email: tony@lathes.co.uk
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EXE Surface Grinder

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One of only a small number of dedicated, miniature surface grinders made world-wide the British-made EXE joins a select group with some of the others being the  American Sanford, made in New Jersey; the pre-WW2 Herbert "Ball-bearing Bench Surface & Die Grinder"; the fine French Lipmec LIP 515, the rare Bulova and the Grenby by an American company (better known for their cylindrical grinders), whose slightly larger table-top unit appears to have been adapted for the Australian Macson and, in recent years, also produced in Taiwan and China and sold under various brand names including Harbor Freight,  Richyoung and Tormach.  The Tormach, produced to a higher level of accuracy and finish, is available with automatic feeds and has travels of 6 by 12 inches - travels for the hand-feed Grenby are not known.
Cast from a Mehanite iron and with its handles in aluminium, the EXE was first manufactured in the early 1950s and remained available until the late 1990s. It was offered in two forms: one for bench mounting, the other mounted on the maker' robust and enormously heavy cast-iron cabinet stand - this, in one form, including a neat, integral dust-extraction system with an exhaust fan and filter bags with a shaking mechanism for cleaning. The other stand was a plain type - in cast iron - easily distinguished from filter type by a hinged door on its front face.
Unlike many surface grinders of its era, the spindle ran not in super-precision plain bearings but in a detachable housing that held pre-loaded, angular-contact ball bearings. To encouraged speedy and safe wheel changes to be made, the grinding wheel was mounted on a quickly-detachable detachable collet - the standard wheel on later machines being 7" x 0.5" x 1.25". Able to stand intermittent overloads of 50%, 0.5 h.p. 3-phase motor provided, via a smooth-running flat belt, two spindle speeds of 2,700 and 3,100 r.p.m. - the change being made (rather inconveniently) by interchanging the drive and driven pulleys. Like most grinders, the EXE had a balanced motor, this being set up complete with its pulley to ensure the smoothest possible running. As any deficiency in the balance of rotating parts - including the wheels - is transmitted to the surface finish, care is needed in handling components from any grinder. Even a worn belt can cause trouble and if the machine has been standing for some time with the belt in place and chemically reacting with the pulley, it's best to fit a new one. Want to check balance? Put a cup of water on any flat surface and switch on; there should be no ripples or disturbance at all. The makers also listed a special high-speed spindle assembly that ran at 15,000 r.p.m., this being intended to make use of very small wheels that opened up the possibility of grinding awkward slots and recesses. It was also possible to specify, at extra cost, a range of  different pulley sizes to vary the standard speeds of both the ordinary and high-speed spindles.
All slideways were hand scraped to a perfect fit and the 12" x 6
3/8" table - intended for hand operation only - ran on V and flat slides with longitudinal and traverse travels of 13.5 inches and 7 inches respectively. Longitudinal drive was by a rack and spiral pinion, the pinion being set at an angle to promote a smoother and easier motion. Mounted on double V-ways, the saddle was driven in and out by an enclosed 10 t.p.i. screw with its bronze nut adjustable to take out backlash. While simple end stops to prevent the table overrunning were fitted as standard, as an option an adjustable stop system could be provided. The assembly consisted of a flat steel bar, perforated with a line of holes, fastened to the front face of the table; two sliding stops were provided, these registering into the holes as required using spring-loaded plungers with the final setting achieved by fine-thread adjusting screws.
Clearance beneath the 7-inch wheel to the table was 9.25 inches - and to the magnetic chuck 6 inches. Vertical travel of the head was 9.75 inches, movement being by an enclosed screw and bronze nut supported on a ball-thrust race nut, the operating handle being engraved on its periphery with lines set 3/16" apart, each division equalling a travel of 0.0005".
The bench model weighed a massive 620 lbs and the cabinet version, complete with dust-extraction equipment, 1360 lbs (over a half-ton) and no, it will not fit in the back of a standard-issue Euro Hatchback - though the bench version will.
To give some idea of the machine's quality, in 1957 a Myford ML7 lathe cost a little over £50 - whereas the EXE was over nines times as much as a bench model - at £447 - and on the stand ten times the price,  at £598. Although surface grinding machines are rarely found in smaller workshops, the compact little EXE is one of the few available that would make an ideal addition to the machine-tool collection of the more enthusiastic amateur.
Standard equipment supplied with each new grinder included a 10" x 5" magnetic chuck, one grinding wheel, a diamond holder for wheel dressing (but not the diamond), two special spanners and an oil gun.
EXE also made a range on very interesting, unusual small lathes.

EXE precision miniature 12" x 6"  surface grinder

High-speed grinding spindle. This unit interchanged with the standard spindle and was able to run at up to 15,000 rpm.

This fine example of an EXE is currently for sale

Seldom found: an EXE grinder on its maker's stand with built-in dust extraction equipment

A well-preserved EXE miniature surface grinder with an interesting set of modifications to the control system. The owner writes:
The large box on the front controls the motion with the help of the main drive inverter (out of view underneath the back of the bench). First there's a limit switch on the infeed; if this trips it disables the inverter that shuts everything else down. The box contains 3 relays - one of which controls the traverse forwards and backwards based on the limit switches on top the intermediate carriage. These are tripped by the sliding stops (not original, as this function was missing). The second relay supplies the power for the motor - either 12v for slow speed or 24v for high (neither are fast by commercial standards, but intended to emulate what you might achieve by hand, but without the pain) - via the motion control relay. The final relay turns on 240v output for a powered rotary table for grinding round things - piston rings perhaps. The switches are as follows: first controls inverter enable via the rear limit (one NO contact). Second selects low volt relay or high volt relay (one NC and one NO contact); both need the inverter internal relay to be on (programme only to turn on when the motor is up to full speed). The third switch selects high or low voltage output to the motor (two NC and two NO contacts). The fourth is a three-position switch selecting clockwise or counter-clockwise table rotation as well as a centre off (six NO contacts). The box also contains a centre-tapped toroidal transformer that feeds (via 3A fuses) to a bridge rectifier for the 24v and a full wave rectifier for the 12v. The transformer is permanently on (subject to the mains supply in common with the inverter) to supply voltage to the relays which have 24v coils.
Beyond the electronics you'll notice the rather spindly rods around the limit switches. These actuate a ratchet attached to the infeed. Slight variation is possible by moving the position of the pivot on the limit switch arm. Fully out gives 10 thou (slightly variable!), right in cuts this to 5 thou. The ratchet wheel (tried to take a photo, but there wasn't enough room to get the camera to focus on a decent shot) was made on the machine itself with a wheel dressed at an angle and a simple spin index. The ratchet has check pieces to stop the pawl falling off. The gears are home made (20 DP). The motor gear is steel, the idler (needed to enable disengagement) is brass and the final one is Tufnol, mounted on an aluminium boss.
This is a Mk. 2 version - the Mk. 1 used an old car wiper motor and the idler provided a second stage of reduction. It was too slow and the motor packed up (not designed to run backwards!). This prompted the move to 24V and the Parvalux unit. I decided to incorporate the rotary capability into the same controls, having previously used the table independently, at the time of this upgrade.
Only very minor modifications were made to the machine to fit this assembly.
I'm not sure much more 'automation' is possible without resorting to a PLC and steppers, though this would give more in-feed flexibility and open the possibility of vertical control. However, I doubt that I'll ever bother!



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EXE Surface Grinder
email: tony@lathes.co.uk
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