oct 1, 2019 #2

    Tim1974

    Tim1974

    Tim1974

    Well-Known Member

    Joined:
    Feb 16, 2016
    Messages:
    47
    Likes Received:
    6
    Cheep drill bit ?
    What material where you drilling ?
    And what speed ?
     
    BIGTREV likes this.
  3. Oct 1, 2019 #3

    Luiz Fernando Pinto

    Luiz Fernando Pinto

    Luiz Fernando Pinto

    Member

    Joined:
    Jun 21, 2019
    Messages:
    7
    Likes Received:
    0
    Gender:
    Male
    Location:
    São Paulo - Brazil
    It´s not a cheep drill bit, it´s a dormer A002. And i thought that was a fake Dormer but it´s not. I alread taltked to Dormer and my outfitter.

    So, i´m not sure what material it is, but it is a low carbor, i think. It´s a shame, but the previouly drill that I made were ok, for example, 8mm diameter.

    It was about 500 rpm.
     
  4. Oct 1, 2019 #4

    Luiz Fernando Pinto

    Luiz Fernando Pinto

    Luiz Fernando Pinto

    Member

    Joined:
    Jun 21, 2019
    Messages:
    7
    Likes Received:
    0
    Gender:
    Male
    Location:
    São Paulo - Brazil
    Look why i thouth it was a fake Dormer tool, but it is not.

    3 reasons.

    1 - The chip that came whith the tool.
    upload_2019-9-30_22-29-0.png

    2 and 3 - A bad ending, at the chanfer edge and blurred letter.
    upload_2019-9-30_22-31-32.png

    Despite the photos, it's not a fake or cheap drill.

    So, after all, that's why i am thinking it was the large pre drill hole
    Or my lathe is too small... vibration, low robust, etc,... contributed to this.
     
  5. Oct 1, 2019 #5

    Tim1974

    Tim1974

    Tim1974

    Well-Known Member

    Joined:
    Feb 16, 2016
    Messages:
    47
    Likes Received:
    6
    Yer looks like it grabbed , I wouldn’t normally drill out so little (when possible)
     
    Luiz Fernando Pinto likes this.
  6. Oct 1, 2019 #6

    TonyM

    TonyM

    TonyM

    Well-Known Member Project of the Month Winner

    Joined:
    May 15, 2017
    Messages:
    240
    Likes Received:
    126
    Gender:
    Male
    Occupation:
    Retired
    Location:
    North Bohemia Czech Republic
    That does not look right even or especially for a second cut. It does not look overheated as I would expect with hard material which in any case would have shown with the 10mm drill. It definitely looks like a faulty drill bit.
     
    BIGTREV, Luiz Fernando Pinto and JRR like this.
  7. Oct 1, 2019 #7

    Tim1974

    Tim1974

    Tim1974

    Well-Known Member

    Joined:
    Feb 16, 2016
    Messages:
    47
    Likes Received:
    6
    yer your right tony looking at the pic agan on a bigger screen its not right at all ! unless the first drill work hardened the material ??? but yer you would see more heat , hmmmm wish i could run a file over the drill bit and see if its hard !
     
    Luiz Fernando Pinto likes this.
  8. Oct 1, 2019 #8

    Luiz Fernando Pinto

    Luiz Fernando Pinto

    Luiz Fernando Pinto

    Member

    Joined:
    Jun 21, 2019
    Messages:
    7
    Likes Received:
    0
    Gender:
    Male
    Location:
    São Paulo - Brazil
    Thanks a lot for the discussion. I will send the drill for my supplier,
    he requested to send to him. Any new information i´ll post it here.
     
  9. Oct 1, 2019 #9

    Nick Hulme

    Nick Hulme

    Nick Hulme

    Well-Known Member

    Joined:
    Oct 6, 2008
    Messages:
    334
    Likes Received:
    80
    10mm pilot for 11mm final? :D
    That's most of your problem right there, running it at 500rpm with 0.5mm engagement compounds the mistake as it will rip the edges off a drill bit more often than not, a 5mm pilot would be better.
    This is not a case of a drill fault, it's tool abuse ;-)
     
    Tim1974 and Luiz Fernando Pinto like this.
  10. Oct 2, 2019 #10

    tornitore45

    tornitore45

    tornitore45

    Well-Known Member HMEM Lifetime Supporter

    Joined:
    Jan 17, 2009
    Messages:
    744
    Likes Received:
    110
    What a ridiculous statement!

    Holes are reamed with 0,3 mm diameter difference.
    Holes are enlarged by a trifle all day long by the thousand, in hard material without any problem.
    500 RPM for a 10 mm is actually a bit slow, which eliminates overheating.
    Low carbon steel does not work harden appreciably, an can almost be drilled with a screwdriver.
    The drill may be a fake after all, faker can print brand logos.
    The ugliness of the end is a good case for a fake.
    The drill may have slipped through the hardening process.
     
    johnmcc69 and BIGTREV like this.
  11. Oct 2, 2019 #11

    Nick Hulme

    Nick Hulme

    Nick Hulme

    Well-Known Member

    Joined:
    Oct 6, 2008
    Messages:
    334
    Likes Received:
    80
    The only relevance of that statement is that a reamer is not a drill.
     
  12. Oct 2, 2019 #12

    mcostello

    mcostello

    mcostello

    Member

    Joined:
    Sep 6, 2011
    Messages:
    335
    Likes Received:
    34
    Do it all the time with no problems. Don't buy extra fancy drill bits either.
     
  13. Oct 2, 2019 #13

    tornitore45

    tornitore45

    tornitore45

    Well-Known Member HMEM Lifetime Supporter

    Joined:
    Jan 17, 2009
    Messages:
    744
    Likes Received:
    110
    Nick you need to learn how to learn from those that know more than you.
    Mountains of experience say you are wrong, why do you insist in defending something wrong?
    By the way, from the point of view of the reamer cutting into the hole the geometry is essentially the same and that is why a drill bit can cut into a hole slightly undersized just like a reamer. The difference is that a reamer has multiple flutes keeping a better center and cutting a rounder hole, something a drill bit may not do because is allowed to wander, but that difference is meaningless to the issue at hand.
     
    TonyM likes this.
  14. Oct 2, 2019 #14

    Nick Hulme

    Nick Hulme

    Nick Hulme

    Well-Known Member

    Joined:
    Oct 6, 2008
    Messages:
    334
    Likes Received:
    80
    I am endlessly amused by you, please do keep it up :D
     
  15. Oct 2, 2019 #15

    tjwal

    tjwal

    tjwal

    Well-Known Member

    Joined:
    Sep 22, 2013
    Messages:
    71
    Likes Received:
    6
    I agree with Nick. The pilot hole shouldn’t be much bigger than the web of the final drill. Whether that caused the problem or not I don’t know.
    John
     
  16. Oct 2, 2019 #16

    tornitore45

    tornitore45

    tornitore45

    Well-Known Member HMEM Lifetime Supporter

    Joined:
    Jan 17, 2009
    Messages:
    744
    Likes Received:
    110
    Yes I am a funny guy. Please tell me what evidence you have to support your rambling about drilling. Again people drill with little stock removal all the times, you seems to be the only one incapable of doing so. Because... you are too pompous to learn.
     
    BIGTREV likes this.
  17. Oct 2, 2019 #17

    tornitore45

    tornitore45

    tornitore45

    Well-Known Member HMEM Lifetime Supporter

    Joined:
    Jan 17, 2009
    Messages:
    744
    Likes Received:
    110
    The picture shows flute that look like were machined with an hatchet.
    What could possibly be additionally wrong with that tool.
     
    BIGTREV and johnmcc69 like this.
  18. Oct 3, 2019 #18

    TonyM

    TonyM

    TonyM

    Well-Known Member Project of the Month Winner

    Joined:
    May 15, 2017
    Messages:
    240
    Likes Received:
    126
    Gender:
    Male
    Occupation:
    Retired
    Location:
    North Bohemia Czech Republic
    Tornitore is absolutely right. It's common practice to double drill for a better sized finished hole and certainly 1mm is not too little to remove for a finishing cut.
    That drill has the cutting edge and the rest of the surface removed exactly as if the material being cut was harder than the drill. It is not burnt which indicates to me that the drill is not hard and I would hazzard a guess is not even HSS.
     
    OrangeAlpine and BIGTREV like this.
  19. Oct 3, 2019 #19

    Richard Carlstedt

    Richard Carlstedt

    Richard Carlstedt

    Active Member

    Joined:
    Jul 9, 2007
    Messages:
    39
    Likes Received:
    9
    Occupation:
    Retired Manufacturing Engineer
    Location:
    Green Bay ,Wisconsin
    Late to the party, but I have seen similar drill damage to the flutes when the drill
    was accidentally run in reverse.
    Enlarging holes with minimal increases is common in industry, but feed rate
    becomes more critical as the drill wants to pull due to the helix angle
    Rich
     
    Luiz Fernando Pinto likes this.
  20. Oct 3, 2019 #20

    Luiz Fernando Pinto

    Luiz Fernando Pinto

    Luiz Fernando Pinto

    Member

    Joined:
    Jun 21, 2019
    Messages:
    7
    Likes Received:
    0
    Gender:
    Male
    Location:
    São Paulo - Brazil
    It was not reverse mode, i never use this way.
     

Share This Page