loquin
Well-Known Member
A couple of weeks ago, I was trying to determine the diameter of a bolt mounting circle, and the only accurate measurements I could take (because it was a 5 bolt pattern) was the separation between the bolt holes.
The closest I could get for that measurement was approximately 1.76 inches.
Now, I'm sure you machinists out there already have a chart to check, or a formula written down, but after some searching, I was able to get an answer.
The formula to use is:
D = S / Sin(180/N)
where:
D is Bolt Circle Diameter
S is the Bolt Spacing
N is the Number of Bolts
If I plug 1.76 inches, and 5 bolts into the above formula, I get 2.994 inches. So, it looks like I have a 3 inch - 5 bolt pattern.
To go the other way, if you know the bolt circle diameter, and need to measure spacing for drilling holes, (when you don't have a means of indexing the holes,) the formula is:
S = D • Sin(180/N)
Here's a table to use with values for Sin(180/N):
....N.. Sin(180/N)
The closest I could get for that measurement was approximately 1.76 inches.
Now, I'm sure you machinists out there already have a chart to check, or a formula written down, but after some searching, I was able to get an answer.
The formula to use is:
D = S / Sin(180/N)
where:
D is Bolt Circle Diameter
S is the Bolt Spacing
N is the Number of Bolts
If I plug 1.76 inches, and 5 bolts into the above formula, I get 2.994 inches. So, it looks like I have a 3 inch - 5 bolt pattern.
To go the other way, if you know the bolt circle diameter, and need to measure spacing for drilling holes, (when you don't have a means of indexing the holes,) the formula is:
S = D • Sin(180/N)
Here's a table to use with values for Sin(180/N):
....N.. Sin(180/N)
- N/A(you're dividing by zero, so I guess you get a black hole...)
- 1.0000
- 0.8660
- 0.7071
- 0.5878
- 0.5000
- 0.4339
- 0.3827
- 0.3420
- 0.3090
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