Adjustable parallels with radiused edges. Can you suggest a set for over 1" range?
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    Default Adjustable parallels with radiused edges. Can you suggest a set for over 1" range?

    I need a set of rounded edge adjustable parallels for the range from 1" up. Is anybody aware if those ever existed? Based on old metrology texts, they did. Maybe you know the brands/model, have one for sale or can accurately (and affordably ) convert a regular set into a radiused one?

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    I've never seen any, but the idea seems quite useful in some situations. Any chance that you can use telescoping gages (point contact instead of line contact)? Those are still widely available.

    Actually, since you say "for 1 inch up", you may have to make your own unless you find some marvelous obscure source for millwright's gear. 1-3/4" collapsed/2-1/4" expanded is the largest standard size of adjustable parallel readily available. It's often inconvenient to use adjustable parallels close to their maximum expanded size, too.

    It should not be very difficult to mount a parallel on a spindex or Supergrind or something similar to put a radius on the contact faces with very light grinding on a surface grinder. Of course, you'd want to be very careful to preserve the parallelism between the opposing radii!

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    B&S makes these for up to 1", calls them parallel hole gages.



    You could add a parallel between them for larger dimensions.

    I have one adjustable parallel in a set that someone form ground a shape on both halves that resembles an involute tooth. I suspect a form dressed wheel on a surface grinder would fix up a regular adjustable parallel no problem.

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    Quote Originally Posted by MichaelP View Post
    I need a set of rounded edge adjustable parallels for the range from 1" up. Is anybody aware if those ever existed? Based on old metrology texts, they did. Maybe you know the brands/model, have one for sale or can accurately (and affordably ) convert a regular set into a radiused one?
    See Mud's note on what they are and SF's on how to extend. You'd want to make-up only an external frame to keep it all in alignment if you plan to do that.

    The "usual sizes" show up on eBay now and then, and seldom cost much. Steam rail and steam ship era, most likely the heavier use period. Metrology on the shop floor was rather more basic, that era, than what we have accustomed ourselves to having, lo the past 60 - 80 years.

    Which, BTW, does beg the question if there isn't a less-cumbersome means out there for YOUR application as well?

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    Mud, thanks for the photo! Do those have any tongue/groove/clamp feature like more common adjustable parallels, or are the angled faces just plain flat?

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    They are just flat, you hold them together with your fingers and drop them in the hole.

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    Quote Originally Posted by sfriedberg View Post
    Mud, thanks for the photo! Do those have any tongue/groove/clamp feature like more common adjustable parallels, or are the angled faces just plain flat?
    Some resemblance to topslide rails on an auto-pistol.

    These are meant to be used one-handed - or nearly so- and if need be down in a hole, up from under, or around a corner by feel, not in direct eyeshot where one could read a bore-gage. If even the shop HAD a bore gage, back in their heyday. Few ever did.

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    Quote Originally Posted by thermite View Post
    Some resemblance to topslide rails on an auto-pistol.

    These are meant to be used one-handed - or nearly so- and if need be down in a hole, up from under, or around a corner by feel, not in direct eyeshot where one could read a bore-gage. If even the shop HAD a bore gage, back in their heyday. Few ever did.
    You are describing adjustable parallels, not tapered hole gages.

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    Mad, thank you for the picture. I have the set, and that's why I was interested in sizes 1" and up.

    SF, I just don't think I'm good enough for this DIY project. My idea was to grind along the edge (vs.across) using a form dressed wheel on a surface grinder. But keeping the crowned edges parallel, centered and properly radiused would require more experience.

    I even got an idea to round a regular set and then cut it into 3-4 shorter pieces. The screw(s) wouldn't be useful though.

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    Quote Originally Posted by Mud View Post
    You are describing adjustable parallels, not tapered hole gages.
    Of course I am.

    The radiused-edge adjustable parallels suited for use in vetting ID bores.

    Why would I WANT to describe tapered bore gages? Those are are a different animal ENTIRELY, and not even under discussion herein at all.

    ??

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    Quote Originally Posted by MichaelP View Post
    My idea was to grind along the edge (vs.across) using a form dressed wheel on a surface grinder.
    I think that's a better idea than mine, to be honest. I'd probably do a rough grinding pass with a flat dressed wheel before putting the radius on.
    But keeping the crowned edges parallel, centered and properly radiused would require more experience.
    thermite gave the essence of an idea to make it practical. Suppose you're doing this from scratch. Rough out your wedges. Grind the angled faces flat, using a vise on the surface grinder. Perpendicularity to the side faces is important, but exact angle is not (at this stage). Make a ramp at the desired wedge angle, using a sine plate or a purpose-made fixture. Without removing the ramp from the surface grinder, grind all the "outside/parallel" faces. That will ensure that all the wedge angles match within your set.

    You can use a hard "fence" on the ramp to ensure the wedges are all lined up with the surface grinder X travel. If the wedges are all the same thickness (they aren't in the B&S sets), you only need to fuss with the cross feed positioning once. However, a good eyeball alignment of the dressed radius on the wheel with wedge blank is probably all you need, as it's not critical that the max point of the radius be on the centerline of the wedge body. I would still use the fence to ensure the radius is ground parallel to the wedge face. That part is pretty important, even if the offset of the radius is not.

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    Quote Originally Posted by MichaelP View Post
    Mad, thank you for the picture. I have the set, and that's why I was interested in sizes 1" and up.

    SF, I just don't think I'm good enough for this DIY project. My idea was to grind along the edge (vs.across) using a form dressed wheel on a surface grinder. But keeping the crowned edges parallel, centered and properly radiused would require more experience.

    I even got an idea to round a regular set and then cut it into 3-4 shorter pieces. The screw(s) wouldn't be useful though.
    How crucial is full-length bearing on the bore being inspected?

    Can you rig a pair of planer gages with a connecting bar?

    Is there a barrier to use of a dial bore gage? How about a Flexbar Indical?

    As said - the use of these has gone rare because we have other, handier, choices as are affordable NOW, but once were not.

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    Quote Originally Posted by thermite View Post
    Of course I am.

    The radiused-edge adjustable parallels suited for use in vetting ID bores.

    Why would I WANT to describe tapered bore gages? Those are are a different animal ENTIRELY, and not even under discussion herein at all.

    ??
    Since I'd never seen these before, I did a bit of reading today. At least one 1987 textbook that Google showed me called these radius-edge adjustable parallels "tapered parallels". Interestingly, there was no reference there to the more familiar flat-edge adjustable parallels. That particular book is a 6th edition, so that piece of text may have been written decades earlier.

    On a previous PM thread, a photo of the old B&S catalog page was included. B&S called these "Taper Parallel Gages".

    So it seems that the "taper" refers to the wedge shape of the two components, not to tapered bores. And the terminology seems to have shifted to "adjustable parallel" at some point, perhaps around the time that the sets of individual wedges were pushed out of the market by the self-guiding-and-clamping pairs of wedges.

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    Quote Originally Posted by MichaelP View Post
    My idea was to grind along the edge (vs.across) using a form dressed wheel on a surface grinder. But keeping the crowned edges parallel, centered and properly radiused would require more experience.
    Not really. Just do it in reverse.

    Use precision-ground and pre-vetted FULL ROUND rods to serve as the working edges, each side.

    Now a very ordinary mill - no grinder even required - can cut a Vee in flat stock to place them in. It need not be perfect. The edges won't need 100% bearing to be stiff enough to take a measurement with.

    An EXTERNAL measuring instrument transfer-off as "is" whatever is, is. These are "indirect reading" devices, regardless.

    And.... you are not building a nut splitter or a log splitter.

    Or so I hope!

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    Yes, I thought about it to avoid the radiusing procedure. But grinding a "V" in the hardened adjustable parallel which is 9/32" thick will still need to be quite precise in terms of parallelism and straightness. The former is obvious, the latter is needed to avoid errors if the rod sags during OD measurement or slides along the groove after you remove it from the bore. In this respect, it would be much better and easier to have the rods permanently attached to the parallels. But brazing or soldering it would cause distortion and require regrinding.

    If I had a wire EDM and were proficient in using it, I guess many problems would disappear. Heck, if I were a die and tool maker without an EDM, I guess I wouldn't procrastinate either.

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    Quote Originally Posted by thermite View Post
    Of course I am.

    The radiused-edge adjustable parallels suited for use in vetting ID bores.

    Why would I WANT to describe tapered bore gages? Those are are a different animal ENTIRELY, and not even under discussion herein at all.

    ??
    OK. Show me a picture of those radiused edge adjustable parallels that work like the top slide of an auto pistol..

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    The B&S radiused set is great when you want to check a small bore. It reveals bore diameter (just mic the part that extends) and a bit about straightness and parallelism. However, a three point bore gage can probably do as good a job of mapping most issues (bore not cylindrical, tapered, etc.) and once you get above 1" three point bore gages and bore mics are pretty commonly and cheaply available.

    I've got the B&S set, but between pin gages to 1/2" and decent 3 point bore mics from 1/2" and bore gages above 3" up don't much use them.

    That said, Mud's idea of using a series of parallels between the existing tapes seems pretty good; especially if some sort of makeshift cage helped keep them together. One possible caution with the rounded-edge parallels is that they pretty much center themselves in a small bore. The larger the bore, the more likely they might bet a bit cocked to one side or the other?

    At some larger bore diameter I suspect two fairly large parallels (or three with an inserted one in the middle) will have even less "feel" and accuracy than sweeping a telescoping gage top and bottom in a bore.

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    Quote Originally Posted by Mud View Post
    OK. Show me a picture of those radiused edge adjustable parallels that work like the top slide of an auto pistol..
    Not an unreasonable request, quite reasonable, rather.

    Not everyone has had this class of goods in their own hands.

    Here is the first one that popped up:

    https://patentimages.storage.googlea.../US4168574.pdf

    There are others. It should not be a surprise they have variations. Patents force that even when better ideas have not already done so.

    Dimensions of the "Tee" and mating "Tee groove" are not the same as the slide rails of an auto pistol - there's no BARREL to be accommodated down the middle as requires splitting the Tee, optionally reversing it outside in, or inside out. Happens I have "some of each".

    The basic concept, however, IS the same.

    The two pieces are meant to be able to slide, one over the other, but NOT mean to separate in use and fall on the floor in two separate impact zones.

    That would make the parallels too clumsy to handle, and the firearm bloody dangerous to fire! See Walther and P-38, which actually HAS been known to shed its top slide in hard firing, even though that was not in the original plan!




    I brought it up because I first had Mark One Eyeball on these around fifty or sixty years ago - loooong before Google started hosting patents or personal confusers, the internet, or Google yet existed.

    AND.. because the very presence of rails or dovetails or any similar feature on the two mating parts once separated make the insertion of any intermediate spacer not already purpose-built and fitted by the same maker a "non trivial exercise".

    Any field-expedient DIY to be done-up in a shop with only average equipment, not a precision metrology shop, has to jump through a few hoops to either CLEAR those rails, grooves, dovetails - wotever by the OEM's choice - and rely on the external cage I mentioned to prevent all the now LOOSE bits falling on the floor...

    ELSE has to be machined and fitted to UTILIZE those rails or other interlocking features to just as high a standard of fit and accuracy as if the factory had done and QC'ed it themselves.

    I did say "non trivial", yah?

    There are saner and more convenient methods for gaging larger bores than that extrapolating off this tired old wheel with DIY high heels, falsies, or stilts.

    Anyone as needs pitchers of such, just ask. Or google and "images". Not hard to find those, either.

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    So they exist in concept.

    I see.

    The gages I posted a picture of in this thread don't work like that.

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    Quote Originally Posted by Mud View Post
    So they exist in concept.

    I see.

    The gages I posted a picture of in this thread don't work like that.
    More than just "concept". The rule, not the exception. Not hard to find more than that one example. I am not he who needs to do that.

    Most adjustable parallels and even planer gages, ANY maker, US or foreign, have SOME form of interlocking feature so they remain in predictable sliding proximity and aligned on the same long-axis, "in plane", yet, AS a handy set rather than flail about like loose angle setting wedges in THEIR different realm.

    Useful-enough buggers in their zone, those wedges, but you won't be surprised the independent wedges surely are (independent..) can now and then need three hands plus yer Putz, a stiff tongue, or "duck" tape to get into place when one needs to stack them.

    Why are you going against such a widespread history over "factory mated" adjustable parallels?
    You have a set of "weird ones" - mebbe held together by magnetism? Or witchcraft?

    Surely SOMETHING prevents those side-stepping or going off at odd angles like a stack of wrung gage blocks done careless-like?

    Show US a picture of the sliding surfaces of YOUR ONES, then!

    We still like to learn new stuff, too!



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