Free Tap Speed and Feed Calculator
Free Tap Speed and Feed Calculator
Threads per inch
Tap Feeds and Speeds Basics
Tapping Feeds and Speeds are pretty easy to calculate because they’re constrained by the thread that is being tapped. Everything starts from Tapping Speeds
What Tapping RPM or Tapping Speed Should I Use?
That depends upon the material you’re trying to tap and the diameter of the tap. For a more sophisticated calculator that will figure that out for you as well as help you find the right TPI value and work in Metric, keep reading!
Recommended Surface Speeds (SFM) by Material
We can find the recommended surface speed to tap many materials in this table:
Aluminum – Cast Alloys 60
Aluminum – Diecast Alloys 70
Aluminum – Wrought Alloys 80
Gun Metal 50-60
Cast Iron – Grey 30-60
Cast Iron – Ductile 50
Cast Iron – Alloys 15-30
Malleable Alloy 20-40
Magnesium Alloys 50-70
Nickel Alloys 10
Nimonic Alloys 10-12
Mild Steel 30-50
Steel – Medium Carbon 35
Tool Steel 15-25
Cast Steel 25
Titanium Alloys 10
Stainless Steel – 300 Series 10-20
Stainless Steel – 400 Series 15
Zinc – Diecasting 80
Given SFM from the table, plus the tap’s diameter, we can calculate rpm with this formula:
Spindle RPM = SFM / circumference of tap
circumference of tap = PI * tap diameter
BTW, that’s from our article on RPM from Surface Speed if you want the details.
Tapping Feed Rate & Tapping Feed Rate Formula
Given the spindle rpm’s the Tapping Feed Rate is just how fast we have to feed to move one full thread per spindle revolution. It’s our spindle rpm divided by our threads per inch (TPI).
So if we’re going 1000 rpm and cutting a 20 TPI thread, we need to advance 1000/20 = 50 IPM. That’s our Tapping Feed Rate
Pro Power Tap Feeds and Speeds Calculator
Quick and dirty calculators like the one above are what you see most often on the web, but most machinists and CNC’ers need more than they can offer. That’s why we make the G-Wizard Calculator, a serious power tool for folks like you.
Here’s what G-Wizard’s Tap Speeds and Feeds Calculator looks like:
G-Wizard Tap Feeds and Speeds Calculator…
– Handles both Form and Cut Taps
– Large Material Database
– Tortoise-Hare slider for pinpoint control in difficult materials
– Metric and Imperial units
– Extensive Thread Database:
Extensive Thread Database…
The thread database includes tapping drill size recommendations with thread percentages for both cutting and form taps.
Want to Avoid Breaking Taps?
Of course you want to avoid breaking taps. A broken tap can ruin your whole day. I hate it, but I have largely quit breaking them by using G-Wizard.
It’s because of that thread database with the % Thread info. Here’s the dirty little secret of tapping:
The recommended hole size for tapping is usually not the best. There is no one perfect size, but you can often do a lot better by considering the thread percentage.
The deal with thread percentage is the recommended tap drill sizes you find in most online charts and on the tap packaging are for 75% threads. That’s conservative from a strength standpoint, but aggressive from the standpoint of over-stressing your tap. Premium tap makers like Guhring actually recommend 60% to 70% percentage of thread for most applications because it significantly lowers the torque force required to tap without giving up much thread strength. That means you’re way less likely to break the tap and you’re sacrificing very little holding strength.
You can learn a bunch more from our article on tap drill sizes, but now you know enough to greatly reduce your chances of breaking a tap.
Our G-Wizard Calculator includes this powerful Tap Speeds and Feeds Calculator and a whole lot more. Try this more powerful calculator (and much more) just by signing up for our 30-day trial. That’s right–most of the calculators can still be used after the trial expires. For example, you can still access the Thread Database with it’s percentage of thread table.
To sign up, simply visit the G-Wizard page.
Need to Program Tapping on a CNC?
We’ve got you covered with this great article on tapping g-code. It even includes information on our easy Conversational CNC Wizard for tapping.
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