Off Hand Grinding
Operator holds work piece by hand and presents it to the abrasive belt. Offhand grinding is used if the work pieces are dissimilar or is of irregular in shape
Machine speed between 3,500 and 7000 SFPM is a good working range for most applications. All grinding should be below the center line of the contact wheel and work piece brought up to the belt.

Offhand Grinding is divided into 3 Categories:

  1. Rough Grinding
  2. Shape and Dimensioning
  3. Finish and Polishing

Rough Grinding:

  • Grits: 24 Through 50
  • Belt Speed: 5,500 to 6,000 SFPM
  • Contact Wheel: 90 Durometer with 3 to 1 Groove to Land or 70 – 90 Durometer with 2 to 1 Groove to Land

Shaping and Dimensioning:

  • Grits: 60 Through 150
  • Belt Speed: 5,500 to 6,000 SFPM
  • Contact Wheel: 50 to 70 Durometer with 1 to 1 Groove to Land

Finishing and Polishing:

  • Grits: 100 Through 400
  • Belt Speed: 5,500 to 6,000
  • Contact Wheel: 40 to 50 Durometer

Sheet and plate Dimensioning
This application is almost exclusively Stainless Steel or Titanium. Plates are ground to very high tolerances. Single head machines, multiple passes with progressively finer grits.

Roughing Finishing
Stainless Steel 50 - 120 grit 150 - 320 grit
Titanium 60 - 120 grit 120 - 180 grit

 



Centerless Grinding
Outside diameter grinding that does not require the work to be mounted on centers or driven by an independent power source. The work rests on a work rest blade that is driven by and controlled by a regulating wheel, while the abrasives belt running at normal speed does the grinding. Nearly all centerless grinding are wet operations.

Roughing:

  • Grit 40 -50
  • Contact Wheel 70 – 95 Durometer with 1 to 1 or 2 to 1 groove to land

Intermediate:

  • Grit: 60 – 120
  • Contact Wheel: 55 – 70 Durometer with 3 to 1 or 4 to 1 Groove to land

Wide Belt Sanding and Finishing
Application: belts over 18” wide for sanding of flat surfaces

Categories:

  • Final Dimensioning
  • Intermediate sanding
  • Finish sanding
  • Rough lumber planning

Final Dimensioning: To develop a uniform dimension. Coarse grit abrasive 36 to 120 grit usually used. The dimensioning head should be removing 60% to 65% of the total stock removal required.
Intermediate Sanding: This sanding head is to remove coarser grit scratches and bring work piece to final tolerance, 25% to 35% of the total stock removal. Grit range 100 to 150.
Finish Sanding: Provides the final scratch pattern. Shock removal should not exceed 10% of total. Finish head should utilize a platen. Grit range 120 to 320
Rough Lumber Planning: Initial surface operation for lumber bringing it to a uniform thickness and removing milling marks. Grits used are 24 and 36 with heavy Ywt backing.


 Automatic Grinding

Four Common Types:

  1. Rotary Index
  2. Rotary Continuous
  3. Continuous Horizontal
  4. Conveyorized

Roughing:
Grinding Method:
Rubber Contact Wheel 70 to 90 Duro Grit 36 – 60
Slack of belt Grit 36 – 60
Cloth Contact Wheel Grit 36 – 60

Shaping & Dimensioning
Grinding Method:
Rubber Contact Wheel 70 – 90 Duro Grit 80 – 120
Rubber Contact Wheel 50 – 70 Duro Grit 80 – 150
Slack of Belt Grit 80 – 150
Cloth Contact Wheel Grit 80 – 150

Finishing & Polishing
Grinding Method:
Rubber Contact Wheel 50 – 70 Duro Grit 180 – 220
Rubber Contact Wheel 30 – 50 Duro Grit 180+
Slack of Belt Grit 180+
Cloth Contact Wheel Grit 180+


 Platen Grinding

The belt is backed up at the point of contact with the work piece with a hard plate. This provides a rigid support for precise stock removal. A matching tolerance can be generated on a large run of matching parts.

Grit Selection:
Roughing: 36 though 50
Intermediate: 60 though 120
Finish & Polish: 150+


High Pressure Grinding
Pressures from 300 to 700 P.S.I.

Fixed Force Grinding:
Force applied directly to the work piece, pressure remains constant throughout operation.

Fixed Cut Rate Grinding:
Feed controlled. The cut rate or material removal rate is determined by feed and the set depth of cut.
Grit: 24 and 36 grit used almost exclusively .


Narrow Belt Sanding

Belts 6” to 8” and up to 355” long which are used for final sanding and polishing

Common Types:

  1. Stroke Sander
  2. Edge Sander
  3. Mold Sanding

Stroke Sander:
Belt runs horizontally above a table that supports the work piece and reciprocated under the belt to sand the full width of the work piece. Mainly used for final sanding on furniture parts.

Four Types of Stroke Sanders

  1. Hand block
  2. Hand Lever
  3. Automatic Stroke
  4. Thru-feed Automatic Platen Sanders

Edge Sander:
Used primarily used for sanding square edges on panels. Has a platen and rest table on both the front and back of machine with a half round at one end. The belt is backed up by a vertical platen, with horizontal work rest table in front of belt with provision for the belt to oscillate while in use.
2500 – 4000 SFPM
Mostly use Xwt backing in 80 – 120

Mold Sanding:
Contour shape sanding mostly on furniture parts, by the use of hand held formed black, stationary formed block or Automatic thru feed mold sanding. Maximum product flexibility very important for mold sanding.
2,500 – 4,000 SFPM
Grits 100 - 120