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thickness sanding  how, what grits? http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=50156 
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Author:  Clay S. [ Thu Jan 11, 2018 8:31 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
" But I’m 100% convinced any thickness could be used" I know 6 inch will work  You just rip it to 3" and it works every time. 
Author:  Mike OMelia [ Thu Jan 11, 2018 8:38 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
So, clay, what ur saying is only one thickness can ever possibly wrap a particular drum? 
Author:  bcombs510 [ Thu Jan 11, 2018 11:51 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
Mike OMelia wrote: So, clay, what ur saying is only one thickness can ever possibly wrap a particular drum? Mike, in the ultimate showing of Brad has too much free time... Here are a couple videos where I do the patented roll paper test with both 2 1/2" and 2 3/4" paper. Hopefully this shows what I mean and if you can come up with some way to not have to cut the paper that is great. Or better yet, if you come up with a way where it will work for all drum widths, even better! Plus it was fun to learn how to use my son's GoPro. http://www.youtube.com/watch?v=_DPCIHDj ... e=youtu.be http://www.youtube.com/watch?v=Sx9gO8sT ... e=youtu.be Sorry about the dust collection hose getting in the way. Also, I could have done better with angling the camera. Maybe next time! 
Author:  George L [ Fri Jan 12, 2018 10:17 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
Clay S. wrote: Tape is your friend ... My old fingers can't work those stupid clips that don't really hold the strip in place at the far end of the drum. I usually just run a piece of strapping tape around the last inch or so of the sanding strip and drum. You don't have to worry about where the strip ends. Unless you really need that last bit of width it could be a nonmathematical solution. I'd like to hear more about this idea. You just tape the final edge of the roll to the drum, instead of fighting to insert it into the clip? Brilliant! Fiddling with those stupid clips has taken the fun out of my workshop time on more than one occasion. 
Author:  Clay S. [ Sat Jan 13, 2018 9:27 am ] 
Post subject:  Re: thickness sanding  how, what grits? 
"I'd like to hear more about this idea. You just tape the final edge of the roll to the drum, instead of fighting to insert it into the clip" It does work, but you lose an inch or two of sanding width. I use strapping tape or cellophane tape and wrap it completely around the drum and edge of the sandpaper (sometimes more than once). You have to stick the ends down good so it doesn't peel off when the drum is spinning. It is a little easier on the fingers, and when the end that goes into the clip tears off and leaves the strip an inch too short it allows you to continue using it. "So, clay, what ur saying is only one thickness can ever possibly wrap a particular drum?" No, actually if you don't mind a small portion of the end of the drum not being covered by sandpaper, you can cut an angle on the opposite (inner) side of the strip so it can slip into the clip. 
Author:  Mike OMelia [ Sat Jan 13, 2018 12:06 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
bcombs510 wrote: Mike OMelia wrote: So, clay, what ur saying is only one thickness can ever possibly wrap a particular drum? Mike, in the ultimate showing of Brad has too much free time... Here are a couple videos where I do the patented roll paper test with both 2 1/2" and 2 3/4" paper. Hopefully this shows what I mean and if you can come up with some way to not have to cut the paper that is great. Or better yet, if you come up with a way where it will work for all drum widths, even better! Plus it was fun to learn how to use my son's GoPro. http://www.youtube.com/watch?v=_DPCIHDj ... e=youtu.be http://www.youtube.com/watch?v=Sx9gO8sT ... e=youtu.be Sorry about the dust collection hose getting in the way. Also, I could have done better with angling the camera. Maybe next time! Very interesting. Nothing like a video example to illustrate the problem. I looked at the manuals for the 16 and 22 inch drums. They provide the same info. The paper diagram shows a 15 3/4" taper, and is based on a 3" width of paper. Let me get my pencil and calculator out. Thanks Brad. Excellent work. 
Author:  Mike OMelia [ Sat Jan 13, 2018 2:26 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
I have a formula to test. Maybe, Brad, you can try? It defines the straight length along the edge to determine the taper. Use it to mark the paper, draw a straight line across the paper, and then use a straight edge to mark the taper from there to the corner. The rest is as you did it before. If it works, I will explain more: This assumes a drum sander with a 5" diameter. The Jet 16" is 5". L is straight edge length of taper (not the angled length) L = sqrt(w^3/(DL/nwraps  w)) w is paper width, nwraps is what you see on drum with 3" paper, counted from taper cut point to taper cut point. I see 7 on my 22" drum. DL is drum length. Everything is in inches. For my sander, I get around 15.5" for 3" and 7.5" for 2.75". 5" for 2.5". You will need to do your own calculations for 16" drum. The square root and possibility of a negative number limits things. This means for wider paper, number of wraps is reduced. Kind of makes sense. My length of 15.5 is precisely correct based on manual. sqrt(3^2 + 15.5^2)=15.78 (close enough to 15.75) 
Author:  Mike OMelia [ Sat Jan 13, 2018 2:35 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
I just noticed something in the equation. Drum diameter not there. So it will work for any diameter as long as you know the number of wraps for the paper it was designed for. (3") 
Author:  bcombs510 [ Sat Jan 13, 2018 2:37 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
I will give it a try later tonight. I’ve got half a dozen things going on in the shop today. Sent from my iPhone using Tapatalk 
Author:  Mike OMelia [ Sat Jan 13, 2018 3:02 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
Me too. You got me stuck on this. Dang it. U might ask why 15 3/4 works for 1020, 1632, 2244. Good question. I think 3" paper width drove design lengths. There appear to be other tapers that work. Also turns out that the numbers I calculated above for 2.75" (7.5) will work on your drum. For 2.5", same thing. Maybe. There will probably be a downside to this in that some of the end of the drum will be unusable. 
Author:  bcombs510 [ Sat Jan 13, 2018 3:18 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
Mike OMelia wrote: Me too. You got me stuck on this. Dang it. U might ask why 15 3/4 works for 1020, 1632, 2244. Good question. I think 3" paper width drove design lengths. There appear to be other tapers that work. Also turns out that the numbers I calculated above for 2.75" (7.5) will work on your drum. For 2.5", same thing. Maybe. There will probably be a downside to this in that some of the end of the drum will be unusable. What I noticed was that the number of wraps with 3” paper was always drum length  1 / 3. So for my 16” it was 15 / 3 so 5 wraps. Same for 22” drum  21 / 3 = 7 wraps. Any idea where that 1” consistently gets lost? The paper goes edge to edge so why is it consistently drum width  1? Sent from my iPhone using Tapatalk 
Author:  Mike OMelia [ Sat Jan 13, 2018 3:35 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
I don't know. What I do know is this is based on "wrapping efficiency". The ratio of the drum area to the paper area. For the 2.75 and 3 paper, there is only 5 and 7 wraps possible (on 16 and 22) For the 2.5" paper, on your drum. there is 5 and 6 wraps possible. 5" edge, 11" edge. 
Author:  Mike OMelia [ Sat Jan 13, 2018 5:28 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
I take it all back. This problem does not appear to have a (good) solution. Other than Abranet making proper widths. There appears to be one where you make a longer (MUCH longer) taper, but who wants to do that? 
Author:  mountain whimsy [ Sat Jan 13, 2018 7:04 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
How many luthiers does it take to wrap a sanding drum....... 
Author:  Mike OMelia [ Sat Jan 13, 2018 7:47 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
It is a surprisingly difficult problem. One that does not appear to have a simple solution without leaving gaps. What makes it really hard is ending up at the right location where the clips are. Jet sanders are ubiquitous. Why would Mirka make a width jet sanders cannot use? 
Author:  Mike OMelia [ Sat Jan 13, 2018 8:32 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
I think I’ve figured it out. 2 3/4”. What u think? 
Author:  bcombs510 [ Sat Jan 13, 2018 8:37 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
Looks good. What’s the formula? Sent from my iPhone using Tapatalk 
Author:  Mike OMelia [ Sat Jan 13, 2018 8:48 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
No formula Brad. 15 3/4” taper as per manual. But, ignore the 3” clip off end. Use only half or so of the clip width. Apparently that’s the key. Have no idea if this would work for 2.5”. Maybe you could verify? 
Author:  bcombs510 [ Sat Jan 13, 2018 8:51 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
Wow, that is really surprising! I will give it a try. Sent from my iPhone using Tapatalk 
Author:  Mike OMelia [ Sat Jan 13, 2018 8:51 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
The clip channel is 1.25” wide. I noticed on all my current rolls I was only using 0.8”. Got me thinking. Maybe the idea of that width is for some flexibility on width. 
Author:  bcombs510 [ Sat Jan 13, 2018 8:52 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
Mike OMelia wrote: Jet sanders are ubiquitous. Why would Mirka make a width jet sanders cannot use? The Abranet is not marketed for drum sanders. It’s for Mirka’s palm vac sander. Sent from my iPhone using Tapatalk 
Author:  Mike OMelia [ Sat Jan 13, 2018 8:53 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
Please do Brad. I feel awful for spending my whole day on this. Lol!! 
Author:  Mike OMelia [ Sat Jan 13, 2018 8:59 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
bcombs510 wrote: Mike OMelia wrote: Jet sanders are ubiquitous. Why would Mirka make a width jet sanders cannot use? The Abranet is not marketed for drum sanders. It’s for Mirka’s palm vac sander. Sent from my iPhone using Tapatalk Not true. That was the whole point of this thread. Abranet makes drum rolls. Or at least, it was one of the points. 
Author:  Mike OMelia [ Sat Jan 13, 2018 9:18 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
Brad, how did u figure out 2 1/2 would work? 
Author:  bcombs510 [ Sat Jan 13, 2018 9:46 pm ] 
Post subject:  Re: thickness sanding  how, what grits? 
Mike OMelia wrote: Brad, how did u figure out 2 1/2 would work? Because I was focused on the number of wraps. At 2 1/2” each wrap was 1/2” short of where 3” paper landed. Since the 16” drum took 5 wraps and each wrap was 1/2” short it left me with 2 1/2” or one more full wrap. I know what you mean about Mirka selling Abranet on a roll, but I don’t think they are targeting that for drum sanders. Their palm vac is 2 3/4” wide and it’s pictured on the wrapping for the roll. Sent from my iPhone using Tapatalk 
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