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  1. #1
    Join Date
    Sep 2009
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    Sydney
    Posts
    666

    Default Hercus 9C Pulley Upgrade

    Disclaimer; I am not a machinist. I would class myself as a garage hack that likes to do the odd project Hercus 9C Pulley Upgrade

    I do however love my little Hercus 9C lathe. It was a very cheap grab and after some fettling has served me well for years. It wasn’t really until I tried to turn down some 110mm discs recently though that it really struggled. The major issue was the belt slipping off the flat pulleys.

    I didn’t worry about it before now because I quite like the safety of the belts slipping, but I’m now doing more work and it’s becoming a barrier, plus I hope I’m better on the lathe now to not need as much of a safety margin.

    I have a great old motor on the lathe on a VFD, so torque is no longer a problem, but putting that power into cuts is.

    The solution was a v belt pulley upgrade. It’s not a direct bolt on option but close to it. I had a chat with Mal at Australian Metalworking Hobbyist and was lucky enough to score a recently acquired set of pulleys. For those that have a Hercus and haven’t heard of Mal, acquaint yourselves. He’s a saviour to us Hercus owners.

    Step 1 was to bore out the rear pulley. My lathe is an early 1940’s machine with a 7/8” motor pulley shaft. Easy enough to do as I already have a lathe Hercus 9C Pulley Upgrade




    One that’s done it’s easy to pull the spindle and swap the pulleys.



    I don’t have to run the belt as tight as I used to and the motor puts all that power straight in the the spindle. The extra speed also gives me just over 1000 RPM which is great because I’ve now moved over to CCMT inserts and that extra speed will definitely gel better with carbide:



    Testing the cutting ability I thought I’d try it on my usual setup, the change gears running on the slowest feed speed. Cuts 25 thousandths with ease and even up to 35 thousandths was cutting but a lot of chatter. So it seemed like 25 was the sweet spot.

    Next up I changed the 16 change gear for the 32 to see what effect that would have.... wow! Another level.

    Not only did this setup hog material off but the machine was doing it with ease. I was taking 20 thousandths cuts at 800 RPM and the chips were spitting off the insert with a blue hue, incredible. The ones below are from the first set of cuts, but the second setup was flicking off small chips that I couldn’t pull out of the shop vac Hercus 9C Pulley Upgrade



    Couldn’t be happier, the machine is easily much more capable for a relatively cheap investment!

    Next stage will be an electronic lead screw, moving away from change gears as they’re a pain in the bum. Hence why I never change them and leave the lathe setup on the slowest feed.

  2. #2
    Join Date
    Oct 2010
    Location
    melbourne, laverton
    Posts
    1,910

    Default

    Far out .pretty neat little set up mate. Ive considered bumping the speed up on my plain bearing hercus c .A fair few times. Not by much just to 900 or 1000. thinking i wouldnt use at flat out very much. I just didnt want to be the guy saying here that ive trashed my spindle and head stock, I really would like a rollor bearing head stock hurcus. ill have to run some tests. to see how far off .025 i can cut with the factory set up.
    Any qay i am sure Mal wouldnt steer you wrong. so looks like a preety good upgrade.

  3. #3
    Join Date
    Sep 2009
    Location
    Sydney
    Posts
    666

    Default Hercus 9C Pulley Upgrade

    Top speed is around 900 RPM I think on the C according to Mal, but I tend to max on the second last pulley which is just shy of 900 RPM. I’m like you, don’t feel that comfy going flat out on the highest pulley.

    According to Mal the C has a higher material removal capability because of the lack of torque being used for crossfeed etc. I can certainly say my C has a lot of material removal power now, which will make a huge difference to turning times.

    Would be interested to compare material removal vs the flat belts. Let me know how you go and I can compare from my end too. The material I was playing with yesterday was pretty tough, non descript steel.

  4. #4
    Join Date
    Oct 2010
    Location
    melbourne, laverton
    Posts
    1,910

    Default

    UMM i had a feeling that the c modal was ment to be 700 plus rpm top speed. That's just a hasey guess.
    random mystery steel hay. i now it well.

  5. #5
    Join Date
    Sep 2009
    Location
    Sydney
    Posts
    666

    Default Hercus 9C Pulley Upgrade

    Reading a home shop machinest thread looks like you might be right, but plenty of people running plain bearing southbends at 800-900 rpm for years with minimal impact. I’m not sure I’d run mine much above 850 RPM as even then is humming along pretty fast.

    I’d likely keep the pulley with the best torque (second down) and run the motor a little faster to keep the torque.

    I noticed that on the carbide run the chip load got better the smaller the diameter got (at about 600 RPM), so I suspect 850 is probably the max with the 32T running the feed.

    That’s the annoying thing about change gears, you can’t easily try different feeds. Hence the reason I’m going electronic leadscrew at some point. Also means I can get rid of the eBay RPM gauge.

    For those that haven’t seen it, this is what I’ll be buying in to. Looks like an amazing bit of kit:


    https://youtu.be/10Ketpqq-eM

  6. #6
    Join Date
    Aug 2021
    Location
    Sydney
    Age
    46
    Posts
    116

    Default

    Interesting thread and hope its no problem to bring back a thread from 2020.

    Really lovely looking lathe and nicely set up there neevo.

    Happy New Year,
    Steve.

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