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Semi-Automatic Underpinner

Product Number: 04-001

The U-300 is a bench-top, frame joining machine and the most popular model of custom framer, sign and graphic shops. It is compact, well constructed, and built for many years of trouble free operation. The design of the U-300 allows the operator to set the front and back measuring stops for V-Nail insertion. The frame is then moved across the nail head and V-Nails are driven or stacked anywhere along the frame joint. The V-Nail insertion is actuated through the use of a pneumatic pedal.

Purchase Package
  U-300 Purchase Package
(1) 7mm Nail Head
(1) 10mm Nail Head
(1) 12mm Nail Head
(1) Single Vertical Positive Placement Clamp
(1) Single Metal Pressure Plate
(1) Magnetic Support for Vertical Placement Clamp
(1) Blue Rubber Pads (SW)
(1) Yellow Rubber Pads (MW)
(1) Black Rubber Pads (HW)
(1) 4mm Allen Wrench
(1) 5mm Allen Wrench
(1) Magnetic V-Nail Pick-up Tool
(1) Machine Manual
Accessories & Replacement Items
P/N Item Description
04-032 Extension Wings Kit
04-047 Floor Stand Option
04-167 Magnetic Base for Clamp Assembly
41-221 Single Placement Vertical Clamp Kit
04-020 Single Metal Pressure Plate
04-023 Magnetic - Single Metal Pressure Plate
04-026 Blue Replacement Pad (recommended for SW)
04-025 Yellow Replacement Pad (recommended for MW)
04-024 Black Replacement Pad (recommended for HW)
04-059 Round Felt Pad, Small, 6/PK
41-160 Adjustable Fence (2 knobs)
41-333 Fixed Fence - 120 degree
41-334 Fixed Fence - 135 degree
41-134 Round Rubber Pad
41-157 Adjustable Fence (2 Knobs)
41-333 Fixed Fence - 120°
41-334 Fixed Fence - 135°
04-090 Nail Head – 3mm
04-095 Nail Head – 5mm
04-091 Nail Head – 7mm
04-092 Nail Head -10mm
04-093 Nail Head – 12mm
04-094 Nail Head – 15mm
Power Requirements

Compressed Air 4NI at 5 Bar

CE Compliant

Sales & Technical Documents
AMP U300.jpg U-300 AMP Sellsheet 1-9-15.jpg


U 300 Semi- Auto/
Pneumatic Underpinner

Unique Performance Features

  • Features pneumatic loader to eliminate nail jams
  • “Soft Clamping” pneumatic feature for damage free joints
  • Quick-change, magnetic pad hold down feature fitting most moulding profiles
  • Small table-top footprint needed – 19” (485mm) wide x 18” (456mm) length x 14” (356mm) high
  • Operates only with pneumatic air, no electrical hook-up needed
  • Dual function foot pedal for separate control of mould clamping and V-Nail insertion
  • Designed with a unique, trouble free piston V-Nail driver block-blade system for years of dependable single and multi-stacking operations

Frame Joining Capabilities

Moulding Width
(min to max)

Moulding Height
(min to max)

Max Distance
Between V-Nails

¼” up to 3 3/4”
(6-60 mm)

¼” up to 3 ¼”
(6-80 mm)

3 1/4” (80 mm)

Pre-set V-Nail
Position Stops

V-Nail Sizes

V-Nail Channel


5, 7,10,12,15 mm

220 V-Nails/channel

Machine Dimensions & Weight

Width 18 ¾” (480mm)
Length 11 ¾” (300mm)
Height 11 ¾” (300mm)

70lbs. (32kg.)

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