Which profile for a 3/4 inch edge?

[EWTHeckman]

The project I'm currently working on needs a rounded edge on 3/4" thick piece of wood. The edge is already routed with a 3/4" diameter bit, but I need to sand it. Which LS 130 profile will work best for this job?

 

[tbellemare]

I'd use the 6mm radius concave pad, 490163. If you load it with Rubin and you don't get a tight fit on your bullnose, loosen one edge and pull it out slightly, which will slightly increase the radius.

That's a nice feature of the concave pads, the radius is actually variable depending on how you load the paper.

Tom

EDIT:
corrected backward thinking...

 

[EWTHeckman]

Thanks Tom.

I'm kind of surprised at the recommendation. I was expecting something along the lines of the 18 mm or 25 mm concave, or possibly creating my own.

How would you do it with the 6mm? My guess would be to let the sandpaper "float" in the curve and then work the sander around to both sides of the board. But I could just as easily be wrong on this one.

Just to make sure we're on the same page, this is the profile I'm talking about:

[attachimg=1]

 

[tbellemare]

At first I thought about the full concave profiles but I don't think they'll get the results you want. If the parallel edges aren't the correct distance apart, I don't think you gain anything by completing the bullnose. I've done similar sanding jobs and I used a quarter-round profile and "walked" it around the bullnose as I moved it up and down the length. It works well and the flats can then be brought truly coplanar to the flats on the work piece.

I recommend Rubin when you leave the paper loose in the base concavity of the pad. It has a strong backing and holds up well without the full support of the radius. To the contrary, if you want the paper to conform really closely to the pad, a flexible backing is superior.

Tom

 

[EWTHeckman]

Thanks Tom. That makes sense.

Two more questions…

I'll be using Granat for the rest of the sanding. Is Granat's backing good enough to use for this part, or is the Rubin backing actually stronger? Will there be a noticeable difference in the results between the two types of papers? (This work will be painted.)

Thanks for your help.

 

[waho6o9]

Hi,

I agree that  for the 3/8" bead profile you would need to do a custom pad.  And I would suggest either Brilliant 2 or Granat  abrasive for a small detail such as the bead  because it is thinner and will fold into the tight shape better. You will still need to go easy though to avoid blunting the bead.

Here are some links that may be helpful with the LS130. Some are for threads here on FOG and some are for threads on talkFestool.  Also the custom pad I made does not use the "sand in" method , it just wasn't needed for the shape I did.

Custom Pad

LS130 Review

Grit changing tip.

Another review

Seth
http://festoolownersgroup.com/festool-tools-accessories/ls-130-sander-question/

SRSemenza  has great tutorials on making profiles on the L130 sander.  Have fun.   [smile]

 

[tbellemare]

Merry Christmas, Ed!

I think you'll be fine with Granat. It has a synthetic backing that is weaker than Rubin but should be fine if you don't press too hard for too long. I personally think that the results from Granat will please you also.

Tom

 

[EWTHeckman]

It has a synthetic backing that is weaker than Rubin but should be fine if you don't press too hard for too long.

I'll be sanding roughly 30 feet of edge. That strikes me as probably being "too long." It sounds like I should be using Rubin for this edge.

Thanks for the help!

 

[stairman]

why does the profile need to be machine sanded?

did you cut the bullnose with a quarter round bit (top  -then bottom?)

30ft isn't much to sand in any case,  but the Granat has been impressing me everytime I stick one on and sand with it.  they just go forever!  As a matter of fact,  I haven't actually worn one out sanding wood...  -not yet anyway.

if cut cleanly with a bullnose cutter, I would hand sand with 150g wrapped around a sanding sponge,  and move on...
if, on the other hand, it had been cut by making top then bottom passes with a quarter round bit,  I would either take a cleaning pass with a bullnose bit (whether against a fence, or using a template or using the guiderail)

OR  I would get out the dremel and some scrap flat steel,  and cut out a scraper.  you  need less percentage of radius than the profile...  since this profile = 180deg, your scraper should be more like 160deg.

spent, thin kerf saw blades make dandy scrapers,  as does a number of things you can find in the trashpile on most jobsites.

cut it close with a cutoff wheel (dremel), use a (dremel) sanding drum on slow speed to finish the shape,  lap the sides,  then burnish as you would any other scraper.
you'll be surprised how easy it is to make one,  and once you do,  you'll have opened a new door for yourself...

My forte is stair-work.  particularly curved stairs.
In about 20min to 1/2hr, I can usually make a pair of sides + a top handrail scraper set (of typically complicated profiles),  and with this, I can smooth out and actually FORM dead-accurate handrail profiles from the roughest fittings/stock you ever saw...
grinding and sanding,  it would never happen!

remember though,  when scraping,  you'll have to go back with sandpaper and ROUGH-UP everything you scraped, because scraping produces such a glass smooth surface, that it won't take a stain very well.
-still,  a LOT easier than trying to sand something into shape in the 1st place 

 

[waho6o9]

Thanks for the tip stairman, gonna give it a try.  [wink]