Locating features

[redvan22]

Hi,
How does a professional machinist find features on a part to be transferred to a workpiece?

IE:
I want to make a new compound slide handle assembly with bearings for my mini lathe to eliminate the slippage of the dial that drives me mad. This part of the design wasn't thought out very well to begin with.
I found a video that does exactly what I need step by step but the author made a few mistakes primarily because he didn't locate key features properly like the screw. It's off center because of the gib.
How can I get these measurements accurately to avoid issues?

 

[T. J.]

A photo of the part you’re trying to make would aid in giving you specific advise

 

[redvan22]

A photo of the part you’re trying to make would aid in giving you specific advise

So there's no specific method.

 

[Asm109]

You use measuring tools. calipers, micrometers. You can even use the handwheels on a mill and a test indicator in the spindle to make measurements. Or the DRO if you got one.
Give us a specific need and there will be at least 3 different ways of measuring it. Then this thread can drive off into the weeds arguing endlessly which method is the best. Good times.

 

[twhite]

Also as you are making a new one. You can decide where to put everything you need. Obviously some things will be pretty much set. On those measure them and make a sketch. From there you can put stuff wherever you want. You will have solid dimensions as you created them. Oh do not worry about messing stuff up. We all do that more often than we like to admit


Cutting oil is my blood.

 

[GT-6 Racer]

So there's no specific method.

Very difficult to advise without details. But generally between micrometers, hole gages/pins, and the surface plate and associated equipment (surface gage, gage blocks, DTI etc) you can reverse engineer most anything.

 

[redvan22]

Understood.
My primary task is to get the hole for the compound slide screw in the right place horizontally and vertically since it's offset from the center line. I figure once I get that located, I can locate off that to get my other locations for mounting bolts, etc. My workpiece is wider than needed and once I get this done, I'll trim it to the correct width. The height is already cut.

However, I thought that if I thread a bolt into a hole, I could determine the distance from the edge of the workpiece to the side of the bolt. Add half the diameter of the bolt and that would give me the center of the hole. But, because of the thread pitch, I could be off by several thousands and that would be a problem.

Similarly if I could put a pin in the slide screw bore, I could find the center but I don't have pins that large.

That's why I asked if there was a specific method. I've thought about it from several angles but felt I needed a professional perspective.

 

[redvan22]

You use measuring tools. calipers, micrometers. You can even use the handwheels on a mill and a test indicator in the spindle to make measurements. Or the DRO if you got one.
Give us a specific need and there will be at least 3 different ways of measuring it. Then this thread can drive off into the weeds arguing endlessly which method is the best. Good times.

I have everything you mentioned and a little more but no pins and I think that is what I really need. A photo would probably help greatly in this as suggested.

Once I start to dismantle the cross slide, I will post a few photos.

 

[redvan22]

Very difficult to advise without details. But generally between micrometers, hole gages/pins, and the surface plate and associated equipment (surface gage, gage blocks, DTI etc) you can reverse engineer most anything.

Surface plate and gage would get me most of my measurements once disassembled. Great idea, thanks.

 

[GT-6 Racer]

Surface plate and gage would get me most of my measurements once disassembled. Great idea, thanks.

sure thing glad I was helpful. You could also make a measurement pin for the larger hole and a collared screw for the threaded hole to use as datums on the plate before you disassemble the lathe.