I have always wondered about the accuracy of the speed indicator on my Hardinge HLV H lathe, also, the numbers are now almost disappeared. I struggle to get tool life out of my HSS tool bits which I suspected was because the spindle was running too fast. I decided to fit a Hall effect tachometer.
Total cost was low $9.99 plus $2.99 shipping for the display, $9.99 for a project box from Radioshack and $3.99 for a 12V power connector. I had a 12v power supply wallwart.
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Marked out the facia, drilled out the corner points:
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Milled out the cover for the display:
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made a little bracket that picked up on the gearbox cover fasteners for a magnet to be superglued to the inside of the spindle hand wheel:![]()
The bracket mounts on the back and is protected by the collet closer bracket when it is in place
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Connections are straightforward![]()
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I mounted it on top of the speed control panel![]()
Looks good and reads very well.
WhenI tested the upper and lower rpm settings i discovered that the limit switch kicked in at 1,075 RPM on the upper limit of the low speed (1,000 RPM on the analogue display) and 435 rpm (Indicated at 125 RPM). my suspicion was correct, the lower trip needed adjusting, now adjusted down to get 140 RPM (the belt gets tight at that point.
The tachometer works so well I put one on my mill as well. The mill had a VFD but with step pulley belts, calculations have to be made. I can now get spindle RPM as I mounted the magnet on the spindle pulley.
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All I need now is a RPM versus surface speed chart now, does anyone have this in an Excel spreadsheet or other form so I can post it next to my machines?
Total cost was low $9.99 plus $2.99 shipping for the display, $9.99 for a project box from Radioshack and $3.99 for a 12V power connector. I had a 12v power supply wallwart.
Marked out the facia, drilled out the corner points:
Milled out the cover for the display:
made a little bracket that picked up on the gearbox cover fasteners for a magnet to be superglued to the inside of the spindle hand wheel:
The bracket mounts on the back and is protected by the collet closer bracket when it is in place
Connections are straightforward
I mounted it on top of the speed control panel
Looks good and reads very well.
WhenI tested the upper and lower rpm settings i discovered that the limit switch kicked in at 1,075 RPM on the upper limit of the low speed (1,000 RPM on the analogue display) and 435 rpm (Indicated at 125 RPM). my suspicion was correct, the lower trip needed adjusting, now adjusted down to get 140 RPM (the belt gets tight at that point.
The tachometer works so well I put one on my mill as well. The mill had a VFD but with step pulley belts, calculations have to be made. I can now get spindle RPM as I mounted the magnet on the spindle pulley.
All I need now is a RPM versus surface speed chart now, does anyone have this in an Excel spreadsheet or other form so I can post it next to my machines?