Page 1 of 2 12 LastLast
Results 1 to 15 of 29
  1. #1
    Join Date
    Feb 2003
    Location
    Garvoc VIC AUSTRALIA
    Posts
    12,766
    Post Thanks / Like

    Default How Long Does A Drill Bit Last?

    How Long Does A Drill Bit Last between sharpening.

    I'm thinking of making a cnc drill for repetitive drilling, I'll setup a coolant/lubricant feed.

    As I see it the biggest problem may occur when a bit goes dull and the computer keeps trying to drill more holes. I can't think of any way for the cnc program to detect a dull bit. So I expect the bits need to be retouched before they dull off. But how long does a bit last?

    Next question,
    What is the name of the the twist drill bit that has a small centre drill on the cutting tip?
    Regards, Bob Thomas

    www.wombatsawmill.com

  2. # ADS
    Google Adsense Advertisement
    Join Date
    Always
    Location
    Advertising world
    Posts
    Many
     
  3. #2
    Join Date
    Dec 2005
    Location
    Gold Coast
    Age
    57
    Posts
    1,070
    Post Thanks / Like

    Default

    To answer the second question first, Bob, is It a "centre bit" that you're thinking of? For drilling the centre hole in metal for lathe work.

    To answer the first, I've been told that if you have the skills to get your drill bit sharpened properly, and have the right amount of pressure on it during drilling so that a consistent curl of metal is spun out of it, a type of self-sharpening process takes place and drill bits can last for ages. But we need someone like Ashore or Woodlee to confirm or deny this.

  4. #3
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    14,525
    Post Thanks / Like
    Blog Entries
    7

    Default

    Quote Originally Posted by Rossluck View Post
    To answer the second question first, Bob, is It a "centre bit" that you're thinking of? For drilling the centre hole in metal for lathe work.

    To answer the first, I've been told that if you have the skills to get your drill bit sharpened properly, and have the right amount of pressure on it during drilling so that a consistent curl of metal is spun out of it, a type of self-sharpening process takes place and drill bits can last for ages. But we need someone like Ashore or Woodlee to confirm or deny this.
    Right pressure is essential but using a lube/coolant, even on soft metal, is also an important factor. This really shows itself when drilling hard steel. When I drill chainsaw bars with a Cobalt bit I get 2 or 3, 6 mm holes between sharpenings with no lube, but I don't know how many with lube because I lost count (maybe 10 or 12) and the bit is still OK.

    What about Auto sharpening? Put one of those drill doctor thingos within reach of the CNC and get it to go there for a touch up every 20 or so holes?

  5. #4
    Join Date
    Feb 2007
    Location
    Katherine ,Northern Territory
    Age
    60
    Posts
    1,983
    Post Thanks / Like

    Default

    MMMM how long is a piece of string?
    There are many variables that will play the field here ,what type of material you are drilling , speed of the drill , feed rate ,coolant and the angle that your drill is sharpened.What type of material the drill is made from ,ie HSS , Cobalt HSS or carbide, stellite.

    One would need to make sure your sharpening angles are correct for the type of material ,and that your speed and down feed are at the correct rate.
    One helpful source for such information is Suttons who make twist drills.They have or had a small booklet full of information on such matters .

    As far as auto sharpening goes ,I guess a certain amount of wear on the drill would achieve this , but the geometry of a correctly sharpened drill presents the cutting edge to the material at such an angle to enable it to cut much like a chisel , behind the cutting edge is the rake angle which is clearance for the cutting edge .To sharpen a drill you need the grind the whole face down along the rake angle . As the cutting edge on a drill wears it become slightly lower than the rake angled face behind it which causes rubbing rather than cutting .
    Coolant is important for not only removing heat from the cutting edge , but also a lubrication for both the cutting edge and the drill swarf .Swarf that packs tight into the flutes holds heat ,can jam between cutting edges up along the flutes and the job and creates more heat and possible breakage of the drill

    Center drill maybe , but I have a set of Dewalt Extreme drills I bought just recently ,I thought they would be good for wood drilling,as brad points .They have a smaller diameter starting tip to start the hole for the larger true diameter of the drill.Much like a step drill for counter boring holes for socket cap screws.They are murder on acrylic , absolutely grab the material and cause major havoc.Lousy on wood too ,I mean they drill holes ok ,but cause chipping and splintering on exit holes.
    I was planning to do a review on them and post in the forum.

    Just thinking on how we sharpen drills ,I use a bench grinder and use a coarse and fine wheel for finishing ,then straight to the job with no thought on the condition of the cutting edge .To my mind it must be a series of grooves much like a serrated knife ,would the cutting be better if it was honed to a finer edge like we do to our wood chisels , plane blades and lathe tools?

    Kev.
    "Outside of a dog a book is man's best friend ,inside a dog it's too dark to read"
    Groucho Marx

  6. #5
    Join Date
    Nov 2008
    Location
    Qld. Australia
    Posts
    600
    Post Thanks / Like

    Default

    Quote Originally Posted by echnidna View Post
    What is the name of the the twist drill bit that has a small centre drill on the cutting tip?
    Dewalt "Pilot Point"?

    Great drill bits. Must get some again. I used them years ago and they drill a really quick neat hole and don't grab when breaking through.

    http://cgi.ebay.com.au/DEWALT-29-PIE...mZ290296157095

    Nev

  7. #6
    Join Date
    Sep 2008
    Location
    Queensland
    Posts
    735
    Post Thanks / Like

    Default

    why would you need a CNC drill press/machine?

    ok as for the drills i know that there are charts you use when programing the NC's showing the RPM the feed, size of the drill and i think you need to consider the material you are using ........if you use these calculated feeds and speeds then the drill bits will last a very long time for most applications so much so i dont think you need to worie about them going blunt oh and i would be using a proper cutting oil ......um yeah i dont think coolant should be needed would just make more of a mess. if you have to drill lots of holes for stuff why dont you get a gang of drill presses will be so much cheaper and maybe put auto feeds on the quills so you can get that good feed into the material oh and buy good D-bits Sutton is good we use them at work.

    you really haven't given us much info as to what you want to do with this CNC, is it for commercial use or home use? what kind of jobs do you want this for? what material do you want to drill?

    hope i can help

    Patrick

  8. #7
    Join Date
    Feb 2003
    Location
    Garvoc VIC AUSTRALIA
    Posts
    12,766
    Post Thanks / Like

    Default

    The cnc drill is for drilling hundreds or thousands of holes in mild steel plate and RHS etc,
    The cnc will only speed the actual drilling process a little bit.
    But as it can be set and left to do the drilling it eliminates many man hours of work, freeing time up to do other tasks.
    Using pilot drill bits should mean lower probability of wandering,eliminating centre punching and layout times.
    Cnc also gives repeatable accuracy.

    Thanks to everyone for all the excellent advice



    Thanks Nev, I couldn't think of the name of the Pilot Drill Bit.
    Regards, Bob Thomas

    www.wombatsawmill.com

  9. #8
    Join Date
    Jun 2007
    Location
    Hinchinbrook
    Age
    58
    Posts
    15,856
    Post Thanks / Like
    Blog Entries
    1

    Default

    less than 15 seconds some times Bob especially if they are 1/8" and less
    They break far to easy
    Being down is the low side of being up it shows the road ahead is a steep climb but at the top the view is always special. Then we just coast along till we hit the trough again. Sometimes when coasting we pick up speed and the steep climbs pass by like your on a plain.
    http://woolnwood.blogspot.com

  10. #9
    Join Date
    May 2005
    Location
    Newcastle
    Age
    63
    Posts
    3,926
    Post Thanks / Like

    Default

    Pretty well what every one has said if you get all the variables right coolant, speed, feed, for the material you are drilling , drill cutting angle , type of drill and material the drill is made from
    It also depends on how you are sharpening the drill , by hand or machine sharpening
    BTW are you going to set this cnc up and walk away or will you be monitoring it , you can see a drill getting blunt by the shavings that are comming off their colour size etc
    Ashore




    The trouble with life is there's no background music.

  11. #10
    Join Date
    Feb 2003
    Location
    Garvoc VIC AUSTRALIA
    Posts
    12,766
    Post Thanks / Like

    Default

    I'd prefer to let the cnc drill do it's job while I go & do something else.

    As a drill bit gets blunt it will take longer to drill a hole given the same feed pressure,
    So the obvious feed method may be by counterbalance with an cnc rewind.

    When the time to drill increases too much its then time to resharpen.
    It may be better practise to swap drill bits each say 1000 holes and avoid dulling problems that way.

    I usually sharpen by hand but it may be desireable to machine sharpen the cnc drill bits.
    Regards, Bob Thomas

    www.wombatsawmill.com

  12. #11
    Join Date
    May 2005
    Location
    Newcastle
    Age
    63
    Posts
    3,926
    Post Thanks / Like

    Default

    The machine sharpen is the way to go that way the drill is constant and you can work out a suitable time interval to change.
    When I was working with one we changed the tools with each run and never made that many , usually 100 max , a lot of stuff was 1 off for a specific task , the last cnc stuff I worked with was in the early 70's when it was in its infancy and Newcastle steel works only had 4 cnc machines and I worked on one for 3 months as an apprentice, so I am curious as to how you monitor feed pressure , is the feed not a mechanical amount ,
    Ashore




    The trouble with life is there's no background music.

  13. #12
    Join Date
    Feb 2003
    Location
    Garvoc VIC AUSTRALIA
    Posts
    12,766
    Post Thanks / Like

    Default

    Quote Originally Posted by Ashore View Post
    The machine sharpen is the way to go that way the drill is constant and you can work out a suitable time interval to change.
    When I was working with one we changed the tools with each run and never made that many , usually 100 max , a lot of stuff was 1 off for a specific task , the last cnc stuff I worked with was in the early 70's when it was in its infancy and Newcastle steel works only had 4 cnc machines and I worked on one for 3 months as an apprentice, so I am curious as to how you monitor feed pressure , is the feed not a mechanical amount ,
    I agree the idea of a motor driving a drill feed without some form of pressure control may become a problem.
    That's why I'm considering a mechanical feed using a counterweight (cable and pulley is simple & reliable) which is merely released by a cnc controller and reset to up (home) position by a cnc motor.
    Regards, Bob Thomas

    www.wombatsawmill.com

  14. #13
    Join Date
    Jun 2007
    Location
    sydney
    Age
    55
    Posts
    3,348
    Post Thanks / Like

    Default

    What thickness material are you think of drilling,you would probably have to peck.

  15. #14
    Join Date
    Feb 2003
    Location
    Garvoc VIC AUSTRALIA
    Posts
    12,766
    Post Thanks / Like

    Default

    3mm and 6mm thick steel
    Regards, Bob Thomas

    www.wombatsawmill.com

  16. #15
    Join Date
    Oct 2003
    Location
    Sydney,Australia
    Posts
    2,959
    Post Thanks / Like

    Default

    To detect a blunt drill bit: surely the drill motor would draw more current, so some form of current monitor would send data to the CNC controller board & computer. When the current draw falls outside a certain range, it stops drilling & signals for human intervention. This should also work for other sorts of machine problems too such as broken drills.

    The latest FWW has a similar setup shown for their saw blade test, they use a 'clamp on' type of multi-meter to measure amperage drawn by a table saw.

Page 1 of 2 12 LastLast

Similar Threads

  1. new drill press: quill stroke vs drill bit length ?
    By bannock in forum GENERAL & SMALL MACHINERY
    Replies: 2
    Last Post: 21st Jun 2008, 07:09 AM
  2. Review - Drill Doctor 750X Drill Bit Sharpener
    By Dean in forum WOODWORK - GENERAL
    Replies: 2
    Last Post: 26th Nov 2007, 08:56 AM
  3. Extra long twist drill bits
    By JB in forum HAND TOOLS - POWERED
    Replies: 6
    Last Post: 22nd Jul 2006, 07:43 PM
  4. Impact Drill - Damaging drill bits
    By BassTeQ in forum HAND TOOLS - POWERED
    Replies: 18
    Last Post: 9th Sep 2005, 08:16 PM
  5. Watch those long drill bits
    By kenmil in forum WOODIES JOKES
    Replies: 5
    Last Post: 4th Apr 2004, 10:49 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •