Ever since I fixed the 1960s Hilma 125mm hydraulic vise that came with my mill, I have been wondering if it is working correctly. In other words, does it generate 3.5 metric tons of clamping force as originally specified in the manual? (I worry about this when using the big planing head, thinking what would happen if the work came loose).
So I ordered two parts on the internet, a 400 BAR/5800 PSI glycerine-filled pressure gauge (ebay 321383675506, 9.35 Euro) and a 42mm ID/52mm OD/10mm deep polyurethane hydraulic seal (ebay item 251811089118, 4.84 Euro) and made a force gauge.
The force gauge reads up to 5.8 metric tons (5800 kg x 2.2 lbs = 12760 lbs = 6.4 US tons). The diameter of the piston is chosen so that 1 metric ton of force (1000 kg) reads 1000 PSI on the scale. Since the scale goes up to 400 bar = 5800 PSI, it can read up to 5.8 metric tons.
Image may be NSFW.
Clik here to view.
Here is a sketch. (Oops, where it reads r=42mm it should say d=42mm, sorry!)
The piston is turned from steel, 42mm diameter, 20mm long. Chamfer the inside end 1mm at about 20 degrees, then polish with 200/400/600/1000 wet-or-dry paper and WD40, then with emery paper. Leave a little stub on the outside end so that the clamping force is applied in the center of the piston. After polishing out the machining marks, mine was about 41.97mm diameter. That's fine, the seal allows for a bit of slop.
The body is turned out of a 40mm length of 70mm round steel rod. The first part you do on the mill. Mill flats on the top and sides (this is not really needed, but made it easier to clamp, looks nicer, reduces size and weight). Drill and tap for the gauge (11.8mm hole 10mm deep, 5.5mm hole 20mm deep, tap G 1/4", kiss bottom 1 or 2mm deeper with a sharp 10mm end mill). Second part you do on the lathe. Mount the body in a 4-jaw universal chuck, centered 4.5mm below the middle of the 70mm round. Bore a 42mm diameter hole to fit the piston snugly, then polish it as above. Turn an inside groove to hold the seal, 52mm diameter, 10mm wide, starting 5mm from the front face.
Clamp the body at an angle around 30 degrees, and drill a 4mm connecting hole at an angle to connect the piston chamber to the gauge as shown. Make the hole kiss the top of the chamber so air can not be trapped in that area.
Finally, tighten in your gauge, and see which way the face lines up. Then use the thread spacing (G 1/4" is 19 threads per inch) to determine the thickness of the copper washer sealing washer that you need to make the meter face foward, and turn it the washer to that thickness, ID 5.3mm, OD 9.8mm. Test washer thickness, adjust as needed, then remove gauge and washer. (You can also buy an EN837 compression washer that has a range of one full rotation, but I couldn't find where to buy one easily, so DIY was faster.)
Image may be NSFW.
Clik here to view.
Here are the parts. Body and piston were from the scrap drawer. The new seal and glycerine-filled pressure gauge cost 13 Euros.
Image may be NSFW.
Clik here to view.
Note the connecting hole angled at the top of the piston chamber.
Image may be NSFW.
Clik here to view. Image may be NSFW.
Clik here to view.
Assembly:
Wash the parts with alcohol and blow dry. Deform the seal into a kidney shape and insert. Be careful not to damage the sealing edges. The open gap faces towards the back.
Fill a saucepan with ISO 46 hydraulic oil, put the piston and body inside. Stir to eliminate bubbles, Turn body over to eliminate any air trapped in or around the seal. Then put the piston in (chamfer inwards) and use a woodworking clamp to force the piston into the seal. All of this is done inside the saucepan so no air can get inside. When about 5mm of the piston is projecting out, turn the body so that the gauge opening is upwards and remove from the oil bath. Don't let oil drain from the gauge opening, no air should enter! Insert into your milling vise, put in copper washer, screw in gauge loosely so oil can bleed out around the threads. Now tighten the vise to force the piston in. When 2-3mm of the piston is still sticking out, tighten the pressure gauge home.
I was happy to find that my vise generates 3.5 tons of clamping force by just cranking it the three rings. If you first disable the hydraulic mechanism and snug it, then engage and tighten using the hydraulics, it goes to 4.2 tons.
A few more photos are in the next post.
If you want to build a gauge that shows force in US tons, use a 40mm diameter piston, which has an area of 1.947 square inches. Then one US ton (2000 pounds) will display as 2000 lbs/1.947 square inches which is close to 1000 psi.
Total time to build was about 4 hours.
So I ordered two parts on the internet, a 400 BAR/5800 PSI glycerine-filled pressure gauge (ebay 321383675506, 9.35 Euro) and a 42mm ID/52mm OD/10mm deep polyurethane hydraulic seal (ebay item 251811089118, 4.84 Euro) and made a force gauge.
The force gauge reads up to 5.8 metric tons (5800 kg x 2.2 lbs = 12760 lbs = 6.4 US tons). The diameter of the piston is chosen so that 1 metric ton of force (1000 kg) reads 1000 PSI on the scale. Since the scale goes up to 400 bar = 5800 PSI, it can read up to 5.8 metric tons.
Image may be NSFW.
Clik here to view.
Here is a sketch. (Oops, where it reads r=42mm it should say d=42mm, sorry!)
The piston is turned from steel, 42mm diameter, 20mm long. Chamfer the inside end 1mm at about 20 degrees, then polish with 200/400/600/1000 wet-or-dry paper and WD40, then with emery paper. Leave a little stub on the outside end so that the clamping force is applied in the center of the piston. After polishing out the machining marks, mine was about 41.97mm diameter. That's fine, the seal allows for a bit of slop.
The body is turned out of a 40mm length of 70mm round steel rod. The first part you do on the mill. Mill flats on the top and sides (this is not really needed, but made it easier to clamp, looks nicer, reduces size and weight). Drill and tap for the gauge (11.8mm hole 10mm deep, 5.5mm hole 20mm deep, tap G 1/4", kiss bottom 1 or 2mm deeper with a sharp 10mm end mill). Second part you do on the lathe. Mount the body in a 4-jaw universal chuck, centered 4.5mm below the middle of the 70mm round. Bore a 42mm diameter hole to fit the piston snugly, then polish it as above. Turn an inside groove to hold the seal, 52mm diameter, 10mm wide, starting 5mm from the front face.
Clamp the body at an angle around 30 degrees, and drill a 4mm connecting hole at an angle to connect the piston chamber to the gauge as shown. Make the hole kiss the top of the chamber so air can not be trapped in that area.
Finally, tighten in your gauge, and see which way the face lines up. Then use the thread spacing (G 1/4" is 19 threads per inch) to determine the thickness of the copper washer sealing washer that you need to make the meter face foward, and turn it the washer to that thickness, ID 5.3mm, OD 9.8mm. Test washer thickness, adjust as needed, then remove gauge and washer. (You can also buy an EN837 compression washer that has a range of one full rotation, but I couldn't find where to buy one easily, so DIY was faster.)
Image may be NSFW.
Clik here to view.
Here are the parts. Body and piston were from the scrap drawer. The new seal and glycerine-filled pressure gauge cost 13 Euros.
Image may be NSFW.
Clik here to view.
Note the connecting hole angled at the top of the piston chamber.
Image may be NSFW.
Clik here to view.
Image may be NSFW.Clik here to view.
Assembly:
Wash the parts with alcohol and blow dry. Deform the seal into a kidney shape and insert. Be careful not to damage the sealing edges. The open gap faces towards the back.
Fill a saucepan with ISO 46 hydraulic oil, put the piston and body inside. Stir to eliminate bubbles, Turn body over to eliminate any air trapped in or around the seal. Then put the piston in (chamfer inwards) and use a woodworking clamp to force the piston into the seal. All of this is done inside the saucepan so no air can get inside. When about 5mm of the piston is projecting out, turn the body so that the gauge opening is upwards and remove from the oil bath. Don't let oil drain from the gauge opening, no air should enter! Insert into your milling vise, put in copper washer, screw in gauge loosely so oil can bleed out around the threads. Now tighten the vise to force the piston in. When 2-3mm of the piston is still sticking out, tighten the pressure gauge home.
I was happy to find that my vise generates 3.5 tons of clamping force by just cranking it the three rings. If you first disable the hydraulic mechanism and snug it, then engage and tighten using the hydraulics, it goes to 4.2 tons.
A few more photos are in the next post.
If you want to build a gauge that shows force in US tons, use a 40mm diameter piston, which has an area of 1.947 square inches. Then one US ton (2000 pounds) will display as 2000 lbs/1.947 square inches which is close to 1000 psi.
Total time to build was about 4 hours.