Unknown tools

I have recently acquired a small quantity of scrap steel rods,or so I thought. Upon examining them closely I found that 12 of them were some kind of measuring rod. The rods were of various sizes ranging from 6" long to 4" long. Four of these rods were turned down at one end the others were turned down at both ends. The turned down sections had a flat ground on to them,and on the flat was stamped the imperial diameter of the rod. Two of the rods were wrapped in greased paper, perhaps indicating they were a manufactured item as opposed to home made. I guess they were made to measure holes so that the appropriate drill size could be selected,however there might be a more interesting explanation. Any thoughts ?

Mandrels? Do they have centre holes each end, possibly slightly counterbored for a shallow recess? Are they slightly smaller diameter at one end, and possibly hardened?

I used mandrels years ago to grind aspects of cutting tools located accurately located off the bore. For example, grinding concentric registers for truing the cutters up before use, grinding the radial faces of the cutting edges with a thin grinding wheel.

See:

**LINK**

Bill

Diameters?

Pictures?

Mandrels!

These sound like extension rods for internal micrometers . I have a set of very old starrett mics which have a load of rods they clamp into a collet on the basic mic . The ones I have go up to 15 inches bit OTT for ME.

Thought they would be good with bed clamp for end stops on the ML7. When I get round to it.

If you look at Starrett on google there details of the modern version, the only diff is insulated grip to stop hand heat causing expansion.

When I get round to it story of my life.

JK

If your rods are different diameters my theory is wrong. Any. Chance of pics of the ends of the rods .

Thanks "Bill Davies 2". That is exactly what they are. Tapered mandrels. Some do have a + sign stamped on them.

As it happens I have to cut some small gears and these will be just what I want. I am pleased now that I bought those "scrap" rods

I'm glad you identified them, Roger.

The ones I used were for holding high speed steel gear-cutting hobs, and hardened; some were hard chrome plated.

These mandrels had a taper of only a few tenths of thous, as the diameter of the bores were within close tolerance, being ground and honed.

If you find tapers of several thou or so, then I would sugest they are for 'soft' work; turning or milling, but remember these are friction fits, so the cutting forces need to go towards the larger end.

We used a hand powered mandrel press, but not much force was required to press them in, but as I said previously, this was for grinding operations.

Bill

Thanks Bill davies2. There is only a few tenths of thou difference in taper on these. Why would some of them have a turned down section and flat at only one end and the others at both ends ?

Roger, the flats are for driving dogs, and you might find size and perhaps other info stamped or etched on the flat surface. It is possible, with care, to grind oppposite surfaces by turning the mandrel and work end-for-end, to avoid any changes to the work's position with regard to its centre line. Given the very slight taper, for precision work, the workpiece could cant very slightly, and opposite faces would not be parallel. Having said that, when I was "bossing and facing" the ends and registers of cutters, I pressed the mandrel out, turned the work around, and pressed the mandrel in again.

I have a vague memory of one end sometimes having a ring (or am I thinking plug gauges), but certainly one end was often shorter than the other.

The [driving plates/dogs, catch plates] I used were lighter than the lathe types, and with arms off both sides, similar to the third picture here:

https://katalog.mav.cz/categories.php?rozbal=3443

This reduces any imbalance in the work, which might otherwise show up in the roundness/concentricity of the work.

Here is an example with flats on both ends:

http://www.ebay.com/itm/TTC-Lathe-And-OD-Grinder-Mandrel-Diameter-1-3-4-Overall-Length-10-/231948753418?hash=item3601391a0a:g:A3oAAOSwcvdXPHvJ

My Machinery Handbook (17th Ed., 1964) mentions mandrels in the index, but calls them arbo[u]rs in the text, and recommends 0.006" per foot for turning. Each end is shown the same length, and it doen't mention their use for grinding.

My Workshop Technology Pt (Chapman, 1968) shows the steps in grinding a headed bush, by grinding the bore, then, on a mandril, grinding the ODs and faces on one side, reversing mandrel and work, then facing the other end.

Bill

Sorry, I didn't embed the links:

Drving dogs: **LINK**

Mandrel with flats: **LINK**

Bill