changing alloy ratio

[rfd]

for a 1:20 alloy, that would mean 1# of tin and 20# of lead, which yields 21# of 1:20 alloy.

at 5-1/4# batch of that 1:20 alloy would be 1/4# tin and 5# of lead.

if i wanted to change that 5-1/4# batch of 1:20 alloy to 1:30 alloy, i should add 2-1/2# of lead for a new total of 7-3/4# of 1:30 alloy.

is this correct thinking?

[JSnover]

Check it. I think 5 1/4 + 2 1/4 should equal 30 quarters, then add 1/4 tin

[rfd]

Check it. I think 5 1/4 + 2 1/4 should equal 30 quarters, then add 1/4 tin

i'm not sure.

the 1:20 alloy is 1/4# tin and 5# lead = 5-1/4#, no?

making that 5-1/4# 1:20 alloy into a 1:30 alloy would mean increasing just the lead ratio, which means just adding 2-1/2# of lead to that 5-1/4# 1:20 alloy, which then yields a 1:30 alloy that now contains 1/4# tin and 7-1/2# lead for a total of 7-3/4# 1:30 alloy ... no good?

[jmort]

You had it right 20 pounds/units of lead and 1 pounds/units of tin. So if you want 1/4 of that you could multiply by .25 and get 5 and 1/4 pounds of each respectively.

[petroid]

You are close. In 5 1/4# of 1:20 there is 1/4# tin. You need to add lead to raise the total weight to 7 3/4# which is 31x1/4# parts for 30:1. So add 2 1/2# of pure. At this point exact composition is not too critical though. If you added 2 1/4# you would be at 29:1

edit I think you got it before I typed this

[montana_charlie]

And ... increasing the lead content by 50% (2.5 lbs.) will give you the 30-1 ratio.

[williamwaco]

for a 1:20 alloy, that would mean 1# of tin and 20# of lead, which yields 21# of 1:20 alloy.

at 5-1/4# batch of that 1:20 alloy would be 1/4# tin and 5# of lead.

if i wanted to change that 5-1/4# batch of 1:20 alloy to 1:30 alloy, i should add 2-1/2# of lead for a new total of 7-3/4# of 1:30 alloy.

is this correct thinking?

You are doing it the hard way.

Measure in ounces instead of pounds.

5 and 1/4 pounds is 84 ounces
84 / 20 is 4.2 ounces.

[bangerjim]

Download the free excel alloy calculation spreasdheet on here.

It does all the math for you..........if that is not your strong suite.

banger

[rfd]

[rfd]

Download the free excel alloy calculation spreasdheet on here.

It does all the math for you..........if that is not your strong suite.

banger

i'd rather understand the perecentage logic and do it myself. i think i've got it. it's too easy. thanx.

[bangerjim]

Still..........get the spreadsheet.

It allows you to easily do "what if" senerarios with various alloys and calcuate the resultant hardness. Fun to play with also!

I use it all the time on my iPhone and iPad when in the shop. You do not need to run it on a PC.

banger

[JSnover]

i'm not sure.

the 1:20 alloy is 1/4# tin and 5# lead = 5-1/4#, no?

making that 5-1/4# 1:20 alloy into a 1:30 alloy would mean increasing just the lead ratio, which means just adding 2-1/2# of lead to that 5-1/4# 1:20 alloy, which then yields a 1:30 alloy that now contains 1/4# tin and 7-1/2# lead for a total of 7-3/4# 1:30 alloy ... no good?

Yes, I should have written that more carefully. I subtracted the tin to start with.
Like Jim said, get a spreadsheet or some sort of cheat sheet for quick reference. You can break it down into ounces, pounds, quarters, whatever.

[jsizemore]

rfd your doing fine. If you do mess up you can remelt.