"Depth clock" query

I am struggling to remember the name of this device but it was amazingly accurate for measuring shoulders in internal bores which seems like an otherwise difficult task with just a rule.

The depth gauge had an "interchangable" head which allowed to use really small probes for the smallest of measuring tasks and a digital read out.

It had a granite base and a supporting arm with really solid construction, there was also a decent amount of travel on the probe.

I think it was mitutoyo who made it but i was wondering if there were any second hand ones flying around at the moment, i wouldnt expect them to be cheap but curiosity has got the better of me.

Michael W

Not really sure of correct terminology but it sounds like a "Plunger" style dial gauge. I use the kind of set up you describe with self made probes to screw on the bottom of the plunger and get to small shoulders etc. For good accuracy the dial gauge needs to be set up as near vertical as possible. I have a dial gauge with 1" travel that suits my needs.

More thoughts it may be called a Comparitor.

Yes you're on the right track, it was a plunger style dial attached to a vertical base, i found it was incredibly useful for precise measurement, if you combined this with your more typical measuring devices like the mic and caliper you could measure nearly anything other than angles and hole positions.

I suppose it wouldn't be a world away to convert either a digital or dial plunger d.t.i into a more rigid setup with a movable arm/bracket/column? sounds like a project in the making considering the cost of the real macoys as it were. The only limiting factor being i dont really know how to shape granite lol :P i guess a hefty piece of steel/iron would do just as well.

Michael W

An interesting vid from oxtools on resurfacing a surface plate

I do have a 24"x24" surface plate but as it is usually covered in junk most checking/marking out is done on the mill table. I set a plunger clock up on a magnetic base and zero to slip gauges if required. Lots of home made styli to get on to ledges.

Hello Michael,

If you have access to a surface grinder, with coolant, you can cut your lump of granite ( from a kitchen bench top maker or headstone maker ) with a cheap diamond saw sold for the lapidary people. To square it up use ordinary silicon carbide grinding wheels say 37C30MB or 37C36KV, they cut quickly and give a good finish. You can chamfer the corners as well.

Regards, John

Michael,

These sometimes turn-up secondhand, at reasonable prices.

MichaelG

Its promising to hear some people have come up with their own homemade varieties as this precision equipment is normally prohibitively expensive for a model engineer.

Hi john, i do know someone who has a surface grinder, the type of one with a reciprocating table and maybe he'd do it for a reasonable price, it would be no doubt the best material to go for if you want a sturdy flat base.

and Michael, I haven't seen anything like that before, it looks pretty neat - ex industry? reminds me of an old fashioned Smiths RPM gauge set, complete with rubber tipped inserts, that was given to me on the off chance, maybe i'll put some pictures of it up. Its nice to see these old devices people have sometimes forgotten existed. I've already used mine to make an RPM chart for my inverter.