Note that this is an unusual pad in that it has 5/16-24 internal threads, rather than the more usual external threaded stud for tool attachment.
The internal thread makes this pad suitable for use with the 3M 3" Pistol Grip Buffer - which has a 5/16-24 external threaded drive shaft; see Related Products, below.
The backup pad itself has a 5/16-24 internal thread, and the kit includes five adaptors that convert it to 1/4-20 external threads, 1/4-20 internal threads, 1/4-28 external threads, 5/16-24 external threads, or 6mm-1.0 external threads.
This pad features the 3M Clean Sanding hole pattern for superior vacuum-assisted dust extraction.
It can, however, be used to back up ANY 3" Hookit™ abrasive disc (regardless of hole pattern), with or without use of a vacuum.
• Medium density yellow foam pad with a slightly flexible edge - good for flatter surfaces
• Appox. 45° tapered bevel provides some edge flexibility
• Hookit pad face holds the disc securely, allowing easy attachment and removal
• Sold by the each; 5 per case
Heavy on the technical side...
Should you use a soft or firm sanding disc backing pad?
After you have decided between Stikit or Hookit, and chosen no-hole or clean sanding discs, and selected the disc diameter, you will still often be left with the choice of a firm or a soft backing pad.
• As a general rule, you should use coarser abrasive discs on firm backing pads, and finer grit discs on soft backing pads.
Soft Backing Pads
• The advantage of a soft pad is that its surface can flex to some extent, conforming to the shape of the surface being sanded.
This facilitates higher surface contact, more consistent material removal, and less gouging.
• Soft pads are not intended for use with very coarse abrasive discs for heavy duty work, as the higher stresses induced by very coarse abrasives fatigues the foam prematurely.
• Having said that, a soft pad can be used with coarse grit discs for heavy material removal on rounded surfaces - like a sailboat hull - where it would be difficult to maintain full surface contact with a stiffer, firm backing pad.
Just don't expect the soft pad to last as long.
Firm Backing Pads
• Using coarse discs on a firm backing pad works very well, as long as the work surface is flat.
Using a firm pad on a curved surface can easily result in hard-to-remove gouges and scratch marks.
If the surface isn't flat - again, like a sailboat hull - you will generally want to use a softer pad for full surface contact, no matter what the grit of the sanding disc.
• Firm pads are also recommended for leveling uneven surfaces - such as paint brush strokes and runs.
In this application, a soft pad might simply conform to raised areas, rather than cutting them down.