Festool Owners Group

FESTOOL DISCUSSIONS => Festool How To... => Topic started by: JG on May 23, 2021, 10:24 AM

Title: Sandpaper buildup
Post by: JG on May 23, 2021, 10:24 AM
Hey foggers,

I am looking for some assistance with an ongoing issue when sanding outdoor rails, decks, etc.  Using my RO 125 or 90 sander with my CT36 vat.  Before sanding, I thoroughly scrape the paint in all directions to remove any loose or peeing paint.  I use 60 grit Granat sandpaper.  I originally set the suction on vac at max and speed on sander to 6.  The sanding paper gummed up with paint rather quickly.  I reduced the suction to half and the speed to 4.  Still encounter the issue.  I have experienced it on several jobs.  Having issues uploading the picture.   Any ideas what the problem is or how to resolve it?  Also, can the sandpaper be cleaned? I go through a lot of sandpaper quickly.  Thanks.

Jim
Title: Re: Sandpaper buildup
Post by: squall_line on May 23, 2021, 10:38 AM
How much of the paper is in contact with the surface?

Are the holes on the surface or free-floating when you're using it?
Title: Re: Sandpaper buildup
Post by: SRSemenza on May 23, 2021, 10:45 AM
For paint and finish removal you really have to keep the sander moving (even with the speed turned down) to avoid melting the paint onto the paper. Lots of fast passes to get the job done. It won't take care of the problem 100% but it helps.

Seth
Title: Re: Sandpaper buildup
Post by: Alanbach on May 23, 2021, 11:27 AM
I would recommend that you try a box of Festool’s Saphir sandpaper. For that application I would try 36 grit. My bet is that it will change your life😊 (at least for this particular application).
Title: Re: Sandpaper buildup
Post by: Alex on May 23, 2021, 11:49 AM
Some paints simply do not dry out as hard as others. This is especially true of water based paints, which are often of inferior quality. I just accept that I have to use more sandpaper on such paints.
Title: Re: Sandpaper buildup
Post by: Vondawg on May 23, 2021, 12:11 PM
Perhaps you’ve already discovered using a putty knife at an angle, lightly..knocks off the gummed up spots on your sand paper (while machine is rotating)…like said, water base finishes are almost always prone to this


Title: Re: Sandpaper buildup
Post by: Bert Vanderveen on May 23, 2021, 02:20 PM
A block of natural rubber is used to clean sandpaper. In a pinch the sole of a Clarks desert boot will do, too.

Search for "sandpaper cleaning block" and you’ll fine, even at Walmart’s!
Title: Re: Sandpaper buildup
Post by: Cheese on May 23, 2021, 03:31 PM
Perhaps you’ve already discovered using a putty knife at an angle, lightly..knocks off the gummed up spots on your sand paper (while machine is rotating)…like said, water base finishes are almost always prone to this

I used to use a putty knife but it tended to knock off the grit if I wasn't really careful, I now use one of these in the Rotex mode.

https://powertecproducts.com/71002-abrasive-cleaning-stick-8-1-2/

[attachimg=1]
Title: Re: Sandpaper buildup
Post by: Crazyraceguy on May 23, 2021, 06:11 PM
Stripping paint and fine sanding of finishes up to a polished state both share the same problem.
With fine grits, the paper loads up and causes pigtails. Little blobs build up and it is generally referred to as "corning"  (at least in the US)
With stripping, the same thing happens, but the symptoms are different. The paper loads up and quits cutting. The blobs get hot and (depending on the paint type) melts and gums up more.

Both of these are caused by one of two things.
1) The material is not cured enough.
This usually happens when the finishing process is hurried. The finish or filler has not dried long enough.

2 The abrasive is too fine. Simply switching to a lower grit and/or a coated abrasive. These are designed for stripping/ anti-clogging.

Starting with an abrasive that is too fine, not only wastes paper, it wastes time too.
Title: Re: Sandpaper buildup
Post by: Alanbach on May 24, 2021, 12:28 AM
As I alluded to above, I think that 60 grit on an older heavy film finish is too high a grit. It causes you to have to make the sander to work too hard and that creates excess friction and the associated heat it generates. I also think that Granat is great sandpaper but NOT ideal for removing paint. I really think that you will have greatly improved results with Saphir and with a lower grit like 36.