Form Tapping 4-40 in 303 Issues
Close
Login to Your Account
Results 1 to 20 of 20
  1. #1
    Join Date
    Nov 2019
    Country
    UNITED STATES
    State/Province
    California
    Posts
    4
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Default Form Tapping 4-40 in 303 Issues

    Long story short, I can't get a single tapped hole without the tap breaking in 303. It doesn't even make it .125 deep before snapping. This is my first experience with stainless, so I'm sure there's a myriad of things I'm screwing up that I'm not aware of, despite my best efforts at utilizing Google.

    Just to verify I wasn't getting slippage or encoder problems, I tapped a bunch of 1/4-20 in aluminum with no issues, so the machine seems fine (Haas 2005 Mini Mill w/ rigid tapping). I was also able to use a straight flute plug tap from a cheap tapping set from amazon to tap about .2 deep (simply a 'screw it, let's try this moment'). It snaps if I go the full required depth to get full threads, unsurprisingly. It got further than the form taps have though.

    Anyways, details....

    Material: 303
    Tap: Form Balax 4-40 2B TiN
    Tap Drill: #39

    I'm using 20 SFM. Flood coolant (Kool Mist)

    When drilling, I'm taking a .002 chip load at 50 SFM and .045 pecks.

    I'm using an ER16 collet for holding. I don't appear to be getting slippage when marking with a sharpie.

    I raised the feed height to ensure the spindle is up to speed and synced with the Z axis.... just trying to cover my bases.

    I'm considering going to a #38, or even a #37 (#39 is recommended by Balax), but figured I'd see if anyone had some input here before continuing my campaign of death to 4-40 taps and my bank account.

  2. #2
    Join Date
    Jun 2006
    Country
    UNITED STATES
    State/Province
    Alabama
    Posts
    1,883
    Post Thanks / Like
    Likes (Given)
    1089
    Likes (Received)
    738

    Default

    You say Kool Mist, I don't believe that is flood coolant? You need a lot of lube when form tapping. Maybe program the machine to dip your tap into a bottle of real tapping fluid before it enters the hole to be tapped.

  3. #3
    Join Date
    Sep 2018
    Country
    UNITED STATES
    State/Province
    Oregon
    Posts
    401
    Post Thanks / Like
    Likes (Given)
    155
    Likes (Received)
    143

    Default

    The KoolMist is a red flag to me. That stuff is super light duty coolant, with very little lubricity. You need real lubricity, especially form tapping stainless, and especially junk stainless like 303. Before the machine taps have it program a stop and open the door, put tapping fluid in the hole and then run it. See how that does.

  4. #4
    Join Date
    Nov 2013
    Country
    UNITED STATES
    State/Province
    Utah
    Posts
    4,638
    Post Thanks / Like
    Likes (Given)
    1222
    Likes (Received)
    2601

    Default

    I'd probably try a #38 (.1015") Drill. The #39 (.0984") is about .001" smaller than the theoretically ideal start hole size (.0993"). 303 SS is squishy enough. Either way, get a set-up piece, and try a few holes. Roll tapping small holes always takes me a try or 4.

    R

  5. #5
    Join Date
    Mar 2014
    Location
    Nebraska
    Posts
    370
    Post Thanks / Like
    Likes (Given)
    42
    Likes (Received)
    232

    Default

    Have you tried starting the thread with the machine and then finishing by hand? If the tap doesn't break off then my guess would be a machine problem. I understand you tapped 1/4-20 in aluminum but these are a lot finer threads in a lot less forgiving material. Do you have a floating tap head by chance?

  6. #6
    Join Date
    Nov 2013
    Country
    UNITED STATES
    State/Province
    Utah
    Posts
    4,638
    Post Thanks / Like
    Likes (Given)
    1222
    Likes (Received)
    2601

    Default

    Sorry, but IMO using a floating tap holder, when your Machine is equipped with Rigid tap, is only compounding an issue.

    R

  7. Likes aj, TeachMePlease, Larry Dickman liked this post
  8. #7
    Join Date
    Feb 2005
    Location
    Akron, OH
    Posts
    1,858
    Post Thanks / Like
    Likes (Given)
    289
    Likes (Received)
    1396

    Default

    I'm with Rob, I don't think you can form tap with a tension/compression holder. Form tapping you need to push HARD, there's no cutting edge to progressively make a groove and pull the tap in. I suspect you're dancing around the top until you run out of spring in the holder, and by then the hole's too boogered up to do anything with.

    303 cuts nicely because of the sulfur, but it doesn't bend or form worth anything, for the same reason.

  9. #8
    Join Date
    Nov 2019
    Country
    UNITED STATES
    State/Province
    California
    Posts
    4
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Default

    Quote Originally Posted by Rstewart View Post
    You say Kool Mist, I don't believe that is flood coolant? You need a lot of lube when form tapping. Maybe program the machine to dip your tap into a bottle of real tapping fluid before it enters the hole to be tapped.
    I've been using Kool Mist #77 for a while as a flood coolant, and they say it can be used that way, but I'll look into doing what you mentioned with tapping fluid. Thanks!

    I'll also give a #38 a try as well, thanks R.

    Thanks for the input all, I'll get back to it after the holiday and report back.... fingers are crossed!

  10. #9
    Join Date
    Nov 2013
    Location
    north of Bean town
    Posts
    448
    Post Thanks / Like
    Likes (Given)
    71
    Likes (Received)
    140

    Default

    .1015 dia drill and tap form fluid(i like hangsterfers red stuff personally)

    I Roll Tap hundreds of 4-40 holes in Ti cp2 every month and almost(knock knock)never break one, BUT i dont tap to depth in the machine, i only go .100 deep then bring it to .220 deep by hand

  11. #10
    Join Date
    Sep 2002
    Location
    People's Republic
    Posts
    3,336
    Post Thanks / Like
    Likes (Given)
    275
    Likes (Received)
    2187

    Default

    real tapping fluid

  12. #11
    Join Date
    Jan 2013
    Location
    Plainfield, Indiana, USA
    Posts
    1,745
    Post Thanks / Like
    Likes (Given)
    1328
    Likes (Received)
    928

    Default

    You give s/f details for drilling but no info at all for the s/f of the tap.

    Lose the spray mist. Use a brush and apply high sulfur cutting oil (available at Lowe's, Home Depot, etc.) to the tap. Less mess than mist and works better.

  13. #12
    Join Date
    Feb 2014
    Location
    Sunny South West Florida, USA
    Posts
    2,881
    Post Thanks / Like
    Likes (Given)
    10698
    Likes (Received)
    3274

    Default

    Quote Originally Posted by Red James View Post
    You give s/f details for drilling but no info at all for the s/f of the tap.

    Lose the spray mist. Use a brush and apply high sulfur cutting oil (available at Lowe's, Home Depot, etc.) to the tap. Less mess than mist and works better.
    Quote Originally Posted by smb44
    I'm using 20 SFM
    And if it's a 4-40, I'd hope like heck he's using a feedrate of .025/Rev

  14. #13
    Join Date
    Apr 2013
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    201
    Post Thanks / Like
    Likes (Given)
    2
    Likes (Received)
    101

    Default

    Quote Originally Posted by gustafson View Post
    real tapping fluid
    +1
    Koolmist is useless for anything hole related. I've done a lot of 4mm threads in 303 just putting a dab of tapping oil on each hole. That was using a cut tap though.

  15. #14
    Join Date
    Apr 2019
    Country
    UNITED STATES
    State/Province
    Arkansas
    Posts
    862
    Post Thanks / Like
    Likes (Given)
    276
    Likes (Received)
    324

    Default

    Is this a xometry test part?

    Sent from my Pixel 3 using Tapatalk

  16. #15
    Join Date
    May 2011
    Location
    cincinnati
    Posts
    75
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    10

    Default

    Here are the parameters we use:
    flood coolant in Haas vf3 (we use cool rite)
    spot drill first
    #38 drill running 2900rpm 4.3 feed, peck full out .1 increments to .43" deep
    ridged tap in er 16 collet 250 rpm to .312 deep.
    never had a problem breaking taps. maybe have 5 or 6 hundred holes on the tap now.

  17. #16
    Join Date
    Apr 2019
    Country
    UNITED STATES
    State/Province
    Arkansas
    Posts
    862
    Post Thanks / Like
    Likes (Given)
    276
    Likes (Received)
    324

    Default

    Quote Originally Posted by trademarkmachine View Post
    Here are the parameters we use:
    flood coolant in Haas vf3 (we use cool rite)
    spot drill first
    #38 drill running 2900rpm 4.3 feed, peck full out .1 increments to .43" deep
    ridged tap in er 16 collet 250 rpm to .312 deep.
    never had a problem breaking taps. maybe have 5 or 6 hundred holes on the tap now.
    That's aweful fast for inconel!

    Sent from my Pixel 3 using Tapatalk

  18. #17
    Join Date
    Feb 2011
    Location
    ct. usa
    Posts
    22
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    5

    Default

    i also use a premium substrate for the tap HSS with cobalt and a coating like altin plug tap if you have the room instead of bottom taps
    the drill size does make a difference try the #38 it should give you 61.75% full thread the #37 will probably be to large giving about 47% thread causing the minor dia to be to large
    Also have found when tapping 303ss material you can buy 303 or a premium grade 303 that is made to be easier cutting

  19. #18
    Join Date
    Nov 2013
    Country
    UNITED STATES
    State/Province
    Utah
    Posts
    4,638
    Post Thanks / Like
    Likes (Given)
    1222
    Likes (Received)
    2601

    Default

    Quote Originally Posted by as9100d View Post
    That's aweful fast for inconel!

    Sent from my Pixel 3 using Tapatalk
    It's awful slow for Acetal. But since we aren't talking about either of those materials, it's strange to add commentary.

    R

  20. Likes AARONT, eaglemike, TeachMePlease liked this post
  21. #19
    Join Date
    Feb 2013
    Location
    Madison, WI
    Posts
    1,029
    Post Thanks / Like
    Likes (Given)
    1135
    Likes (Received)
    672

    Default

    Ditch the KoolMist. Use some anchorlube. As previously mentioned change the drill size to a #38.

  22. Likes as9100d liked this post
  23. #20
    Join Date
    Apr 2014
    Country
    UNITED STATES
    State/Province
    California
    Posts
    799
    Post Thanks / Like
    Likes (Given)
    1011
    Likes (Received)
    535

    Default

    As others have said, get some decent tap lube in there. Kool Mist is only good for cut tapping small holes in 6061, and even then would not be my first choice. It's about 2 clicks above water if sprayed. High sulpher cutting oil would be good. I've used STP in a pinch when nothing else was around or open and I had to get the job going. There's also some sort of grease type stuff in the yellow and green tube laying around most shops that I use for center lube for a dead center (can't remember the name right now). That would tap far better than Kool Mist in your situation.
    I've had to ream holes at times when form tapping in some materials to get hole size after tapping to be in tolerance. Might be something to think about since you have a problem at this point.
    Good luck!


Tags for this Thread

Bookmarks

Posting Permissions

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