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Studer FS21 & FS21a
Form and Tool & Cutter Grinder


One of the more impressive makes and model of "Form and Tool & Cutter Grinder", the Fritz Studer FS21 (and almost identical FS21a) were Swiss-built machines first manufactured in the late 1950s.
This complex, highly-versatile machine was aimed at allowing cutters to be profile ground, the makers claiming that tests by a 'well-known' firm showed that, in comparison with cutters ground on a conventional tool & cutter grinder (or for cutters given relief on a cam-operated machine) tooling costs fell by 50% and machining costs to one-fifth of their previous level. It was also discovered that profile-ground cutters could be used more successfully for arduous "climb milling" - where work is pulled into the cutter rather than travelling against it - which was not the case for cam-relived cutters. The technique employed was to grind a land at the required relief angle on the complete profile of the teeth and then set a positive clearance angle - the latter being possible without the need for a correction template. Other advantages claimed for the machines were their ability to produce a surface finish on cutters three to four times finer than by cam relieving; a profile accuracy in the order of 0.001" (0.025 mm); less material removed during each regrind and a slower dulling of the cutter edge, the overall result of these features being the ability for a machine tool to take deeper cuts, a longer life between cutter regrinds together with them enjoying a longer overall service life.
On the FS21 the maximum cutter diameter that could be accommodated was 250 mm (9.8") with a length of up to 175 mm (11") or 175 mm (6.9") with a length of up to 280 mm (11").
On the FS21a the maximum cutter diameter that could be accommodated was 355 mm (14") with a length of up to 120 mm (4.7") or 250 mm (9.8") with a length of up to 150 mm (5.9").
On both machines the maximum distance between centres was 275 mm (10.8") and the smallest concave radius that could be ground was 0.5 mm( 0.2").
The weight of the FS21 was 450 kg (1000 lbs) and that of the FS21a 550 kg (1200 lbs).


The bay in the Studer factory at Glockenthal-Thun, Switzerland where Studer FS21 machines were erected



A typical work-holding arbor for the Studer FS21 - five different versions were available

Quill with roller bearings and a No. 4 Morse taper socket, three Morse adapters 4 to 1,
4 to 2 and 4 to 3 and, right, the cylindrical setting mandrel with its extractor

Quill with roller bearings for double-taper collets Type E40 and the required spanner

Roller bearing No. 5 Morse taper quill and three Morse adapters 5 to 2,
5 to 3 and 5 to 4 and, right, the cylindrical setting mandrel with its extractor

End mill bracket Part No. 55 complete with a rotatable and
axially-adjustable workhead to take the various quills as shown above

Table-mounted tailstock and its full and half No. 1 Morse centres

A pair of hinged arbor brackets with two clamps to hold cutters with diameters from 3.9 to 14 inches (100 to 355 mm)

Another of the many work arbors listed, this being available with diameters of 50, 60, 70 and 80 mm (1.96", 2.36", 2.75" and 3.12$"). Each had two ball-bearing races 42 mm in diameter with clamping lengths from 50 to 150 mm (2" to 6"). Each arbor came with three pairs of spacers, two collars and two clamping rings.

Even a small crane with an extension arm was listed, this being used to assist with the loading of heavy cutters and their brackets

Toolholder for "flat-form" cutters with a maximum shank dimensions of 63 x 44 mm (2.5 " x 1.6"). The unit
Cam complete with a tapered gib strip with a adjusting screw, four shims of 2, 4 10 and 15 mm (0.08", 0.15", 0.39" and 0.59") and one side packing piece 8 mm (0.3") thick

Precision adapter to take diamond grinding wheels of 150 mm ( 5.9-inch) diameter

An intermediate plate that allowed standard arbor brackets to be used on the FS21a