Gallery, Projects and General > How do I??

How to measure "square" for scraping? Angle plate

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PekkaNF:
Thanks Sparky,

That book is new to me and pretty exhaustive, I paged it trough and it looks very interesting. Although most of the methods and equipment is out of my reach.

That stand looks nice, how does it works?

Pekka

DavidA:
I understand that somewhere, in a pleasant, tranquil part of the country, is a big house that holds (gently, but quite securely), Madmodders who thought (and still think) that they can get the accuracy of their lathe, milling machine etc, 'just a little closer' to 'spot on.

They drift off to sleep in the early hours but wake up suddenly muttering' Ah, now I see how to do it'.

Poor souls. There is nothing we can do for them.

Dave :D

sparky961:

--- Quote from: Manxmodder on October 18, 2015, 02:29:48 PM ---Sparky,I really like the look of the gauge stand you've made. I'd be very gratefull to see some dimensioned drawings if it's not too much trouble.

--- End quote ---

New thread with gauge drawings and details here: http://madmodder.net/index.php/topic,11054.0.html

PekkaNF:

--- Quote from: sparky961 on October 18, 2015, 03:47:12 PM ---
--- Quote from: Manxmodder on October 18, 2015, 02:29:48 PM ---Sparky,I really like the look of the gauge stand you've made. I'd be very gratefull to see some dimensioned drawings if it's not too much trouble.

--- End quote ---

New thread with gauge drawings and details here: http://madmodder.net/index.php/topic,11054.0.html

--- End quote ---

Thank you for sharing it.

I have been reading about this method and talked yesterday to one mechanical engineer about this method. We concluded following:

1) To be sure DTI needs to be zeroed to a good standard, cylindrical square would be nice.

2) Arch a the toe of stand is not critical, but it must be of continuos curve to high degree. Also large radii is preferable, small one is a bit more critical (smaller radii than stylys radii is a bit counterproductive).

I don't have any other type of base than magnetic bases. I haven't got any threepoint or flat base that would fit to my price range.

I'm thinkking of building one.

1) Base: Shape and fabrication?
* round with thin rim? lapping flat
* Trilobular with balls on the corners? Only front with continuous smooth curve?
* Square, thin lapped sides, large radii on front?

2) Arm. I sort of like comparator type heavy upright pole.
* Would be nice to have it fairly straight, but I can't see why it MUST be nearly perpeticular, if the DTI is rigidy mounted.

Other way would be to make it all square and sweep DTI instead of the base, but that would make sense only if the contraption would be BIG.

What do you think?

Pekka

sparky961:
I think you're on the right track, sort of, with pursuing the fabrication or purchase of a cylinder square.  I say "sort of" because I think you might be taking it to a level of precision slightly beyond what's required.  I think a lathe that's painstakingly set to cut with taper less than you can measure with your most sensitive mic (so likely within 0.0001) is more than acceptable.  Get a nice fine finish on it and check along the length for consistency.  Unless you're doing something way beyond home shop stuff, or even precision fabrication, I think lapping is a bit excessive and may cause you to get stuck in the process instead of producing results.

Beyond my additional comments in the other thread, the squaring gauge I built has proved to work very well.  I've reproduced measurements to fractions of a 10th interpolating between graduations on my 0.0001" DTI.

Many, if not most quality angle plates I've seen are square within 0.0002 over 6".  A few I've checked are dead on to the best of my visual discrimination.

The only advantage a cylinder square has, in my opinion, is that it is self-proving.  Even if the base isn't perpendicular (they make them on purpose like this too) or there's a slight taper, it is still a functional tool.  You just have to be careful where around the circumference your line contact is, and know the exact difference in diameter where your gauge contacts it so you can mathematically adjust.

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