FELL PRECISION LEVEL

I posted a more in depth response on Practical Machinist 16 January 2023 explaining how to re-fill the newer models that did not use a solder potted lens and soldered fill hole. I left included it for posterity...after all these things are getting close to 100 yrs old!



Hello, I just found this thread, so sorry for the delay!



Here a bit of history of the level developed by my great-uncle Bill in the 1930s. WW2 was a gravy train for his product! he died in 1968 from too much alcohol and probably ether!

I made that rectangular version of the Fell level some thirty years ago. The fluid inside is pentane; bad idea in the 1980s. Extremely flammable hydrocarbon. The intent was a safer fluid that would prevent globules from forming, but isopropyl alcohol is better, and it will prevent globules from forming. Originally the fluid was ether.

First design; the lens was soldered into its cup via a titanium ring that was fused to the glass in an induction oven. The lens/fused ring was then photo etched, ground with a radius on the bottom, and then soldered to a stainless steel cup which had a blob of solder on the bottom predrilled to be used to inject the bubble's fluid (ether) later; very high tech for 1938! Same potting was used up until the developers death in 1970 when the technique was lost to posterity since the developer, William Fell, would not allow his employees to run the induction fusing process.

The people who acquired the business, Fell's employees, had NO engineering experience, and they ran the business into a dead end by selling off existing inventory. Once those level vials made by my uncle in the early 60s were gone, that was it, and the new owners were stumped. They sold off the tooling for $10,000 at an auction in 1978.

In the late 70s I hooked up with the auction buyer of the level business tooling, and we stumbled along for about TEN years. The buyer, who had NO mechanical acumen made the calls; bad calls! Eventually he gave up, and filed bankruptcy. I acquired what was left for $5,000 cash. I went back to square one to try to redevelop a product that would work; still without using a soldered lens.

A restart of the product by me was about 1989 which did not solder the lens. That superior hermetic sealing process was lost to posterity. After 1989, the lens was potted with epoxy into an alum casting. The potting of the lens is with 3M epoxy. Later an aluminum oxide powder was added as a cosmetic filler to attempt to more closely math the thermal characteristics of the aluminum "cup". So the early versions of this had epoxy and the later, after 1989 had epoxy/alum.

The newer epoxy potted vials. They have a fill hole comprised of two 6/32 screws in a hole tapped with a plug tap, and a sealer between the first and second screw. The first screw created a mechanical seal while the sealer cured. Originally the sealer/gasket was SUPERGLUE (cyanoacrylate) which FAILED after a year. I didn't realize the Pentane used would DISSOLVE the cyanoacrylate, but later that was replaced with a dental cement, Resiment, a perfect use for it that I got from my dentist Dr. Marler; RIP! The dental cement cures in about 30 seconds, so it was a fantastic solution where we could see the seal was good almost right away. Like the cavity fills in teeth the cement is inert after curing. I still have one I sealed more than thirty years ago, and it has not leaked! Note the cement was painted over with Testor's model paint; aluminum color. I would NOT seal the hole. That way one can always add a bit more alcohol when it leaks out over time.

As far as the bottom of the level housing, it can be ground on a Mattison grinder just fine. No need to scrape it. Scraping was done before the bottom design was cut with a diamond pattern on the rectangular ones of suction relief grooves. The first models had concentric rings cut in the bottom to relieve the suction when lifting off of a surface.

Accuracy of the level potted with epoxy; about half of production had to be scrapped...at the time the only way to verify the lens was made properly was to seal it in.

You can find a picture and the product flyer by Googling Thomas Butler Technology or "Fell Precision Level images." The level product manufacture has been defunct for more than 25 years.

There are only about thirty rectangular levels with the epoxy potting out there. In 1985, I went back to school on the GI Bill and became a software engineer, and the product was scrapped in 1995. Believe it or not, I took about 200 units to the scrap yard. I think I got about fifty bucks for the pure cast iron. I still have the stainless steel vial cup blanks. They make great shims for this and that.

There is a YouTube video by Keith Rucker which demos the earliest version of the level that had a contoured housing, and that level was nearly impossible to calibrate...the vial has three feet which are lapped flat. It then sits on a radius that is ground inside the compartment when the vial sits. As the vial is move on the x or y axis, in theory, it moves over the radius and adjust the calibration. the vial was held down by a 12 inch long torsion wire spring held in place by that black Bakelite ring on top of the level which has the company name on it. There are four long screws. One at each side and one at each end. These are used to push the vial over the radius in order to calibrate it; a real impossible task..

In the 1960s, the level grid lines were laid out using a positive on POSITIVE photoresist. After exposure under UV, the lens was etched with hydrofluoric acid creating grid lines in the glass lens; very dangerous...this new way of putting the grid on allowed adding the company name text. prior to photo etching, the grooves were cut with a diamond saw. Once the grid lines were cut or etched, a powdered black glass mixed with water was painted on to fill the grooves. This was then fired in a kiln and the black powdered glass melted into the grooves of the grid lines. After that, the lens was ground on a lapping wheel with a radius; same process used for telescope lenses except instead of a parabola a radius was ground. I spent many hours of my lifetime at that grinding machine, but only for the FIFTEEN years I was involved in the project.

Glad I found this page on Hobby Machinist before I passed on. BTW, what did I do after going back to school? Worked on election software for thirty years. Developed some of the FIRST "drones"/quadcopters around 2010. Now ubiquitous since the Chinese got involved. Search "Rockford quadcopter" on Google; 2013 was the best with "roof inspection".

Now while I'm in retirement, as part of my photography passion, I'm about to start up a product to make focus rail stacking gizmos! Just recaptured my website name from a squatter who had it for ten years! It's worth noting that while my time spent on the level business was not the money maker I had hoped, what I learned while working on the levels gave me machinist knowledge that I have used all my life in various endeavors. I had machine shop in high school, but working on the level business I was free to do as I please and experiment.

I think every student in high school should take machine shop class. Not to become a machinist, but just to get an idea of how things are made. That car part didn't come out of thin air. A tool & die maker probably made the tooling to stamp the parts.

Lastly, my Great Uncle was paranoid about the Chinese or Japanese copying his level; he NEVER shipped to the Far East, and they have never made a comparable product! Look at all the technology they have copied from the West and are now selling back to us! Go figure!

BTW The patents have expired, so if anyone is interested in creating such a product have at it! Be sure to file a design patent though and have LOTS of startup cash!
 
ThomasRkfd said:
I posted a more in depth response on Practical Machinist 16 January 2023 explaining how to re-fill the newer models that did not use a solder potted lens and soldered fill hole. I left included it for posterity...after all these things are getting close to 100 yrs old!



Hello, I just found this thread, so sorry for the delay!



Here a bit of history of the level developed by my great-uncle Bill in the 1930s. WW2 was a gravy train for his product! he died in 1968 from too much alcohol and probably ether!

I made that rectangular version of the Fell level some thirty years ago. The fluid inside is pentane; bad idea in the 1980s. Extremely flammable hydrocarbon. The intent was a safer fluid that would prevent globules from forming, but isopropyl alcohol is better, and it will prevent globules from forming. Originally the fluid was ether.

First design; the lens was soldered into its cup via a titanium ring that was fused to the glass in an induction oven. The lens/fused ring was then photo etched, ground with a radius on the bottom, and then soldered to a stainless steel cup which had a blob of solder on the bottom predrilled to be used to inject the bubble's fluid (ether) later; very high tech for 1938! Same potting was used up until the developers death in 1970 when the technique was lost to posterity since the developer, William Fell, would not allow his employees to run the induction fusing process.

The people who acquired the business, Fell's employees, had NO engineering experience, and they ran the business into a dead end by selling off existing inventory. Once those level vials made by my uncle in the early 60s were gone, that was it, and the new owners were stumped. They sold off the tooling for $10,000 at an auction in 1978.

In the late 70s I hooked up with the auction buyer of the level business tooling, and we stumbled along for about TEN years. The buyer, who had NO mechanical acumen made the calls; bad calls! Eventually he gave up, and filed bankruptcy. I acquired what was left for $5,000 cash. I went back to square one to try to redevelop a product that would work; still without using a soldered lens.

A restart of the product by me was about 1989 which did not solder the lens. That superior hermetic sealing process was lost to posterity. After 1989, the lens was potted with epoxy into an alum casting. The potting of the lens is with 3M epoxy. Later an aluminum oxide powder was added as a cosmetic filler to attempt to more closely math the thermal characteristics of the aluminum "cup". So the early versions of this had epoxy and the later, after 1989 had epoxy/alum.

The newer epoxy potted vials. They have a fill hole comprised of two 6/32 screws in a hole tapped with a plug tap, and a sealer between the first and second screw. The first screw created a mechanical seal while the sealer cured. Originally the sealer/gasket was SUPERGLUE (cyanoacrylate) which FAILED after a year. I didn't realize the Pentane used would DISSOLVE the cyanoacrylate, but later that was replaced with a dental cement, Resiment, a perfect use for it that I got from my dentist Dr. Marler; RIP! The dental cement cures in about 30 seconds, so it was a fantastic solution where we could see the seal was good almost right away. Like the cavity fills in teeth the cement is inert after curing. I still have one I sealed more than thirty years ago, and it has not leaked! Note the cement was painted over with Testor's model paint; aluminum color. I would NOT seal the hole. That way one can always add a bit more alcohol when it leaks out over time.

As far as the bottom of the level housing, it can be ground on a Mattison grinder just fine. No need to scrape it. Scraping was done before the bottom design was cut with a diamond pattern on the rectangular ones of suction relief grooves. The first models had concentric rings cut in the bottom to relieve the suction when lifting off of a surface.

Accuracy of the level potted with epoxy; about half of production had to be scrapped...at the time the only way to verify the lens was made properly was to seal it in.

You can find a picture and the product flyer by Googling Thomas Butler Technology or "Fell Precision Level images." The level product manufacture has been defunct for more than 25 years.

There are only about thirty rectangular levels with the epoxy potting out there. In 1985, I went back to school on the GI Bill and became a software engineer, and the product was scrapped in 1995. Believe it or not, I took about 200 units to the scrap yard. I think I got about fifty bucks for the pure cast iron. I still have the stainless steel vial cup blanks. They make great shims for this and that.

There is a YouTube video by Keith Rucker which demos the earliest version of the level that had a contoured housing, and that level was nearly impossible to calibrate...the vial has three feet which are lapped flat. It then sits on a radius that is ground inside the compartment when the vial sits. As the vial is move on the x or y axis, in theory, it moves over the radius and adjust the calibration. the vial was held down by a 12 inch long torsion wire spring held in place by that black Bakelite ring on top of the level which has the company name on it. There are four long screws. One at each side and one at each end. These are used to push the vial over the radius in order to calibrate it; a real impossible task..

In the 1960s, the level grid lines were laid out using a positive on POSITIVE photoresist. After exposure under UV, the lens was etched with hydrofluoric acid creating grid lines in the glass lens; very dangerous...this new way of putting the grid on allowed adding the company name text. prior to photo etching, the grooves were cut with a diamond saw. Once the grid lines were cut or etched, a powdered black glass mixed with water was painted on to fill the grooves. This was then fired in a kiln and the black powdered glass melted into the grooves of the grid lines. After that, the lens was ground on a lapping wheel with a radius; same process used for telescope lenses except instead of a parabola a radius was ground. I spent many hours of my lifetime at that grinding machine, but only for the FIFTEEN years I was involved in the project.

Glad I found this page on Hobby Machinist before I passed on. BTW, what did I do after going back to school? Worked on election software for thirty years. Developed some of the FIRST "drones"/quadcopters around 2010. Now ubiquitous since the Chinese got involved. Search "Rockford quadcopter" on Google; 2013 was the best with "roof inspection".

Now while I'm in retirement, as part of my photography passion, I'm about to start up a product to make focus rail stacking gizmos! Just recaptured my website name from a squatter who had it for ten years! It's worth noting that while my time spent on the level business was not the money maker I had hoped, what I learned while working on the levels gave me machinist knowledge that I have used all my life in various endeavors. I had machine shop in high school, but working on the level business I was free to do as I please and experiment.

I think every student in high school should take machine shop class. Not to become a machinist, but just to get an idea of how things are made. That car part didn't come out of thin air. A tool & die maker probably made the tooling to stamp the parts.

Lastly, my Great Uncle was paranoid about the Chinese or Japanese copying his level; he NEVER shipped to the Far East, and they have never made a comparable product! Look at all the technology they have copied from the West and are now selling back to us! Go figure!

BTW The patents have expired, so if anyone is interested in creating such a product have at it! Be sure to file a design patent though and have LOTS of startup cash!
Click to expand...
Wow....just wow!
 
Well I am very happy to hear from You and to listen to your story.
I still use my Fell but NO ONE other than my self has touched it or even carried it in the box.
Mine has the concentric circles in the base.
Many years ago I tried to touch up the calibration.....it was beyond difficult.
 
aliva said:
Nice but as Rucker said it will drive you nuts. How accurate does the average home shop machinist really need.
Click to expand...
I have 2 Moore and Wright precision levels that are accurate to .003 per foot. Very easy to use.

@ThomasRkfd I'm so sorry that some idiots ran your family business into the ground. I would have loved to get a Fell level. In late 1970s I was just beginning machining and wouldn't have known what a Fell level was... bad timing on my part!
 
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