Author Topic: How big can you step between Grit?  (Read 3231 times)

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Offline rdr

  • Posts: 61
How big can you step between Grit?
« on: April 30, 2017, 05:21 PM »

Looking for some advice on stepping between grit levels to aid my purchase plan for a ROTEX 90

I need a one stop sander for smallish projects including paint removal around old window frames and such but also prepping wood for finishing. Whilst on occasion the wood will be cabinet size plywood sheets it won't be at a production scale so I'm thinking the 90 will suffice my needs.

Anyway, with regards to ordering abrasives with it i note a lot of the videos for the Rotex seem to demonstrate a method of stepping through the grit levels one at a time.  Whats peoples thoughts on skipping a few grit levels either at the low or high end? Do you really need to work through every grit to get to where you want to be? 

This is purely me thinking from an initial outlay perspective, the abrasives do cost quite a bit at the outset.

Any thoughts appreciated

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Offline neilc

  • Posts: 2124
Re: How big can you step between Grit?
« Reply #1 on: April 30, 2017, 06:32 PM »
If you are stripping paint and then going to repaint, I'd suggest maybe starting at 80 -> 120 -> 150 would be fine for a painted finish.  For a natural / stained finish I'd start at 120, then 150 and potentially want to go up to 220.  Skipping grits is more apparent in a natural / stained finish than a painted one.


I have the Rotex 90 and 150.  The 90 is a nice sander and great for tight quarters, but I would not want to do a lot of large panel sanding with it long-term.  Fine for an occasional piece, but a larger sander would be more satisfying.

I've been happy with Granat grit paper for most of my sanding as a universal paper.

Make sure you pick up extra delta velcro backing pads for the RO-90.  You will find that with paint removal, you may go through a few on the corners.

Offline tjbnwi

  • Posts: 5048
  • Cedar Tucky Indiana
Re: How big can you step between Grit?
« Reply #2 on: April 30, 2017, 07:09 PM »
I don't skip grits, make sure you wipe the surface off before stepping up a grit. You need to remove the previous grit from the surface.

Tom

Offline Jesse Cloud

  • Posts: 1699
  • Festooling at the end of a dirt road in New Mexico
Re: How big can you step between Grit?
« Reply #3 on: May 01, 2017, 12:14 AM »
I seldom do paint finishes, so no opinion.  But for fine finishes, you need to remove all the scratches from the previous grit before moving on to a higher grit.  If you skip a grit, this can still be done, but it will take much longer.  Ironically, I don't have time to skip grits.

Offline Holmz

  • Posts: 3749
Re: How big can you step between Grit?
« Reply #4 on: May 01, 2017, 03:43 AM »
The step-through-em scheme is further supported by some sellers (maybe Marino) selling assortment packs with every grit.

If the RO-90 is used for finishing in the non-rotary (Random Orbit) mode, then the Mirka screens also come in an assortment pack.
They are as good or better in most way except for the ability to tear at the edge.
So in Rotary mode, I would advise against the screens without any real evidence that they do not work.

Offline w802h

  • Posts: 201
Re: How big can you step between Grit?
« Reply #5 on: May 01, 2017, 07:15 AM »
I wouldn't hesitate to go from 180 to 220, but I wouldn't make a corresponding size move from 60 to 100.  It's really important -particularly in the lower grits - to remove the coarse scratches as others have said.  The material can matter as well.  A painted wooden surface can be left at a lower grit.  For exterior work this is often necessary to improve adhesion.  For interior stain work, it depends on the material.  Red oak has a pretty coarse grain and sanding well into higher grits won't necessarily improve the wood.  Dark-stained maple is unforgiving when it comes to swirl marks and blotching so I prefer a scraped finish which seems to improve my work in both cases.  My last caveat is what you are sanding.  A floor and a piece of furniture have different grit ranges associated with their respective tasks. 

Offline rst

  • Posts: 1497
Re: How big can you step between Grit?
« Reply #6 on: May 01, 2017, 07:25 AM »
My first job in 1971 was in a finishing department of a high end custom kitchen factory.  The factory primarily produced maple, oak, and pine  kitchens.  All wood was sanded to 150 before coming to the finish area to be stained or painted.  Every grit in ascending order was used.  The rational behind using every grit was that each grit would be used for a shorter time to erase the scratches from the grit before.  After sanding the maple and oak would be sprayed with water, reopening the grain for the stain or sanding sealer to penetrate deep into the wood.

Offline grbmds

  • Posts: 1683
Re: How big can you step between Grit?
« Reply #7 on: May 01, 2017, 10:13 AM »
I have found that it never pays to skip grits. Whatever grit you start with, the best plan is to move up to the next grit, rather than skipping grits, until you get to the last grit you feel you need to use. So, if you started with 40 grit to strip paint off, then 60, 80, 100, 120, 150, 180, 220 (or sometimes 240), 320, 400, till you at your final grit. With new wood, you may not need to start as low as 40. With bare cabinet grade plywood, since I believe it is already sanded to 120, there is no point in starting below 120.

As to what you finish with . . . To some degree that's up to you. I've finished with gel wipe-on polyurethane and stopped at 150 or 180, but usually it's better to go to at least 220. Others may go beyond that.

I don't do a lot of painting so am not able to give you a recommendation on where to stop. However, again, I wouldn't skip grits.

Always wipe down the piece between grits. If you don't, you run the high risk of a scratch pattern that reflects the residue from the previous grit. Wiping of the previous grit's residue really does make a difference. It can be vacuumed off also with a small soft brush attachment, but wiping ensures that there is nothing left from the last grit.
Randy

Offline Michael Kellough

  • Posts: 2866
Re: How big can you step between Grit?
« Reply #8 on: May 01, 2017, 01:57 PM »
I usually jump 50%. example 100 to 150 to 220.
If the work is pretty smooth to start with I'd start with 120 or higher.
I wouldn't use a courser grit than needed just to stick with a preordained sequence.
Results are what matter.

I decide which grit will be the last depending on type of finish and then work (think) backward to choose the grit steps.

There are just too many grits that are too close together these days IMO. 220 then 240? No way.
In the old days (when such rules of thumb were laid down) there were only four or five grits.


Offline SRSemenza

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Re: How big can you step between Grit?
« Reply #9 on: May 01, 2017, 02:37 PM »
I usually jump 50%. example 100 to 150 to 220.
If the work is pretty smooth to start with I'd start with 120 or higher.
I wouldn't use a courser grit than needed just to stick with a preordained sequence.
Results are what matter.

I decide which grit will be the last depending on type of finish and then work (think) backward to choose the grit steps.

There are just too many grits that are too close together these days IMO. 220 then 240? No way.
In the old days (when such rules of thumb were laid down) there were only four or five grits.

And probably a lot more hand sanding.

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I skip grits (one not two or more) on a regular basis. But it depends on the work. I have most  (all?) of the grits so that I can decide on my starting and ending point and whether or not I want to skip and choose based on the work.

Stripping paint? I will start at  40, 60, or 80 depending on how tough the paint is. And generally in Rotex mode ( I like speed 4). Then stay at the same grit or back track one when switching to random orbit. Which helps get rid of the Rotex swirls quickly. If I started with 60 or 80 I will go to 100 next. If I started with 40 I will add 80 in to the mix. And make sure that 100 is very thorough since this is the last point that will easily take out the Rotex marks. Next 150 and depending on the repaint maybe 180, maybe stop at 150.

There are a lot more variables than just is it OK to skip or not to skip.  Which doesn't make it easy to buy abrasives and not end up getting them all unless you are doing a limited range of types of work. And it seems that everyone has there favorite grit and progression. EX- I use 120 the least and others will say they wouldn't do without it.

 @rdr   For your RO90 purchase line up with an eye towards  multiple tasks  and not needing to buy every grit at the start. I suggest  60 Granat, 100 Rubin, 150 Rubin, 180 Rubin or Granat,  240 Granat in the round shape. And 60 Granat, 150 Rubin, 240 Granat in the delta shape.  You can do a whole variety with that line up quite well.  I suggest the 240 rather than 220 because it is a bit farther from 180 and a bit closer to 320. Just add others as you decide you want/ need them. There are lots of skips in that but it will do the job without breaking the bank.  Oh, I am not a Granat does it all guy so that's why the Rubin.  I also like Cristal and Brilliant but those are gone except for old stock.

Seth
« Last Edit: May 01, 2017, 02:41 PM by SRSemenza »

Offline rdr

  • Posts: 61
Re: How big can you step between Grit?
« Reply #10 on: May 01, 2017, 02:42 PM »
Thanks for all the comments guys, really useful.

Given the first tasks will be striping frames I think I will concentrate on building up a collection of lower grits first and overtime build up a collection as and when the jobs require.

Regarding the decision of the RO90, I made the decision purely for the primary job at hand of stripping and prepping frames where the Delta function and smaller pads will suit. I plan to make some cabinets so will see how it goes with the 90 if it does prove tedious or invective then its an excuse to buy another toy  [smile]

Offline Holmz

  • Posts: 3749
Re: How big can you step between Grit?
« Reply #11 on: May 01, 2017, 04:01 PM »
Thanks for all the comments guys, really useful.

Given the first tasks will be striping frames I think I will concentrate on building up a collection of lower grits first and overtime build up a collection as and when the jobs require.

Regarding the decision of the RO90, I made the decision purely for the primary job at hand of stripping and prepping frames where the Delta function and smaller pads will suit. I plan to make some cabinets so will see how it goes with the 90 if it does prove tedious or invective then its an excuse to buy another toy  [smile]

The 60-120 and the delta sound like what you need for the R090 and the good paper media.

Then maybe go buy a proper 6" (Bosch, or Roybi, dewalt) for finish work on flat pieces., which will need grits in 80-220/240 (Usually 120/180/240. The worst of the bunch will be beaver along better than the RO-90, but for window frames and the like, they would not be as good.

Offline Pnw painter

  • Posts: 95
Re: How big can you step between Grit?
« Reply #12 on: May 01, 2017, 04:41 PM »
If you look at the mfg data sheets they'll often list what grit to use to prep the surface prior to painting. Work backwards from there.

The quality of your sanding also differs If you'll be apply clear finishes or stained finishes vs. painted finishes.

If you want the very best finish I wouldn't go much more than every other grit like others have said. I'd also recommend using Granat for just about everything other than some special circumstances.


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Offline Cheese

  • Posts: 3253
Re: How big can you step between Grit?
« Reply #13 on: May 01, 2017, 04:51 PM »
I'd just add that if you do use the RO 90 for large panels, make sure to use a hard pad, 495623, to help mitigate any dishing of the surface.

Offline neilc

  • Posts: 2124
Re: How big can you step between Grit?
« Reply #14 on: May 02, 2017, 12:28 AM »
@TylerC In trying to answer this question, I went to the old 'abrasives selector' listed in the nav on this site.  Well, it's no longer an 'abrasives selector' so you might want to change that nav item. 

Where is the DETAIL on papers now?  Here's an example of your product page on sandpaper - https://www.festoolusa.com/accessory/499148---stf-delta7-p220-ru210#Overview

Nowhere on that page does it say 1) what sander it works with, or what materials it's best for.  And the image adds nothing.

Matthew posted this in 2007 - http://festoolownersgroup.com/festool-tools-accessories/festool-abrasives-details/msg13771/#msg13771

It used to be on the Festool USA site but links to it now get a 404 error.  One more thing to alert the guys in Germany to.

It's way out of date from 2007 - 10 years ago.  But I'd think there might be an updated version you can include in the reference section on the USA site?

neil






Offline TylerC

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  • Posts: 939
Re: How big can you step between Grit?
« Reply #15 on: May 02, 2017, 08:41 AM »
@TylerC In trying to answer this question, I went to the old 'abrasives selector' listed in the nav on this site.  Well, it's no longer an 'abrasives selector' so you might want to change that nav item. 

Where is the DETAIL on papers now?  Here's an example of your product page on sandpaper - https://www.festoolusa.com/accessory/499148---stf-delta7-p220-ru210#Overview

Nowhere on that page does it say 1) what sander it works with, or what materials it's best for.  And the image adds nothing.

Matthew posted this in 2007 - http://festoolownersgroup.com/festool-tools-accessories/festool-abrasives-details/msg13771/#msg13771

It used to be on the Festool USA site but links to it now get a 404 error.  One more thing to alert the guys in Germany to.

It's way out of date from 2007 - 10 years ago.  But I'd think there might be an updated version you can include in the reference section on the USA site?

neil

We're actually planning to launch a new abrasives page on the site today(?). It will be kind of a combination of the abrasive search from the old website with the table that's available in the 2017 catalog.

Clarification: This will initially be for the US website only.

Offline neilc

  • Posts: 2124
Re: How big can you step between Grit?
« Reply #16 on: May 02, 2017, 09:37 PM »
Thanks Tyler!  Please share when it's live,

Offline bebum

  • Posts: 3
Re: How big can you step between Grit?
« Reply #17 on: June 05, 2017, 06:21 AM »
Adding my 2 cents: from my experience, insufficient dust brushing/vacuuming can do more damage than skipping grits. Especially that sandpaper tend to loose small amount of abrasive grains that can remain in wood for a long time during sanding (we did some experiments using microscope).