Take a look at your plastic fasteners. For instance look at Tri-Lobe, Hi-Lo Screws for Plastics or 30 degree screws:

The 45 Degrees Thread Profile Tri-Lobe Thread Forming Screws is use special for Plastics Material,

provided High-Resistance to Pull-out and Steip-out. Use lower Drive Troque and smaller Boss.


Here is a sell sheet for some:
Thread-forming screws are ordinarily less
expensive than thread-cutting screws and
the threads they produce offer the highest
resistance to backout. Their advantages
are offset to a degree, however, by the fact
that they can cause a high and concentrated
hoop stress. While the stiffer plastics
usually cannot absorb this stress, resins
with flex moduli of 1,380 MPa (200,000
psi) or less can. Included in this category
are most unreinforced Zytel® nylon resins
(the new family of crystalline nylons with
amorphous-like properties being specifically
excepted). Use of conventional
thread-forming screws with these resins
produces strong joints.
Stress generated by thread-forming screws
generally is too great for resins in the second
category, those plastics with flex moduli
ranging between 1,380 and 2,758 MPa
(200,000 to 400,000 psi), and thread-cutting
screws should be employed. Delrin®
acetal resin is an exception, however, as are
those grades of Zytel® based on 612 nylon.
The low coefficients of friction offered by
these two materials literally smooth the
way, permitting threads to be formed with
a minimum of stress.
When using a thread-forming screw with
material in this stiffness group, however,
consideration should be given to Trilobe™
or Hi-Lo™ screws, specifically designed to
reduce radial pressure.

FYI ABS has a Flexural Modulus 1.61 - 5.90 GPa / 233 - 856 ksi