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Filippo,

Is that measurement without paper on it? Mine seems dead on without.

I found that my 16/32 has somewhat the same problem with paper on though. I have attributed it to not getting the paper tight enough in the middle as I am winding it on. When I have someone help me with changing the roll out, the difference is usually about .005 or less. Just my observations with my Performax sander. I hope this helps!

Mike

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I'm outside looking in, just farther from the window than most.

Filippo my friend .015 - .020 variation is way to much IMHO.

With my little 10-20 Performax I only see .002 - .003 variation max anywhere on the plate. Of course I am also doing double pass sanding too.

It's interesting how often people will ask if the double pass sanding is accurate....... and they feel the need for a larger machine.

I have noticed too that the machine will continue to take stock off with additional passes even when you do not adjust the drum. With this said I wonder what your results would be after two additional passes and not touching the drum adjustment.

As mike indicated people do have trouble winding the paper tight enough on the drum so I agree that this is something to check too.

Also, what paper are you using - Performax or something else? I have yet to switch from Performax papers and I wonder if some of the alternatives are consistently the same thickness.

I set mine up with a machined aluminum block, three clip leads, a nine volt battery and a small lamp. I clip side of one lead to the drum, the other side to the lamp. The second lead (wire with alligator clips) goes from the other side of the lamp to the + of the battery and the final one from the - of the battery to the block. When the drum touches the block the light goes on. With this set up I can make the drum parallel to the feed belt within .002"

Before I did this I turned the piece every trip through the machine and that made the edges thinner than the center.

I was ready to get rid of the 22/44 before that.

One other thing - I had to drive a hardwood wedge in to get the thing adjusted. The spring wasn't strong enough. If anyone is really interested I could take a picture.

Steve

What happens if you run the piece through a second or third time at the final setting to reduce flex related outages?

I can't remember, is this fresh grit? Is the feed belt worn in the middle?

I just assembled and set up my 16-32 yesterday, of course it is light years beyond the home made unit that I used for 25 years......what I see is that there is a degree of deflection (drum/table?) that is dependant on the amount of resistance (pressure due to material thickness and width) at any given moment.
Profiled to shape tops are coming out thinner on the edges, though within about .2mm (.004-.008"). I am also reversing orientation per pass.
For classical tops this is ok as I want them thinner at the edges anyway though I think I will try to sand items as square as possible (i.e. even out the resisitance or deflection through the pass as much as possible) and continue to tweak the adjustments.
Overall, I am quite happy with it.

Filippo, I spent a few hours a couple weeks ago getting mine all dialed in, too. It's difficult to get it perfect. When I called Performax, they told me to check the platform under the feed belt.

For what it's worth, to anyone wondering how to check their drum for level, I used a 1x2 piece of hardwood, marked a line on it, and placed the tips of feeler gauges on the line. That way I knew the height of the board was exactly the same each time I checked. I laid all of my feeler gauges out for easy access. I'd find the gauge that just barely made contact with the drum on one end of the drum, and then I would do the same at the other. I adjusted the height until they were within a few thousandths of each other, with the shallower of the two on the motor side of the drum so that the edges of the soundboards and backs will be a few thou thinner than the centers.

I never adjusted mine. I just ran several different sized boards through it to use as sleds. I get to within a .001 - .002" over 16".

If you get inconsistent flex in your arm, you may be taking too heavy of a cut or your arm may need to be tightened.

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http://www.chassonguitars.com

I set my 16-32 up with no paper on the feed table or drum.
Then I put those papers on-I use 60 grit to do the heavy removal on hardwoods-80 on tops.
And check the set !
I've found some of the belts vary in thickness-also put them on tight-no play!
I end up with less then .005" difference.
Mine is 10 years old!!!!
I've thinned 100's of sets with no problem-do not try to take to much off at once!
As Dave said turn the set around to get a more even sanding!!

But as someone that started out planning all my woods by hand
I find this a small -very small problem!!!!


Mike

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Mike Collins

16-32 here and I get about 0.005" difference on the edges, with the motor-side thinner. I also either flip or reverse orientation every pass.

I think the "thicker in the middle" problem is due to the open end floating up during the cut on the 22-44, it would stand to reason that this would be less of a problem on the smaller models.

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The member formerly known as erikbojerik....

A very small problem indeed Mike.
I rather doubt this machine was created with guitar makers in mind (especially considering the open ended design which allows one to sand things like wide door panels or butcher block table tops).
I suspect the tolerances we use are infinitesimal to most folks who own these.

Mike, when you change grits from 160, about how many thou will it take to remove the scratches? I've been doing everything with 100, and I can tell it's not the most efficient use of the paper. At $40 a pack, I'd like to get as much use out of them as possible.

Filippo... I have a 16/32. My experience is exactly like Mike's... I use 60 and 80 grit, and flip the material over each pass. I've had mine for over 10 years, with no problems. I think it's important to remember that these things are sanders and not edge tools. If you had that much variance in a planer or a joiner you would have a real problem...
That said... something that should help is to run a few passes WITHOUT lowering the drum when you're near your final dimension. I think that should help get your tolerance closer to perfect.

long

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"No man ever steps in the same river twice, for it's not the same river and he's not the same man.” -Heraclitus of Ephesus

Filippo, your MDF test is with just a single pass, right? Doing your measurement with thickness calipers?

If "yes" to both, I think you're on the right track with the table.

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The member formerly known as erikbojerik....

Filippo - I've noticed on my 16/32 that, when the paper gets loose, the extra play collects at the motor end of the drum, not in the middle. Mine definitely sands more at the edge (or both edges if I'm reversing the feed each time) if this happens, but I don't know if the error is comparable to yours - I tighten the paper when I notice it happening.

JIm

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Jim Kirby
kirby@udel.edu

Flippo, my 22/44 is the same as Jims, the paper tends to get play at the motor end, causing a bit more to be removed from the edge. Have to constantly take a look at that paper and adjust for that. Works great when the paper is good, nice even removal. As also mentioned, I really creep up on the final results, seems to work better with smaller removal increments....

Best
Bruce

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Bruce Herrmann
"What lies behind us and what lies before us are tiny matters compared to what lies within us."

My instruction book from 1998 says to leave a gap between the last 2 layers for the last few inches & to leave the paper to the out side edge of the 1 inch groove in the drum so as the paper pulls tight it will not overlap -or
get loose!

Try this -I hope it works for yas
IT has for me!
Mike

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Mike Collins

My instruction book from 1998 says to leave a gap between the last 2 layers for the last few inches & to leave the paper to the out side edge of the 1 inch groove in the drum so as the paper pulls tight it will not overlap -or
get loose!

Try this -I hope it works for yas
IT has for me!
Mike

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Mike Collins

Flippo,
How thick is the MDF that you used in your test? If it's 3/4", I'd wonder if the pressure of the sander- especially with multiple passes, is enough to deflect it near 0.020". But maybe that's another way to test your machine. If you put the stock to be sanded on a thick, stiff sled- using double-stick tape- you should be able to eliminate bed deflection from the problem analysis. I haven't heard of this problem on any of the forums I frequent, this is really a puzzle...

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Gene

Politicians and diapers must be changed often, and for the same reason- Mark Twain