(1) Type of hole and chip handling
(2) Extrusion cutting, spiral chip flute tap
- Ideal for blind holes and deep hole machining
- Recommended for materials that produce blocking chips
- Ideal for interrupted cutting
The spiral chip flute tap is very thin and is the most vulnerable part of the tap design. Therefore, the speed is 30% to 40% lower than the straight flute tap to avoid breakage.
(3) Pull out the cutting
(4) Straight flute taps
- The strongest tap
- Recommended for materials that are subject to chip breaking, such as brass and cast iron or hardened steel
- Usually requires coolant or gas to flush the chips in the flutes
- Can have a variety of cutting cones
– Taper (Form A) “A” – initial cone
– Plug (Forms B & D) “B/D” – cone
– (Form C) “C” – semi-flat bottom or modified flat bottom
– (Form E) “E” – flat bottom
(5) Squeeze tap: The processing feature is that no chip is generated in the through hole or the blind hole.
(6) Comparison between cutting tap and extrusion tap
(7) Influence of bottom hole size on extruded thread
Tap coating
(1) Advantages of coating
1 surface treatment
- Improve the appearance of HSS taps
- Does not change the size of the tap
2 tap life is improved
- High wear resistance
- Reduce friction and power consumption
- Reduce chipping and breakage
- A little increase in surface hardness
3 improve the surface quality and dimensional accuracy of the screw hole
- Cutting edge remains sharp
- Lubricating
- Reduce load and scratches
- Minimum built-up edge
(2) What is built-up edge?
The workpiece material is welded or sewn to the accumulation on the chip edge.
(3) Traditional surface treatment
(4) Film coating
The success of tapping
(1) Determine the percentage of threads
The drill hole size determines the percentage of the thread bottom diameter to the thread height. The larger the drill diameter you use, the smaller the thread height ratio achieved!
(2) Selection of bottom hole size
The preferred thread height is 65% to 70%!
The 83% height thread is only 2% larger than the 65% height thread, but the tapping torque is more than twice!
(3) Frequently asked questions
1 cause the cause of the topping
- Manual tapping
– Manual feed is not coordinated, feed is too fast or too slow
- Machine tapping
– Improper programming of asynchronous tapping cycles
- Screw machine
– Lead screw wear or screw adjustment nut loosening produces backlash
- Cam feed machine
– Concave contours are not right or worn
- Pneumatic or hydraulic machine
– Uncontrollable, too high or too low
- Gear feed machine
– improperly adjusted gears or worn backlash
2 solve the problem of topping
For the most precise threads, the feed should be synchronized with the spindle speed! The feed and spindle rotation must match the thread pitch.
(6) Advantages of CNC machine tool synchronous tapping
- Thread depth control
- Hole to hole size is consistent
- Eliminate topping
- Can re-attack if necessary
(7) Choice of tool holder
- For asynchronous tapping
– CNC machine with drilling feed with fixed tapping cycle
– cam, gear, pneumatic, or hydraulic feed mechanism
- For synchronous tapping
– When you encounter an oversized/small size thread
(8) Tool holder maintenance
Proper tool holder maintenance ensures high quality threads and the life of the tap.
- Internal mechanisms should not have chips and debris
- Regular lubrication ensures flexible movement of parts and prevents rust
- Test the handle frequently, especially when using water-soluble coolant
Fault discharge
(1) The thread is too large
Tapping CNC setting
When tapping a CNC machine without a rigid tapping cycle:
- Programming feed rate to 95%~98% of tap reversal
- Use an elongated handle or a telescopic handle with compression lock
When tapping on a CNC machine with a rigid tapping cycle:
- Tap lead programming for feed 100%
- Use integral shank or synchronous shank
If the top is cut, the end of the thread gauge is passed:
- Reprogramming, following the "non-rigid" procedure
- Consider using a quick-change connector. Can have a minimum of "floating"
(2) Chip winding
Change the wire cone
→Straight slot
→Small helix angle
- Shortened cutting cone
- Change the front corner shape
- Increase the number of slots
- Change speed
- Small hook
- If it is rigid tapping, increase the boring cycle
- Consider extrusion taps
(3) Lubrication selection
For tapping, the purpose of lubrication is to reduce friction. Therefore, in general, the tapping uses a lubricant instead of a coolant; in the case of a coolant, an EP (ultra-high pressure) or HP (high pressure) additive is added.
The tap has a fixed amount of feed, controlled by the pitch of the tap, and the feed rate can be adjusted to the control load.
(4) Coolant application
Tap selection basis
Before choosing a tap, we need to understand:
- Type of hole, through hole, blind hole or deep hole
- Minimum drilling depth
- Minimum thread depth required
- Whether to consider extrusion taps
- Tapping workpiece material
