Matte Finish on Small Parts w/o Bead Blaster?

I want to be able to make custom front & rear sight blades for target pistols. These need to have a durable, black, non-reflective finish. I think the commercial ones are lightly bead blasted, and then blued. The finish is certainly more durable than paint. If they do use bead blasting, they don't do much, so the sharp edges are preserved.

I don't have a bead blasting setup, and I'm wondering if I can easily produce the same effect through other means. One option might be etching, another might be pressing/hammering sandpaper into the critical surface(s). The material would be steel. Some front sights start out round, and those would probably be drill rod. The rear sight blades would be cut from ~ 0.040" sheet.

Any ideas?

Thanks!

Doug White

Reply to
Doug White
Loading thread data ...

Blasting something that small would be easy and wouldn't need much of a compressor, even using one of those gravity feed paint-gun lookalikes. However, you could try tumbling with small sharp ceramic media in a vibratory tumbler. Have to balance the uniformity of the surface dings with how much sharpness you are willing to lose on the edges. Not sure what to try for etching, but you could submerge them in a salt water solution with shaking for a while to rust the surface, and then use something like EvapoRust to clean it back off. Might give a pleasing surface.

----- Regards, Carl Ijames

I want to be able to make custom front & rear sight blades for target pistols. These need to have a durable, black, non-reflective finish. I think the commercial ones are lightly bead blasted, and then blued. The finish is certainly more durable than paint. If they do use bead blasting, they don't do much, so the sharp edges are preserved.

I don't have a bead blasting setup, and I'm wondering if I can easily produce the same effect through other means. One option might be etching, another might be pressing/hammering sandpaper into the critical surface(s). The material would be steel. Some front sights start out round, and those would probably be drill rod. The rear sight blades would be cut from ~ 0.040" sheet.

Any ideas?

Thanks!

Doug White

Reply to
Carl Ijames

A lot of bullseye target shooters "blacken" their sights, either with a spray on substance or even a carbide torch, to prevent glare so the finish of the front sight blade is immaterial but if you want to blue it an acid bath will produce a non reflective surface ( I use a tile cleaner commonly sold in supermarkets here for cleaning tile bathroom floors).

The rear "sight blade"? Don't you use an adjustable rear sight, with an anti glare surface?

Reply to
John B.

I routinely take parts such as these to an outside vendor to have them black oxide coated; in lots of 100 or thereabouts the cost is something like fifty cents or so each.

The company is called AB plating and they're located on 46th just off of Columbia in Portland, Oregon.

Reply to
PrecisionmachinisT

Maybe tumbled?

Reply to
Bob La Londe

Front blades have been made so the rear surface doesn't cant forward or or stick straight up but cants to the rear. No light from above can reach the rear surface and light from behind is reflected down then up. A similar approach has the rear surface canting forward in total but comprised of several individual and smaller surfaces canted to the rear.

Hul

Doug White wrote:

Reply to
dbr

Greetings Doug, I have had to put matte black finishes on parts for customers. Even though they specified a finish wanted they did not specify any process or processes. I had to put this finish on copper alloys and various steels. The quantities were fairly low. What I found that was the most repeatable for different materials, safest, and ultimately the lowest cost, was sandblasting followed by blackening using a solution made for either copper alloys or steels. A small blasting cabinet is cheap and worked for the parts I was doing. One would work for you too. The blackening solutions are also pretty cheap and the toxicity and general level of hazard low. I tried acids for ecthing steels but they were too much trouble to deal with. I think your best bet is to buy a small sandblasting cabinet and commercial blueing solutions. Eric

Reply to
etpm

. A small blasting cabinet is cheap

For parts as small as you are doing I think you could make a blasting cabinet out of cardboard and use this blaster from Harbor Freight.

formatting link
The expensive part would be an air compressor.

Dan

Reply to
dcaster

I believe that I've seen discussions here indicating that vibratory tumbling with ceramic media can produce a nice "frosted" finish (IIRC, followed up with some pictures, obviously not on here.) Selection of media size and shape for your parts (to process them, but not ruin the edges) is probably best done in consultation with a media supplier.

Reply to
Ecnerwal

" snipped-for-privacy@krl.org" wrote in news: snipped-for-privacy@googlegroups.com:

The manual says to run it at 150 PSI, but they give no indication of the CFM it requires. I have a tiny compressor that will fill a 5 gallon tank to 100 PSI if I'm patient. I wonder if I could do much with one feeble toot on the very small parts I need.

For the $14, it might be fun to try.

Doug White

Doug White

Reply to
Doug White

I saw the manual said maximum pressure is 150psi but didn't see any mention of a recommended pressure during my quick look. I have one that looks just like that though and can say that it works fine at half that maximum pressure so I wouldn't worry, just get one and get on with the job.

Reply to
David Billington

What David said. In fact, I think you will need a pertty low pressure to get just the matt finish you want without rounding edges. You can also make a new nozzle with a smaller diameter if you don't want to use the nozzles it comes with. The nozzle will wear fast if just made from steel but if you are doing only a few parts it won't matter. You can, of course, buy smaller diameter ceramic nozzles but I don't know if they are available for the cheap blaster. Eric

Reply to
etpm

I have another blasting gun that had a hardened steel nozzle and when that wore out I made a collar out of hex brass with 1/2" x 26TPI thread and made nozzle inserts out of ERW steel tube 3/8"OD 16swg and flared the end where the injector nozzle went in. Cheap and easy to make so I wasn't worried when they wore out but they would typically last a couple of hours of near continuous blasting before the side of the nozzle wore through and it needed to be replaced so not bad for plain mild steel tube.

Reply to
David Billington

As David said, the manual says 150 psi max, not typical. I think I would try one of the gravity feed guns instead, like item 93221 since it says only 1.7 cfm at 90 psi (I just suspect you will get more uniform blasting with gravity feed, who knows). The reviews are pretty good, just put on a pressure regulator and start at about 60 psi. That's where one glass bead manufacturer recommended we run in our big cabinet at work for best finish and best bead life. I've used the previous generation of part 68228 on a couple of blast cabinets and they worked just fine. Get the smallest box they sell of medium glass beads and of aluminum oxide, and try both and see which gives the best finish.

" snipped-for-privacy@krl.org" wrote in news: snipped-for-privacy@googlegroups.com:

The manual says to run it at 150 PSI, but they give no indication of the CFM it requires. I have a tiny compressor that will fill a 5 gallon tank to 100 PSI if I'm patient. I wonder if I could do much with one feeble toot on the very small parts I need.

For the $14, it might be fun to try.

Doug White

Doug White

Reply to
Carl Ijames

It would run that thing for maybe 6 seconds, if you're lucky. A 1/8" nozzle uses 30cfm at 140psi.

formatting link

Grab half a dozen old 20# propane tanks, hook them together, pump 'em all full, and you _might_ get a minute out of it.

Sandblasters are just glorified gaping holes in your air tank.

Reply to
Larry Jaques

Absolutely. Beeg hole in the tank that drags along the abrasive and flings it against the item being blasted. But if you can supply enough air for your needs, you'll like the results - part that looks fresh from the factory molds, even if it's been around 50 years and rehabbed a dozen times before.

The regular table-top or floor model blast cabinets from Harbor Freight, Northern Tool or the ilk are your best bet - and get or make the dust recovery vacuums or cyclonic separators on the exhaust.

Don't mess around with Cardboard Boxes, they aren't going to cut it. Especially if you want to capture and reuse the media more than once. Not to mention the Silicosis issues from uncontained dust...

To get any useful work out of the blast cabinets you need a Bare Minimum of "5 Sears Horsepower" (3-HP Actual) compressor - "7.5" (5) Horsepower is better, those require a motor starter.

The factory labels lie like a rug, claiming the HP at the Stall Point

- you have to do the math on the running amps on the motor. But the electric motor makers like AO Smith won't lie for Sears or C-H, they simply leave the Horsepower box on the nameplate blank or marked "Special". But they are marked with the full load amps, which you can cross on the chart in "Ugly's References" or the NEC to the actual HP.

Same thing with tanks, bare minimum of a 60-gallon, 80 is more better.

I have the Husky (Campbell-Hausfeld) "5-HP" 2-stage 80-gallon and on larger pieces I have to stop blasting for a minute and let the air build back up - the trick is starting back up soon enough that the compressor doesn't kick out. It's better to run continuous for an hour than to stop and start 6 or 10 times in an hour.

You do NOT want to short-cycle the compressor motor more than 3 or 4 times an hour or you heat-soak and burn up the windings.

If you'll be doing this industrially, running the cabinet in a production mode, invest in a Screw Compressor - between 5 to 10 HP per workstation. They can run all day, every day, for years, and easily keep up with the demand - and they have an Unloader so it stops pumping and keeps running, much better if you get a Demand Charge on your power..

The rule on gasoline engine driven compressors is the Net work done is about half that on the engine nameplate too - which is why the 13-HP to 15-HP 30-gallon compressor (the size they put in the back of a pickup for field servicing truck tires) is the bare minimum for effective bead blasting from an engine driven compressor. You get 6 to 7.5 HP electric equivalent of actual air out of them.

Don't try this with the 7-HP "Hot Dog" style gas compressors for Roofers and Framers, not large enough for a blast cabinet.

Reply to
Bruce L. Bergman (munged human readable)

The OP only wanted to blast some custom front and rears sights for a target pistol so this isn't a large blasting job so likely the small compressor he has will be fine and he already has it.

Reply to
David Billington

Harbor Freight has two models. The other one might use less air. I have one and it works pretty well on small things and I have never used it a anywhere near 150 psi.

The cardboard box will work as long as you do not blast the cardboard. If you decide to make this the permanent solution then a better box would be good.

Dan

Reply to
dcaster

"Carl Ijames" wrote in news: snipped-for-privacy@news6.newsguy.com:

Thanks to everyone for their input. 1.7 cfm at 90 psi sounds like something I can handle with my current compressor & tank setup.

It occured to me that jewelers might use very small blasting setups, and I was correct. Rio Grande has a couple small cabinets with blasting "pencils" that sound perfect:

formatting link
Blaster/336248?Pos=3

The air requirements are similar to the gravity feed gun from HF.

Apparently the cabinet is made by Cyclone, and they can be had cheaper if you shop around:

formatting link

Too bad I just missed Christmas...

Doug White

Reply to
Doug White

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.