# Copying something precisely.



## SoIll914 (Jan 23, 2017)

A newbie question, but here goes. Lets say you have a part with holes you can measure but not move to your mill or lathe. Youd like to make a copy of this part but whats making me scratch my head is how do you measure existing holes in relation to where they are located. I mean how could i measure existing holes to know EXACTLY where to layout holes to drill and copy a part.


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## Billh50 (Jan 23, 2017)

It would all depend on the part. it is easy to measure holes to a flat edge or even a diameter with just a vernier. Other shapes may require a different approach.


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## mikey (Jan 23, 2017)

If the part to be reproduced can be removed then I would place it on the material you're going to make the new part from and trace the outline (to cut it to shape later) and then use transfer punches to mark the hole locations. Or, if the surface that your part will attach to has threaded holes you can make the new part minus the holes, thread some transfer screws into the holes, and put the new part in place. A tap over each transfer screw will mark the holes for you. 

If the old part has square edges you can also just measure their locations. This is slower and has more potential for error. I would opt for the above myself.


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## Wreck™Wreck (Jan 23, 2017)

What do you mean by "exactly"?


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## SoIll914 (Jan 23, 2017)

Basically this is the jist of the part. Probably 2" wide by 4" long by 5-6" tall. The thing im wanting to know is how to make these drill holes on a copied part line up as accurately as the part itself. Its not a part i think i can layout on paper and trace drill holes.
Edit: this part is a non critical part for a machine i run at my job. I wanted to try and make a replacement for practice but im new and do not know of the most accurate way to insure the bolt holes will line up.


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## JimDawson (Jan 23, 2017)

I normally sit down and make a drawing of the part.  This may take the form of a rough sketch with dimensions with pencil & paper for a simple part to a very detailed CAD drawing for something more complex.

The measuring is normally done with digital calipers, but I also have a small height gauge at my desk which simplifies some dimensions.  Normally I will find the hole centers by measuring both hole edge to hole edge, then do the math to find the centers.  The get hole edge to part edge in both the X and Y axis.

For maximum accuracy I use gauge pins in the holes and measure over those, then use a surface plate and height gauge or indicators for deriving the hole to edge distances.  Measurements may also require the use of radius gauges and angle gauges.

How you approach the job depends on how accurate you need to be, using calipers will normally get you close enough for most work.


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## JimDawson (Jan 23, 2017)

SoIll914 said:


> Basically this is the jist of the part. Probably 2" wide by 4" long by 5-6" tall. The thing im wanting to know is how to make these drill holes on a copied part line up as accurately as the part itself. Its not a part i think i can layout on paper and trace drill holes.
> Edit: this part is a non critical part for a machine i run at my job. I wanted to try and make a replacement for practice but im new and do not know of the most accurate way to insure the bolt holes will line up.



If you can measure the original part, then just use those numbers to drill the holes on your mill.  Start at one corner and get absolute X/Y dimensions to the hole locations.  Even if you don't have a DRO, this is simple, just trust your dials and count turns.  I did tool & die work that way for years.


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## SoIll914 (Jan 23, 2017)

So you think i can get by just grabbing my vernier and taking the smallest unit measurement i get from the edges of the holes to the edges of the part? Sounds easy enough


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## JimDawson (Jan 23, 2017)

Do you not trust your vernier or your ability to use them?  For most work, you will be fine.  I don't know that accuracy this job requires, but you should be able to measure +/- 0.001.  Typically you would drill the hole 0.016 to 0.032 oversize for standard clearance.


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## SoIll914 (Jan 23, 2017)

I think thats my question. How would i get absolute x/y dimentions on the drilled holes with a vernier. What points are measured? Or is it not possible?


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## JimDawson (Jan 23, 2017)

It's very possible.

Measure hole edge to hole edge then add the hole diameter, that gives the center to center distance.  Part edge to hole edge plus 1/2 the hole diameter gives the center distance from the part edge.  Add that to the center to center distance and that gives you the location of the second hole from the part edge.

This works as long as all of the hole diameters are the same.  If the holes are different diameters, you do the same thing but add half the diameter of each hole to get the center to center distance.

You already have a 3D model, just move and size the holes in the drawing to match the actual measurements of the part that you want to copy.


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## SoIll914 (Jan 23, 2017)

Ok, thank you! That model is just a stand in for the actual part.


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## Wreck™Wreck (Jan 23, 2017)

Since you can not describe what you mean by "exactly" no one can help you.


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## JimDawson (Jan 23, 2017)

SoIll914 said:


> Ok, thank you! That model is just a stand in for the actual part.




Time to make the model look like the real part !


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## SoIll914 (Jan 23, 2017)

Well i tried to articulate my question as best i could. Thank you jim for hanging in there.


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## Wreck™Wreck (Jan 23, 2017)

SoIll914 said:


> Well i tried to articulate my question as best i could. Thank you jim for hanging in there and not acting like a smartass.


Not smartass at all, "exactly" is entirely relative to what one requires, do you require hole center dimensions in the  <>.005 range or the <> .0005 range, this makes a considerable difference when asking for advice.
A better question would be "how do I determine tapped or drilled hole positions within the normal error inherent in such features". 

"Exactly" is not possible.


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## bfd (Jan 24, 2017)

how many holes? if its even then measure across two opposite holes and add one hole diameter this gives you the bolt hole circle dia. indicate the part in on  a mill table and move over from off center this is where you would place the first hole then index to the other holes. if you start a conversation with me I can give you a lot more det


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## rgray (Jan 24, 2017)

One thing I think I've learned (questionable) is that a drill will not make a truly accurate hole. So then we use a reamer, but the reamer will follow the not necessarily accurate drilled hole. The cure was to use an endmill to make the hole with a more accurate placement first , which can then be reamed to size.
This practice was for critical hole placement (like two parts that must dowel pin together) and is not necessary for most applications where a larger clearance is used.


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## jmarkwolf (Jan 24, 2017)

I use my DRO.
Drop a pin guage in one hole, zero out your DRO, move to each successive hole and do the same. Write down the locations of the hole.
I can "decipher" odd ball mounting hole patterns this way as well.


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## sanddan (Jan 24, 2017)

You could use a transfer punch to locate the hole on the new part. Pick the size that fits snug in the hole.

https://www.amazon.com/Neiko-02621A...74&sr=1-4-catcorr&keywords=transfer+punch+set

You can also make one by turning a point on the end of a bolt. This could be used to transfer the location or by measuring point to point to get the hole spacing.


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## SoIll914 (Feb 5, 2017)

After measureing every which way im going to test run a peice for alignment of all four holes before making the finished part. Ive got 3/16s holes 0.07" off the edge and 0.10" off the front so from what i gather my x axis hole center is 0.19375 and y axis hole center is 0.16375 so where these two lines intersect, when i do layout, will be where i start my 3/16s hole. Unlesd im missing something.


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## Izzy (Feb 5, 2017)

Measure from inside edge to inside edge of the 2 holes being drilled then add the diameter of the holes to be drilled to that number and that will give you the exact center to center distance of the 2 holes. Then measure from the outside of the hole to edge of the part in 2 spots 90 degrees from eachother. This way the hole distance center-center and position of the 2 holes is the same as the part being re-produced. I used this method to remake pair of ball joint mounting plates. And both parts came out identical!


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## Wreck™Wreck (Feb 5, 2017)

0.16375

Very funny!


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## SoIll914 (Feb 5, 2017)

Does it normally help people to let them know you think somethings funny? Why even post anything?


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## Wreck™Wreck (Feb 5, 2017)

Yes, praise always helps.

Also you appear to not get the joke, 0.00005 is 5 ten millionths of an inch, easily achieved by home hobby machinists I assume.


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