1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  2. We want to wish everyone a healthy, happy New Year, full of joy and success. God bless you, and thank you for supporting The Hobby-Machinist.

    Dismiss Notice

First Boring Head.

Discussion in 'QUESTIONS & ANSWERS (Get Help Fast Here!)' started by tweinke, Jan 8, 2017.

Tags:
  1. tweinke

    tweinke United States Active User H-M Supporter-Premium

    Likes Received:
    108
    Trophy Points:
    43
    City:
    Fairmont
    State:
    Minnesota
    So as you can guess I would like to get a boring head. It will be used on a PM-727 mill. Is there an appropriate size based on the mill size? Also if you could have only one boring head what would be the most useful size. Speaking of size I am working under the assumption that a 2 inch one is good for about a 2 inch bore. Money is an object in this purchase so any comments in that regard would be good too. It would sure be nice if I could find an article related to boring heads that addresses all this but I have had no luck finding what I am asking. Opinions guys? :confused 3:
     
  2. wawoodman

    wawoodman himself, himself H-M Supporter-Premium

    Likes Received:
    330
    Trophy Points:
    83
    Location:
    Seattle, WA
    City:
    Seattle
    State:
    Washington
    How long is a piece of string?

    I would wait until you actually have a need for one: an actual project. That will keep you from buying one that's either too big, or too small, and having to buy the other one, anyhow. That being said, a 2" is probably a good start. Watch a few videos, and see if you can say "I can see myself doing that..."
     
    mikey and JimDawson like this.
  3. JimDawson

    JimDawson Global Moderator Staff Member Director

    Likes Received:
    3,202
    Trophy Points:
    113
    City:
    Sandy
    State:
    Oregon
    A 2 inch boring head will easily bore a 6 inch hole. Most boring heads have a horizontal tool holder position, you stick the boring bar out sideways.
     
    mikey likes this.
  4. mikey

    mikey Active User H-M Supporter-Premium

    Likes Received:
    798
    Trophy Points:
    113
    City:
    Honolulu
    State:
    Hawaii
    The bigger the mill, the bigger the head the mill can handle. I don't know what that size is on a PM-727, sorry.

    If I could only have one head in my hobby shop, it would be a Criterion DBL-202 head. These come in two flavors, a 202A or 202B; the former takes 3/8" bars and the latter, 1/2". It has three bar positions, two on the bottom and one horizontal position. With bars in these positions, you can bore from 0.050" to 6.687" holes. The holes each position can bore to overlaps so the range is seamless.

    The leadscrew is calibrated in direct reading 0.001" increments; dial in 0.005" and your bore gets 0.005" bigger. I have found this head to be well-balanced, very accurate and versatile. They have a 7/8-20 threaded back to accept shanks of various types and sizes, including R8.

    Note that boring range is sort of misleading. The larger the bore, the greater the centrifugal and centripetal forces are so balance becomes an issue with big holes. If your mill can go slow enough then you can go bigger - go too fast and the mill will vibrate and can even take a walk across the shop.

    Criterion no longer exists but you can buy NOS or used heads on ebay. Brand new, these heads went for close to $300.00 retail but new and used heads in good shape can be had for considerably less. If these heads have a weak spot, it would be the way the dovetail was cut. There is a tiny bit of metal at the base of the dovetail and if the user failed to adjust and use the head properly, the dovetail can snap off so look at pics carefully to avoid buying junk. Make sure all the screws are there and ask if the ball bearing under the gib screws are also present.

    The DBL series was one of the most copied boring heads to come out of Asia. You can buy an exact copy for about half what the original cost. Personally, I would go for a Criterion myself. I have two heads from this company and they have been trouble-free and precise.

    EDIT: I should clarify that one dovetail on a Criterion head is slotted to create an adjustable gib. The amount of metal at the base of this gib is very thin so care must be used when adjusting it. It is more than adequate for normal use but an ignorant user can eventually snap it off.
     
    Last edited: Jan 8, 2017
    bobl, Subwayrocket and JimDawson like this.
  5. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

    Likes Received:
    1,689
    Trophy Points:
    113
    Location:
    USA
    City:
    Sacramento
    State:
    California
    Really, Mike? I can hit it once in a while... ;)
     
    hman, JimDawson and mikey like this.
  6. Subwayrocket

    Subwayrocket United States H-M Supporter - Premium Content H-M Supporter-Premium

    Likes Received:
    270
    Trophy Points:
    63
    City:
    Scranton/Wilkes-Barre
    State:
    Pennsylvania
    With your machine I would buy a Shars. I had a mill same design like the 727 . The accuracy of a higher priced boring head would be negated by a little wobble in the quill and some "give" in the column which all adds up . I have a knee mill now but still use the Shars boring head, it's not too bad. I have been able to get slip fits with it .
     
    tweinke and mikey like this.
  7. mikey

    mikey Active User H-M Supporter-Premium

    Likes Received:
    798
    Trophy Points:
    113
    City:
    Honolulu
    State:
    Hawaii
    Ummm, well, I mean, it's possible, right?

    Okay, okay, the screw is calibrated in thousandths of an inch. Whether or not you can hit it is a whole other thing!
     
    JimDawson likes this.
  8. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

    Likes Received:
    1,192
    Trophy Points:
    113
    Location:
    Victoria, Texas
    City:
    Victoria
    State:
    Texas
    Criterion was bought out by Allied Machine & Engineering Corp. in 2013 and still sold under the Criterion label by AMEC. MSC is still selling them. Unfortunately, they are slowly getting out of our price range for use H-M use!

    Ken
     
    Last edited: Jan 8, 2017
    mikey likes this.
  9. mikey

    mikey Active User H-M Supporter-Premium

    Likes Received:
    798
    Trophy Points:
    113
    City:
    Honolulu
    State:
    Hawaii
    True, Ken, thanks for pointing that out.
     
  10. tweinke

    tweinke United States Active User H-M Supporter-Premium

    Likes Received:
    108
    Trophy Points:
    43
    City:
    Fairmont
    State:
    Minnesota
    Well so far I've learned a lot from you guys, yes I do have a project in mind and will need holes about 2 1/2 inches so I guess a 2 inch may be my best bet.
     
  11. mikey

    mikey Active User H-M Supporter-Premium

    Likes Received:
    798
    Trophy Points:
    113
    City:
    Honolulu
    State:
    Hawaii
    If you can swing the cost, Borite cobalt bars are very nice to use in these heads.
     
    4gsr likes this.
  12. rick9345

    rick9345 United States Active User H-M Supporter-Premium

    Likes Received:
    67
    Trophy Points:
    28
    City:
    Minneapolis
    State:
    Minnesota
    boring/facing head for future use. Use mine for more facing than I thought I would,no need to tear down and reset on the lathe. Mill becomes more useful.
    I have a tree boring head(actually 2) can also bore inside and out side tapers.
     
  13. tweinke

    tweinke United States Active User H-M Supporter-Premium

    Likes Received:
    108
    Trophy Points:
    43
    City:
    Fairmont
    State:
    Minnesota
    Remembering that a PM-727 is not a Bridgeport or Kearny and Treker and my budget you guys have inspired me so far to keep looking for a used head and possibly skip the Shars or the like head if I can find something that still fits the budget. More comments are certainly welcomed!
     
  14. petertha

    petertha Canada H-M Supporter - Premium Content H-M Supporter-Premium

    Likes Received:
    125
    Trophy Points:
    43
    City:
    Calgary
    State:
    Outside US / Canada
    Borites are very nice & good value IMO. Also, making custom tools from inexpensive offshore boring bars is a viable option especially if you happen to use the same inserts for lathe boring bars (which is what they are intended for).
     

    Attached Files:

    mikey likes this.
  15. Subwayrocket

    Subwayrocket United States H-M Supporter - Premium Content H-M Supporter-Premium

    Likes Received:
    270
    Trophy Points:
    63
    City:
    Scranton/Wilkes-Barre
    State:
    Pennsylvania
    I would just get a shars . Swap out the set screws and it's not too bad at all . You're never going to realize the higher accuracy of a $300+ head with a column/bench mill . Not rigid enough, play in the quill, column, table adds up. Like I said, I had a bench mill with the shars , now I have a knee mill and still use the shars . I can produce slip fits with the shars head and the dial is actually pretty accurate. I've got a few indexable bars for it now, but the cheap ones they give you work fine. I've bored cast , steel , alum . The Shars boring head is a typical Shars product. Anything i've ever got from them im happy with.
    Is their stuff Criterion, Kurt, Yaesu, Sandvik, Mitutoyo ? No , but it's good stuff for the money and not far off the high priced stuff in quality.
    Good luck whatever you get .
     
    Last edited: Jan 12, 2017
    mikey likes this.
  16. EmilioG

    EmilioG United States Active User H-M Supporter-Premium

    Likes Received:
    93
    Trophy Points:
    28
    City:
    HUNTINGTON
    State:
    New York
    With Mikey's help, I wound up getting two Criterion DBL 202B's. One was an original design with a different gib cut that is thicker,
    but supposedly more difficult to adjust. I did not find that. In fact, it makes for a stronger head. Both heads are in great shape and were had for
    a very good price. I also bought Borite cobalt boring bars. As Mike told me, you can regrind Cobalt bars easier than carbide.
    You can't go wrong with one of those boring heads. The ball bearings and set screws can
    easily be replaced, and Allied sells a hardware kit to replace these parts if needed. I think these heads will last a long time with proper care and use.
    Very solid and well made.
     

    Attached Files:

    Last edited: Jan 12, 2017
    Bob Korves and mikey like this.
  17. petertha

    petertha Canada H-M Supporter - Premium Content H-M Supporter-Premium

    Likes Received:
    125
    Trophy Points:
    43
    City:
    Calgary
    State:
    Outside US / Canada
    I've never disassembled one. Where are the ball bearings located?
     
  18. mikey

    mikey Active User H-M Supporter-Premium

    Likes Received:
    798
    Trophy Points:
    113
    City:
    Honolulu
    State:
    Hawaii
    Under the gib screws.
     
  19. petertha

    petertha Canada H-M Supporter - Premium Content H-M Supporter-Premium

    Likes Received:
    125
    Trophy Points:
    43
    City:
    Calgary
    State:
    Outside US / Canada
    oh, do you mean like a single bearing ball between screw & gib? I was thinking like a ball bearing race.
     
  20. mikey

    mikey Active User H-M Supporter-Premium

    Likes Received:
    798
    Trophy Points:
    113
    City:
    Honolulu
    State:
    Hawaii
    Yes, just a ball between the screw and gib.
     

Share This Page