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  1. #1
    hdrider63's Avatar
    hdrider63 is offline Aluminum
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    Default Rigid tapping speeds

    I have a part to run out of 303 SST with a 10-32 thread through it. I was wondering if you guys use a formula to figure rpms? I am rigid tapping now at 850 rpms but I have no idea if there is a better speed to run at. I'm using a hss tap and water soluble. Any suggestions? Thanks.

  2. #2
    SteveinAZ's Avatar
    SteveinAZ is offline Stainless
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    Sounds pretty fast... you're tapping @ ~42 sfm. I looked up what Balax recommends - they recommend 20 sfm in 300 series SS - although they do not specify any difference between 303 and 316, I think I'd dorp it down to about half of where you're at. If it's a blind hole, you will want to drop another 25-50% in sfm. Make sure your coolant concentration is high, like 10-12%, or maybe some Moly Dee is in order.

    If you are not using a thread forming tap, try one...they work great and the cold formed threads are really nice - just finished a job with about seventy 10-24 threads in T316, used a Balax "Thredfloer" tap and first and last hole were perfect (dribbled Moly Dee in every blind hole just to make sure).

    If your doing a through hole, and don't want to stand there dribbling tapping fluid, you can program a move into a small cup full of fluid off to the side of the table to pick up fluid, and then go thread...with a thread forming tap instead of a cutting tap, you don't have to worry about chips either.

    Steve

  3. #3
    Matt@RFR is online now Stainless
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    All I do is use the same speed as I would with a HSS drill the same size. Works for me and is easy to remember.

  4. #4
    rosie is offline Hot Rolled
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    My old bosses used to piss and moan that you're sapposed to run at surface footage for the hss tool. All of the guys I worked with (15+ years over me) ran almost all taps under 3/8 at around 400 rpm depending on the machine. If they had to figure ipm on the machine they'd get an rpm that would make the feedrate a whole number.

    I just got in from tapping 900 thru holes(.120 wall thickness) in 304 stainlesss 1/4-20 with a $10 cleaveland (J&L sale item) tap at 400 rpm. The tap had a silver hint of color to it, but all cutting edges were beautiful. I could have ran it faster, but I remember my old coworkers bitchen about braking taps.

    I do want to try form taps soon, I have heard many good things about their reliablity.

    Just my .02

    Rosie

  5. #5
    hdrider63's Avatar
    hdrider63 is offline Aluminum
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    Smile

    Thanks for the information guys. I'll try form tapping too, just out of curiosity. I don't use them much. We'll see if it works for me.

  6. #6
    doug925's Avatar
    doug925 is online now Titanium
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    I use the following SFM's:
    (I normally buy Vega brand taps btw)

    303= 20sfm
    316= 12sfm

    4140A= 30sfm
    4140HT= 20sfm

    6061= 75sfm
    2024= 115sfm

    Plastics about the same as 6061 if I am using coolant, and about 300rpm if not.

    Best of luck,

    Doug.

  7. #7
    machinist man is offline Aluminum
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    I'll second the forming taps. I've used 10-24 in blind holes in 316L stainless and haven't had a problem with them at all. One guy I know said he used them for tapping 4-40 holes in 400 series stainless and had good luck with them. As far as speed goes, doug's chart above pretty much nails it.

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