Mast Base Turning Blocks

Mast Base Turning Blocks are used primarily to lead halyards, reef lines and other control lines aft from the base of the mast. These Blocks are available in a variety of configurations that are attached to the Mast, the Deck, or a Mast Step or Deck Collar.

Mast mounted Turning Blocks are usually hinged on a vertical Pin allowing a fair lead to a wide variety of points on deck.

Deck mounted Turning Blocks

Mast mounted Turning Blocks

Simple Swivel Blocks can be used where the mast step or deck collar provides bails or other attachment points.

These highly-specialized Blocks are

attached to the Mast or the Deck. Some Mast Steps and Deck Collars, (Notably some produced by Isomat and Z-Spar) have provisions for even Pad Eyes , or to bails

Simple Swivel Blocks can be used where the mast step or deck collar provides bails or other attachment points. Some Mast Steps and Deck Collars, (Notably some produced by Isomat and Z-Spar) have provisions for even Pad Eyes , or to bails

with delrin or aluminum sheaves are available for attachment to Isomat Mast Steps and Deck Collars, for leading halyards and other lines aft. Block Studs are available separately for use with other blocks or attachments. Special Isomat Mast Step and Deck Collar Bails are also listed below.
Some Isomat Masts have integral Welded Exit Boxes at the base of the mast for leading internal halyards out of the Mast at Deck level, eliminating the need for Mast Base Turning Blocks. For Parts for them, See Welded Mast Base Exit Boxes.

Blocks with Studs for New-Style Steps and Collars
Block Studs Only
Blocks only with Bolt, for Steps and Collars using Block Studs
Mast Step and Deck Collar Bails
Blocks only with Shackle, for Steps and Collars using Bails

Blocks with Studs for New-Style Steps and Collars
SS Blocks with delrin or aluminum sheaves are specially designed to attach to all New-Style Isomat Mast Steps and Deck Collars. Blocks incorporate a 12mm SS stud, threaded (3/8-16) on the end, and include special Nut. SS Nut slides into recess in side of deck casting and block screws in through hole in top. New design allows Block to remain upright without spring, yet still allows full articulation.

*Mast Base Turning Block w/ 2" Sheave: NGA-40:* Block with 2" (50mm) diameter delrin sheave will accommodate lines up to 7/16" (12mm) diameter. Designed to attach to all New-Style Isomat Mast Steps and Deck Collars with 12mm (1/2") holes, special nut is included. Safe working load is 1750 lbs. (795Kg).
*Mast Base Turning Block w/ 2" Aluminum Sheave: NGA-40A:* Block with 2" (50mm) diameter Aluminum sheave will accommodate wire up to 3/16" diameter and lines up to 7/16" (12mm) diameter. Designed to attach to all New-Style Isomat Mast Steps and Deck Collars with 12mm (1/2") holes, special nut is included. Safe working load is 1750 lbs. (795Kg).
*Mast Base Turning Block w/ 2 3/8" Sheave: NGA-41:* Block with 2 3/8" (60mm) diameter delrin sheave will accommodate lines up to 1/2" (14mm) diameter. Designed to attach to all New-Style Isomat Mast Steps and Deck Collars with 12mm (1/2") holes, special nut is included. Safe working load is 2250 lbs. (1020Kg).
*Mast Base Turning Block w/ 2 3/8" Aluminum Sheave: NGA-41A:* Block with 2 3/8" (60mm) diameter Aluminum sheave will accommodate wire up to 1/4" diameter and lines up to 1/2" (14mm) diameter. Designed to attach to all New-Style Isomat Mast Steps and Deck Collars with 12mm (1/2") holes, special nut is included. Safe working load is 2250 lbs. (1020Kg).

Block Studs Only Block Studs Only, to fit all Isomat Steps and Collars are available separately for use attaching items including shackles and other blocks. All Block Studs are Stainless Steel with an upper attachment hole.
Threaded Block Studs for New-Style Steps and Collars Threaded Block Studs with nuts to fit New-Style Steps and Collars are available separately for use attaching items including shackles and other blocks. New-Style Block Studs have a threaded lower end to fit special Nut. Special SS nut slides into recess in side of deck casting, Block Stud screws into nut through hole in top of deck casting.
Threaded Block Stud - Lightweight: NG1-22: NG-1 SS Block Stud with nut to fit all New-Style Isomat Steps and Collars. SS nut slides into recess in side of deck casting and Block Stud screws in through hole in top. Stud is 42mm (1 5/8") long x 12mm (15/32") diameter with a 1/4" (6mm) hole for attachment of shackle or block. Lower end has an 8mm thread x 3/8" (10mm) long. Includes special large nut.
Threaded Block Stud - Heavy-Duty: NG2-22: NG-2 SS Block Stud with nut to fit all New-Style Isomat Steps and Collars. SS nut slides into recess in side of deck casting and Block Stud screws in through hole in top. Stud is 52mm (2 1/16") long x 14mm (9/16") maximum diameter with a 12mm shaft and a 5/16" (8mm) hole for attachment of shackle or block. Lower end has an 8mm thread x 3/8" (10mm) long. Includes special large nut.
Threaded Block Stud - Wide: NG2-22W: Heavy-Duty Wide NG-2 SS Block Stud with nut to fit all New-Style Isomat Steps and Collars. SS nut slides into recess in side of deck casting and Block Stud screws in through hole in top. Special Wide Stud is suitable for direct attachment to a variety of Blocks with Bolt for Block Studs, below. Wide Stud is 50mm (2") long x 16mm (5/8") wide with a 12mm shaft and a 1/4" (6mm) hole for attachment of shackle or block, hole can be drilled to 5/16" (8mm) for select applications. Lower end has a 3/8-16 thread, nut is included.
Special Mast Step Block Studs
NG2 Mast Step Block Stud - 12mm Special NG60: NG2-20PX: Special SS Clevis Pin-shaped Block Stud is used for attachment of shackle or block to lead halyards aft. Fits in integral recessed hole in *NG60-4* Mast Step. Block Stud is installed from underside of Mast Step Casting, Mast Step must be removed to install Block Studs. Large head Block Stud is 12mm (<1/2") diameter x 45mm (1 3/4") long (maximum), with a 30mm (1 3/16") grip length and a 6mm (1/4") hole for shackle pin or Block bolt.
NG2 Mast Step Block Stud - 12mm Small: NG2-20PS: Special SS Clevis Pin-shaped Block Stud is used for attachment of shackle or block to lead halyards aft. Fits in integral recessed hole in NG60-4, NG70-4, and other Mast Steps. Block Stud is installed from underside of Mast Step Casting, Mast Step must be removed to install Block Studs. Small head Block Stud is 12mm (<1/2") diameter x 45mm (1 3/4") long (maximum), with a 30mm (1 3/16") grip length and a 6mm (1/4") hole for shackle pin or Block bolt. F305/385,460/560E
NG2 Mast Step Block Stud - 14mm Special - NG80, NG86: NG2-20PL: Special SS Clevis Pin-shaped Block Stud is used for attachment of shackle or block to lead halyards aft. Fits in integral recessed hole in *NG80-4, and NG86-4* Mast Steps. Block Stud is installed from underside of Mast Step Casting, Mast Step must be removed to install Block Studs. Special Block Stud is 14mm (9/16") diameter x 54mm (2 1/8") long (maximum), with a 35mm (1 3/8") grip length and an 8mm (5/16") hole for shackle pin or Block bolt.

Blocks with Bolt for Block Studs Blocks incorporate a 1/4" SS Bolt and Nylon Washers for attachment to all Block Studs and Mast Step Block Studs listed above. Washers allow for centering block on Block Stud, Bolt is tightened to allow Block to remain upright regardless of halyard tension.
Bolt-on Turning Block w/ 2" Sheave: NGA-40UA: Black Aluminum Block with 2" (50mm) diameter delrin sheave will accommodate lines up to 7/16" (12mm) diameter. Includes 1/4" SS Bolt, Locknut and Nylon Washers for use with all *NG1* and *NG2* Block Studs and Mast Step Block Studs. 2W
Bolt-on Turning Block w/ 2" Aluminum Sheave: NGA-40UAA: Black Aluminum Block with 2" (50mm) diameter Aluminum sheave will accommodate wire up to 3/16" diameter and lines up to 7/16" (12mm) diameter. Includes 1/4" SS Bolt, Locknut and Nylon Washers for use with all *NG1* and *NG2* Block Studs and Mast Step Block Studs.
Bolt-on Stainless Turning Block w/ 2" Aluminum Sheave: NGA-40USA: Stainless Steel Block with 2" (50mm) diameter Aluminum sheave will accommodate wire up to 3/16" diameter and lines up to 7/16" (12mm) diameter. Includes 1/4" SS Bolt, Locknut and Nylon Washers for use with all *NG1* and *NG2* Block Studs and Mast Step Block Studs.

Bolt-on Turning Block w/ 2 3/8" Sheave: NGA-41UA: Black Aluminum Block with 2 3/8" (60mm) diameter delrin sheave will accommodate lines up to 1/2" (14mm) diameter. Includes 1/4" SS Bolt, Locknut and Nylon Washers for use with all *NG1* and *NG2* Block Studs and Mast Step Block Studs. 5W
Bolt-on Turning Block w/ 2 3/8" Aluminum Sheave: NGA-41UAA: Black Aluminum Block with 2 3/8" (60mm) diameter Aluminum sheave will accommodate wire up to 1/4" diameter and lines up to 1/2" (14mm) diameter. Includes 1/4" SS Bolt, Locknut and Nylon Washers for use with all *NG1* and *NG2* Block Studs and Mast Step Block Studs.
Bolt-on Stainless Turning Block w/ 2 3/8" Aluminum Sheave: NGA-41USA:
Stainless Steel Block with 2 3/8" (60mm) diameter Aluminum sheave will accommodate wire up to 1/4" diameter and lines up to 1/2" (14mm) diameter. Includes 1/4" SS Bolt, Locknut and Nylon Washers for use with all *NG1* and *NG2* Block Studs and Mast Step Block Studs.

Mast Step and Deck Collar Bails Special Mast Step and Deck Collar Bails are used with most Isomat Mast Steps and Deck Collars.
NG1 Mast Step & Deck Collar Bail: NG1-20: SS Formed Bail is used for attachment of blocks and lines. Fits in integral slots of NG37 and smaller Mast Steps, and in sides of NG70 and smaller Deck Collars. Bails are installed from underside of Mast Step or Deck Collar Casting, Casting must be removed to install Bails. Bail is made from 8mm (5/16") rod, and is 2 1/16" (53mm) long x (maximum) 1" (25mm) high.
NG2 Mast Step & Deck Collar Bail: NG2-20: SS Formed Bail is used for attachment of blocks and lines. Fits in integral slots of NG46 and larger Mast Steps, in sides of NG86 and larger Deck Collars, and in aft side of all Deck Collars. Bails are installed from underside of Mast Step or Deck Collar Casting, Casting must be removed to install Bails. Bail is made from 10mm (3/8") rod, and is 2 3/4" (70mm) long x (maximum) 1 15/16" (50mm) high.
NG3 Mast Step Bail Assembly: NG3-20A: SS Formed U-bolt type Bail is used for attachment of Boom Vang or/and standard blocks for leading halyards aft. Fits in integral holes in NG105 Heavy-Duty Mast Step. Bail Nuts are installed from underside of Mast Step Casting, Mast Step must be removed to install Bail(s). Bail is made from 12mm (1/2") rod, and is 3" (78mm) long x 1 9/16" (40mm) between centers. Assembly includes Bail and (2) 12mm jam Nuts.

Blocks with Shackle for Steps and Collars using Bails Swivel Blocks incorporate a SS Shackle for attachment to Bails on all Old-Style Mast Steps and Collars, and on New-Style NG 105 Mast Steps. These blocks are also used for Spinnaker Halyards, and in a variety of other applications.
SS Swivel Block w/ 2" Sheave: NGA-40SS: SS Block with 2" (50mm) diameter delrin sheave will accommodate line up to 7/16" (11mm) diameter. Schaefer 05 SS Block has 1/4" strap Shackle and a 1750 lb. safe working load.
Swivel Block w/ 2" Sheave: NGA-40SB: Black Aluminum Block with 2" (50mm) diameter delrin sheave will accommodate line up to 7/16" (11mm) diameter. Schaefer 05 Block has 1/4" strap Shackle and a 1750 lb. safe working load.
Swivel Block w/ 2" Aluminum Sheave: NGA-40SBA: Black Aluminum Block with 2" (50mm) diameter Aluminum sheave will accommodate wire up to 3/16" diameter and line up to 7/16" (11mm) diameter. Schaefer 05 Block has 1/4" strap Shackle and a 1750 lb. safe working load.

Swivel Block w/ 2 3/8" Sheave: NGA-41SS: SS Block with 2 3/8" (60mm) diameter delrin sheave will accommodate line up to 9/16" (14mm) diameter. Schaefer 07 SS Block has 1/4" strap Shackle and a 2250 lb. safe working load.
Swivel Block w/ 2 3/8" Sheave: NGA-41SB: Black Aluminum Block with 2 3/8" (60mm) diameter delrin sheave will accommodate line up to 9/16" (14mm) diameter. Schaefer 07 Block has 1/4" strap Shackle and a 2250 lb. safe working load.
Swivel Block w/ 2 3/8" Aluminum Sheave: NGA-41SBA: Black Aluminum Block with 2 3/8" (60mm) diameter Aluminum sheave will accommodate wire up to 3/16" diameter and line up to 9/16" (14mm) diameter. Schaefer 07 Block has 1/4" strap Shackle and a 2250 lb. safe working load.

High-load Swivel Block w/ 2 3/8" Sheave: NGA-42SS: High-load SS Block with 2 3/8" (60mm) diameter delrin sheave will accommodate line up to 9/16" (14mm) diameter. Schaefer 08 SS Block has 1/4" forged Shackle and a 2750 lb. safe working load.
High-load Swivel Block w/ 2 3/8" Aluminum Sheave: NGA-42SSA: High-load SS Block with 2 3/8" (60mm) diameter Aluminum sheave will accommodate wire up to 1/4" diameter and line up to 9/16" (14mm) diameter. Schaefer 08 SS Block has 1/4" forged Shackle and a 2750 lb. safe working load.

Large Swivel Block w/ 3 1/4" Aluminum Sheave: NGA-43SSA: Large SS Block with 3 1/4" (82mm) diameter Aluminumsheave will accommodate wire up to 1/4" diameter and line up to 5/8" (16mm) diameter. Schaefer Series 10 SS Block has 3/8" forged Shackle and a 3750 lb. safe working load.

Spars, Rigging, and Hardware for Sailboats