Lathe Height Gauge

Eight Toolmakers Buttons:- Cost = $2.40 for machine screws.

These are used for precise location of machining points on a job, with the aid of micrometer or calipers. The button can then be used to accurately position the work on the lathe or milling machine, with the aid of a dial indicator.

Normally the diameters available are 0.3", 0.4", 0.5" [Imperial] - 8mm, 10mm, 12mm [Metric] - one button is always longer than the other 3 in a set of 4. I work in both systems so it is of no real advantage to have either Imperial or Metric, either way I have to convert dimensions half my time. I decided to make the button diameter based on a precisely machined piece of dot-matrix printer shaft I already had, saving on the machining & accept that the diameter is not quite so convenient for calculations.

I decided on making the buttons 1/2" & 3/4" long. The machine screws selected were socket head UNC #6-32 at both 3/4" & 1" long. The rod I used determined the diameter at 0.460" or 11.69mm. Rods from printers are made to a precision of 1/10 of a thou I'm told, (better than I can measure anyway).

The full (double) set of buttons consists of 2 at 3/4" high & 6 at 1/2" high, plus a stand & Allan key.
The far right hole on the stand is made as a clearance hole on the bolt thread, this way I can be used as a guide to help in tapping - keeping the tap perpendicular to the base.

Cross section of a button. The counter bored recess (top) is for a bolt head & washer.

Countersunk lower end reduces the amount of base in contact with the work, reducing problems of burrs or distortion caused by drilling & tapping, which would upset positioning of the button. It also reduces the amount of base area that needs to be lapped.

The hole must allow the bolt to move by at least 50% to 75% of the bolt's diameter, but less than the head diameter.

The procedure for making Toolmakers Buttons starting with an old printer shaft, socket head machine screws, washers:

	Face off the shafting in the lathe.
	Bore a hole through a few inches of the shaft - I made the hole 1/32" smaller than the bolt head diameter. This makes the hole 'sloppy' enough for the button to be able to move, but the bolt can't pass completely through it.
	Countersink the base with a centre drill slightly smaller than the shaft Dia. to leave a narrow land (about 1mm all around I used a 3/8" centre drill).
	Part off the button at 1/2" for 3/4" bolts or 3/4" for 1" bolts.
	Repeat the facing off, countersinking & parting off for each button.
	Put each button back in the lathe chuck lightly, face off & counterbore the top end by about 1mm (I used a 3/8" end mill to do this).
	Fix a small rod of copper, brass or aluminium in the toolholder. Using a small amount of grinding paste, the bottom end of each button is then lapped against the piece of rod, until smooth & polished. This makes the button slide easily on the work & helps assure that the base is perpendicular to the long axis of the button.
	Assemble each button with its bolt & a small washer.
	I used an old piece of aluminium cut from a sewing machine to make the stand. Each button fits into a threaded hole to keep it secure. There was an extra hole drilled in the stand equal to the diameter of the tap, this can then be used to make sure holes in the work are tapped truly perpendicular to its surface, when the tap is started through this hole.

Lathe Cutting Tool Height Setting Gauge: - Cost $0.50

Although I made this from scrap cast iron, it could equally have been made from aluminium, brass, steel or even a good machineable piece of plastic.

As an alternative to milling from square section, it could also be made from round bar, by turning a wide groove at the required position & parting it off. The only difference is that it will look a bit like a chess piece.

To simplify getting the position of the groove at the correct height, make the unit slightly over height, measure it & then face-off the base by the excess amount, bringing it too the correct centre height of your lathe.

Don't rely on the nominal centre height that the lathe manufacturer claims - measure it - better to play safe than risk having to make it twice. When completed, compare it to a centre mounted in the headstock, then you know it will be OK.

	This gauge sits on the cross-slide & gives a reference height for setting up lathe cutting tools. The 1" thick block of scrap cast iron it was cut from cost me $10, I guess I used less than $0.50 worth. Between uses I just give it a spray with WD-40 to inhibit rust development. I try to do this each time I use either machines or tools, or if an item is unused, once every week or so.
	The cast iron block I used. This tool is the little block top right. The block bottom right will be used to make a new compound slide base.
	The end mill, held in the 4-jaw chuck aligned with dial gauge, the vice aligned with a square - Note: the vice is clamped & bolted to my home made angle plate.
	The first slot being end milled, before flipping over & milling the second slot. I am using an old 9/16" end mill owned by my father (from the 1960's, at least 37yr old).
	The final height gauge in use setting the height of a cutting tool. It's a simple, but very useful accessory. Of course, dimensions would differ between lathes - mine worked out to be 25 x 25 x 70mm, the tool height notch at 54.09mm above the cross-slide - this equals the centre height, above the cross-slide.