Die Size, Not Brand Names

Ignore the marketing list of connector names and read the die widths. A terminal with a 1.6 mm wide barrel needs a 1.6 mm nest. If the smallest nest is 1.9 mm, your JST PH contacts will be crushed flat instead of rolled inward.

True B-Crimp Profile

A correct open-barrel die curls both wings inward and down into the strands, forming a B shape in cross section. Cheap tools fold the wings flat or overlap them. If the crimp looks like a squashed tube, the tool is wrong for the job.

Ratchet vs Precision Squeeze

A ratchet will not release until full compression, which makes results repeatable for beginners. A precision non-ratcheting tool like the PA-09 lets an experienced user feel the crimp and stop short on delicate contacts. Both are valid, for different people.

Separate Insulation Crimp

A proper terminal has two sets of wings: a conductor crimp on bare strands and a rear insulation crimp that takes the strain. Tools with a single flat nest cannot form both correctly, and the strain relief is what stops the wire fatiguing.

Jaw Alignment & Build

Hold the jaws to a light. Any visible offset between the upper punch and lower nest produces lopsided crimps forever. Japanese-made tools hold alignment far better than pressed-steel imports, which is most of what you pay extra for.

If you work with the whole JST family rather than just XH, the SN-2549 is the smarter ratchet to buy. Where the SN-28B starts at DuPont size, this one adds finer nests that reach JST ZH 1.5 mm and PH 2.0 mm, the two pitches that show up constantly on LiPo balance leads, small sensor boards, GPS modules and drone flight controllers. It still handles VH 3.96 mm and DuPont at the coarse end, so a single tool covers most of a hobby electronics bench. The trade-off is that the finest nest still cannot do JST SH 1.0 mm, and the ratchet pressure is slightly firm for very thin conductors.

The IWS-3220M is what you reach for when the terminals get genuinely small. Its range runs from 0.03 mm² to 0.52 mm² (AWG 32 to 20), which is the territory of JST SH 1.0 mm, ZH 1.5 mm, D-Sub machine contacts and the tiny Molex and JAE pins used inside cameras, displays and drone electronics. It gives you the repeatability of a ratchet at a size where most tools simply cannot reach, and that combination is rare. Expect a learning curve: at this scale the terminal has to sit perfectly in the nest, and holding a 32 AWG strand steady while you close the jaws takes practice and often tweezers.

The PA-20 is the PA-09’s bigger sibling and the natural companion to it. Its four nests span roughly 1.6 mm to 2.3 mm barrel widths, picking up exactly where the PA-09 stops: JST VH 3.96 mm and SM contacts, Molex KK and SL terminals, TE and Hirose housings, and thicker DuPont-style pins in the 22 to 18 AWG range. Same Japanese grinding, same clean B-crimp, same non-ratcheting feel. Own the PA-09 and PA-20 together and you have properly formed crimps from hair-thin signal wire up to power leads, which is why this pair turns up on so many professional benches.

The SN-01BM is the budget answer to a specific complaint: the SN-28B is too coarse for small signal terminals. This one narrows the range to 0.08 to 0.5 mm² (AWG 28 to 20) and shapes the nests for JST PH 2.0 mm and XH contacts, DuPont pins and D-Sub signal contacts. Giving up the big 3.96 mm nest buys you noticeably better results on the small stuff, which is the right trade for anyone wiring sensor breakouts, servo leads and module harnesses. It is not in the ENGINEER class for alignment, but per dollar it is the best small-terminal ratchet here.

Once a harness carries real current, the terminals get bigger and the 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, PC power and fan connector pins, and non-insulated spade terminals. It is the tool that finishes the set: pair it with an SN-01BM or SN-2549 and you have signal wiring and power wiring both covered on a modest budget. Do not expect it to do anything delicate; the smallest nest here is coarse by design.

Buying one tool for everything?

Get the ENGINEER PA-09. It covers the widest useful band of JST and DuPont contacts with the best crimp quality of anything here.

Making Arduino jumper harnesses?

The iCrimp SN-28B plus a bag of DuPont pins and shells is the cheapest route to tidy, custom-length 2.54 mm cables.

Repairing drone or LiPo leads?

Balance leads and flight-controller pigtails are JST PH and ZH. The SN-2549 is the one cheap ratchet that reaches both.

Working below 24 AWG?

Camera ribbons, JST SH 1.0 mm and D-Sub machine pins need the IWS-3220M, which ratchets all the way down to 32 AWG.

Building products, not prototypes?

Run the PA-09 and PA-20 pair. Repeatable B-crimps from 32 AWG signal wire to 18 AWG power, with jaws that stay aligned.

Crimping power and fan pins?

JST VH, larger Molex and 4.8 / 6.3 mm spades need the SN-48B. Pair it with a small-terminal crimper for full coverage.

Do I really need a dedicated crimping tool, or can I just solder the pins?

You need the tool. Soldering wicks solder up into the stranded wire and turns a flexible conductor into a rigid one, so the wire snaps right where the solder stops, usually after a few weeks of vibration or flexing. Open-barrel terminals are designed for a cold gas-tight crimp: the conductor wings roll into the strands and the insulation wings take the mechanical strain. A correctly crimped DuPont pin will typically outlast the wire. If you only ever make a handful of connections, pre-made jumper cables are a fair alternative, but any custom-length harness needs a real crimper.

What is the difference between an open-barrel and a closed-barrel crimp?

An open-barrel terminal starts as a flat U shape with two pairs of wings, and the die curls those wings inward to form a B-shaped cross section. JST, DuPont, Molex KK and D-Sub contacts are all open barrel. A closed-barrel terminal is already a tube, like an insulated ring or spade lug, and needs a completely different oval or hex die that compresses the tube. This is why a car-audio spade crimper makes a mess of JST pins: the die shape is wrong, not just the size. Every tool in this guide is an open-barrel crimper.

Why do my DuPont crimps keep pulling out of the wire?

Almost always one of four things. First, too much insulation stripped, so the rear wings clamp bare wire instead of jacket and there is no strain relief: strip about 2 mm and no more. Second, the terminal is sitting in a nest that is too large, so the wings fold over instead of curling in. Third, you are crimping both wing pairs in one nest, when the conductor and insulation wings usually need separate positions. Fourth, the wire gauge is too thin for the terminal, in which case fold the stripped end back on itself to double it up before crimping. A good crimp survives a firm tug on the wire.

Ratcheting or non-ratcheting: which should I buy?

If you are new to crimping, buy a ratchet. It will not release until the jaws reach full compression, which removes the most common beginner error of under-crimping and gives you repeatable results without any feel for the tool. Experienced users often prefer a precision non-ratcheting tool like the ENGINEER PA-09 because you can stop short on a fragile micro contact, adjust position mid-squeeze and back out of a misaligned terminal without damaging it. Most ratchets have an adjustable pressure wheel, and it is worth dialling that in on scrap terminals before you trust it.

Can one tool cover every JST family from SH to VH?

Not properly. JST SH contacts are around 1.0 mm wide and JST VH contacts are close to 4 mm, and no single set of dies forms a correct B-crimp across that whole span. The practical answer is two tools. A small-terminal crimper such as the PA-09, SN-2549 or SN-01BM covers SH, ZH, PH, XH and DuPont, and a larger one such as the PA-20 or SN-48B covers VH, SM, Molex and spade terminals. Any listing claiming full SH to VH coverage in one tool is stretching the truth, and the crimps at one end of the range will be poor.