A Small Piece Machine Tap Contain So Much Information

Are you “entangled” by the machine tap again?

Blade collapse, chip winding, burr on the tooth, missing tooth and broken

Tapping is a relatively difficult processing procedure because its cutting edge is almost 100% close to the workpiece. So, we should consider various problems that may occur in advance, such as the performance of workpiece, the selection of cutting tools and lathe, and how are the cutting speed rate and feed.

The Selection of Machine Tap

Selection of machine taps

First of all, five questions should be clarified before tapping:

1. What is the material of cutting workpiece?
2. What is the hardness of workpiece?
3. Is the processed screw hole a through hole or a blind hole?
4. How deep is the screw hole or how thick is the workpiece?
5. What are the types and sizes of screw holes to be processed?

Selection of the Flute

The appearance of straight flute, spiral flute, tip spiral flute

Straight flute tap: The first choice with more wide application, Through-hole or blind hole, non – ferrous or ferrous metals can be processed, the price is the cheapest. But the pertinence is also poor.

Spiral flute tap: suitable for blind hole on middle or low hardness material. When cutting, it’s very sharp. But the disadvantage is the durability is not that good.

Spiral point flute: It is beneficial for chip removal. And compared with straight flute type, it’s more durable and suitable for through holes.

1. Simple Comparison of Straight Flute Machine Tap, Spiral Flute Machine Tap, and Tip Spiral Flute Machine Tap

• Spiral Flute Machine Tap

Spiral flute taps are mainly used for blind holes. When processing on the high hardness and intensity workpiece, smaller helical angle taps could improve the intensity during processing.

Comparison of Spiral Flute Taps and  Spiral Point Taps

Spiral flute tap is suitable for blind holes, and chips removal are discharged upward. While the chips of spiral point taps are discharged downwards.

The Threading of Special Workpiece

Machinability of the workpiece is the key to thread difficulty or easy. It is very important to change the geometric shape of the cutting part of the tap, especially its rake angle and the degree of the concave amount.

A process on High-Intensity Workpiece

For high hardness material, front angle and the amount of concave are usually small thus increasing the strength of cutting edge. The long chip material needs a larger rake angle and concave amount in order to roll and break chips. Machining on harder workpiece requires a larger back angle to reduce friction and fully cooling the cutting edge.

A process on Different Hardness Material

For example, when processing on stainless steel, spiral flute taps with smaller helix angle will be selected to cope with the hard and sticky characteristic, so that we can carry out durable cutting and chip removal of blind hole tapping.

Common Problems in Tapping Process of Taps

	When the cutting force is too large, or the tap is badly worn and not replaced in time, the cutting resistance will suddenly become large, then the tap will break.
	The head of the tap is worn out and it is still used again, which leads to poor finish of the machined thread surface.
	Unreasonable design of tap groove  leads to unsmooth chip removal, then leads to chip winding on the tap.