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MT-3 Spindle Collets & Adapters

A collet is safer to use than a chuck & typically has a lower total indicated readout (TIR). The ER-40 double-angle collet is an industry standard affording high precision & ready availability. An MT-3 collet holder is available. Each ER-40 collet has a wide (0.04") clamping range so a 23 collet set provides continuous size coverage from 0.12" (nominal 1/8") through 1.02" (nominal 1") or 3.05mm ~ 25.9mm. The 15 sizes that come in the set (fitted case included) are shown in the table in bold numbers; the other eight collets (all n/32nds sizes) were purchased separately. Specifications: wide holding range, accuracy 0.0001", self-releasing design, high precision collet chuck with different shanks available (MT-3, MT-4, MT-5, R-8) & a spanner wrench. The MT-3 collet chuck I received had a ½-12 TPI tapped hole for the drawbar (not a common thread). I made a drawbar from rod threaded ½-12 TPI on one end & ½-13 TPI on the other end. There are milled flats for a wrench.Snap the collet into the nut's eccentric ring before screwing it onto the spindle. This ring is the collet extraction mechanism. Do not tighten the nut onto an empty collet as damage could result.

ER-40 collet set (above). Collet chuck shown with a MT-3 shank.
The plugs are used to fill the collet when holding very short parts;
allows good clamping without distorting/damaging the collet.
Each plug is stamped with the collet's nominal size.
Also see chucks for 5C collets.

Collet table showing continuous size coverage.
White sizes were the original set & green sizes were added.

MT-3 collet set from Phase2+. Drawbar made from ⅜-16 threaded stock. Steel end plug machined to fit the spindle hole. Flare nut with a washer used. Collet sizes range from ⅛" to ¾" by 1/16ths (no continuous size coverage). To remove a part, make the nut flush to the end, hold the part & collet while gently knocking out the bar using a large, hard plastic-faced mallet or brass hammer.

MT-3 collet set from Phase2+ & a ⅜"-16 drawbar made from threaded rod.

¾" MT-3 collet mounted into the Jet's spindle.

These MT-3 end mill holders from Phase2+ each have a set screw that engage the end mill flat.
These holders are for both ⅜" & ½" shank end mills. For use with the Jet BD-920N lathe spindle.

MT-3 to ¾-16 TPI taper (from LMS), allows using Taig or Sherline chucks & other accessories on the Jet BD-920N or other MT-3 machines. Allows accurate fabrication of large-shank end mill holders for use on the Taig mill & lathe. I've made end mill holders by both reaming & boring. Boring is very accurate (0.0005" TIR) but a slower process. It is better to indicate (mount) the blank arbor by its threads before boring than to grip it on the outside surface.

A finished end mill holder for the original-design Taig lathe/mill. Blank arbors (steel) #1132, from Taig.
⅜" shank end mill shown (Enco). Milled flats for a ⅞" wrench & uses a ¼-20 set screw.
 This type of arbor is not needed (nor mountable) if you use the superior upgraded
Taig mill ER-16 spindle but is still usable for the lathe.

Caution: Large end mills easily exceed a Taig's capacity thus requiring small cuts.

Taig collet on the Jet 9x20.  Also see small chucks mounted on the Jet using the MT-3 to ¾-16 TPI taper.
Taig collets are size limited & made of soft steel but can be easily customized e.g., threaded for 10-32 to turn down screws.
The 5C collet chuck or ER-40 are better work-holding alternatives.