I want to create the "Best Sanding Blocks Ever"

I've been using both blocks this week on the Chevelle hood with 80 and 180 paper to finish before 2K. I didn't get a picture after finishing with the poly primer blocking, but I really like the boards. I never even picked up my AFS 22" to compare. I did an X pattern sand along the radius sections of the hood using the edge of the board and had no issues with possible gouging with noted sharp edges. I try to stay away from using my round Dura-Block for this.
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My biggest concern is the AFS block at 22"has a higher crown in the middle and how much hand placement and pressure affect the block sanding surface. I would think that the slightly thicker polycarbonate would be better than the thin stainless.
This is a 64 Fairlane I did with the AFS. I remember being very light with pressure on the board with 80 grit.
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Crash thats what I was referring to is with a little more work it could be trued up. What grit of sandpaper did you use
For the quarter round edges, I started with a brief round of 80 grit to start the shape, and quickly went to 150 then 220 to get the shape I wanted. For the block face, I actually started with 320, which was also the finishing grit for my quarter rounds, but I actually wish I'd started with 220 because the surface was far enough off to warrant it, which surprised me. I finished the face with 600, which seems smooth enough for normal PSA paper to adhere and release as expected.
 
Wow just got back today and opened my box.
I have not opened a new box in many years with this attention to detail.

The quality of the items in the box is the very best and an actual case of over engineering!!

Great job, im helping a friend with a high-dollar vette, and we will get to use them one day this weekend.

Dean, you did a great job all the way around.
 
For the quarter round edges, I started with a brief round of 80 grit to start the shape, and quickly went to 150 then 220 to get the shape I wanted. For the block face, I actually started with 320, which was also the finishing grit for my quarter rounds, but I actually wish I'd started with 220 because the surface was far enough off to warrant it, which surprised me. I finished the face with 600, which seems smooth enough for normal PSA paper to adhere and release as expected.
Crash thanks for sharing your expertise with all of this great feedback they will be the best blocks ever!

The photo is a few passes over the 320 on a Collins Micro flat table. I will try going to 220 later and then 320.

This is the short block
 

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Black diamond results, epoxy, please ignore the nibs... Great blocks, my only suggestion, as mentioned previously, have the foam cut so they can be stored in the original box with the rods still installed.
When I am able to lay down epoxy like that, I won't be apologizing to anyone

That foam cutout is a great idea and very easy to implement.
It will be in place for next shipment.
I'm also going to bump out the cutouts in the foam for storing the rods. It's a little tight right now.
 
When I am able to lay down epoxy like that, I won't be apologizing to anyone

That foam cutout is a great idea and very easy to implement.
It will be in place for next shipment.
I'm also going to bump out the cutouts in the foam for storing the rods. It's a little tight right now.
My first time spraying with the Iwata LPH400-LV 1.4 set up per the guys on this forum. Light years better than my old set up.
 
What was your gun set up?..Thanks
Basically the settings from this post by DHutton about clear, but gun inlet at 23 psi because it was primer not clear, from a post by Chris Hamilton.

 

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Been using raw acrylic and PC and have not noticed that. Stuff is plenty straight as is. If it is off a couple of thousandths I don't see where that is going to hurt anything.

I bought a bunch of tools from a closed down machine shop a few months ago, including a 30x36" cast iron surface plate. It has an extremely noticable low spot that measures only .003" deep. Human hair is .003". Before I got into machining and didn't have any precision measuring tools I always wondered how straight/flat we were able to block sand a panel... after getting some tools and a bit of experience, the flatness that blocksanding is able to achieve is pretty impressive.

Even a .002" low or high spot on a poly/acrylic block would really distort the reflection in the face of the block and you'd easily be able to feel it by hand. These comments got me curious, so I got out a surface gauge and .0001" indicator to measure surface variations in a piece of scrap polycarbonate. Since the surface plate needs resurfacing, I used the ways of my lathe, out on the end where there is less wear. Over an 8" sweep there was less than .0002" variation in the polycarbonate. I also checked the top rail of a bed side that I had block sanded with a 3/8" thick poly block and 180 paper, and it had less than .0005" variation over a two foot section. Finer paper should improve the flatness.


YcwL1puh.jpg



Zeroed at the starting point.

lahCT0ah.jpg



~4" down from the starting point.

RfUUeiZh.jpg



~8" from the starting point. Starting to run into some wear in the ways at this point so I stopped here.

WA9oexHh.jpg



 
Dean I used your best blocks ever a couple days ago and they worked great! I liked the flexibility of the longer block without the rods for curves and crowned areas. I can see a 24 inch block with flex a good add. Great work Dean!
I would like to have a one inch wide block about 16-18 inches long with curved edges on it so it can roll into transitions. Maybe soft rubber type handle so it can flex. Anyone seen this type of block?
 
I bought a bunch of tools from a closed down machine shop a few months ago, including a 30x36" cast iron surface plate. It has an extremely noticable low spot that measures only .003" deep. Human hair is .003". Before I got into machining and didn't have any precision measuring tools I always wondered how straight/flat we were able to block sand a panel... after getting some tools and a bit of experience, the flatness that blocksanding is able to achieve is pretty impressive.

Even a .002" low or high spot on a poly/acrylic block would really distort the reflection in the face of the block and you'd easily be able to feel it by hand. These comments got me curious, so I got out a surface gauge and .0001" indicator to measure surface variations in a piece of scrap polycarbonate. Since the surface plate needs resurfacing, I used the ways of my lathe, out on the end where there is less wear. Over an 8" sweep there was less than .0002" variation in the polycarbonate. I also checked the top rail of a bed side that I had block sanded with a 3/8" thick poly block and 180 paper, and it had less than .0005" variation over a two foot section. Finer paper should improve the flatness.


YcwL1puh.jpg



Zeroed at the starting point.

lahCT0ah.jpg



~4" down from the starting point.

RfUUeiZh.jpg



~8" from the starting point. Starting to run into some wear in the ways at this point so I stopped here.

WA9oexHh.jpg



Been pondering this for a few days. Does the flatness of the block result in a panel with the same flatness? I would have guessed that proper diagonal blocking pattern would average out the block flatness but I am not positive on this.

Don
 
Dean I used your best blocks ever a couple days ago and they worked great! I liked the flexibility of the longer block without the rods for curves and crowned areas. I can see a 24 inch block with flex a good add. Great work Dean!
I would like to have a one inch wide block about 16-18 inches long with curved edges on it so it can roll into transitions. Maybe soft rubber type handle so it can flex. Anyone seen this type of block?
This was the idea I was referring to as well Dean. Loving the blocks, my only feedback would be the weight is pretty hefty and I can see a lighter block being more friendly on verticals. Second one is that on a curvy car, think VW beetle, when doing fenders and such only part of the block actually makes contact. Prior to getting your blocks my go to block for this was the Durablock half paper width block. It works but the paper wanted to kink if I tried to form anything more than a subtle arc. I would have to pull the paper and reapply at my desired arc to avoid this. With your block I do not seem to have this issue at all and it lets me transition across different radiused parts without all the fuss. A half paper width version of your large block would be perfect for curvy cars.
 
Been pondering this for a few days. Does the flatness of the block result in a panel with the same flatness? I would have guessed that proper diagonal blocking pattern would average out the block flatness but I am not positive on this.

Don
I think the criss-cross pattern really does tend to alleviate some block defects as well as shortcomings in technique, like uneven pressure on the block surface and such. Good flatness of the block may be one of those things that stacks the deck against problems, like an overkill air system. Start with the best stuff you can, then if something goes wrong, you have already eliminated as many variables as possible. That's how I think of it, anyway.
 
The slight difference in variation in these blocks won't transfer to the panel, and .0002" is nothing anyway. I'm sure there is a lot more variation in sandpaper thickness down the length of the block, at least until you get to finer grits. In general terms a machine shops might use B grade surface plates that are within .0002" flatness out in the shop to check their work, A grade blocks (.0001" flatness) for final inspection/quality checks, and AA grade (.00005") flatness would be appropriate for extremely precise use, like temperature controlled clean rooms. The closed down machine rebuilding shop I got a lot of my tools from said that they worked to .0002" tolerance when rebuilding machining equipment.

This isn't an exact comparison but when lapping surface plates to reduce surface variation, the lap's surface inconsistencies don't necessarily transfer into the plate being lapped if the correct technique is used, and the two plates can improve the surface variations of both plates since the abrasive is working against both plates. These are nearly perfectly dead flat surfaces to begin with, so only the highest points of each plate are in contact when lapping which is what lets each plate improve as they are lapped- only the highs are in contact and are being abraded down to the low spots. Because the plates are cast iron or granite- hard and inflexible, they don't flex into the low spot of the other plate. You wouldn't try to lap, or "block sand" a surface plate with a soft or flexible lapping plate, you'd be making things worse.

That's one of the great things about poly/acrylic blocks, they're a very flat surface to begin with- the surface is visually/optically clear of distortion/waves/ripples so like a lapping plate it's flat/consistent enough to use to create the same or better surface finish on a body panel. And like laps, since the surface is hard the block won't dip down into the low spots and will only shave down the high spots. Picking the block with the correct amount of flex to keep even surface pressure over a curve means that the high spots along the curve will be taken down until the whole area is shaped into a constant arc. This is a big reason acrylic/poly blocks are such a big advantage over soft blocks- they always bend in a constant arc so the block can shape a curved panel correctly, and the hard surface will only cut the high spots. The surface of soft blocks will absorb localized high spots, and don't flex in a constant arc so they can't create a constant arc, they'll only follow the existing shape and can only 'round over" localized high spots instead of cutting them perfectly flat. Poly/acrylic blocks' hard surface won't allow that to happen.
 
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