All Springer/NP/PCP Air Gun Discussion General > Machine Shop Talk & AG Parts Machining
Material wear questions
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TF89:
I have questions regarding wear rate on various metals. Here is the context. Purchased a BNM Shroud/Breech kit. As a side note, very nicely done regarding machining and powdered coating.
Back to the subject. The breech has been milled from a block of some type of aluminum, not sure if it is 6061 or 7075 suspect that it is a T6. Purely guessing and thinking more along the lines of it being 6061.
I don’t have a machine shop to do this work, so it is all being done by hand power tools. Looking to sleeve the bolt probe hole in the breech with 7/16th hobby brass tube, believe these are made with copper and zinc with a 56-60 hardness.
I have three scenarios:
1) Sleeve the aluminum breech bolt probe 7/16th hole with brass tube, turn down crosman 7/16th barrel to .406 and use that for the new bolt. I have already done this using a drill motor, kept it fairly concentric, it is about .005 out of round on, still fits the brass tube well. This way the polished steel is moving against the brass tube.
*NOTE* I’m using a scrap crosman barrel because it already has a hole drilled through that is very close to center and is easy to bring up to 7/32”. I have the ability to grind it down to size, just don’t have a drill press to center drill a hole and keep it even close to tolerances. I then will be using either a music wire sleeved with a 7/32nd brass tube as the strengthening core for the bolt probe or just use 7/32nd music wire for the bolt probe.
*NOTE* Love my notations. The reason for wanting the brass over the music wire is to eliminate the carbon steel from rusting.
2) Leave the aluminum breech hole as is, take the 7/16th brass tube as the outer sleeve over the turned down steel barrel. This way the brass tube is moving against the aluminum surface.
3) Sleeve the aluminum hole with the 7/16th brass tube using a 13/64th brass tube to fit inside that tubing. I would then again use the crosman barrel to fit inside that for strength. This would have brass against brass.
Really after all that. What I’m looking for is the best wear attributes. Stainless steel on aluminum is the stock setup. I’m don’t know how much difference in wear there is when using brass on aluminum, brass on brass and of course steel on brass. The biggest reason for the question is because I want to use a probeless bolt system and need to remake the bolt to do this.
I hope that made sense.
Rob M:
ill throw my hat in here. I think the breech is 7075, way different than 6061 in most regards.I dont see a super high wear rate here.. I liked the brass moving along the smooth aluminum combo
Rocker1:
Md nylon don't think you can wear it out, easy to machine and can get any size , self lubricating to a extent.
http://www.ebay.com/itm/7-8-Diameter-Nylon-6-6-MD-Plastic-Rod-Priced-Per-Foot-Cut-to-Size-/281695061811
David
Privateer:
I only hope you posted that link as an example.
His shipping costs are crazy!!
:o
Rocker1:
It is Just example jeez he is ridiculus dang. David
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