Tapers: Self-holding
A self-holding taper is a type of machine tool spindle/taper shank connection where the friction between the male and female tapered surfaces is strong enough to hold the tool in place during operation without the need for a drawbar or clamping screw.
The contact area is large.
The taper angle is small (usually 2°–3° included angle).
This shallow angle creates enough friction to resist slipping under torque.
JACOBS TAPERS
Key Features of Jacobs Tapers
Purpose: Quick, secure way to mount a drill chuck.
Holding method: Like Morse tapers, Jacobs tapers rely on friction between shallow-tapered male and female surfaces.
Taper angle: Very small (about 2.33° included, depending on the size) so the chuck stays put under torque but can still be removed without excessive force.
No threads or screws: Purely a push fit — tap it in to seat, wedge to remove.
JACOBS LARGE SMALL TAPER# DIAMETER DIAMETER LENGTH --------------------------------------- 0 .25000" .22844 .43750 1 .38400 .33341 .65625 2 .55900 .48764 .87500 2 short .54880 .48764 .75000 3 .81100 .74610 1.21875 4 1.12400 1.03720 1.65625 5 1.41300 1.31611 1.87500 6 .67600 .62409 1.00000 33 .62401 .56051 1.00000 ---------------------------------------
MORSE TAPERS
Many cutting tools especially drills, reamers, counterbores, countersinks come with morse taper shank
Morse Tapers are common in: Drill presses, lathes, tailstocks, and smaller milling machines.
Sizes: MT0, MT1, MT2, MT3, MT4, MT5, MT6, MT7 (increasing size).
Holding principle: You insert the tool shank into the machine spindle by pushing or lightly tapping it in.
Removal: Done with a drift key or ejector slot.
LARGE SMALL MORSE DIAMETER DIAMETER TAPER# (A) (B) LENGTH --------------------------------------- 0 .36510" .25200 1-15/16 1 .47500 .36900 2-1/16 2 .70000 .57200 2-1/2 3 .93800 .77800 3-1/16 4 1.23100 1.02000 3-7/8 4-1/2 1.50000 1.26600 4-5/16 5 1.74800 1.47500 4-15/16 6 2.49400 2.11600 7 7 3.27000 2.75000 9-1/2 ---------------------------------------
Taper shank tools are used by machinists, metal fabricators, and machine tool manufacturers in operations requiring high torque and precision, especially for drilling metal and other materials on drill presses and milling machines.
Their design creates a self-locking, high-friction fit, ensuring a secure, stable, and high-torque connection directly into the machine's spindle or tailstock, eliminating the need for collets or chucks.
Who uses them
Machinists and Metal Fabricators: These professionals rely on taper shank drills for their stable and secure connection, which is ideal for heavy-duty drilling tasks in metalworking.
Machine Tool Manufacturers: Builders of machines that use drill presses and milling machines incorporate taper shanks for the smooth and stable operation of their equipment.
Automotive Industries: Manufacturers in the automotive sector and other fabrication workshops use them for various drilling needs.
Computer Numerical Control (CNC) and Vertical Machining Centers (VMC) Shops: The precision and stability of taper shanks are valuable in these automated environments.
Why they are used
High Torque and Stability:The Morse taper system provides a secure, self-locking fit through friction, allowing for high-torque transfer without the use of chucks or collets.
Precision and Alignment:The taper design ensures excellent centering and axial alignment, which is crucial for precise drilling operations.
Ease of Use:For stationary machines like drill presses, taper shanks are inserted directly into a corresponding socket, making them easy to mount and remove.
BROWN & SHARPE TAPERS
Overview
A Brown & Sharpe (B&S) taper is a style of self-holding taper originally developed by the Brown & Sharpe Manufacturing Company in the late 1800s. It’s less common today than Morse or Jacobs tapers, but you’ll still encounter it in older lathes, milling machines, and arbors.
Key Points
Where You’ll See B&S Tapers
- Older milling machines (arbor mount)
- Horizontal mill arbors for slitting saws or gear cutters
- Grinding machine spindles
- Specialized workholding arbors
LARGE SMALL B+S DIAMETER DIAMETER TAPER# (A) (B) LENGTH --------------------------------------- 1 .23922" .20000 15/16 2 .29968 .25000 1-3/16 3 .37525 .31250 1-1/2 4 .40233 .35000 1-1/4 5 .52315 .45000 1-3/4 6 .59961 .50000 2-3/8 7 .72537 .60000 3 8 .89873 .75000 3-9/16 9 1.06705 .90010 4 10 1.28927 1.04465 5-11/16 11 1.53176 1.24995 6-3/4 12 1.79681 1.50010 7-1/8 13 2.07310 1.75005 7-3/4 14 2.34375 2.00000 8-1/4 15 2.61458 2.25000 8-3/4 ---------------------------------------
Jarno Taper
The Jarno Taper is 1:20 on diameter, 0.600" on diameter per foot, .050" on diameter per inch.
A Jarno taper is a style of self-holding machine taper designed to be mathematically consistent, making it easy to calculate its dimensions without reference tables.
Key Features
- Type: Self-holding (small angle, holds by friction)
- Angle: About 1.49° per side (≈ 2.98° included angle)
- Length rule: Size number directly relates to dimensions:
- Large diameter (inches) = size ÷ 8
- Small diameter (inches) = size ÷ 10
- Length (inches) = size × 0.5
- Example: Jarno #8 → Large dia. = 1.000″, Small dia. = 0.800″, Length = 4.000″
- Purpose: Used in tailstocks, spindle tapers, and tooling arbors
- Advantage: Easy to machine or identify without charts
Common Uses
- Lathe tailstock centers
- Drill press arbors (older models)
- Precision grinding machines
- Special tooling requiring easy interchangeability