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  1. #1
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    Default Repair thread - Hafco ST-12 circa 2003

    Hey all,

    I picked up a Hafco ST-12 on the marketplace here from a local. Had some known issues and this is a thread about getting to the bottom of some of them.

    What I can confirm from the poring over parts images is that this saw is NOT the same as the current model that it closely resembles, the SB-12. The internals look almost exactly like the current ST-12D, so I think that the ST-12D is the evolution of the unit I have - it's now got a full shell not just a "contractor" stand like mine has, and the motor is mounted underneath the arbor not behind the saw, but the rest of the guts of mine look more like the ST-12D than the SB-12 even though the form factor is the same as the SB-12.

    What I also believe is that this is one of the generic Taiwanese units that were sold with many different badges on from many different vendors. The Baker 305mm saw discussed in another recent thread, and Aldav's "Jonesway" one, both look pretty identical except for colour. I've also seen ads for older Toolmac and other brands that all look identical.

    The first problem to deal with is the saw won't return to true 90* from the table. I've been over the saw and the first issue I have noted is some missing grub screws, and I believe they're contributing to the 90* problem.
    So you'd think a grub screw right, shouldn't be hard to replace should it? Well, either did I to start.
    They are M6, 1.25 pitch.
    Normal M6 screws are 1.00 pitch, so these seem to be "unique". Anyone have suggestions where I might get some?

    Fallback: I'm contemplating drilling out and tapping to M8 as at least I can get M8 1.25 pitch at big green shed (in packs of 2, with 10 free other size/lengths I don't need).

    I'll post up some pics tomorrow showing some of the current fixes applied and some other questions
    @Aldav can I ask you to confirm if your height raise/lower

  2. #2
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    Quote Originally Posted by poundy View Post
    They are M6, 1.25 pitch.
    Normal M6 screws are 1.00 pitch, so these seem to be "unique". Anyone have suggestions where I might get some?
    Are you sure that they’re metric? 1/4” 20tpi is pretty close to 6mm 1.25.

  3. #3
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    Quote Originally Posted by Colin62 View Post
    Are you sure that they’re metric? 1/4” 20tpi is pretty close to 6mm 1.25.
    Good point. No, I'm not 100% sure, I have used a thread pitch gauge and they match 1.25, I've put them against a 8mm 1.25 and they mate as I'd expect, and I've started a M6 1.0 in one of the threads, seeming to match the size - but I never thought that something that looked such a perfect match might not be metric. Which given my surname I kinda should have ( ) Today I'll go buy a mix pack at BGS and confirm, then off to a bolt store to find individual packs as I am pretty sure I'll be needing a few but none of the other sizes...

  4. #4
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    @Aldav, in your picture of the height adjuster, can you tell me two things about the barrel that's visible:
    1) does the body of the
    barrel clear the end of the trunnion when you return to 90* ? It's the area opposite side of the shaft from where your picture was taken.
    2) does the end of that barrel, under the loose washers, have anything hanging off it? I'd describe mine as having a larger washer welded on the end, but it has a tab hanging off one side - which looks to have broken off.


  5. #5
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    One of the things I'd talked to Aldav about was the tilt adjustment not returning to 90*. On inspection, there were a couple of issues - one obvious one less obvious.

    First was that the mechanism had a lot of slop in the system. When you reversed direction, it would take a long time before it started to change the blade. Looking at this, you could see the entire shaft actually pulled into the machine - fix that as a first priority.

    Looking at the mechanism, the shaft runs through a bushing inside the casting. The bushing was loose, and it moved as well as the shaft. There is a hole for a grubscrew in the base of the casting - but it's empty That's one of the spots I needed to replace from the above request (although I just stole a less important one from the machine to take it's place first). The bushing is also eccentric - I assume that's to allow adjustment of where the shaft exits the body of the saw, and if there's inaccuracies in the castings. The other thing with this area is that the shaft would pull out extra compared to the bushing movement - there was a collet on the shaft but it was loose.

    My first go was to replace the grub screw in the base, but that seemed totally ineffective in holding the bushing in place. No matter how tight I drove the grub screw, didn't work. So I went and got a collet that could fit the bushing where it protruded from the casting and locked it down - that worked wonders, no more slop there. I also tightened the other collet, and that too meant the shaft didn't move and the slop was all gone - but it introduced a lot of tension in the system. Trying to adjust the angle it'd be quite sticky - workable but not great.

    After a further message chat last night with Aldav describing what I did, and sleeping on it, I decided to go back to basics and pulled everything off that I'd added, and tried adjusting the bushing and shaft, and voila, a lot of tension removed... and, I managed to get the bushing to hold in place (so far), so a double win! Here's a picture of how this area looks now...
    20200103_100920.jpg

    OK, second problem in this area is a little less impactful (it seems) and was not as easy to spot until I had the whole tilting arbor out of the machine, but here's a pic.... the last few cast iron teeth on the tilt mechanism have chips So far the mechanism seems to still be working, so this is a watch-and-see area for me. I don't know how it'd go getting someone to build up the teeth with a welder and re-grind that to the rough shape, but that'd be how I'll approach it if it becomes an issue.
    20200103_100931.jpg

  6. #6
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    Sorry for the delay Brett. Had a job to do this morning and have been trying to get some decent pic's to post.

    Firstly concerning the height adjuster:
    1) The barrel clears the trunnion extension (that the angle adjustment is connected to at the bottom) by about 3mm when the blade is set to 90*. I hope this is what you are after.
    2) The only thing connected to the barrel is the angle pointer. If you don't have an angle pointer that'll be what's broken off.

    Following are a couple of pictures of the worm gear end of the rise and fall mechanism:
    #1 is with the blade mechanism fully raised.
    #2 shows the relative position of the worm gear and fixed shaft housing just as the drive takes up. Note that gap, which equates to approx. one full turn of the handle.

    The reason that your tilt mechanism is so tight is that the hole does not contain a grub screw, it is designed for a bolt (machine screw) and locking nut. See picture #3. The thread is indeed M6 x 1.25 (just to be difficult). While not common this thread is used in machine parts and furniture from time to time. You will also notice from #3 that my saw has an adjustable machine screw and locking nut on the stop bar where yours just has the bare steel bar.

    Just for completeness in this thread here's the link to the Grizzly manual, which is the best I've come up with for these saws - https://cdn0.grizzly.com/manuals/g1022proz_m.pdf - yes, I know it's for 10" saws, but the mechanicals are the same. Also a couple of pictures of my saw for comparison purposes.
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  7. #7
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    I'm pretty sure you realise this but just in case. The winding rods of both the rise and fall and tilt mechanisms run in an off-centred steel tube that is best kept lightly oiled. By turning the steel tube in the housing you are able to adjust the meshing between the worm drive and the mating teeth.
    Forum members PM me for a discount on all my products - https://www.ebay.com.au/str/aldavsstore

  8. #8
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    thanks again Adlav, you've been more than accomodating. It's not like I was in a hurry

    Anyway, after this morning's adjustments the tilt mechanism is running MUCH more freely, so I am leaving it be.

    However, your image #3 really does show me that I have an M6 1.25 problem to resolve but for now, the grub screw damn tight in it's current position seems ok, but I am sure that with use it'll only get less-ok. Anyone with leads on M6 1.25 bolts and nuts?

    Height adjuster is now resolved too - the pointer ! Yep that's what's missing, probably in the collateral of that barrel coming loose. I've tweaked it's position so that I have no concerns about the position against other parts of the trunnion (another thing I suspect was happening originally).

    My next problem is not a problem with the saw itself, it's just with my space to use it - there is none! I now need to contrapt something to allow me to move it out into the yard to use it, as the set of mobility wheels that it came with are ok to move around a nice level floor but not up and over the humps and gutters and grate that I have at the back of the shed. That's going to take a bit more effort in more than one way - getting the heavy thing onto and off of something that has more travel and can support that weight isn't going to be trivial - and to do it safely will also be interesting. Maybe I need to become a welder after all?

  9. #9
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    Quote Originally Posted by poundy View Post
    Maybe I need to become a welder after all?
    5 of my machines are on mobile bases I made myself. The welds don't have to be pretty.
    Forum members PM me for a discount on all my products - https://www.ebay.com.au/str/aldavsstore

  10. #10
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    wanna show pics of those?

    I ideally would want something I can jack it up onto / off of so it can be "semi permanently" on stable ground once I get it to position. Non-trivial engineering problem?

  11. #11
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    These are the two with which I'm most pleased, I won't show the others as they're really only made out of junk that was at hand. Both of these are the same design and use 65mm angle frames and 50mm lockable casters. They raised the height of the machines less than 10mm, which suits my relatively short stature. What you're talking about would require bigger wheels (at least 75mm) and that would make this design much more difficult because of having to accommodate a full 360* swivel of the locking foot paddles. Might give you food for thought though.

    All the machines are easy to manoeuvre even the table saw with the Incra 92 inch rails with an additional rail support. I couldn't be happier. Wish I owned a cabinet saw though, maybe one day.
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  12. #12
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    Hi , you can weld a plate on the front and back angle iron to extend it to fit bigger castors, you can weld 2 pieces of angle iron in a sort of z shape to get extra for the castors without gaining any height

  13. #13
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    thanks Slave. (er that sounds somewhat off)

    My issue is actually I need to GAIN height to get the machine where I need because of the uneven area at the garage door - it goes, from the garage floor there's a rain runoff barrier / speed hump, then down to a drain, then a slow rise back up to the level area behind the shed. That's why I was thinking about something that allowed me to lift it up - roughly thinking 100mm for clearance - and then lower it in place. Although a 100mm higher table wouldn't be tragic right now I suspect (less vertically challenged than some, it would seem), and yes the Z-shaped outriggers for castors was one of the things I'd thought about if needed...

    I happen to have a set of these in the garage for another movable object that might need them less than the saw I have a mate not far away who has a welder (and a son who has done more welding than I have) so maybe a more detailed plan needs to be hatched! And I think i have a temporary (timber) plan as well, but it may not be sufficiently stable, only time and experimentation will tell

  14. #14
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    Quote Originally Posted by aldav View Post
    The thread is indeed M6 x 1.25 (just to be difficult). While not common this thread is used in machine parts and furniture from time to time.
    I can't find any reference to an M6 x 1.25, only M6 x 1 or lower. A 1/4" UNC thread is almost identical in pitch being 20 TPI which is a 1.27mm pitch, just slightly larger diameter. The only way to confirm would be to measure the sample grubscrew with a vernier or mic to see if it is closer to 6mm or 1/4"

  15. #15
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    Quote Originally Posted by Treecycle View Post
    I can't find any reference to an M6 x 1.25, only M6 x 1 or lower. A 1/4" UNC thread is almost identical in pitch being 20 TPI which is a 1.27mm pitch, just slightly larger diameter. The only way to confirm would be to measure the sample grubscrew with a vernier or mic to see if it is closer to 6mm or 1/4"
    I've done that Dallas. It's definitely 6mm x 1.25. They do exist, but don't ask me why. M6-1.25 x 45mm Class 8.8 Metric Hex Head Cap Screw With Captive Washer- Yellow Zinc - H. Paulin & Co.
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