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post #1 of 9 (permalink) Old 09-16-2019, 10:39 AM Thread Starter
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Default New guy looking for build guidance/advice

I have a piece of C675 manganese bronze, 4.125"X 18". So i am thinking about building a BP cannon and I would like to use this material. First question is this material suitable for my intended purpose? I was thinking mountain howitzer style that would have a golf ball sized bore. Found this print online and was thinking to follow it at about a 60% ratio. What say the experts?
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post #2 of 9 (permalink) Old 09-16-2019, 12:56 PM
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colchester,

Welcome to the Board! I am always curious to know how you found us.

I think that the 12 pound Mountain Howitzer is an awesome choice. We have built a few of these in smaller bore sizes.

Building to that print will keep you well within safety ratios with the powder chamber.

I have not found the machinability of C675. Machining of the cascabal area may require patience.

Keep us advised and don't drop that 78 pound blank on your foot.

Michael
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post #3 of 9 (permalink) Old 09-16-2019, 01:58 PM
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My guy came back from lunch. Machineability is 30%. . . ouch. The good news is that blank would cost somewhere around $600.

Michael
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post #4 of 9 (permalink) Old 09-16-2019, 03:44 PM Thread Starter
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Quote:
Originally Posted by irishman View Post
colchester,

Welcome to the Board! I am always curious to know how you found us.

I think that the 12 pound Mountain Howitzer is an awesome choice. We have built a few of these in smaller bore sizes.

Building to that print will keep you well within safety ratios with the powder chamber.

I have not found the machinability of C675. Machining of the cascabal area may require patience.

Keep us advised and don't drop that 78 pound blank on your foot.

Michael
Thanks for the welcome looks like my kinda place. I stumbled on the forum when I was doing research for this project.
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post #5 of 9 (permalink) Old 09-18-2019, 03:51 AM
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Here is a data chart for C67500 Manganese Bronze; click on the Mechanical Properties tab. Quite a bit of variation in tensile strength depending on temper.


C675 Manganese Bronze

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post #6 of 9 (permalink) Old 09-18-2019, 10:01 AM Thread Starter
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Here is a data chart for C67500 Manganese Bronze; click on the Mechanical Properties tab. Quite a bit of variation in tensile strength depending on temper.


C675 Manganese Bronze
As stated above Im a newb here. Staring at the chart for a bit looks like condition
060 has a ys 207ksi and is 65 rhb
H01 has a ys 290-310 and 77-83 rhb
H02 has a ys414 and 90 rhb

So a couple questions
Are any of these conditions unsuitable for my intended use. Barrel wall would wind up at 1.040" and would be 1.260 around the powder chamber after scaling it to golf ball size bore.
If I need to determine what the condition of the material that I have is can I simply do a rockwell hardness test and fit the result to the chart. I do not have a cert sheet on this stock I determined the alloy by XRF analysis. I have access to a bench rockwell tester.
Thanks
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post #7 of 9 (permalink) Old 09-18-2019, 10:54 AM Thread Starter
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My guy came back from lunch. Machineability is 30%. . . ouch. The good news is that blank would cost somewhere around $600.

Michael
Tell me about the 30% machineability. This stuff faced and turned real nice but I notice it resisted the center drill a bit more than most stock that I machine. How would it compare to 1018 CRS I built a golf ball cannon using 1018 a few years back but I gave it to my uncle as a gift machined pretty nice the deep hole took a while
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post #8 of 9 (permalink) Old 09-18-2019, 11:19 AM
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Quoted from Wikipedia:

https://en.wikipedia.org/wiki/Machinability

Machinability rating
The machinability rating of a material attempts to quantify the machinability of various materials. It is expressed as a percentage or a normalized value. The American Iron and Steel Institute (AISI) determined machinability ratings for a wide variety of materials by running turning tests at 180 surface feet per minute (sfpm).[8] It then arbitrarily assigned 160 Brinell B1112 steel a machinability rating of 100%.[8] The machinability rating is determined by measuring the weighed averages of the normal cutting speed, surface finish, and tool life for each material.[8] Note that a material with a machinability rating less than 100% would be more difficult to machine than B1112 and material with a value more than 100% would be easier.

Machinability Rating= (Speed of Machining the workpiece giving 60min tool life)/( Speed of machining the standard metal)

Machinability ratings can be used in conjunction with the Taylor tool life equation, {\displaystyle VT^{n}=C}VT^n = C, in order to determine cutting speeds or tool life. It is known that B1112 has a tool life of 60 minutes at a cutting speed of 100 sfpm. If a material has a machinability rating of 70%, it can be determined, with the above knowns, that in order to maintain the same tool life (60 minutes) the cutting speed must be 70 sfpm (assuming the same tooling is used).[1]
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post #9 of 9 (permalink) Old 09-19-2019, 02:23 AM
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060 has a ys 207ksi and is 65 rhb
H01 has a ys 290-310 and 77-83 rhb
H02 has a ys414 and 90 rhb



Fortunately or unfortunately, the chart has both inch measurements and metric measurements. Your YS numbers are metric and the units are MPa (mega Pascals.) The psi values are in the row above the metric ones.

GG
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