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how to measure motor mount holes reliably?


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miles&Jules
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how to measure motor mount holes reliably?

Hi guys..total noob question here.
I still haven't worked out a reliable way to accurately measure the bolt holes in a motor for face mounting. What do you guys do? I have been 3d printing up a pattern doing slight adjustments until it fits perfect….but that seems like to much messing around to just drill two damn holes.
[URL=http://s1091.photobucket.com/user/milesandjules/media/IMG_2209.jpg.html] [/URL]
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Post Sat Jan 10, 2015 2:47 pm 
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Nick
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There are two techniques I like to use:

Place two screws in opposite holes, preferably use cap head screws and screw them all the way in to make the measurements more accurate. Using a caliper, measure across the outside of the screw heads and then the inside. Add the measurements together and divide by two to get the spacing between the holes or the bolt circle in this case.

For that motor with an offset shaft, the best measurement option is to not measure anything at all! You can buy or make a set of screw-in transfer punches that mark the motor mount with the screw locations. Here are some commercial screw-in xfer punches:



The type with a hex head are more accurate and faster to use. You can easily turn a point onto the head of a screw; its easier if you make the point larger than the one shown. For small screws, screw on a number of nylock nuts and grip the nuts in the lathe jaws.

When using more than three xfer punches at the same time, its important to get the points aligned at the same hight or not all the punches will make a mark. I like to cover the area with several layers of painter's tape , which is softer on the punch points and leaves a mark with little pressure on the part.

For that motor, I would drill a hole the diameter of the motor shaft and use that to position the motor. Then you just press the motor into the mounting plate and there should be six tiny punch marks. If one or two punches do not transfer, just drill the ones that did and screw the motor lightly to the plate, the remaining punches will now transfer in the correct places.
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Post Sat Jan 10, 2015 4:00 pm 
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Glen
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To add to what Nick said RE the calipers, if you have digital ones, just measure the diameter of one screw then reset the calipers and measure between the outside of the two bolts assuming they are the same diameter Smile

If you get a set of transfer punches as well you could take the faceplate off and just put them in the threaded mounting holes to mark it out. A bit dodgy but it works Razz
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Post Sat Jan 10, 2015 4:04 pm 
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miles&Jules
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Man how come i never heard of those transfer punches…..genius as usual. thanks guys. Very Happy Very Happy Very Happy
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Post Sat Jan 10, 2015 4:23 pm 
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Ellis



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Post Sat Jan 10, 2015 10:43 pm 
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Valen
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is it wrong that I'd take the case off, sit it on a scanner put a ruler on said scanner, scan the bastard in, make it a background image in rhino then just cad it up over the image? ;->

(use the ruler to set the scale)

Also keep in mind that most things will be in round numbers so if its 6.98mm from zero odds are its 7mm ;->
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Post Mon Jan 12, 2015 10:14 am 
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miles&Jules
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Hey Ellis... that little diagram is great…i just drew it up and made a 3d printed stencil to help with drilling. Where do ya get those designs from ? I didn't realise it was a standardised layout.

Who would design a 60 degree angle for hole placement…ridiculous?

thanks miles
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Post Thu Jan 15, 2015 5:46 pm 
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miles&Jules
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[URL=http://s1091.photobucket.com/user/milesandjules/media/IMG_2219.jpg.html] [/URL]

here is the stencil …just tested and it works great…then i just drill out the middle shaft hole with a 13mm and its done..the bit out the side is for clamping or screwing it in place to keep it aligned . Very Happy
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Post Thu Jan 15, 2015 8:12 pm 
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Ellis



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Gearbox is one of the standard ones being pumped out of the far east by the bazillion, just searched for a manufacturer of the type you have and pasted their dimension sheet for the faceplate. Razz
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Post Thu Jan 15, 2015 9:21 pm 
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