Holes from the edge.

[praetor]

How do I get precise measurements of hole positions from an existing part to make several copies of the same part? Would i use this method:

http://www.metalwebnews.com/formulas.../hole-dim.html

How about measuring hole center distance from part's edge, (distance from edge of part to center of hole, basically using X and Y positions), is there a formula or something for that?

My predicament, I need to make a few of these plates (in following pics) with accurate hole positions, how do I ,basically, go about doing that exactly?

[widgitmaster]

While the procedure in your link is perfect for measuring the distance between holes and slots, a slightly different procedure is needed to measure from an edge.

I my shop I have a set of gage pins, and with a tight fitting pin I can measure from the edge to the side of the pin. Then add that number to 1/2 the pin diameter.

Eric

[Geof]

The most precise if somewhat tedious way is to put it in your machine and dial in to the holes and sides.

[One of Many]

You have 1 large hole and 2 screw pattern groups that need to be in relation to each other and the part body. Both screw patterns are symetrical to the center line and referenced to one common edge, top or bottom. You can use the method link there for each group, but that will depend on the holes roundness. A cad drawing can help verify the true positions of the patterns relations, to the centerline and referenced edge.

It appears that the bottom face had alignment pins(one broken off) that referenced the position of the plate to its mating part. Technically, those would also be tooling points to set the 4 hole mounting pattern and large hole location(which may have been cast in?). Tooled accordingly on a fixture, all the holes could be worked in one setup, relative to the pins, not an edge.

DC

[praetor]

OK, widgetmaster, so you're saying after inserting a tight fitting pin in one of the holes, I would take my calipers and place the top jaw on the edge (for example: taking measurements for one side; the top left hand corner hole of the piece) and the moveable jaw of the caliper to the outside (right hand side) of the pin to establish distance and then add 1/2 the pin diameter? Is this correct?

for example:

lets assume the hole is .250 inch, I find from the edge to the side of the pin is .750 I would add half the dia. of the pin, .125 to .750. So from the edge to the center of the hole the distance would be .875? Sounds logical.
I know that this is remedial to most of you, but I never had to work with very close tolerance, just enough accuracy to suffice and seeing how this current project is a commsioned one i wanted to make sure everything was a precision fit. And where else can an advanced amatuer get good answers to such questions but through the members of cnc zone ( this is me being very appreciative) Again, Thanks widgetmaster and Geof for your suggestions. I'll posts pics of finished items, I know, I know...it's not a machine build, but to me it's something just the same, to be proud of.

[praetor]

Thanks One of Many, you prove a valid point. But as a challenge I wanted to do this manually, mostly because I killed my keling stepper drivers for my cnc mill (x and Y) and am waiting for new ones to come in, so figured until then...let me try manual milling. but I saved your suggestions to my notes...i find it valuable. I can never say it so much, thanks.

[widgitmaster]

Yes, I do agree with Geoff, using the mill as a coordinate measuring system is an accurate and easy method.
Also, the part is a casting and all holes look to be symmetrically centered in one axis, therefore you only need to get the lead-in dimension for the other axis!

As you can see from this thread, there are many ways to achieve the same results! The only variable is the tools and machines at your disposal! So as a good machinist, you need micrometers, a caliper, a dial indicator, and an edge-finder! With these, you can do most tasks with relative accuracy!
Eric

[BillTodd]

I read somewhere about using a tap screwed into a threaded hole in order to locate the hole centre correctly - seemed like a good idea to me

[praetor]

Yeah, you're right widgetmaster; there are quite a bit of ways to achieve hole location accuracy and I've always used my cnc mill to do so but seeing as how my [cnc] mill is down I figured I'd learn to do things manually for the hell of it and what better way to take on the challenge than to make do with manual machining on commissioned pieces?

But this also shows me, much like a scientific calculator being used to add 2 and 2 to get 4 (which is in and of itself overkill), we've become accustomed to the convenience of technology and leave behind what it means to do things manually (think of automatic doors when they're out of order, we can't help but to think, "CRAP!", and then feel forced to try and push a door open and not noticing the sign over the door handle telling us to pull) So I am going to pick up my wooden club and beat things into precision by teaching myself how to machine things manually, (until my Keling drivers arrive in a day or two), again jus for the hell of it. I'd like to thank all of you for taking the time to share some ideas and suggestions on this topic.

[tomthemacman]

Making some video camera parts there? I've seen far too many plates like that, usually attached to the bottom of a camera though.

It's a Sony standard, as far as I know. The screws should be metric for threading into the camera, M3 according to the document I just looked up, so the clearance holes should be just over that size, with the appropriate countersink. I'd check the size though, since the info I got was from a Panasonic.

Good luck with the project, and whatever it is, it'll probably be pretty classy if it has a quick release like this on it!