TG collets (TG38 – TG200)

TG is the heavy-grip alternative to ER. It trades reach for holding power: more slots mean more faces clamping the shank, and the shallower 4° seat angle converts nut torque into more grip. The price you pay is a bigger nut and a much smaller collapse range.

Dimensions by size

Compiled from five published tables. Where makers disagree the range is shown and the conflict is called out below the table.
Size	Body Ø (mm)	Overall length (mm)	Capacity (mm)	Agreement
TG38	14.07	26.0	#0 tap to 5/16" tap	Single source
TG50	19.3	36.5	1.1 – 13.5	Length single source; capacity 2 sources agree
TG75	27.0	46.8	2.6 – 20 lower bound varies	Length & body agree; lower bound conflicts
TG100	32.5 / 35 conflict	60.4	2.6 – 25.5	Length agrees; body Ø conflicts
TG150	47.6 / 50.8 conflict	76.2	11.6 – 40 lower bound varies	Length agrees; body Ø and lower bound conflict
TG200	67.8	82.6	25 – 50 (1"–2" in 1/4" steps)	Single source

Conflicts we did not resolve for you.

TG100 body Ø: one maker publishes 32.5 mm, three publish 35.0 / 35.03 mm. The 35 mm figure is better corroborated.
TG150 body Ø: 47.6 mm versus 50.8 mm — two sources each way.
Capacity lower bounds: TG75 is published as 4 mm, 2.6 mm, 3 mm and 1 mm by different makers; TG150 as 4 mm, 2 mm, 11.6 mm and 12 mm. The upper bounds agree well (20 and 40 mm); the lower bounds do not.

Because TG has almost no collapse range, the lower bound matters less in practice than it does on ER — see below.

What makes TG grip harder than ER

	TG	ER
Seat angle at the collet base	4°	8°
Slots / clamping faces	More slots, so more faces on the shank	Fewer
Collapse range	Very small — treat as one size per collet	About 1 mm per collet (0.5 mm on ER11)
Nut diameter	Large	Comparatively slim
Grip under heavy load	Higher	Lower

The 4° seat angle is the mechanical reason: a shallower wedge converts the same nut torque into more radial force, in the same way a Morse taper holds with less pull than a steep taper does. The published collapse range is quoted by one maker as “a full 1/64" (0.5 mm)”, but the practical rule from every other source is simpler — buy one TG collet per shank diameter.

The reason people stop using TG

It is not grip. It is reach. The TG nut is substantially larger than the collet body, so when you mill a pocket the nut hits the wall before the cutter reaches the floor. The usual workaround is to buy extended-reach end mills, which costs you rigidity — the exact thing TG was supposed to give you.

So the honest selection rule is:

Use TG when the shank is large, the cut is heavy, the tool is long, and the work is open.
Use ER when you need to reach into pockets, swap diameters often, or cover odd shank sizes with a small number of collets.
Use C power or SK when the specific failure you are chasing is the cutter pulling out.

TG collets and TG chucks

TG collets are not interchangeable with ER collets even when the capacity happens to overlap — the seat angle and the nut thread differ. For nut torque values see nuts, spanners and torque.