MB1-FORGED Muscle Back

The grindworks MB-1 FORGED is a small muscle back iron designed for players who appreciate beautiful lines and soft feel. Control, stability and accuracy are all strong points of this precision forged S20C iron.

Inspired by legends such as the Spalding Top Flite Professional and Bridgestone J’s Professional Weapon among others, the MB1-FORGED is a modern evolution of design, materials and manufacturing. Our designer and technical advisor worked hand in hand together from pencil drawings to CAD, and from resin samples to forging molds, to test samples to final products. A process spanning nearly a year of revisions, testing, alterations and even more testing before reaching the final product.

The curved and stepped design of the MB1-FORGED allows us to gradually move the center of gravity from lower to higher as the irons progress from long to short, a  feature we have dubbed Dynamic Gravity Progression.

DGP helps each iron perform more inline with what it is intended to do, for example, the 4 iron has the lowest CG making it easier to launch the ball in the air and get more distance. The mid irons 5, 6 and 7 irons, have a a slightly raised CG to balance launch and distance as well as control and accuracy. The short irons, 8, 9 and PW have a raised CG which create a much more stable trajectory and more spin allowing a player to aim at the pin with more accuracy and spin control.

The grindworks MB-1 FORGED is aimed at the better player and good ball striker who wants no compromises in feel and accuracy.

Number 4# 5# 6# 7# 8# 9# Pw
Loft ( ° ) 25 28 32 36 40 44 48
Lie ( ° ) 60.5 61 61.5 62 62.5 63 63.5
Offset (mm) 3.2 3 2.8 2.6 2.4 2.2 2

Shafted Specs for Reference – N.S. PRO Modus3 Tour 120 X

Number 4# 5# 6# 7# 8# 9# Pw
Length (inches) 38.25 37.75 37.25 36.75 36.25 35.75 35.25
Balance D2.5 D2.5 D2.5 D2.5 D2.5 D2.5 D2.5
  • CONFORMING to R&A Groove Rule
  • Outer Hosel Diameter: 13.5mm
  • Inner Hosel Diameter: 9.2mm (Taper Tip)
  • Hosel Depth: 30mm
  • Right Handed Only
grindworks MB1-FORGED
Materials S20C Carbon Steel
Finish Chrome Mirror/Satin
Type Muscle Back
Design Dynamic Gravity Progression
Characteristics Feel, Control, Accuracy
Target Athlete golfer, better player, improving player

As a premium Japanese components brand, this grindworks product is available pre-assembled with a standard shaft and grip (listed below) or custom fit with your choice of shaft and built to your specs by any grindworks authorized dealers.

grindworks original cord grip (round or ribbed)


grindworks original rubber grip (round only)


N.S. Pro ModusTour 120 Steel Shaft


N.S. Pro 950GH



At grindworks we believe, an iron isn’t only about beauty but all about functional beauty. We designed the MB-1 Forged with smooth curved lines in mind. These flowing curves are not only intended to provide a beautiful visual appearance but also allowed us to create a progressive flow of the center of gravity, increasing all around performance and usability.

Dynamic Gravity Progression makes the long irons more forgiving and easier to launch and hit for distance thanks to the lower CG placement. The mid irons see the CG gradually shift higher thanks to a calculated change in the size and position of muscle back’s curves. The mid irons produce an all around trajectory with balanced distance and accuracy. The short irons see the CG shifted away from the sole and higher in the head which create a more penetrating trajectory aimed right at the pin for optimal accuracy and control.

The grindworks MB1-Forged is a muscle back with added ease of use and forgiveness to go along with great feel and control.