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rws
09-20-2007, 01:15 PM
Who/where can etch accurate circles on glass? Circle sizes (diameter) would be .224, .243, .308, and maybe a couple others.

Rusty Marlin
09-20-2007, 01:49 PM
Use the cartridge case of matched size and and chuck it in a drill press, indicate it staight, than a dab of valve lapping compound on the glass and spot the ring on with the case turning in the chuck.

obviously this could be done more accuratly/repeatably with machined tubes.

Dawai
09-20-2007, 02:22 PM
Tolerance is??

a quick rubber mask and a $20 spot sand blaster from Hf?

Alistair Hosie
09-20-2007, 02:37 PM
I agree with Dave sand blaster with masked of areas you don't want touched.I have done this it's instantanious looks good .Alistair

Your Old Dog
09-20-2007, 03:11 PM
If you don't mind my asking, how can these be used to any advantage in ballistics, cartridge loading or any other use? I'd sure be interested to hear any new technique or applications.

Dawai
09-20-2007, 03:46 PM
YOD:

after getting high-pressure indicators on some reloads, I made a case length block out of steel. Not like the post for circles, but.. I had a target rifle with short chamber throat, the case on some rounds would touch the rifling and cause high pressure. After adding in the block to my setup rig on my reload bench I didn't have further trouble. I hand filed it to right size after milling it close.
A lee crimp instead of using the taper crimp will tighten the group also. It make round crimps at the end of the brass, gives starting consistent pressure regardless of case length.

Not sure what he is doing with the glass, maybe sorting unmarked ammo/yard brass? With the berdan priming of some cheap rounds, I quit picking it up.

I bought 1000rds of Israelie wooden bullets, People laughed at me, but I got brand new boxer primed 308 brass. It tightened it up again. You should have seen the eyes on the guys picking up brass at the range. It had a hebrew head stamp. ONE clean bullet hole at 50 yards, a pretty flower at 200..

Weston Bye
09-20-2007, 08:26 PM
Stained glass supply stores sell a hydroflouric acid-based etching cream. the Glass is covered by a resist - paint, varnish, possibly parafin wax. Test what you have on a piece of scrap. The pattern is scratched in the resist and the cream is applied for a few minutes. Very fine lines are possible. Certain photosensitive resists are available for silkscreening and printed circuit work may be compatible for glass etching. The cream is acid based but I once watched a glass worker spreading it with bare fingers and suffering no visible harm. I wouldn't try it.

brunneng
09-20-2007, 08:45 PM
Well, I could do it for cost. I have an etching laser.
Depends on the tolerance as the beam is focused at 0.003" 0.005". Also depends on how opaque the line needs to be. The laser doesn't work quite as well as a sandblaster where you can keep going over the mask to vary the density.

If you need absolute precision and crispness of line edge.. like for using an eyeloupe... then I would draw a black mask at some multiple of the finished size. Like 4x or 10x. Then take it to a photo shop and have them make a reduced print on transparent material, emulsion side down. Use that to expose a photoresist that has been applied to the glass and chemical etch as in circuit boards.

Or get a piece of artists frisket. Apply it to the glass. Use a compass with a sharp blade to cut the circles and use the chemical etching cream from the art store. You have to make sure the edge is burnished down well as it can creep under. It makes a very even etch, and can be reapplied to deepen the etch.

Kevin

Evan
09-20-2007, 10:57 PM
The cream is acid based but I once watched a glass worker spreading it with bare fingers and suffering no visible harm. I wouldn't try it.

Don't even think of it. Hydroflouric Acid is a very bad actor. Contact with skin causes no immediate symptoms but it is easily absorbed through the skin. Nothing will be apparent until the next day or two. It works very slowly but will cause deep internal acid burns that often require amputation and can even cause death just by getting some on your hands.

Once the acid is in the body there are few treatment options. The only one that is effective must used early and is also risky. It involves upsetting the acid base balance to try and neutralize the HF Acid.

lynnl
09-21-2007, 12:41 PM
Evan you can be so depressing at times. :D

Seriously, what else is this hydoflouric acid contained in? Want to make sure to give it a wide berth!!

Evan
09-21-2007, 12:56 PM
Seriously, what else is this hydoflouric acid contained in?

Nothing much else at the consumer level to worry about. It's used in the semiconductor industry to etch silicon and there may be other uses.

Here is some scary info:



United States

More than 1000 cases of HF exposure are reported annually. Actual incidence rate is unknown.



HF acid burns are a unique clinical entity. Dilute solutions deeply penetrate before dissociating, thus causing delayed injury and symptoms. Burns to the fingers and nail beds may leave the overlying nails intact, and pain may be severe with little surface abnormality.
Severe burns occur after exposure of concentrated (ie, 50% or stronger solution) HF acid to 1% or more body surface area (BSA), exposure to HF acid of any concentration to 5% or more BSA, or inhalation of HF acid fumes from a 60% or stronger solution. The vast majority of cases involve only small areas of exposure, usually on the digits.

Mortality/Morbidity


Local effects include tissue destruction and necrosis. Burns may involve underlying bone.
Systemic fluoride ion poisoning from severe burns may be associated with hypocalcemia, hyperkalemia, hypomagnesemia, and sudden death.
Deaths have been reported from concentrated acid burns to as little as 2.5% BSA.http://www.emedicine.com/emerg/topic804.htm

rws
09-21-2007, 01:48 PM
OK, here's the need:

In my shooting sport, a "plug" is used to score targets. The big flaw in using a plug is the paper tears, and can also be influenced by the condition of the backer (cardboard, or coroplast) and how shot up it is.

So there has been some talk of a reticle device, that is a magnifier and has different caliber circles etched on it. One would flatten out the paper, then align the circle on the punched hole.

The circle would have to be accurate to size, and relatively small and fine.

Mcgyver
09-21-2007, 02:16 PM
Viton O rings. at elevated temps they release hydrofluoric acid - this is a hazard with fires around mechanical stuff, IE engines. guys use O rings sometimes in steam engines, scares me away, because how the heck do you know if that O ring you pull out of a drawer is viton or not? (I know every super heated steam probably isn't hot enough, but who wants to chance it).

Its common use as a silicon enchant is interesting, I did some googling and found this from some U of Texas lab. while it is definitely nasty, the control point seems to be exposure time, although god knows what someone was doing using it without gloves. this refers to 49% concentration as per link at the end. something i plan on staying away from.



HYDROFLUORIC ACID

We use a 10% hydrofluoric (HF) acid mixture for etching SiO2. HF is EXTREMELY DANGEROUS, and we use it ONLY IN THE HF ETCHING HOOD. AT NO TIME IS ANY OTHER PROCESSING TO BE DONE IN THIS HOOD. One major problem with HF is the fact that it does not hurt immediately after exposure. When it does begin to hurt a few hours after exposure, it is too late. It will slowly eat through tissue over the course of several days, until it reaches bone, where it is neutralized by calcium. It is excruciatingly painful.

Although an HF burn is very serious, it is also very easy to prevent. Only when the acid is left in contact with the skin for an extended period is it dangerous. Our procedure is very simple: always wear the green gloves when working at the HF etch station, and rinse them with water frequently. When you finish, rinse thoroughly, and finally rinse your hands and arms. The etch station itself is designed to minimize the chance of exposure, but always be VERY CAREFUL. I have never seen a serious HF accident, but this is only because all the labs I have worked in treat it with healthy paranoia. Please do not break my record.


http://weewave.mer.utexas.edu/DPN_files/courses/FabLab/Fab_Lab_Manual/HFETCH.html

Weston Bye
09-21-2007, 02:33 PM
HYDROFLUORIC ACID

I bought a 3oz. bottle of the etching cream. Have not had the opportunity to use it yet. There is no list of ingredients or strongly worded warning on the bottle about skin contact, although the poision control telephone number is on the bottle and references to hydroflouric acid-like symptoms and antidotes. (I don't have the bottle in front of me now)

The yo-yo that I saw spreading the etching cream with his fingers has been doing this type of work for years and his fingers appeared to be intact and not gnarled stumps. I make no judgement about his mental condition. I suspect that the etching cream is considerably diluted.

Nevertheless, I plan on taking precautions, especially in light of Evan's wonderfully distressing post of information on the subject.

CCWKen
09-22-2007, 12:54 AM
That's some nasty acid in higher concentrates. I would imagine the hobby cream is probably 5% or less. It's used in food processing and putting the frost inside light bulbs. It's also used in some plating and metal treatment compounds. If you want to stay away from it, quit eating cereal and bread. :eek:

meho
09-22-2007, 03:56 AM
How about one of these:
https://www.gearshop.nl/images/IPSC_SO.jpg
Or a plug with a magnifyier:
http://www.theshootersbox.com/store/images/shooting_aids/scoring_plug_93-549.jpg

HTRN
09-22-2007, 05:56 AM
Meho beat me too it. Champions choice sells the Magnified plug, btw.

Does it have to be glass? Why not use a linen tester on top of piece of acrylic with a hole reamed to the right size, and slightly countersink, with the countersink painted black? This is how the sight inserts are made for the insert sights like Gehlmann and Centra.


HTRN

Evan
09-22-2007, 08:18 AM
If you want to stay away from it, quit eating cereal and bread.

Come on Ken, that's like saying if you want to stay away from chlorine then quit eating salt.

There are plenty of useful chemicals we use that warrant taking safety measures, in this case gloves are indicated strongly along with eye protection. It surprises me that you can still buy bleach, lye, hydrochloric acid, white and red phosphorus, acetone, ether, radioactive thorium and americium, methylene chloride and a huge assortment of neurotoxins over the counter with no controls or licensing.

LES A W HARRIS
09-22-2007, 12:58 PM
RWS,

Another no glass option, draw in Cadd, print out on transparency film.

Cheers,

CCWKen
09-22-2007, 06:24 PM
Come on Ken, that's like saying if you want to stay away from chlorine then quit eating salt.

LOL... I know that. I was just just responding to Lynnl. ;)


Evan you can be so depressing at times. :D

Seriously, what else is this hydoflouric acid contained in? Want to make sure to give it a wide berth!!

SteveF
09-22-2007, 07:04 PM
RWS - When I was running the High Power Rifle program at my club I had some plugs from the NRA that were used. I would not have allowed scoring with plugs that someone made.

http://materials.nrahq.org/go/products.aspx?cat=Scoring%20Aids

Steve.

rws
09-24-2007, 11:42 AM
How about one of these:
https://www.gearshop.nl/images/IPSC_SO.jpg
Or a plug with a magnifyier:
http://www.theshootersbox.com/store/images/shooting_aids/scoring_plug_93-549.jpg

Gents,

The scoring plug as shown is what is used now. Champions Choice does sell them, but they have problems.

As I stated before, using a plug is not very accurate, since the paper tears when the bullet goes through, and depending on the condition of the backer material can cause a tear that is not exactly round.

I and a couple others are looking for alternatives, and something like the "scoring aids" is on the right track. We want to score the paper laying flat, instead of poking a device through the hole. We shoot benchrest, and strive for the most accurate way of measuring as possible. I wish some kind of electronic scanning could be devised, which would take all of the "human error" out of the picture, but that is beyond our capabilities.

I'll keep these links and pics, and see if I can come up with something the organization will agree on.

Thanks for the input.