Height Gauge

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Height Gauge

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arnoldb:
Rob, thanks mate :D - Knew I'd get a bit of :poke: though :lol:

Thanks Don :beer: - It should be a useful addition to the shop - though more of a luxury than a necessity... (I reserve the right to change my mind later on though :lol:)

Thank you John. I like that mod from John S a lot - would sure save up on trying to set the jenny caliper on a rule or using the standard digi calipers at a slight angle with an extra 0.01mm to compensate for the angle and scratching up the side of a workpiece :). Hmmm.... Just had an idea I have to check out sometime :med:

Stew, Thanks :beer: - I would like the HRS a LOT more if it produced better finishes though I could get better finishes from it... Still some experience needed I think! No shop tonight; we're having rain for a change and I'm celebrating that :beer: :beer:

:beer:, Arnold

crabsign69:

--- Quote from: bogstandard on November 14, 2010, 03:52:54 PM ---Nice one Arnold.

If you ever get a set of old calipers knocking about, but still working, this idea given to us by John Stevenson is a really worthwhile addition to your tooling.

Precision oddlegs, great for marking out from the edges of materials.

Just grind up as shown.

What is that thing in the back ground with the steel balls? nice im saving for later use more stuff to make yeaaa

John

--- End quote ---

Bogstandard:
It's a small Newton's Cradle, an office 'toy' that was all the rage in the last century.

Bogs

arnoldb:
Some more work on the height gauge...

For the arm I cleaned up some more HRS flat bar, and marked it out. Don't know what I was thinking though; I've become pretty much used to blacken up the entire part and then use very light scribe marks - but today I didn't, and used heavy marks. Some of them will remain on the arm to remind me not to do it in future:

Off to the band saw to get rid of most of the excess - much quicker than milling it all out, and there's a possibly usable off-cut left:

Then on to the mill to clean up to final sizes:

Milling a slot in the bottom that will fit over the leg of the caliper. This was a bit difficult, as I had to have the milling bit fairly far out of the collet for the head to clear the upright "leg" on the workpiece:

I left the caliper in the photo to show that the caliper leg (the one next to the workpiece against the vise jaws) is tapered - well "DUH" - I should have milled the slot on a taper then clearance with the chuck would have been much less of a problem.

A quick rotate later, and milling at the approximate angle of the caliper leg:

The finished slot. It is not centered, as I wanted to leave a bit more meat on the side where the retaining screw holes needed to be made:

On to the scribing tip. A piece of 12mm silver steel (drill rod) clamped up in the vise with the quicky-set of matched V-blocks I made a while ago. I used an old business card behind the v-blocks to ensure they were clamped evenly; this is a great use for old business cards. My vise unfortunately does not have a suitable V-groove; that has to wait for a while still:

Then I milled the top and sides of the silver steel to square and size, and drilled a 3.3mm hole (for M4 threading) on one side; this will be used for Marv's suggestion for threaded rod for measuring depths. Next I drilled and countersunk two holes for M4 countersink screws. I made sure that the holes were countersunk deeply enough that the screw heads will be well below the top level when installed. All this faffing around was to make sure that I can have this side of the workpiece truly flat, as it will become the bottom of the measuring tip:

Next I sawed the partly completed measuring tip off the parent stock and milled the left-over semi-round bit (that was on the bottom in the previous operation) square. It's not imperative that this cut is 100% parallel length-wise to the bottom, but it must be as darn accurate as possible parallel cross-wise to the bottom of the tip-in-making. Then I milled a step into it at the "scriber" end where the threaded hole is, and pivoted it at an approximate angle of 45 degrees and milled the point down. The result - top view:

And bottom view; I did flat-lap all machining marks off the bottom on a bit of 1200 emery - taking as much care as possible to keep it truly flat:

Assembled thus far the lot looks like this:

An example use of Marv's suggestion - I just turned a screw into the hole on the tip, zeroed at the rim edge of the flywheel, and measured the depth of the web:

Of course, it would be best to use a lock nut on the top side to lock down the screw/threaded rod.

I hoped to finish this project today, but the top vernier arm retainer is still left to do, as well as hardening the scribing bit.

Many of you might be thinking I've been a bit blasé about accuracy thus far... - and so I have, except for the bits I pointed out. It all comes down to some simple steps at final assembly that I'll show, well, at final assembly.

:beer:, Arnold

arnoldb:
I finished the height gauge today :ddb: - and used it for the first time as well.

First up - the top caliper retainer. Another bit of HRS sawn off, and lightly cleaned up, then clamped to the top guide for drilling for a couple of M3 cap screws:

I just drilled the holes 2.5mm for threading, then separated the lot and finished the retainer on it's own by enlarging the holes to 3mm for clearance, and counter bored with a 5mm end mill to recess the screw caps for a neater look. A cutout slightly wider than the caliper shank was milled into it - but not as deep as the caliper shank is thick. Then overall dimensions were milled to size, and the result:

The scriber tip was then taken outside - together with a can of oil, and heated red hot and dunked in the oil to cool down. This left it nice and black... So I cleaned off some of the black with emery, and gently heated it again only on the thick side till the cleaned area changed to a light yellow-orange colour close to the scriber tip. I then left it to cool down; that should be enough tempering. Then I cleaned it all up again, and lightly stoned the bottom of the piece on the sharpening stone, followed by quite a bit of stoning on the top angle to get it nice and sharp. It's pretty hard so takes a bit of effort to sharpen up:

Trying to get rid of the black left in the screw recesses seemed too daunting, so I left it ::)

Now for final assembly :dremel:
A flat reference surface is needed; a surface plate would be ideal, but I don't have one. I do have the glass sheet that I use instead, so I thoroughly cleaned an area of it, as well as the underside of the base of the stand and the bottom of the scribing tip.
It's important that the caliper shank stands as close as possible to vertical - but if it's out of vertical by, say, 0.1mm over the 120mm range my caliper has, it would make the princely error of being out by about 0.00005mm over the measuring range... - way more accurate than can usually be measured in a home shop. So I just used a square against the protruding caliper tips to set it vertical in the stand:

Setting the scribing bit level and flat with respect to the base is more important. I did this by holding the scribing arm with the foot flat on the glass, and raising the caliper's top leg into the machined slot. Then a light tighten of the middle screw, followed by the outer ones, and that's that:

To make double sure, I measured the shank of a broken 1.4mm drill both at the tip of the scriber foot:

As well as at the back:

Finally; good to go; I'll get some shorter set screws to replace the ones holding the arm when I get to the nuts and bolts supplier next time:

In use for the first time on my next project:

MUCH easier than jiggling the workpiece to scribe some lines on it with a normal caliper :D - I think I'm going to like this tool!

Regards, Arnold

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