Gyzmo
Plastic
- Joined
- Apr 25, 2022
I am posting my experience for others who may have similar problems with the brakes on their Hwacheon lathes...
I have owned my pre-loved HL435 for over 10 years.
It was a machine that I purchased after my local TAFE (College) fitting and machining workshop (in Brookvale, a suburb of Sydney - Australia) closed down.
The machine was manufactured in 1981 according to the Name Plate, is in reasonable condition for it's age and is fitted with a taper turning attachment.
I have replaced the threading lead screw and half nuts, added a Fagor 20i DRO, a knee operated kill switch and replaced two of the gears inside the Apron.
Back in March (2022) while using the lathe for an hour or so the machine started to emit an odour that smelled like an overheated electrical coil, so I thought one of the contactors in the controls cabinet was overheating. Upon inspection I was unable to locate any electrical fault. I had finished using the lathe for the day so I left it at that.
The following weekend I had been using the lathe for about an hour when I sniffed the electrical odour again.
I rechecked the controls and there was no evidence of any overheating.
Note, I had isolated the electrical supply prior to placing my hands in the controls cabinet - 415 Volts does wonders for the heartbeat, not.
After 10 minutes of head scratching, I had a light-bulb moment... "It must be the brake!".
I removed the lower side panel and lo and behold the outer 20mm of disk was a nice blue colour and, there was mechanical resistance when I rotated the motor pulley by hand.
I removed the caliper and pads to find that the pad engagement with the disk was only half the pad and the caliper pots were jammed in their bores.
The pads were radially 20mm further from the motor shaft axis than they should be and there was no adjustment to bring them closer to the axis.
The calliper installed on the machine was a 2 pot unit, but the unit in the parts manual was a single pot. I suspected that the original calliper had failed and that TAFE had sourced a calliper that fitted the calliper mount, I discovered differently later...
I contacted the Australian Agent for Hwacheon the following Monday and was advised the original part was not available and that Hwacheon could probably supply a calliper but it wouldn't be cheap, so I asked them to give me a price. They responded two days later with a price of A$3500. Way out of my ballpark, well that was the end of that then...
My next step entailed searching the Web to see if I could find a suitable caliper, half a day of searching led to a dead end...
I did however find that the caliper supplied with my lathe was manufactured by Girling and from a Triumph Spitfire (others have mentioned this in this forum but I wasn't a member here until recently), you can even buy four pot aftermarket versions for extra stopping power...
I also found from other people’s Hwacheons that the caliper was not aftermarket because their lathes were fitted with the same calipers...
So, what to do?...
Eventually I decided my only course of action was to manufacture a new hub and disk.
After taking some measurements of clearances, etc. I CADed up my design (refer images 1 - 3) and sourced a slab of 320 diameter 1045 steel for the disk and a slab of 165 diameter 1020 grade for the hub (my supplier couldn't source the 165 diameter in 1045).
Note, the OEM disk diameter is 280mm, my redesigned disk diameter is 320mm.
I then modified the caliper mount and the removed part of the casting with a 111mm dia. hole saw mounted in my drill press followed with a hacksaw, and to finish off, a die grinder.
My next task entailed machining the disk from 20mm to 10mm thick, all went well until the material reached 12mm thick and the disk started to resonate. The thinner the disk became the worse it became. The only way to stop the resonance was to slow the rotational speed down to 32RPM which made the machining process painfully slow with a rough surface finish, I was using ceramic cutting tools...
I had not removed the disk previously so I was unsure of the hub bore diameter. Once the disk was removed I measured the arbour OD to be 65mm Dia.
I decided that I would not remount the disk etc. onto the motor shaft, so I fabricated the hub on my Turret Mill.
I trial fitted the hub and disk onto the motor and voila it all went together... Just. If the disk was any larger it would not have fit...
I had the disk ground on my mate's brake grinder to clean up the poor surface finish and to remove run-out.
I re-mounted the disk onto the hub and checked caliper mount and caliper clearances, spun the disk - no scrapes, grinds or clunks.
I procured a new set of brake pads from my local brake shop (the old ones had a step warn in them), fitted them and bled the caliper and voila, one working lathe.
The brakes also stop the motor much quicker because there is double the pad area engaging with the disk.
I don't know why Hwacheon used the Girling caliper, I assume because at the time it was the cheapest option that didn't lead to a redesign of the caliper mount and/or other parts of the lathe...
I attempted to upload some progress photos this evening but the file sizes are too large and will only accept 10 per upload so will post progressively over next few days...
CAD Images:
Original Disk Assembly:
Modifying the Caliper Mount:
Checking Caliper Mount Clearances:
I have owned my pre-loved HL435 for over 10 years.
It was a machine that I purchased after my local TAFE (College) fitting and machining workshop (in Brookvale, a suburb of Sydney - Australia) closed down.
The machine was manufactured in 1981 according to the Name Plate, is in reasonable condition for it's age and is fitted with a taper turning attachment.
I have replaced the threading lead screw and half nuts, added a Fagor 20i DRO, a knee operated kill switch and replaced two of the gears inside the Apron.
Back in March (2022) while using the lathe for an hour or so the machine started to emit an odour that smelled like an overheated electrical coil, so I thought one of the contactors in the controls cabinet was overheating. Upon inspection I was unable to locate any electrical fault. I had finished using the lathe for the day so I left it at that.
The following weekend I had been using the lathe for about an hour when I sniffed the electrical odour again.
I rechecked the controls and there was no evidence of any overheating.
Note, I had isolated the electrical supply prior to placing my hands in the controls cabinet - 415 Volts does wonders for the heartbeat, not.
After 10 minutes of head scratching, I had a light-bulb moment... "It must be the brake!".
I removed the lower side panel and lo and behold the outer 20mm of disk was a nice blue colour and, there was mechanical resistance when I rotated the motor pulley by hand.
I removed the caliper and pads to find that the pad engagement with the disk was only half the pad and the caliper pots were jammed in their bores.
The pads were radially 20mm further from the motor shaft axis than they should be and there was no adjustment to bring them closer to the axis.
The calliper installed on the machine was a 2 pot unit, but the unit in the parts manual was a single pot. I suspected that the original calliper had failed and that TAFE had sourced a calliper that fitted the calliper mount, I discovered differently later...
I contacted the Australian Agent for Hwacheon the following Monday and was advised the original part was not available and that Hwacheon could probably supply a calliper but it wouldn't be cheap, so I asked them to give me a price. They responded two days later with a price of A$3500. Way out of my ballpark, well that was the end of that then...
My next step entailed searching the Web to see if I could find a suitable caliper, half a day of searching led to a dead end...
I did however find that the caliper supplied with my lathe was manufactured by Girling and from a Triumph Spitfire (others have mentioned this in this forum but I wasn't a member here until recently), you can even buy four pot aftermarket versions for extra stopping power...
I also found from other people’s Hwacheons that the caliper was not aftermarket because their lathes were fitted with the same calipers...
So, what to do?...
Eventually I decided my only course of action was to manufacture a new hub and disk.
After taking some measurements of clearances, etc. I CADed up my design (refer images 1 - 3) and sourced a slab of 320 diameter 1045 steel for the disk and a slab of 165 diameter 1020 grade for the hub (my supplier couldn't source the 165 diameter in 1045).
Note, the OEM disk diameter is 280mm, my redesigned disk diameter is 320mm.
I then modified the caliper mount and the removed part of the casting with a 111mm dia. hole saw mounted in my drill press followed with a hacksaw, and to finish off, a die grinder.
My next task entailed machining the disk from 20mm to 10mm thick, all went well until the material reached 12mm thick and the disk started to resonate. The thinner the disk became the worse it became. The only way to stop the resonance was to slow the rotational speed down to 32RPM which made the machining process painfully slow with a rough surface finish, I was using ceramic cutting tools...
I had not removed the disk previously so I was unsure of the hub bore diameter. Once the disk was removed I measured the arbour OD to be 65mm Dia.
I decided that I would not remount the disk etc. onto the motor shaft, so I fabricated the hub on my Turret Mill.
I trial fitted the hub and disk onto the motor and voila it all went together... Just. If the disk was any larger it would not have fit...
I had the disk ground on my mate's brake grinder to clean up the poor surface finish and to remove run-out.
I re-mounted the disk onto the hub and checked caliper mount and caliper clearances, spun the disk - no scrapes, grinds or clunks.
I procured a new set of brake pads from my local brake shop (the old ones had a step warn in them), fitted them and bled the caliper and voila, one working lathe.
The brakes also stop the motor much quicker because there is double the pad area engaging with the disk.
I don't know why Hwacheon used the Girling caliper, I assume because at the time it was the cheapest option that didn't lead to a redesign of the caliper mount and/or other parts of the lathe...
I attempted to upload some progress photos this evening but the file sizes are too large and will only accept 10 per upload so will post progressively over next few days...
CAD Images:
Original Disk Assembly:
Modifying the Caliper Mount:
Checking Caliper Mount Clearances:
Last edited:
