Sanding/Finishing question grit/speeds

[Thompmd]

Saw an article on Tutorwood from Brian who is a Festool Specialist from Melbourne.

He was referring to getting the most from a RO150.

Interesting article in regards to Rotex vs STD mode and as the grit went higher the speed went lower?? Being new I was wondering if this normal and if that’s what you did?

I tried today on Walnut Sewing Table and sanded from 60 at 6(speed) to 1200 at 1 following his recommendation . To be honest I had trouble seeing much if any difference.

 

[AlexThePalex]

I always leave the speed on its higest. Only VERY rarely do I turn it down, but only if I feel I absolutely have to because I might cause damage to the material. This happens certainly less than once per year for me.

To my feeling the speed of the sander is best left on full because the less power you give the sander the jerkier it will behave.

 

[ear3]

I don't vary speed on sanding at higher grits.  I have no reason to doubt the recommendation, but I have never been dissatisfied with the results at full speed provided all the other precautions have been taken.  I do, however, switch over to the 150/3 from the 150/5 after 400 grit, as I've noticed the smaller sanding stroke gets better results more consistently.  Wiping away the dust from the previous grit, even when using a vac, also helps.

 

[Thompmd]

Learning opportunity for me! I never thought about the stroke difference from 3-5!

I’ve been sanding everything to 1200.

Sometimes on the back I will stop at 320/400, no reason other than lazy I guess.

Tell me more about the stroke difference and if it does make a difference(noticeably). I’m not opposed to a second sander but I would stay with the same 150 size to not duplicate paper.

Also, I use Granat paper for everything, I have some 24 saphir for rough slabs, it definitely removes material in Rotex mode but I spend the rest of the time removing scratches

 

[ear3]

I wouldn't say the 3mm stroke sander is a necessity.  I mainly use it for when I'm sanding veneer, as it is much less likely to burn through thin material than the 5mm stroke sander, which can be quite aggressive.  But as mentioned, I also find it delivers more consistent results with high grit sanding.  Not that you can't get good results from the 5mm or Rotex, but every so often I have found some inconsistency or imperfections when working with the larger orbit sanders above 400, whereas the 3mm stroke sander always delivers.  So nowadays I just default to the 3mm sander when going into the high grits.

24 grit saphir is super aggressive to start at -- are you working with rough cut slabs?  For large flat surfaces I generally work initially with the RS2 to maintain a flat, even surface, then switch over to an ROS around 150 grit.  I would be worried about dishing the surface starting that low with the Rotex.

 

[Thompmd]

Yes, I mostly work with kiln Dried 2-2 1/2” Live edge slabs, mostly Walnut but I recently used some rough 1 1/4” walnut  to make a couple things.  I’m also going to use the 1 1/4” to make some storage for the Festool Sys-AZ’s.

Tell me more about the RS2. I’m also definitely having trouble getting everything flat(can feel with my hand).

I currently only have a Dewalt 735x and the RO150 is my sander. Would my belt sander help keep things flat or do I need what I call an actual sander like a 22/44???

The slabs I get and resell are too big up to 50”w and 16’ long and I can’t justify the cost of equipment of that size.

Just a hobby guy making tables, benches, shelves , etc at this point

 

[ear3]

Here's a good review thread on the RS2.  It's not as fast as the other sanders, but on large panel work, I have found the patience investment really pays off.  No more sinking feeling sighting down the length of a panel and noticing the waviness and dishing from those spots where you pressed in too hard to remove a scratch or a high spot.

When I work with rough slabs, generally my first step is to plane them with a router.  I now use the Woodpeckers slabbing mill to do this work, but you can get the same results by building your own router sled.  The Woodpeckers makes the process more efficient and repeatable, but it is unfortunately ridiculously expensive.  Once that is done, the RS2 starting at 60 or 80 grit will remove the router bit tracks while keeping the surface flat up until you're ready to move to the finishing grits with an ROS sander.

I've never used a belt sander for slab work, though I know some people do employ it in the initial stages for knocking down high spots.  I would imagine it would still be a challenge though to keep everything flat with a belt sander across the entire surface, given how aggressive it is.

 

[Alanbach]

I have an RS2 and it is a great specialty sander! Unfortunately, it has just recently been discontinued and unlike the RAS it became hard to find almost immediately.

 

[Cheese]

Interesting article in regards to Rotex vs STD mode and as the grit went higher the speed went lower?? Being new I was wondering if this normal and if that’s what you did?

I seldom ever change the speed of the sander. 90% of the time all of the Festool sanders are at max speed. The only exception to that is if there is a strange combination of grain pattern and sandpaper grit, then I'll fiddle with the speed to make the sander less jumpy.

 

[ear3]

I had forgotten about that.  I've heard the Bosch OS50VC half sheet sander is fairly comparable to the Festool in terms of performance, though I have not used it myself.

I have an RS2 and it is a great specialty sander! Unfortunately, it has just recently been discontinued and unlike the RAS it became hard to find almost immediately.

 

[rvieceli]

If you are looking for a half sheet sander and can't find a Festool RS2, there are a couple of offerings you should take a look at. One of those is my favorite and suggestion.  [wink]

The Bosch that Edward mentioned is a contender but has a slight problem depending on your point of view. It gets very good reviews all around and is Bosch quality. The problem is that it only takes clamp on half sheet paper or stick on sandpaper. Doesn't do the hook and loop stuff. Actually comes with the punch to make the holes for dust collection. Runs around $300
https://www.amazon.com/Bosch-OS50VC...B00B7EU1I4/ref=sr_1_1?dchild=1&keywords=Bosch+OS50VC&qid=1593623144&sr=8-1

This one is my favorite, the offering from Makita. BO4900V It is basically the same form factor. Is made in Japan and of good quality. The sander takes the normal clamp on half sheet paper BUT it will also take Festool paper intended for the RS2.. Hook and loop attachment and the exact same hole pattern. So you can use your favorite Festool paper. It usually runs around $175 or so although Amazon has a current price of $125 BUT not available until the first week in August. The only inconvenience with this sander is that the dust port is around 20-22mm so you need something to adapt the Festool hose to it.
https://www.amazon.com/Makita-BO490...0000789HT/ref=sr_1_1?dchild=1&keywords=Makita+bo4900v&qid=1593623614&sr=8-1

Ron