What kind of taps to thread in plastic material

[RudydG 62]

Many of my designs require assembling, i print threaded holes, but they have to be "cleaned" (i mean tapped anyway)

Now i use standard machine taps, and follow the basic rules, not to fast, lubricating, and it kind of works, but i think it can be done even better, as these taps are not designed for plastics, and the evacuation of the waste is sometimes problematic.

Anyone got any tips regarding tapping in plastics?

[AndersK 59]

Are you using straight taps in blind holes?

Try spiral taps instead then. They are designed to pull the chips upwards instead of pushing like the straight taps.

 

 

 

 

 

 

[RudydG 62]

2 hours ago, AndersK said:

Are you using straight taps in blind holes?

Try spiral taps instead then. They are designed to pull the chips upwards instead of pushing like the straight taps.

 

 

 

 

 

 

I use straight taps yes. Almost never blind holes, but the evacuation of the debris is the main problem. Maybe i can try these.

Thanks.

[geert_2 558]

I tried tapping too with straight taps (I had never seen those spiraling ones, didn't know they existed), but indeed it didn't work well. Even not when tapping manually and reversing very often: 1/4 turn forward, 1/8 turn backwards. Chips would get stuck and the plastic would melt (even at very low speed, lots of cooling time and lubrication). Also, threads were very weak and got worn-out very soon (M3, M4, M5).

 

So for most of my models, I now use standard nylon M4-screws instead, with a caged nylon nut that can not fall out. This goes a lot faster, and it works better: the thread (nylon nut) is much stronger than a 3D-printed and tapped one, and it can be replaced if required.

 

Mostly variations on these concepts:

 

1. Fully caged nut; the backside of this opening is closed, it is only open on top. If the opening is tight enough, the nut will even be clamped. If slightly wider, it will wiggle, but not fall out (unless you totally remove the screw and hold it upside-down).

 

2. Another variation on the same concept:

 

 

3. Recessed hex opening for keeping the nut. This is a test model to try-out required tolerances for an M4 nut (ca. 7mm diameter between flats).

 

4. I haven't tried this yet, but someone (I forgot the name) suggested using "metrinch" cages for clamping the nuts. They seem to wear-out less than traditional hex holes, and allow tighter tolerances, since problems with 3D-printing are mostly around corners.

 

 

[AndersK 59]

Maybe insert threads could be a better option.

You heat them and press them in.

 

 

Guess you haven't seen a tap like this neither. 😉

Designed for difficult materials to reduce friction while tapping . 

 

[RudydG 62]

2 hours ago, geert_2 said:

I tried tapping too with straight taps (I had never seen those spiraling ones, didn't know they existed), but indeed it didn't work well. Even not when tapping manually and reversing very often: 1/4 turn forward, 1/8 turn backwards. Chips would get stuck and the plastic would melt (even at very low speed, lots of cooling time and lubrication). Also, threads were very weak and got worn-out very soon (M3, M4, M5).

 

So for most of my models, I now use standard nylon M4-screws instead, with a caged nylon nut that can not fall out. This goes a lot faster, and it works better: the thread (nylon nut) is much stronger than a 3D-printed and tapped one, and it can be replaced if required.

 

Mostly variations on these concepts:

 

1. Fully caged nut; the backside of this opening is closed, it is only open on top. If the opening is tight enough, the nut will even be clamped. If slightly wider, it will wiggle, but not fall out (unless you totally remove the screw and hold it upside-down).

 

2. Another variation on the same concept:

 

 

3. Recessed hex opening for keeping the nut. This is a test model to try-out required tolerances for an M4 nut (ca. 7mm diameter between flats).

 

4. I haven't tried this yet, but someone (I forgot the name) suggested using "metrinch" cages for clamping the nuts. They seem to wear-out less than traditional hex holes, and allow tighter tolerances, since problems with 3D-printing are mostly around corners.

 

 

I used this method before, with metal nuts, but is to much "work" in my case. And my threads are only used like 10x, they hold very well (i print them and only clean them up)

[RudydG 62]

1 hour ago, AndersK said:

Maybe insert threads could be a better option.

You heat them and press them in.

 

 

Guess you haven't seen a tap like this neither. 😉

Designed for difficult materials to reduce friction while tapping . 

 

This was a method i wanted to use already. Think it is the best solution. Surely if the heater is build like that, seems a very easy job!

[geert_2 558]

1 hour ago, AndersK said:

Maybe insert threads could be a better option.

You heat them and press them in.

 

 

Guess you haven't seen a tap like this neither. 😉

Designed for difficult materials to reduce friction while tapping . 

 

 

Indeed, I haven't seen this one.   :-)   Seems like I should bring my knowledge about tools up to date.

 

The inserts I have seen on Youtube videos, but not tried myself yet. If you have used them, do they stick well, and does the molten plastic reflow around the ribs well?

 

I have also seen a similar concept, in which the brass insert had to be screwed into the plastic hole, with a sort of self-tapping one-way screw on its outside, so this would get stuck and stay in there. But again, no personal experience.

 

[AndersK 59]

Sorry, should have mentioned that I haven't tried them myself, yet...