Radius measurement - top of bridgeport ram?

[Jay Bolyard]

Hello - does anyone know the radius of the top of the ram on a Bridgeport (circa the 60's) Series I mill? (or have a suggestion on how to reasonably measure)
I need to make a block that interfaces that radius over the 5/8-11 lifting eye hole for the purpose of mounting a new DRO arm.

Thanks in advance.

 

[SIP6A]

Being a casting the radius is different depending on where you measure it. I have made blocks like what your describing, what I did was made a block with clearance in the center and made contact on about the 1/2" on each outside edge.

 

[jims]

A conture gage used in measuring flooring should work.

 

[John Garner]

Sounds like a job for "liquid shim". Auto body filler works well, as will RTV.

 

[Jay Bolyard]

A couture gage used in measuring flooring should work.

That would help me transfer to say a piece of paper... then I could use a compass to attempt to "fit" with a measurable radius? Seems reasonable. Thanks.

 

[Nmbmxer]

Being a casting the radius is different depending on where you measure it. I have made blocks like what your describing, what I did was made a block with clearance in the center and made contact on about the 1/2" on each outside edge.

I agree, use some channel.

 

[Bill D]

It is not round, it is rounded. Lay a pice of solder or copper wire over it and press down so it lays flat/flush. transfer to a sheet of paper and trace the curve with a pencil.
Bill D

 

[eKretz]

That would help me transfer to say a piece of paper... then I could use a compass to attempt to "fit" with a measurable radius? Seems reasonable. Thanks.

Lay a ruler along the arc from the gage. Set the ruler so that it contacts the arc right at the ruler's 1" mark and right at the ruler's 4" mark or something similar. Measure the sagitta between the ruler and the farthest point of the arc at 90° to the ruler (it will be at the center of the two points on the ruler that are aligned with the arc - in the given example it would be at 2.5"). Use math. Close enough.

Liutaio Mottola Lutherie Information Website

Information for builders of stringed musical instruments.

www.liutaiomottola.com

 

[Jay Bolyard]

Update: I found the radius to be very close to 2.75".