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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:
HL435 Brake Disk CAD Drg.jpgHL435 Brake Disk (Plan).jpgHL435 Brake Disk Hub (Plan).jpg
Original Disk Assembly:
20220203_S21-01 HL435 Brake Calliper Fitment.jpg 20220203_S21-04 HL435 Brake Calliper Fitment.jpg 20220203_S21-05 HL435 Brake Calliper Fitment.jpg
Modifying the Caliper Mount:
20220204_S21-04 HL435 Brake Mods.jpg 20220204_S21-05 HL435 Brake Mods.jpg
Checking Caliper Mount Clearances:
20220204_S21-07 HL435 Brake Mods.jpg 20220204_S21-08 HL435 Brake Mods.jpg
Last edited:


Apr 25, 2022
More Photos...
Disk Clearance:

20220204_S21-09 HL435 Brake Mods.jpg
Pad Wear:
20220204_S21-11 HL435 Brake Mods.jpg
Modified Caliper Mount:
20220205_S21-02 HL435 Brake Calliper Mount.jpg 20220205_S21-04 HL435 Brake Calliper Mount.jpg
More images to come...
Last edited:


Apr 25, 2022
Good on yah!

My "purple button".. is that soooo many Machinashitists.. will go whining for YEARS about not being able to get a "part".. run a machine "crippled", let a decent machine sit idle.. even sell-it-on.... or scrap it..

When the SAME GUY.. routinely makes some of the DAMNDEST weird and complex parts .. for CUSTOMERS.... every day of every week, year after year!

Good to see at least the cobbler's children don't long go barefoot in valiant Australia!

"Carry on!"
It's not hard if you put your brain to it...


Apr 25, 2022
More Photos...

The lock nut was a bastard to remove, even with the correct sized hook wrench . Two days of soaking with WD-40 did the trick...
20220423_S21-10 HL435 Pulley & Disk Removal.jpg
The pulley/disk had been removed previously at some point over the past 40 years but they were still tight on the Boss...
20220423_S21-13 HL435 Pulley & Disk Removal.jpg
Removed, finally...
20220423_S21-25 HL435 Pulley & Disk Removal.jpg
Disk mounted on rotary table ready to bore 8 x 8mm holes at 140mm PCD...
20220425_S21-01 HL435 Disk Mounting Holes.jpg
I used a cheap TiN end mill that I threw away after 6 holes (Yes, I used cutting fluid)...
20220425_S21-05 HL435 Disk Mounting Holes.jpg
Countersinking for 8mm csk screws...
20220425_S21-07 HL435 Disk Mounting Holes.jpg
20220425_S21-14 HL435 Disk Mounting Holes.jpg
Cutting the centre hole. I stopped at this point because the disk was sitting directly on the chuck jaws and I didn't want to damage them...
20220508_S21-01 HL435 Arbour Mounting Hole.jpg

More to follow soon, watch this space...
Last edited:


Apr 25, 2022
And More Photos...

I forgot to load these two.
I fabricated an arbour to allow me to face the disk...
20220326_S21-08 HL435 Brake Disk.jpg

This is the start of the resonance issues.
I slowed the speed down to 32 RPM at this point making the final machining painfully slow and the finish very rough...
20220329_S21-01 HL435 Brake Disk.jpg

Machining the hub.
20220508_S21-07 HL435 HL435 Fabricating Arbour.jpg
20220513_S21-09 HL435 Arbour - Milling Shoulder.jpg

165.02, happy with that...
20220515_S21-02 HL435 Arbour - Milling Shoulder.jpg

8 x 6.8mm holes at 140 P.C.D. for 8mm metric coarse threads.
20220515_S21-06 HL435 Arbour - Mounting Holes.jpg

I milled a shoulder into the 8 holes and chamfered them to facilitate better engagement with the screw threads.
20220515_S21-08 HL435 Arbour - Mounting Holes.jpg

Pad engagement with the original disk, no wonder the pistons were binding in the caliper bores...
20220508_S21-11 HL435 Brake Pad.jpg

More to come...
Last edited:


Apr 25, 2022
Milling the Hub...

Cutting the 12mm key way. I don't have a 12mm broach and the key is held captive by the pulley...
20220528_S21-23 Cutting Keyway - End Mill.jpg

Chamfering the edges.
20220529_S21-01 Chamfering Disk Side.jpg 20220529_S21-09 Chamfering Disk Side.jpg

Hub fitment.
20220529_S21-16 Motor Fitment.jpg

Milling Side 2...
I re-tramed the head after this pass.
20220530_S21-02 HL435 Milling Side 2.jpg

That's better...
20220601_S21-01 HL435 Milling Side 2.jpg

Milling to 24mm thick...
20220602_S21-01 HL435 Milling Shoulder Side 2.jpg

Shoulder = 8mm...
20220604_S21-07 HL435 Milling Shoulder Side 2.jpg

More to come...
Last edited:


Apr 25, 2022
To allow me to machine the disk and not damage the hub I used 1/2" tool steel (photo shows 5/16") to space the disk off the hub...
20220607_S21-06 HL435 Milling Disk Centre.jpg

Disk bore = 120mm
I dialed the outside edge to ensure concentricity and torqued each screw to 20Nm.
20220611_S21-07 HL435 Milling Disk Centre.jpg

20220612_S21-06 HL435 Hub Fitment.jpg

The long screws are temporary...
20220612_S21-07 HL435 Hub Fitment.jpg

With some expletives and a bit of patience I managed to fit the disk.
Disk is damn close to the casting though...
20220612_S21-09 HL435 Fitment to Motor.jpg

Wire keeps the grub screw captive...
20220619_S21-03 HL435 Refitting the Boss.jpg

A minor adjustment to the caliper mount casting provides a little more clearance...
20220619_S21-05 HL435 Trimming the Casting.jpg 20220619_S21-07 HL435 Trimming the Casting.jpg
Last edited:


Apr 25, 2022
Run out was 0.02mm.
20220619_S21-09 HL435 Hub Runout.jpg

Refitting the disk after grinding.
20220619_S21-14 HL435 Disk Final Fitment.jpg
20220619_S21-22 HL435 Pulley Fitment.jpg

Lock washer & nut...
20220619_S21-26 HL435 Lock Washer & Nut.jpg 20220619_S21-29 HL435 Lock Washer & Nut.jpg

Damn that's close to the caliper. I removed the caliper and made some minor adjustments to it with a file...
20220619_S21-31 HL435 Caliper Install.jpg

Close also... OEM disk is 8mm, new disk = 10mm.
20220619_S21-32 HL435 Caliper Install.jpg
Pads fitted...
Last edited:


Apr 25, 2022
Fitting new B79 transmission belts (took 3 goes from my parts supplier to source the correct belts) :rolleyes:
20220622_S21-02 HL435 B-Section Drive Belts.jpg 20220622_S21-03 HL435 B-Section Drive Belts.jpg

Re-purposing a defunct electrical link bar into a brake line mount, cut up the middle with my band saw and faced in my mill...
20220624_S21-03 HL435 Brake Line Bracket.jpg
20220624_S21-06 HL435 Brake Line Bracket.jpg
20220624_S21-10 HL435 Brake Line Bracket.jpg

That Works = I used an olive fitting to terminate the brake line...
20220624_S21-12 HL435 Brake Line Bracket.jpg

I bled the brake and and the chuck now stops on a dime...
One more post to go...
Last edited:


Apr 25, 2022
This is the last of it...
I replaced the original electrical isolator switch on the side of the control cabinet with a 3 phase 10 Amp circuit breaker just over 12 months ago.
Unfortunately at the time I was not cognizant of the need to remove the end cover, and then had to remove the breaker to gain access to the brake (traps for younger players).
To provide enough end cover clearance for the next time the cover comes off, I modified it and relocated the breaker housing closer to the control cabinet hinge.

I couldn't remove the fibre glass end cover - the circuit breaker housing was a bit too close to the breaker.
In this photo I had removed the cover screws but the cover was catching against the gearbox drive pulley...
20220422_S21-04 HL435 Motor End.jpg

Cover before and after shots.
20220625_S21-01 HL435 End Cover Mod.jpg 20220626_S21-03 HL435 End Cover Mod.jpg

The HL435 has been up and running now for 6 weeks without a hitch, and I'm happy with the improved brake stopping performance and, no more overheating brake.
For me, this was not a five minute exercise.
When I add up all the hours the whole exercise took around 10 x 10 hour days of my time (I am not a machinist by trade, I'm an electrician).
Would I do something like this again? Yes indeed, it was a good learning exercise for me ...

Thanks for watching...
Last edited:

310 Guy

Cast Iron
Jun 6, 2009
Rosamond, CA
Well done! reminds me that I need to fabricate a similar brake system for my Graziano SAG12. Damn thing takes forever to spin down...


Apr 25, 2022
Well done!

At least ONE shoemaker's child is no longer barefoot, has nice brake shoes!

Any of the rest of you lot as would rather whine "can't get parts", can kiss a multi-puck caliper.
Thanks for the compliment... I posted all this for others to benefit, hope they do...
There are other "little" HL435 projects that I will be undertaking from time to time and will post when I complete and as time permits me.