ER20A M25x1.5 Hexagon Collet Clamping Nut For CNC Milling Collet Chuck Holder

Product Description

Does this nut fit your holder? If the worn nut is marked ER20A and takes an M25 x 1.5 thread, yes. It threads onto any ER20 collet chuck holder and clamps any ER20 collet. The body is steel with a black coating finish and the drive is a hexagon with 6 flats, so a tool change needs one standard hex wrench and nothing else. Nominal thread diameter 25 mm, pitch 1.5 mm. Supplied as the nut only - the holder and the collet stay on the machine. Price on request.

A clamping nut that is failing shows up three ways: the collet stops seating square and runout climbs, the thread galls so the nut binds halfway down, and a replacement ordered from a photograph arrives with the wrong thread because ER16, ER20 and ER25 nuts all look alike at arm's length. This one is specified by standard and thread, so the third problem cannot happen and the first two become scheduled wear.

It is a hexagon clamping nut built to the ER20A standard with an M25 x 1.5 thread: 25 mm nominal thread diameter, 1.5 mm pitch. It draws an ER20 collet down into the chuck taper and keeps it there while the cutter is in the material. The hexagon body carries 6 flats, so the drive side is a plain wrench surface with no slots to chip and no pin spanner to lose.

Compatibility follows one rule: nut standard to holder standard. It fits ER20 collets and ER20 collet chuck holders, which covers CNC milling spindles, machining centres and woodworking router heads running the ER20 series. It does not fit an ER16 or ER25 holder, because those take a different nut standard and thread.

Body is steel, finish is black coating. Supplied as the nut alone, so the collet chuck holder and the collet are separate items. Price on request.

Product Features

Every item below is either a fit dimension or a material choice. On a clamping nut those are the only things that decide whether the cutter runs true.

• ER20A standard. Cut to the ER20A nut standard, so it is matched to a holder by its marking instead of by measuring a thread.
• M25 x 1.5 thread. 25 mm nominal diameter with 1.5 mm pitch; it screws onto the M25 nose of an ER20 holder.
• Hexagon drive. 6 flats, so a tool change is one wrench movement rather than a pin spanner and a slot to line up.
• Steel body. Thread and seating face are steel, and those are the two surfaces that carry clamp load into the collet.
• Black coating finish. A coated outer surface, so a nut that sits in a wet holder between jobs does not come back rusted.
• ER20 collet fit. Takes any ER20 collet already in the rack, so one nut covers the whole collet set on that spindle.
• CNC milling duty. Supplied as an accessory for CNC milling, and listed the same way for woodworking router spindles.
• Spare-part supply. Shipped as the nut on its own, so a worn one is replaced without disturbing the holder.
• Inspectable seating face. The seating face is what pushes the collet in, so it is the surface to look at on every tool change.

Product Parameters

Product Advantages

The usual choice is between buying a whole new holder assembly and ordering a nut from a photograph. Neither is necessary once the part is specified by standard.

• You replace the nut, not the holder. The nut is the wear item. Holder and collets stay on the machine, so the repair is one part instead of an assembly.
• It fits by standard, not by guess. ER20A on the standard line and M25 x 1.5 on the thread line are both checkable against the old nut before you order.
• One wrench, no lost pin spanner. 6 flats take a standard hex wrench, which is already in the toolbox on a machine that runs ER20.
• The collet keeps its seat. Clamp load passes through the nut's seating face into the collet, so replacing a worn nut restores the surface that was doing the pushing.
• Corrosion is pushed back. A black coated body means a nut left in a coolant-wet holder between shifts does not seize or rust.
• Fewer part numbers on the shelf. One ER20A nut serves the whole ER20 collet set, so the stores line stays one item long.
• Orderable from two lines of text. Thread and standard are all a supplier needs, so nobody has to identify a nut by photograph.

Frequently Asked Questions

Will this nut fit my ER20 collet chuck holder?

Yes, if the holder is marked ER20. The nut is ER20A with an M25 x 1.5 thread, and those two markings are the whole check: nut standard to holder standard.

What thread does it use?

M25 x 1.5 - a 25 mm nominal thread diameter with a 1.5 mm pitch. It screws onto the M25 nose of an ER20 holder, so an M19 or M32 nut from another collet series will not interchange.

Do I need a special wrench?

No. The body is a hexagon with 6 flats, so any standard hex wrench that fits the flats will do - no pin spanner and no slotted bearing nut.

Does it come with a collet or a holder?

No. It is supplied as the clamping nut alone. The collet chuck holder and the ER20 collet are separate items and stay on the machine.

Can I use it on an ER16 or ER25 holder?

No. This nut is cut to ER20A with an M25 x 1.5 thread. Other collet series use a different nut standard and a different thread, so they will not fit each other.

What is it made of, and what is the finish?

Steel body, black coating finish. The thread and the seating face are the two steel surfaces that take the clamp load.

Can I use it on a woodworking router spindle as well as a milling machine?

Yes, as long as that spindle runs ER20. The nut is listed as a CNC milling accessory and as a woodworking machinery accessory, and the fit rule is the same in both cases.

How do I tell whether my old nut needs replacing?

Look at two surfaces. A galled or flattened thread and a scored seating face are the two signs that the nut is no longer pulling the collet in square.