Anyone have a Hermann Schmidt Surface Gage

epmtool · Feb 27, 2009

I'm considering making a new surface gage out of some 316 SS.
I like Hermann Schmidt/ Murkins surface gage design due to the fine adjustment.
Does anyone have one of these and do you like it?
Is the base is simply two blocks connected with some spring steel or is it more complicated?

wesg · Feb 27, 2009

I have an Alina like that. Works good, although the range of motion is less than a Starrett type. Nothing more complex than two blocks, AFAIK. Never took it apart.

And I kinda think you want something harder and slicker on the bottom than 316.

SouthBendModel34 · Feb 27, 2009

I'd like to hear more about this because an quick search did not turn up any pictures of this item.

As far as making a surface gauge, you might be better off buying a used one. I often see them at flea markets. Oftimes, the seller does not know what they are, and sells them for peanuts. A typical price is $5 or less.

Then again, you could make yourself a very fancy one and be proud of it forever. Will 316 be hard enough? You will want something hard enough to flatten by scraping.

WizardOfBoz · Feb 27, 2009

I believe that the HS surface gage uses a piece of spring steel as a hinge, rather than using a pivot. This is a very low friction and low-runout (is that the right word?) way of pivoting things. In fact, it's how the Pratt Whitney supermike supports the anvil: two springs support a block that the arbor is on. Very nice. You can kind of see it here:

This from the Hermann Schmidt website.

As far as material, I guess you could go with something "scapeable" like cast iron or meehanite(?) for the base. Or you could go with precision ground A2. Maybe lap the bottom?

You get to decide whether the view is worth the climb, but I've seen these things go for $50-100 on ebay. IF they had gone for $5, I would have won one!

Good luck,

Jim

harrytm · Feb 27, 2009

To answer the original questions:

Does anyone have one of these--yes

and do you like it?----yes

Is the base is simply two blocks connected with some spring steel or is it more complicated? ---- yes and no

Mud · Feb 27, 2009

Heres' some close up pics of one in an ebay auction. I'm told that they are very nice to use, and that the adjusting screw is a very fine thread for fine adjustment.

http://cgi.ebay.com/MURKENS-SURFACE...ptZLH_DefaultDomain_0?_trksid=p3286.m20.l1116

ARB · Feb 27, 2009

I would also stay away from 316. If I was making one for myself i would go with A2 and harden it. I am not sure what my Starrett one is made from but it is fairly hard.

It sure is a fine looking piece. I wish I had know about HS when I was just a brat buying my tools. I would have left the Starrett on the counter for sure.

epmtool · Feb 27, 2009

"Is the base is simply two blocks connected with some spring steel or is it more complicated? ---- yes and no"

whats the no part about??

I was planning on making the base out of 316 so it would be non-magnetic.
My current starrett surface gage is made of pretty soft cast iron so I figured SS will be plenty hard.

I was planning on lapping the bottom with some 600 grit.

David Utidjian · Feb 28, 2009

Starrett makes:
The No. 56 surface gage which is pretty small but handy for some applications. It was made of beautifully color case hardened steel. They still claim to be made of hardened steel.
The No. 57 is big and heavy and made from cast iron with a wrinkle finish paint.
The No. 257 is intermediate in size and weight between the No. 56 and No. 57 and is made of color case hardened steel.

Each one has an involute ground groove on the underside for use on round work, a feature the HS lacks.
Each has two to four push-down pins for referencing the edge of a T-slot or table, a feature the HS lacks.
Each one has a notch in front so that one can use the ball end of the rod like a right angle checker, a feature the HS lacks.
Each one has the rocker arm supported by conical pins at the pivot so that and sideplay of the rocker can be adjusted out. Cheap imitations I have seen do not have this feature. The HS doesn't need it because it uses the spring steel hinge. I think the HS kinematic hinge is a superior arrangement in that respect.

I own three of the No. 257s, one of the No. 57s and one of the No. 56es. I use the 257s the most and really like the push down reference pin feature.

Starrett also makes the No. 995 Universal Precision Gage which has some very nice features. It is similar to a planer gage but has a fine adjustment and extra doodads for attaching scribers and indicators. Mine is color case hardened steel.

I also often use a DTI in the vernier height gage but only on a surface plate.

The HS surface gage looks like a very fine instrument. If I were to copy it I would make it out of A2. I would also add a retractable side plate or make the base piece a little wider and/or longer for the retractable push down pins. it would be hard to live without that feature.

Is there a stainless steel that is both hardenable and non-magnetic?

-DU-

epmtool · Feb 28, 2009

My current surface gage is a starrett 57 and it definately has a permanent spot in my tool box. It works adequately as a squareness gage and surface gage but it just isn't cutting it for the work I am doing now. I am grinding mold impressions that are 1.5 x 9 x 13 and with the my .0001 indicator that far away from the base the fine adjustment is simply not fine enough.

I believe hermann schmidt has ground flats on the edge for checking squareness and I think that would be a hell of a lot easier than lining up my indicator with that ball on the starrett.

I never had to use the V block or push pin feature on my starrett 57.

I'm fairly certain that there is no SS that is hardenable and non-magnetic

David Utidjian · Feb 28, 2009

epmtool said:
My current surface gage is a starrett 57 and it definately has a permanent spot in my tool box. It works adequately as a squareness gage and surface gage but it just isn't cutting it for the work I am doing now. I am grinding mold impressions that are 1.5 x 9 x 13 and with the my .0001 indicator that far away from the base the fine adjustment is simply not fine enough.

Way up there at 13" away from the plate I bet vibration could be a problem also. That and whatever adjustment you make on the rocker will be magnified about 10:1.
I have a couple of extra rods and indicator holder from a Craftsman magnetic base indicator holder that gives me fine adjustment out at the end of the main rod attached to the base. It eliminates the lever arm magnification from using the (now coarse) adjustment on the base rocker.

I have toyed with the idea of making a nicer one as a regular attachment for the Starrett. It uses a spring like one finds on spring calipers and dividers with a slot in the spring for a fine adjustment screw and two plates on a pin pivot with small extension rods for clamping with snugs.

I have already made some of my own snugs. Even the Starrett 57S "Universal Snug" is not universal enough for the stuff I sometimes do.

I believe hermann schmidt has ground flats on the edge for checking squareness and I think that would be a hell of a lot easier than lining up my indicator with that ball on the starrett.

I don't think the HS 'surface gage' does have those flats. It would be better to have a slight curve at the front. After checking their website... it does have a ground section at the back of the base for squareness checking. Cool. They also make a squareness checker with standard for $995

I agree that using the ball end of the Starrett rod is a PITA. I built the squareness checker from the back of "Machine Shop trade Secrets." Works real well.

I never had to use the V block or push pin feature on my starrett 57.

I use them quite often. When you need it it is there. I prefer the four pins on the 257.

After saying all that though... I would gladly trade two of my extra 257s for a Hermann-Schmidt... but not all of them

-DU-

ARB · Feb 28, 2009

One of the tricks you can do with the Starrett is to make a much oversized knob and press it on the existing adjusting screw. This helps greatly when doing fine work.

Not a great picture.

harrytm · Feb 28, 2009

epmtool said:
"Is the base is simply two blocks connected with some spring steel or is it more complicated? ---- yes and no"

whats the no part about??

I was planning on making the base out of 316 so it would be non-magnetic.
My current starrett surface gage is made of pretty soft cast iron so I figured SS will be plenty hard.

I was planning on lapping the bottom with some 600 grit.

Is the base is simply two blocks connected with some spring steel? YES

is it more complicated? NO

Winfield · Feb 28, 2009

There are many advantages of stiction free flexures vs. sliding or rolling bearings when repeatable, precise positioning is needed as seen in the Hermann Schmitt surface gage.

Slocum stated this very well in his chapter on flexural bearings:.

Alexander Slocum “Precision Machine Design” p521:
“Sliding, rolling, and fluid film bearings all rely on some form of mechanical or fluid contact to maintain the distance between two objects while allowing for relative motion between them. Flexural bearings (also called flexural pivots), on the other hand, rely on the stretching of atomic bonds during elastic motion to attain smooth motion. Since there are millions of planes of atoms in a typical flexural bearing, an averaging effect is produced that allows flexural bearings to achieve atomically smooth motion. For example, flexural bearings allow the tip of a scanning tunneling microscope to scan the surface of a sample with subatomic resolution*
*See, for example, G. Binning and H. Rohrer, “Scanning Electron Microscopy”, Helv. Phys. Acta, Vol. 55, 1982.pp 726-735

I make a precision positioner that uses flexures exclusively for all movement. See: http://clementfocuser.com/

amklein · Apr 5, 2009

I hate to kick up and old thread, but i have decided to make one of these myself and I have a couple of questions before I order material.
First, as someone already mentioned, hardened and ground A-2 would make a good base, but what about the other two peices of steel? Is it worth making them out of hardened A-2 or is that just overkill?
Second, what would work well for the vertical rod? I was thinking of using drill rod, as it is already ground round and straight.
Third, what should the spring be made of? I see you can get blue spring tempered 1095 off mcmaster. I could drill it with a carbide drill and get someone to EDM the rest of it out, but would i be able to make it out of annealed 1095, harden and temper it myself?
Fourth, as far as the adjustment screw goes, i dont want to shell out the cash for a 1/4-40 tap, so i was thinking about making a tap from drill rod and hardening it, and while im at it, do the same for the adjustment bolt. Bad idea?
Lastly, someone mentioned grinding in a v-groove and adding pushpins, are they really that usefull? I cant really think of a time when i would need them...

David Utidjian · Apr 5, 2009

amklein said:
I hate to kick up and old thread, but i have decided to make one of these myself and I have a couple of questions before I order material.
First, as someone already mentioned, hardened and ground A-2 would make a good base, but what about the other two peices of steel?

The reason for using hardened and ground A2 for the base is not, particularly, for wear or accuracy. If the base were made out of soft cast iron or even brass it would work well for a lifetime of use. The main reason for using a hard (or hardenable) material for the base is that it will be far less likely to get dinged in use and therefore raising a burr on the edge or a crater on the surface. Many older surface gages were made out of cast iron and the Starrett No. 57 still is. Cast iron tends to not raise a burr or a crater rim when dinged... ot as much as steel anyhow.

Is it worth making them out of hardened A-2 or is that just overkill?

Overkill.

Second, what would work well for the vertical rod? I was thinking of using drill rod, as it is already ground round and straight.

Drill rod is not particularly round nor particularly straight. For this application it is round enough and straight enough. When I made my right angle gage I used Thompson shaft. It is harder, rounder, and straighter than drill rod. You can buy Thompson shaft in convenient lengths from places like McMaster-Carr. It is cheaper to buy than to make it yourself.

Third, what should the spring be made of? I see you can get blue spring tempered 1095 off mcmaster. I could drill it with a carbide drill and get someone to EDM the rest of it out,

You answered your own question I think. Not sure why you would need to EDM the spring steel.

but would i be able to make it out of annealed 1095, harden and temper it myself?

Yes.

Fourth, as far as the adjustment screw goes, i dont want to shell out the cash for a 1/4-40 tap, so i was thinking about making a tap from drill rod and hardening it, and while im at it, do the same for the adjustment bolt. Bad idea?

If you can make or learn-how-to-make a 1/4-40 tap it is an excellent idea. Never a bad thing to learn or figure out how to do something new. If your time is money then... it is a bad economics.

Lastly, someone mentioned grinding in a v-groove and adding pushpins, are they really that usefull? I cant really think of a time when i would need them...

Hermann-Schmidt has a plate that will attach to the side which accomplishes the same thing as the pins. When you need the plate or the pins (or the groove) it is harder to figure out how to do without them than it is to figure out when you might ever need to use them next.

The main reason to use A2 for something like this is twofold. Easy to heat treat. unlikely to distort or crack when quenching.

If you can make as good a copy as a real HS in under 10-20 hours... cool. Even better if you add any and all features you would like and might possibly use.

-DU-

WizardOfBoz · Apr 5, 2009

Winfield and David U.

Thanks for sharing some interesting knowledge and experience. Especially useful is why the different steels are used, and the pics of the focuser. Very cool.

Winfield, is a single flexural member not stiff enough? The Pratt-Whitney supermike has two flexural members that are separate, but have the same orientation, but this is to ensure a near linear movement of the mike anvil. At least, it's a movement that keeps the anvil face parallel to the spindle face. Your setup appears to have two flexural members with slightly different orientations, that allow flex along the a single axis. Was this a design evolution? Did you ever try just one flex member in this design?

Thanks,

Jim

prs3 · Apr 7, 2009

amklein said:
I hate to kick up and old thread, but i have decided to make one of these myself and I have a couple of questions before I order material.

I made mine almost like the HS and any body that has ever used it loves it.
I made my top from .750 X 3.0 X 4.625 A2 Hardened it to 60 RC Drawed it back 3times(from an old toolmaker told me to to help relieve stress)
Bottom- 1.0 X 3.0 X 4.625 same heat treat as top piece. Made feet on bottom .031 deep X .750 x 1.0 and scored them.
Used .500 X 8.0 long X .060 case hardend Thompson rod for the rod.
Used a 3/8-32 X 2.0 set screw for the adjusting knob screw.
Used 1.750 dia. piece of aluminum for the knob.
Used a .0625 annealed spring steel for the spring.
And other little gadgets on it to make it nice.
The tool maker that helped me build it was very impressed with it
If you would like I can send you a copy of my prints on how I made it.
just send me info where to send them

amklein · Apr 8, 2009

So I talked with my teachers about building the surface gage and they gave input on a number of topics. First, for the pushpins and the v-groove, my teacher figured that since it isnt ground, the v-groove on the bottom of the starrett surface gages is for nothing more than lowering the surface contact area, and said that the push pins are indespensable; including them would be a good idea. As for material, we have some donated stock in back that we don't have a use for. Among the peices that are the right size were some D2, D3 and Hampden(sp?) that are up for grabs; I think i will go with the D2. Speaking on the subject of hardening, one of my teachers suggested that prior to the final grind, we cryogenicly treat the peices with the liquid nitrogen that we will be using to perform a shrink fit on another project.

Will using D2 cause any problems other than slower machining and slower grinding? Will I be able to tap holes (1/4-20) in the side and expect them to be in spec after hardening? And last but not least, I was planning on hot salt blueing the peices. I remember reading that stainless steel doesnt take to the process, will D2 be the same?

Thanks in advance,
Andrew

Greg Menke · Apr 8, 2009

I had occasion to use the push pins on a Starrett several weeks ago, double-checking alignment of a shaft on a lathe at the chuck vs 4ft down the shaft in the steady. The pins let me register the base of the gage against the ways.

Regards,

Greg

Anyone have a Hermann Schmidt Surface Gage

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