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16th Sep 2019, 02:43 PM #1Most Valued Member
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Measuring location of numerous holes on a mounting face - how would you do it??
I have a specific job in mind, but possibly this is a general question...
I need to determine the location of a number of holes in a (transmission) mounting face so I can make up some adapters/spacers for mounting it to a different engine.
There might be some pattern/s to the holes, but its definitely not obvious so I'm starting by assuming there isn't one.
For a one-off part the easiest way is probably to just locate them in the new part using transfer punches etc, but I'm likely to need more than one and would rather spend the time up front to get accurate locations and draw it up properly.
To give some context:
- Number of holes: roughly 5-15
- Size of holes/fasteners: 6-12mm
- locations to be within say +/- 0.20mm
- Combination of through, blind, threaded and plain holes
- Part size: would fit inside 400x400 envelope
- Parts are easily handled manually and placed on a surface plate or machine table for measurement if required.
Best idea I've come up with so far is using a mill with DRO and some form of hole locator - but interested in how you experienced blokes would approach the task?
Steve
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16th Sep 2019, 03:12 PM #2
I just purchase a TRANSFER SCREW SET from the US as i need to TRANSFER holes from a gearbox to mounting bosses and they need to be dead nuts in alignment.
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16th Sep 2019, 04:26 PM #3Diamond Member
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I don't consider myself to be experienced but a while ago I fabricated/welded a bell housing to join a 1990s Toyota gearbox to a 1935 Hudson engine. To get the bolt locations at each end I had the relevant pieces set up on the mill and used the DRO and an edge finder.
Its useful to know whether you are dealing with a metric or imperial item. The metric item will tend to have features located in whole mm or maybe .5mm. An imperial item depending on its age will tend to have features located to the 1/32" for old stuff and to the 10s of thous, eg 4.070", for more recent stuff. Designers, like the rest of us, prefer to deal in easy to handle numbers where they can.
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16th Sep 2019, 04:36 PM #4Most Valued Member
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What Bob said. I'd would go that way. It may take some time to edge locate the dozen or so holes but it's the best way to get it pretty close.
SimonGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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16th Sep 2019, 06:25 PM #5
Hi Steve, Guys,
From a drafting perspective. All the holes will be on some radius from a centre and at some angle with respect to a datum.
So find a centre, draw a horizontal line through it and then draw one or more circles corresponding to the hole centres. From that you can now obtain the angles with respect to the centre. Where the angular lines cross the circle will provide the hole centres.
Steve.pdf
Steve.dxf
These two files one a PDF and the other a DFX.
I've based this on a 200 mm radius circle with a 10 mm hole at an arbitrary point on the diameter, it just happens to be 47.1 degrees. Qcad will open the DFX and use whatever opens a PDF for you.
HTH.Best Regards:
Baron J.
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16th Sep 2019, 06:56 PM #6Most Valued Member
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Thanks - but not quite getting what you mean.
I understand locating a hole based on distance and angle from a center point. I can see how it would be useful to locate something like equally spaced holes on a PCD where you know the angle and PCD.
Not sure how that helps me measure "randomly" located holes for a start though.
Bob - what sort of an edge finder did you use? I'm guessing if it was just a wriggler style you'd still need to calculate the hole center?
I was thinking about ways of locating a hole center with a vertical DTI - ideas along the lines of a spring loaded ball or cone that sits in the hole and is at its lowest point when on center. Read the lowest point using a DTI.
A quick internet search turned up "coaxial indicators". I don't have one but looks like the ducks nuts for a job like this.
Steve
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16th Sep 2019, 08:15 PM #7Senior Member
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I think a set of these would be just dandy for this, from Anyi.
Hole center calipers.
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16th Sep 2019, 08:57 PM #8Most Valued Member
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Thanks.
Haven't come across calipers like those before.
Those particular ones are outside my budget at the moment, but the concept has triggered some new ideas.
Steve
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16th Sep 2019, 08:58 PM #9Most Valued Member
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Hi Steve, I have a selection of coaxial indicators you can borrow no problem. I'm a ways south east though.
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16th Sep 2019, 09:06 PM #10Golden Member
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I would make up some round pins that fit the holes accurately and take measurements between holes by measuring across the outside of the pins then subtracting half the diameter of the pins used.
Once you have that ability you use the fact that triangles are defined absolutely by three lengths. Pick three holes take the three measurements between them and now you have those three holes fixed i relationship to each other. Now pick two of those holes and take another two distances to the next hole and you have four holes fixed in relationship to each other. Now just keep repeating that last step.
Reproducing the hole layout can now be done with a pair of calipers.
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16th Sep 2019, 11:22 PM #11Gear expert in training
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You can buy attachments that clamp on to the jaws of normal calipers, but it should be pretty simple to make your own.
Given that your tolerance is +/- 0.2mm, you could just use standard calipers over the edges of the holes and add the radius of each hole for the centre distances.
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17th Sep 2019, 12:21 AM #12Diamond Member
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17th Sep 2019, 01:13 AM #13
Hi Steve,
If you can determine a centre, and measure a distance, you can easily discover at what angle the hole is located from a datum.
Plugging these values into a DRO should give you accurate points. They don't have to be equally spaced on a PCD. Your DRO may have a PCD program but you don't use it. You plug the values in from your reference points.
Maybe I'm not understanding the problem !
I was thinking about ways of locating a hole center with a vertical DTI - ideas along the lines of a spring loaded ball or cone that sits in the hole and is at its lowest point when on center. Read the lowest point using a DTI.
Steve
Using CAD, two circles from a centre, one touching the outside of the hole and the other touching the outside 180 degrees away will allow you to determine the hole centres.
It seems that the forum software is not playing nice at the moment.
I've re-done the files that I sent to show you what I mean. I'll try again later...
Sorry I've just tried again to upload pictures, but the forum system just in't playing nice !Last edited by BaronJ; 17th Sep 2019 at 05:39 AM. Reason: Adding pictures.
Best Regards:
Baron J.
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17th Sep 2019, 07:16 AM #14Golden Member
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It would be very important for the engine crankshaft and the gearbox input shaft to line up on the same axis. Make adaptors where required for this axis on both gearbox and engine, install the dowels to hold it in place then use transfer punch to locate the holes? If blind holes the take one hole as reference point and use adjustable 'V' and caliper to locate (just like the arms in the wall clock).
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17th Sep 2019, 09:52 AM #15Mechanical Butcher
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Trammels are another tool that might be useful.
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