How To Tap Holes - Tips

[GBWM]

A short video on the topic of tapping in a home workshop. Some tips might be handy for beginners.
Cheers!

[carloski]

My taps always break below the surface.

[uv8452]

Some additional hints:
1. See that the drilling is rectangular to the surface
2. Countersink before tapping: lightly on the back and to the tap diameter on the front
3. Take special care that the tap is rectangular to the surface. Assess the right angle from 2 sides against a visually clean backdrop or use a tapping guide.

[GBWM]

My taps always break below the surface.

Same as mine. This one was quite lucky.

Some additional hints:
1. See that the drilling is rectangular to the surface
2. Countersink before tapping: lightly on the back and to the tap diameter on the front
3. Take special care that the tap is rectangular to the surface. Assess the right angle from 2 sides against a visually clean backdrop or use a tapping guide.

You're absolutely right. I'm always countersinking the holes if its posible. Also I'm considering to make "tapping guides" - could be handy.

[DIYer]

Thanks GBWM! We've added your Tapping Methods to our Tapping and Threading category,
as well as to your builder page: GBWM's Homemade Tools. Your receipt:

Tapping Methods by GBWM

tags: tapping

[thehomeengineer]

Hi GBWM

I use machine taps when ever possible as they are brilliant. As this video was aimed at "handy for beginners" I hope you don't mind me explaining the differences between the taps you are demonstrating which may help prevent breakages.

The spiral flute taps are used on blind holes as the swarf being cut is forced out of the hole like a drill.

The spiral point taps are used for through holes as the swarf being cut is force in the forward direction out of the bottom of the hole. Therefore these taps should never be used on blind holes, as guaranteed tap breakage will occur.

Both these types of taps unlike the hand taps (taper,second and plug) do not have to be reversed to break the swarf.

As the swarf is cut and removed either out or forward of the hole being tapped. Depending on the tap and hole being cut. Therefore there is no need to break the swarf. By snapping the swarf on a machine tap, the swarf is then able to be trapped in the flutes which in turn jams and the tap and will result in a broken tap. Where if the swarf is removed in one go prevents this build up of swarf in the flutes on machine taps.

The use of a friction tapping head will also reduce the chances of tool breakage with machine taps, if the tool was to jam the friction head should protect the tap from brakeage.

Hand taps on the other hand need to be cleared as the swarf which remains in the flutes as the tool cuts. So if the swarf is allowed to buildup in the flutes on deeper holes this will cause a jam up and damage. The advantage of hand taps can be used in both through and blind holes, but not as a machine tap due to the swarf is unable to clear during the cutting process. hence in your video the hand tap broke when used in the drill.

I hope this helps in the prevention of tap breakages in the future.

Many thanks again
The Home Engineer

[GBWM]

Actually I wasn't aware there are spiral flute and spiral point taps. I thought there are just straight and spiral taps. I will have to try the spiral point taps. What I love about the "internet community" is - you can have some input for others and you can learn something as well. This is really great.

About the taps I was using here - I was feeling at some point of using one of the spiral flute tap some bigger resistance so as always I just decided to break the swarf. Should I ignore this and try to cut with no swarf breakage? I was a bit worried here honestly. Most of my life I was using usual hand taps or machine straight flute taps.

Thanks for your hints!

[thehomeengineer]

I have watched the video again and you are using both spiral point and spiral flute taps. The gold titanium coated taps you are using are machine taps.

The tap for pushing the swarf forward have a distinct negative rake cutting point at the front of the tap.

Spiral flute taps will cut and remove the swarf a bit like swarf from a twist drill.

When tapping with either style you should tap full depth in one go to prevent the build up of swarf around the tap which causes the main failure of any tap.

Obviously there are also other reasons for tap breakage such as using blunt tap, incorrect sized hole, not using tapping oil, as well as poor workmanship such as side loading the tap.

A well clamped job and well supported tap (tapping head or even a drill chuck if a tapping head is not available) and aligned spindle to tapping hole prevents any unnecessary force on the tap. With a good lubricant and sensible cutting speed breakages can be limited.

I hope this has answered your question and thank you for your reply
The Home Engineer

[GBWM]

Oh I get it. So the hand taps I use are spiral point taps if I'm not mistaken?
Thank you!

[thehomeengineer]

Oh I get it. So the hand taps I use are spiral point taps if I'm not mistaken?
Thank you!

Hand taps normally come in a set of 3 plug, 2nd and taper. The cutting edge of these taps are parallel to the flutes so the swarf once cut fills the flute quickly and hence why it is necessary to break the swarf and clear the tap regularly. On a spiral point tap also known as a gun tap the tip of the first few threads are ground back (negative rake) so this then drives the swarf forward through the hole and away from the tap flutes. There is a distinct difference when looking at the end of the lead of the spiral point tap and hand tap set.