Piston material information for air rifles

[keaw]

I like to know few information about air rifle piston . If you need to make piston, what type of material I can use for air rifle piston?

[Motorhead]

I like to know few information about air rifle piston . If you need to make piston, what type of material I can use for air rifle piston?

Spring gun we'll assume

[nced]

I like to know few information about air rifle piston . If you need to make piston, what type of material I can use for air rifle piston?

Well....I've used DOM (drawn over mandrel) tubing for the piston body because it doesn't have a weld seam inside, I used 01 tool steel for the latch rod which was hardened and tempered on the "catch end", and just a plain ole steel bolt that was machined for fitting the piston seal on the "end plug" . The latch rod was pressed into the "end plug" and pinned and the "end plug" was brazed to the piston shell..........
Variations of my latch rod catch above the factory latch rod.............
Uploaded at Snapagogo.com
I initially used W1 (water hardened) tool steel for the latch rod but I would get stress cracking at the corner of the "catch notch" in the upper design. I still used the "upper rod design" but I switched to O1 (oil hardened) tool steel plus used an end mill with a .015 edge radius so there was no sharp corner and never had stress cracking when quenching after that. Here are a couple pics when I was playing with using molly filled 6/6 nylon for an oring sealed piston cap however I later switched to 6061 T6 aluminum for the caps.
Uploaded at Snapagogo.com
Uploaded at Snapagogo.com
Uploaded at Snapagogo.com

Anywhoo.....my whole purpose of fabricating my own pistons was the fact that a couple decades ago my R9 pistons from the factory were very inconsistent in size and shape plus the latch rods were usually off-center at the skirt. LOL....I measured .060 latch rod end runout on one factory R9 piston.   

[eeler1]

Ed, nice write up & pics

[keaw]

Mr. Ed, really I appreciate your information which is very useful for us. According to your experience you are using DOM (drawn over mandrel) tubing for the piston body. Could you explain is there any different material use for this part? Just we are learners to this industry. if you can give some more information about it such as each parts and suitable material.
what do you think about this material ST35 / F1?

[nced]

Mr. Ed, really I appreciate your information which is very useful for us. According to your experience you are using DOM (drawn over mandrel) tubing for the piston body. Could you explain is there any different material use for this part? Just we are learners to this industry. if you can give some more information about it such as each parts and suitable material.
what do you think about this material ST35 / F1?

I really don't know what tubing is best but I always ordered 4130 cold drawn tubing like this...........
http://www.mcmaster.com/#alloy-steel-tubing/=11zzunr

I think that ST35 / F1 is actually a steel boiler pipe spec so I'm thinking that it would be fine. I know that the HW factory piston skirts are hardened so the factory is using some sort of tube that can be hardened.

The HW95 receiver tube is about 26mm (about 1 1/32") so using a 1" OD tube gives about 1/64" clearance all around to allow for adding buttons. Since the Delrin buttons I use won't gall the receiver tubr I really don't take the time to harden the piston skirts.

For the latch rod I use O1 tool steel with the "latch end" that's hardened and tempered so a file will skate on the catch. I do this simply because  factory HW95 latch end is similar. A while back I bought a Chinese R9 clone (BAM B26) and found that the latch rod catch was soft enough that a file would cut the surface so I really don't know how important the hardening is. I simply chose to match the HW latch rod as close as possible. I'm not sure that the HW latch rod catches aren't simply case hardened because the ductile core would give toughness to the part while providing a hardened surface. Also, simply using cold drawn steel and case hardening the material would prevent the issue I had with stress cracking when "full hardening". Matter of fact, if I make another piston I just might case harden the low carbon A108 rod for the latch rod.

[phoebeisis]

4130 steel is commonly used for GOOD  steel bicycle frames-butted or straight gauge
usually with a   4130 CRMO DECAL on the seat tube-making it  cost more
I occasionally buy    rehab and sell bikes
Good/decent quality steel framed bikes (usually 4130) are easy to sell

[Back_Roads]

 I think i learned something ... not sure what . but thanks