RogueFactor
10-28-2008, 09:57 PM
Here is just a bit of info on the differences of AGD rail bushings:
The rail bushing on the left is an older AGD rail bushing. They were nickel/silver in color, were thinner-walled(wall thickness= ~.021"), and slid into the rails pretty easy. These were the standard bushing used with stainless valves.
The rail bushing on the right is the newer AGD rail bushing. These are brass in color, thicker-walled(wall thickness= ~.025"), and are press-fit into the rails. It requires tools to do so. These are now the standard bushing.
This begs the question...why did they change the bushings? Coincidentally, the change was made right around the same time that XValves came on the market. Why is this important?
As some of you may recall that were on AO around the time that XValves were debuted, Tom made it absolutely clear that because the XValve was made of aluminum its longevity was limited and they would not be warrantied if the threading was to gall or strip over time.
Aluminum is a soft metal in comparison to stainless steel. So a stainless screw in an aluminum valve has a much greater chance of galling/stripping than a stainless screw in a stainless valve.
But why would this matter? Well, the valves move ever so slightly when the marker is fired. Due to weight, the XValves a bit more than the heavier stainless valves and the force of the firing sequence moves the bolt in both directions. Couple that movement with a stainless screw in an aluminum XValve...and you eventually will have galled/stripped threads.
How to mitigate this possible issue? Change bushings with a thicker one that mates tighter with the field strip screw and further limits the movement.
Why didnt AGD just use a shoulder bolt? Using a bushing allows for slight variations in tolerances. So its cheaper to make a field strip screw with a press fit split bushing than it is to make a shoulder bolt.
The bushing also serves a dual purpose to keep the parts of the marker aligned(rail and frame) even when the field strip screw is removed. The rail bushing seats itself in the countersink of the back frame hole. There is no proper depth per se, as long as it completely seats in that hole.
Thats my :twocents:
The rail bushing on the left is an older AGD rail bushing. They were nickel/silver in color, were thinner-walled(wall thickness= ~.021"), and slid into the rails pretty easy. These were the standard bushing used with stainless valves.
The rail bushing on the right is the newer AGD rail bushing. These are brass in color, thicker-walled(wall thickness= ~.025"), and are press-fit into the rails. It requires tools to do so. These are now the standard bushing.
This begs the question...why did they change the bushings? Coincidentally, the change was made right around the same time that XValves came on the market. Why is this important?
As some of you may recall that were on AO around the time that XValves were debuted, Tom made it absolutely clear that because the XValve was made of aluminum its longevity was limited and they would not be warrantied if the threading was to gall or strip over time.
Aluminum is a soft metal in comparison to stainless steel. So a stainless screw in an aluminum valve has a much greater chance of galling/stripping than a stainless screw in a stainless valve.
But why would this matter? Well, the valves move ever so slightly when the marker is fired. Due to weight, the XValves a bit more than the heavier stainless valves and the force of the firing sequence moves the bolt in both directions. Couple that movement with a stainless screw in an aluminum XValve...and you eventually will have galled/stripped threads.
How to mitigate this possible issue? Change bushings with a thicker one that mates tighter with the field strip screw and further limits the movement.
Why didnt AGD just use a shoulder bolt? Using a bushing allows for slight variations in tolerances. So its cheaper to make a field strip screw with a press fit split bushing than it is to make a shoulder bolt.
The bushing also serves a dual purpose to keep the parts of the marker aligned(rail and frame) even when the field strip screw is removed. The rail bushing seats itself in the countersink of the back frame hole. There is no proper depth per se, as long as it completely seats in that hole.
Thats my :twocents: