Dovetail Application Mil Spec 1913

[[To...]]

Some of you out there may already be measuring features like this, so I'm looking for suggestions on how I might check this in Calypso. TIA

Mil Spec 1913 - sample.jpg

[[Ow...]]

Cone calculation checking the position at the specified diameter and then again the diameter at the specified location.
Then do some tangent calculations with result element or use cartesian distance with the cone calculations and top face?

[[To...]]

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Hey Owen, This is not a diameter. It is a linear dovetail.

[[Ri...]]

https://www.thomasmechanicaldesign.com/ ... -rails-gdt

Give this a read.

I'm not entirely certain this can be inspected without a gage.

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[[Ri...]]

I would create alignments that allow me to drive at each surface with "Space points" from nominal geometry.
Then use Caliper distance for the .748 dimension.
The nominal geometry will allow you to investigate deviations.

[[To...]]

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Thanks Very interesting.

[[To...]]

Rolling off of Rick's idea, what do you think of measuring 2 space/plane points at the 2 nominal gage points on the bottom angles. Then, create a 3d Best Fit Alignment and allow the 2 points to best fit translating in X and Z and rotating about Y. Using this alignment, create a line from the 2 points. Create a theoretical line .108 above this. Next, scan 2 lines on the upper angles and intersect the 2d lines with the theoretical line. Check the distances between original 2 points, which I'm guessing will be perfect due to the best fit, and then check the distances between the 2 intersections.

[[Ja...]]

I am thinking if you use both space/plane points on the bottom angles and use 3d best fit alignment, then the best fit will try to saturate at Z co-ordinate such that the distance between the bottom points is very close to nominal (.748) Now building on that when you apply the method to get top two points at .108 from that Z co-ordinate and output distance between them. You can imagine that all the four points (bottom 2 near perfect and top 2 ) will make a trapezoid instead of a rectangle which is intended.

Instead, what do you think of making 3d best fit alignment allowing translation in Z only for two space/plane points on either left or right side so that best fit will try to saturate at Z co-ordinate that passes through center of top and bottom (i.e. at center of .108 nominal). From here you can make four lines on surface and two theoretical lines at .054 and -.054 and get both intersections and reports those distances. will definitely need some more thought into this if this will work in the way intended.

[[To...]]

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Yes, you're right.

Here's another thought. 4 space/plane points at nominal locations. Construct a 3d line from 2 symmetry constructions (#'s 1 & 2), one for each pair of points in the .Z direction (.108). Create a symmetry construction (#3) from the previous 2 symmetries. Loop a secondary alignment using the 3d line for planar and Z origin. Symmetry3 for X origin. Next create 2 theoretical line features, .054 above and below Z origin of alignment . Check intersections of theoretical lines with 45° lines.

[[Ri...]]

.

[[Ja...]]

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Yes, that's what I came up with later on to be the best solution.

[[Je...]]

Scan the 45 degree flanks as 2d lines with high point concentration and slow speed to get maximum data. If you find you have data filtered out, add an additional line scan in the strategy in the opposite direction to fill in the filtered gaps.

Scan the top and bottom 45. On each side at the same location on dove tail. (easiest way is to create a section on the model to ensure this is properly defined). Create at least 1 additional set of scans at the opposite end. You may create as many as you like as you see fit, but 2 sets are minimum.

Create an intersection point between each 45 degree upper and lower flank. Do this for both sides. Creating 4 "sets" of these will allow you to create a center plane on your dovetail that is independent of all other geometry. Use one entire sides sets of points to create a 3d Line. Do this for both sides. Create a symmetry line between.

Use the recall center plane for a sub alignment that utilizes the plane for "Rotation in Space" and relative axis constraint (assuming Z here). Use symmetry line for Planar rotation and relative axis constraint (assuming X here)

Name this Alignment as you see fit (ie "Align_Dovetail_Local"). Create a theoretical plane, set to alignment to "Align_Dovetail_Local" and "Z" nominal to -0.054. Create a second theo plane at +0.054 in the same manner.

Intersect each 45 degree flank 2D-Line measurement with the respective +Z and -Z theo planes. Report X distance between intersections. Report Z distance from top of dovetail to bottom -Z theo plane or individual intersect points. Reporting should be done in "Align_Dovetail_Local" alignment if using caliper or simple distance

Your Z distance is a constant .108, geometry is set from the dovetail actual and you aren't relying on any unrelated features.

There are 100 different ways this method could vary, like you could use 2D Curves in place of 2D Lines to ensure proper geometry is captured, theo planes could be theo 2d lines at locations specified by formula from scanned line nominals, the whole set of upper/lower/left/right scans and intersections could be grouped and set as a pattern and offset a distance with occurrence values. Sky is the limit...

[[Gr...]]

To all I do know that you are looking at a " Picatinny rail " and I have checked these on a optical projector. There are also fit gauges for go/ no checks . Finding the centers is sort of like fitting a bar between angled lines on OGP software. Once you find the "centers " you back measure to see what it actually is . Not much fun.

[[To...]]

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Jeff, I like this method as it measures both ends to create 1 spatial feature, as opposed to a 2d feature at each end.

[[Je...]]

Creates a single spatial feature for reference that can be reported against or reporting can be done independently depending on print requirements. Satisfies all print requirements without question and your gage points are set. I've done 100's of these. Each situation is unique but this is the general work flow.

[[Ow...]]

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It was a quick reply but, damn, I totally misinterpreted that one.
It must of been that "your team is going to it's 3rd Super Bowl in 5 years brain-fog hangover on Monday" 🤣

[[To...]]

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Let me know when you get to 9..... 🙂

[[To...]]

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Jeff Penrod's post regarding using lines on the angles for the secondary alignment worked great. The points process that I came up with, did not work.

[[To...]]

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Jeffrey, this worked perfectly. Thank you.