Die Width, Not Brand Lists

Match the nest width to your terminal barrel. A nest that is too wide folds JST PH wings flat instead of rolling them into the strands.

A True B-Crimp

A good open-barrel die curls both conductor wings inward into a B shape. Flat or overlapped wings mean the wrong tool or the wrong nest.

Ratchet or Precision

A ratchet will not release until the crimp is complete, which helps beginners. Precision pliers like the PA-09 let you feel the crimp on fragile micro pins.

Insulation Crimp

Terminals have a second set of wings that grip the jacket. That strain relief is what stops a sensor lead snapping where it leaves the pin.

Jaw Alignment

Hold the closed jaws to a light. Any offset between punch and anvil gives lopsided crimps forever, which is what the premium tools fix.

If your bench is full of JST connectors rather than plain Dupont, the SN-2549 is the smarter budget ratchet. It adds finer nests that reach JST ZH 1.5 mm and PH 2.0 mm, the pitches you meet on LiPo connectors, small sensor boards and GPS modules, while still handling XH, VH 3.96 mm and Dupont 2.54 mm at the coarse end. One tool covers most of a hobby ESP32 bench. The finest nest still cannot form JST SH 1.0 mm contacts, though.

When the terminals get genuinely tiny, the IWS-3220M is the ratchet that can still reach them. Its range runs from 0.03 to 0.52 mm² (AWG 32 to 20), the territory of JST SH 1.0 mm, small Molex and JAE pins and D-Sub contacts. That makes it the tool for Qwiic and STEMMA QT style sensor cables, camera and display pigtails and the micro connectors on compact ESP32-S3 and C3 boards. Loading a terminal at this scale takes a steady hand and often tweezers.

The PA-20 is the bigger sibling of the PA-09, with the same Japanese grinding and the same feel but nests sized for larger open-barrel contacts and AWG 28 to 18 wire. It picks up where the PA-09 stops, which suits thicker power leads, larger JST and Molex style terminals and heavier Dupont-style pins. Own both and you can crimp everything from thin signal wire to the 18 AWG leads that feed a WLED strip or motor driver with clean, repeatable results.

The SN-01BM narrows the range to AWG 28 to 20 and shapes its nests for JST PH 2.0 mm and XH contacts plus Dupont pins. Giving up the big 3.96 mm nest buys noticeably better results on small terminals, which is the right trade if you mostly make LiPo battery pigtails for ESP32 boards with a PH 2.0 socket, servo leads or short sensor harnesses. It is not in the ENGINEER class for alignment, but it is a cheap way to get decent PH crimps.

Once a harness carries real current, the terminals get bigger and small crimpers run out of nest. The SN-48B handles 3.96, 4.8, 5.08 and 6.3 mm open-barrel terminals across AWG 26 to 16, covering JST VH and SM contacts, larger Molex pins and small spade terminals. That suits the power side of ESP32 builds: LED strip feeds, 12 V pump and solenoid leads and power supply wiring. Pair it with a small-terminal crimper rather than using it for signal pins.

8. ENGINEER PA-21 Universal Connector Crimping Pliers

Another 175 mm, made in Japan ENGINEER plier, the PA-21 targets 1.6 to 2.5 mm contact sizes. It sits between the PA-09 and the larger tools, which makes it a good precision choice if most of your work is Dupont, XH and similar mid-size open-barrel terminals rather than tiny SH pins.

9. Hozan P-707 Open Barrel Crimping Tool

The Hozan P-707 is a Japanese open-barrel crimper with 15 large and small dies in one tool and a toggle action. It suits a shared lab or small production bench where many terminal sizes come through, but it is bigger and costs more than a hobbyist needs for a few ESP32 harnesses.

One tool that does it properly

The ENGINEER PA-09.

Tight budget, mostly Dupont

The iCrimp SN-28B.

Lots of JST connectors

The iCrimp SN-2549.

Tiny SH and micro pins

The iCrimp IWS-3220M.

Battery pigtails only

The iCrimp SN-01BM.

Power and LED wiring

The iCrimp SN-48B plus a small-pin tool.

Can I just solder Dupont and JST pins instead of crimping?

You can, but it is not a good idea. Solder wicks up the strands and makes the wire stiff right where it leaves the terminal, so it tends to crack after vibration or repeated handling. Open-barrel terminals are designed for a crimp, with the conductor wings gripping the strands and the insulation wings providing strain relief.

Which JST connector does my ESP32 board use?

It varies. Many ESP32 boards with a battery input, such as Feather and LOLIN style boards, use a JST PH 2.0 mm socket, while Qwiic and STEMMA QT sensor ports use JST SH 1.0 mm. Larger battery packs and chargers often use JST XH 2.5 mm. Check the board’s documentation or measure the pin pitch with calipers before buying terminals.

Why do my Dupont crimps pull out of the wire?

Usually one of four things: too much insulation stripped (aim for about 2 mm so the rear wings grip the jacket), a nest that is too large, crimping both wing pairs in one nest when they need separate positions, or wire too thin for the terminal. Folding a thin stripped end back on itself before crimping helps.

Ratcheting or non-ratcheting crimper?

If you are new to crimping, buy a ratchet such as the SN-28B or SN-2549. It will not open until the crimp is complete, which removes the most common under-crimp mistake. Precision non-ratcheting pliers like the PA-09 suit experienced users who want to feel the crimp on delicate micro contacts.

Can one crimper cover JST SH all the way to VH?

Not properly. SH contacts are around 1 mm wide and VH contacts are close to 4 mm, and no single set of dies forms a good crimp across that whole range. Plan on a small-terminal tool (PA-09, SN-2549, SN-01BM or IWS-3220M) plus a larger one (PA-20 or SN-48B) if you need both ends.