Edge Pro Glass Blanks

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ricklee4570

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Aug 12, 2010
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It has been a long time since I ordered anything from Edge Pro. Noticed that he does not have glass blanks listed anymore. I use the glass blanks for the polishing tapes. Looking online I do not see them selling anywhere. Anyone know why they were discontinued? Does anyone know of a source?
 
ricklee4570 said:
It has been a long time since I ordered anything from Edge Pro. Noticed that he does not have glass blanks listed anymore. I use the glass blanks for the polishing tapes. Looking online I do not see them selling anywhere. Anyone know why they were discontinued? Does anyone know of a source?
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It looks like Ben replaced them with a polished aluminum blank he likes better.
 
The glass Polishing tape blanks were replaced with the fully machined, not polished, aluminum blanks because they are much flatter with much tighter tolerances. The working surface of the aluminum blanks is coplaner with the reference surfaces within .0007" on the two I measured from the last batch, the glass on extruded bars is nowhere close to this. If you are worried about the aluminum being a softer surface then go with the hard anodized ones. They are not on the website but EP got 100 of them anodized a month ago as a test, and IMO is well worth it. Hard anodized, class III, should not be confused with cosmetic anodizing, class II, not only is it much thicker it is far denser, which is why it won't take color.

Disclaimer- I make the fully machined polishing tape blanks.

Konstantine, how true are your glass blanks?

Here is a photo showing how to measure them. The blank has to sit on three points on the ends. Here I am using two gage blocks.

PTH3.jpg
 
Diemaker said:
Konstantine, how true are your glass blanks?
Here is a photo showing how to measure them. The blank has to sit on three points on the ends. Here I am using two gage blocks.
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I don't have equipment for measuring tolerances like yours. I use 00-class straight edge for the non-destructive flatness check (no light gap) and loose fine silicon carbide + lapping glass for the destructive flatness check (glass specimen becomes frosted evenly on all surface). For checking coplanarity we use digital caliper in 6 anchor points.
I don't know how glass surface can be not flat or not coplanar, at least on 6"x1" surface (because of nature of glass manufacturing). I'm sure Ben has good reasons to cancel glass blanks. We sell both the glass and double aluminum for a long time, and sale ratio is like 100:1.
 
The glass will not be coplanar with the bottom of the aluminum blank, the reference surface, because it has been glued to the aluminum, which itself is not flat, and the glue will vary in thickness. The glass being flat is not as important as the thickness being consistent. Here is a photo showing what a .02" difference in stone thicknesses will do. It shows the progression from 4000 to 6000 Shapton Glass stones on a .03" wide bevel. The 4000 was .02" thicker than the 6000, surprise! Tapes are generally a bit finer than this so the difference will be more pronounced. Current EP polishing tape holders are coplanar within .001", the ones I have measured are .0007", and consistent in thickness holder to holder within .003", which is +/-.0015". Both of these numbers will improve when I make production fixturing, I am currently using a prototype fixture to test the new way I came up with holding them on the mill.

Mismatch.jpg


I don't usually use a microscope when sharpening but I was trying to compare a set of Shapton Glass stones to the new EP Matrix diamond stones to see which grits match between the two.

I talked with Cody and he said he still has a few glass tape blanks lying around. I will get them Friday afternoon and measure them to see how much they vary, if nothing else to satisfy my own curiosity.
 
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You have the very cool example of how the thickness differential leads to inconsistency in sharpening. However, your argument that flatness is not as important as the thickness is incorrect. Both factors impact the consistency, but flatness factor is more important. It's geometric matter.
1) If we have imperfect geometry on Edge Pro stone as a result of wearing with 0.02" differential, we will theoretically have ~0.38° sharpening angle inconsistency across the stone.
2) If we have the different thickness on two ends of Edge Pro stone with the same 0.02 differential, but it's still flat, we will have ~0.19° sharpening angle inconsistency across the stone.
The first factor is more important.
However, 0.02" is still too much for the different thickness and unacceptable for sharpening stones for guided systems. Boride, the supplier for Edge Pro, has the empirical maximum of 0.008". It impacts consistency for 0.08° which I consider acceptable.

Yes, glass blanks will have different thickness too, but it's tiny (0,0015")
 
.02" is .02" either way, I don't understand how you get different angles. If the tape holder thickness varies you will get a convex bevel since the angle changes as the thickness of the tape holder that is contacting the knife changes. Granted it's only a problem if you are using more than one grit. If the stone assembly thickness is consistent you can compensate, if it varies you can't compensate.

True glass is pretty consistent in thickness, but you are stacking aluminum, glue, and glass together so you need to factor the variations of all three, plus the variations of the assembly. The new fully machined aluminum tape holders are one piece, inherently more accurate. Once hard anodized they are pretty hard and wear resistant. Glass is 4.5-6.5 on the Mohs scale and aluminum oxide is 7, I couldn't find the hardness of class III anodize but figure it must be close to aluminum oxide since that is what it is. I think glass on aluminum tape holders are obsolete as they have no advantages over the new EP tape holders that are hard anodized.

When you come up with these angle changes what is the blade angle and hypotenuse you are using?
 
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If a six inch long plate is dished (so not flat in that sense), with the center 0.02" lower than the ends, then the angle from each edge to the center is indeed 0.38 degrees. Very different from flatness as in parallel with the bottom of the blank.
 
I went ahead and bought 6 of the aluminum polish tape blanks. When I place any two face to face there is a gap in the middle. They are not flat. The gap is very noticeable when you put a light behind it. They all appear to be dished in the middle.
 
ricklee4570, I just measured 5 EP aluminum polish tape blanks, they were .0025", .0015", .0008", .0018", and .0018" out of flat, a little farther off than I expected. If you hold these together where the tape goes and hold them up to the light they look very dished. I have always said they are not dead flat, but they are better than any other tape holders that I know of. The three glass topped EP polish tape blanks I got on Friday are .0022", .0113", and .0007". These are 2nds they had lying around. The glass is either not chamfered, too chamfered, or chipped, otherwise there is nothing out of the ordinary about them.

If you want I will trade you "certified" flat blanks for yours, I have around 700 on hand that I can pick from. I just need yours in as new condition so I can add them to my stock once I measure them as good. I will be shipping switchplates tomorow and the Matrix pass-around stone kit a little later this week and could ship your tape holders either time, USPS Priority Mail. You cover shipping to me, I will cover shipping to you.

Based on what I am seeing it looks like my fixture design isn't done, I know I can do better. Most of the variation is near the ends where I am clamping them. For now my target is a maximum of .001" variation, when I achieve that I will cut it in half.

Here is a video showing how I am measuring them.

 
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Diemaker, thanks for your generous offer. I am not a member on here. Please email me at: (deleted by moderator)

I will exchange addresses with you.
 
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I just emailed you. You want to remove your email address as soon as possible to avoid it getting picked up by spammers.
 
Diemaker said:
I just emailed you. You want to remove your email address as soon as possible to avoid it getting picked up by spammers.
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I just took the liberty of removing it to protect his identity. Good to go.
 
Diemaker said:
True glass is pretty consistent in thickness, but you are stacking aluminum, glue, and glass together so you need to factor the variations of all three, plus the variations of the assembly. The new fully machined aluminum tape holders are one piece, inherently more accurate. Once hard anodized they are pretty hard and wear resistant. Glass is 4.5-6.5 on the Mohs scale and aluminum oxide is 7, I couldn't find the hardness of class III anodize but figure it must be close to aluminum oxide since that is what it is. I think glass on aluminum tape holders are obsolete as they have no advantages over the new EP tape holders that are hard anodized.
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I'm not fighting with your product, and I will be happy to sell it. I'm only curious what advantage a customer will have using your precise blank on the final step of progression if the precision of previous stone and the precision of the sharpener are 20x below your level...

PS. Can you give me your email? I have messaged you but got no reply.
 
When did the sharpening become so complicated...:) You are arguing about the blank flatness, but this flatness only matters if the sharpening device can support same tolerances :).
 
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