Height Gauge

[arnoldb]

Eric wanted us "lurkers" to post, and it's been quite a while since I posted here on MadModder, so I'm obliging 

I need a height gauge for my shop, and it's time to build one.  A "cheap" Asian digital caliper will do the measuring, but I do not really want to modify the caliper - the "cheap" ones are expensive here in Namibia, so I want it as backup; just in case...

There are a couple of very simple designs around for turning a normal caliper into a height gauge, but I do want a bit more rigidity from the setup, so I'm slightly over-engineering this one 

I have a couple of meters of 10x60mm hot-rolled flat bar, so - put some of it to use, together with a short bit of 18x40mm HRS that I found.  A bit of 6mm silver steel and some 4mm square HSS completes most of the basic building blocks:

There will be some more material needed to finish the scribing/measuring arm, but I'll add that later when all the dimensions are finalized.

The HRS is pretty horrible stuff to machine, but here goes.
For the base, I set it up in the 4-jaw; just roughly on center.  My lathe faces ever so slightly concave, and this makes it ideal to turn up bases for things that need to stand flat.  A bearing shell is used as a parallel to get the workpiece out from the chuck a bit but flat to the chuck face.  A light tap with a hammer on the workpiece while tightening up the chuck jaws makes the bearing shelll sit pretty tight.  As the bearing shell cannot be taken out between the jaws it is perfectly safe to use it like this while turning.  I do tie it down with some binding wire to the chuck jaws though, as I do not want it to start tumbling around and marring the chuck face should it come loose while turning:


Next the scale needed to get cleaned off the bits...  On to the mill - similar sized bit sticking out from the vise on a bit of a makeshift parallel setup:


And some flycutting later:


The scale really takes a toll on my HSS flycutter, and I got tired re-sharpening it, so I decided to do an experiment.  I bought a couple of carbide tipped tools a while ago; one left and one right-hand.  On my lathe I'm not too happy with the results - so If I stuff up one of these it's not really a waste.  I mounted the right-hand bit in the flycutter; it has an 8mm shank just like my HSS bit I use, so no fussing around needed.  Then I played a bit with feeds & speeds; it turns out the cutter wants my mill's top speed (1200RPM) and a good rate of feed - about 3mm/second  - this is the result:

I was scared of the carbide tip chipping from the interrupted cuts, but it just chewed through all the gunk.  And taking 0.5mm depth at a time at the speed above.  The finish is not quite as good as I get with my HSS cutter, but quite satisfactory - and MUCH faster   

Next all the cleaned up bits was clamped together on the mill bed - to the best accuracy of eyeball MK1 - with the areas I wanted to drill and ream directly above a T-slot for clearance - then a couple of holes drilled at 5mm with the outer two further enlarged and reamed to 6mm:


The middle 5mm hole in the base plate was threaded M6; I'm right-handed, so normally start a hole with my right hand, then finish threading with my left hand, as I tend to have better feeling of what the tap is doing.  I keep my arm in-line with the tap and use my wrist to turn "on the center line", usually just with my forefinger and thumb to twist the tap wrench.  In the next photo my arm is not in line... - it's a bit awkward to do that and handle the camera, and I've never been known for having a rubber body   :

This is the method I have used on hundreds of holes for tapping from M3 upwards, and have not yet broken a tap in these sizes, so it does seem to work.  The one and only tap I've broken so far is an M2 last year; in some work-hardened stainless - and for M2 I use a tapping guide.

The thicker (18x40) block was counter bored and drilled out to take an M6 cap screw; I thought I had a photo of that, but don't...  This was screwed to the base plate, and a 6mm drill and a bit of 6mm silver steel (my collet chuck's one locking lever actually) used to align things through the holes, and then all was clamped together in the mill vise for some more cleanup with the flycutter:

Not a great finish - but at least my mill's tramming is spot on....

The 18x40 block needed a slot milled in it where the caliper will sit.  I measured the calipers I have and their thicknesses range from 2.8 to 3.5mm - for identical-looking calipers.  So I decided to mill the slot at 4mm wide - anyway, my smaller milling bits can't go deep enough.  I may not break many taps, but milling bits are another matter    :

Fortunately I had one spare 4mm milling cutter to finish the job.

Still some work required, but this is how the caliper will sit in the slot:


Some more drilling and tapping for set screws on the base later, and this is the end result so far:


With the caliper installed:


It still needs the scribing/measuring arm and a retainer for the caliper arm to the top section.

I ended up milling a step in the mounting slot so that the caliper's slide can go down right to the bottom; this will make the measuring arm a lot shorter.  This photo shows the end of the caliper and the extra milled space in the slot:


Without any changes except for the upright lengths, the stand will actually take my bigger 200mm caliper as well:


I'd hoped to finish this this weekend; maybe I'll get a chance during the week...

Regards, Arnold

[Rob.Wilson]

About time Arnold   


Rob 

[dsquire]

Arnold

Very nice work and great write up. I can see that a few chaps will have to add that to their to do list. Thanks for sharing it with us. 

Cheers 

Don

[Bogstandard]

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.


John

[sbwhart]

Nice one Arnold

HRS bar is best for this sort of job its nice and stable, Cold rolled steel has lots of stresses in it and will warp when you machine it.

Look forward to next installment

Stew

[arnoldb]

Rob, thanks mate  - Knew I'd get a bit of  though 

Thanks Don  - 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  )

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 

Stew, Thanks  - 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 

 , Arnold

[crabsign69]

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

[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.

 ,  Arnold

[arnoldb]

I finished the height gauge today    - 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   
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    - I think I'm going to like this tool!

Regards, Arnold

[Rob.Wilson]

Nice one  Arnold   

Rob 

[sbwhart]

Nice one Arnold 

Hight gauges are a very useful addition to any shop.

Stew

[madjackghengis]

Hi Arnold, I was going to say I use hot rolled commonly, and if one puts the pieces in some vinegar overnight, it will remove the scale and leave you clean steel to machine, and you don't have to wipe out your high speed cutters, and they will leave a better finish without the scale wearing the edges prematurely.  I also have some scrapers, made by taking a piece of rod, drilling and tapping a hole in the end, and screwing a TNMG insert to the end, with a handle put on the other end.  This is a good scraper for removing the mill scale by force and it works well in taking bumps and nicks out, and deburring a long milled edge, and can't be beat for scraping surface rust of steel or iron without gouging it up, as the negative rake keeps it from digging in.  I even use used inserts on occasion, as they tend to get all their wear in the tips, while most of the work of a scraper like this is on the straight edge between cutting tips.  A scraper like this, with dark sulferated cutting oil will take surface rust off a machined surface leaving it smooth and no more than brown stain as long as it's not pitted, and does even better on machined cast iron surfaces.  An insert will last me a year or more, with two or three of these laying around by different machines and used anytime it seems fit.  It's the hard way to take of hot rolled scale, but it does leave a clean surface.  for what it's worth mad jack

[arnoldb]

Rob, Stew - Cheers lads  

Thanks Mad Jack - I'll keep your suggestions in mind   - I'm always open to ways of doing things.

My photos are missing from the thread at the moment; the hosting server where my images are stored is down...  I hope they get it up again soon! Server's back up

My apologies on behalf of Rob Wilson as well; his photos are stored on the same server So is Rob's 

Regards, Arnold

[madjackghengis]

Hi Arnold, and I thought it was my computer screwing up leaving out all the pictures   the post looks much nicer, and is easier to follow with all the pictures in place, quite a nice job and very useful I would say.  A solution of vinegar also removes blacking from heat treatment, or bluing from guns, and the like, for silver soldering.  I tend to leave the blackening on from heat treatment just to keep me straight on what's been heat treated, and what's still in it's original state.  Now I'm looking forward to what you're going to build out of that lump of metal you scribed with your new height gauge. I hope you put your initials on the gauge assembly, got to leave something for a future owner to puzzle over.  I've just started marking the tools I make, it didn't matter when I was younger, but now that some of my own tools are reaching back into antique range, I look at the marks made by some of their former owners, and wonder what they did with them.  Ta ta for now, mad jack