How to Use a Variable Speed Grinder as a Drum Sander

With the new Cibo wheels and mandrels you can now use your variable speed grinder as a drum sander or satin polishing machine for box tube and stainless steel angle.

100mm wide satin polishing machine such as the Cibo Finimaster can actually be less efficient when trying to polish 50 or 25mm wide box section or stainless steel tube. Here is the latest solution from Cibo Abrasives. In this blog we will show you 4 different processes which work well with a variable speed grinder and a few accessories.

The 4 processes we will look at are:

Aggressive grinding of mill scale to remove pitting & create a grain finish
Grinding of stainless steel mill scale to create a fine 240 or 320 grit satin finish on box tube
Removal of scratches & damage to create a general purpose satin finish on stainless steel
Mirror polishing box tube with 50mm wide belts

The New Grinder Accessories & What They Do:

FMRU/50 – hard rubber drum for 50mm wide abrasive sleeves
- Use the FMRU/50 for aggressive grinding and stock removal
FMRU/50/W – soft rubber drum for 50mm wide abrasive sleeves
- The FMRU/50/W has a much softer contact with the work surface.
- Use it for finishing and blending
FM/SPINDLE/50 – M14 conversion thread for 50mm wheels & drums.
- Fit the spindle onto your grinder to mount the hard and soft rubber drums to mount the abrasive sleeves onto the contact wheel.

Process 1: Aggressive Grinding of Mill Scale to Remove Pitting & Create a Grain Finish

If you need to guarantee full removal of the mill scale pitting then rapid scale removal will be achieved with the use of our FX87 40 grit ceramic grinding sleeves on the hard rubber drum. A particularly good solution if you are removing the metal for weld prep.

Note: The increased performance & lifetime achieved with the new generation of Cibo Ceramic abrasive sleeves means that we no longer recommend zirconia (blue) abrasive belts & sleeves for this application.

Process 2: Grinding & Removing Stainless Steel Mill Scale to Create a Fine 240 or 320 grit Satin Finish on Box Tube

Going to a finer finish it is often better to remove the mill scale with a finer grit belt which will then be easier to blend to the final finish. In this scenario we would often recommend the FX87 P80 grit ceramic belts / sleeves which will still remove the pitting easily, but in a more controlled manner than the P40 grit ceramic grinding belts. In the video we wanted to show what happens when you switch to a softer contact wheel so our second stage process uses the softer wheel and the FF87 P120 grit ceramic sleeves. Using the softer wheel will reduce the risk of bouncing / chatter marks which will almost certainly happen with a harder contact wheel.

Video Note: Watch to see the P120 grit ceramic belts removing the chatter marks (at 90 degrees to the grain finish) which are caused by the coarser belts on the harder rubber contact wheels.

All abrasive belts will leave fine burrs on the surface so for the final 320 grit finish we recommend you blend the surface with our FMTM P280 grit tex / scotchbrite brush.

Process 3: Removal of Scratches & |Surface Damage to Create a Good Satin Finish on Stainless Steel

Need to do a quick fix to a general satin finish? The Ginger Ninja is probably the perfect option. It has a 60 grit ceramic cloth which gives it the grinding power to bite into the mill scale and the tex fleece to soften and blend the final surface.

Video Note: We used a stainless steel angle bar that had been lying around the workshops for some time so it had old sanding marks, mill scale pitting and also some deeper marks from where it had been knocked around a bit too much. After we had cleaned the bar we noticed some deeper marks left in the metal. The video shows how we were able to work on the problem area and remove the marks completely.

Process 4: Mirror polishing box tube with 50mm wide belts

Assuming you have a P120 grit finish which can be achieved using Process 2 then with care and patience a consistent mirror polish finish is easily achievable with your variable speed grinder using the 3M Trizact 237AA sleeves on the softer FMRU/50/W contact wheel.

Use the 237AA sleeves in the following sequence to cut the surface to a super fine finish: A160 (P120 grit), A65 (P280 grit), A30 (P800 grit), A16 (P1400 grit) and A6 (P2000 grit).

A final finish can then be achieved by using our pink polishing soap (PV102) on the FLM/12550 polishing mop

Polishing tip: Always cross-cut the previous sanding marks when aiming for a mirror polish. This will allow you to make sure all previous sanding marks have been removed before you get to the final polishing stage.

Polishing tip: Make sure there is a lot of polish on the FLM polishing mop to get a good coverage of your metal.

Polishing tip: When you believe you are getting close to the final finish turn the speed of the grinder down and reduce the pressure to allow the mop to remove any final marks and polish. The lighter the pressure at the end, the brighter and cleaner the polished finish will be.

Summary:

For fast stock removal and longest belt life use the harder FMRU/50 rubber wheel with the FX87 P40 or P60 grit.
For a finer chatter free finish use the softer FMRU/50/W contact wheel with the P60 ceramic belts to remove any mill scale. The FX87 P80 grit belts to remove deeper surface damage and the FF87 P120 grit sleeves to restore the grain finish.
For general purpose satin finishing and damage removal the Ginger Ninja (FMCMC/60/12050) is the essential tool in your work box.
For mirror polishing use the FMRU/50/W contact wheel throughout the process to prevent any deeper chatter marks showing in the final bright polished finish.
To see all the sleeves available on our website in size 287mm x 50mm follow this link: 287 x 100mm belts