Seig micro mill gear crash

Discussion in 'Mistakes, Blunders and Boo Boos' started by syrtismajor, Jul 29, 2014.

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  1. Jul 29, 2014 #1

    syrtismajor

    syrtismajor

    syrtismajor

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    Take this as a learning experience and a warning...

    Seig Micro Mills are great for a beginner, they are sold under various trade names in the UK (such as 'Clarke', 'Axminster' etc) and I'm sure you can find them under many guises across the word. An example is here.

    One of their features I like is the 'two speed' function (either fast or slow). While this may seem like an ancient feature of the past, I still like it :rolleyes:

    Anyway, to keep costs down they use nylon gears in their gear box:

    [​IMG]

    (the dirt was already in there)

    The top gear on the left is the drive from the motor.
    The gears on the right are on the spindle.
    The two gears on the bottom left are the gears on the Layshaft.

    Here is the removed Layshaft:

    [​IMG]

    Now here are the two gears from that shaft:

    [​IMG]

    The left gear is for the low speed and the right gear... Wait! What's that? Is there something missing on the right gear?

    [​IMG]

    Gah! Two missing teeth!

    Yes, I broke a gear in my micro mill :hDe:

    I was only taking off less that 1/4 of a millimetre on a fly-cutter and there was a 'crack'. This was followed by some rattling and rumbling.

    The mill was stopped immediately so I could assess the damage. With the power off I cracked open the top to see the missing teeth.

    Lesson learned today:

    Do not overload a Seig micro mill!


    Warning:

    It could happen to you! (if you own one yourself)

    This can be shown by this 'Crap-o-cad' diagram of the gear placement (be aware that in reality the gears on the left would be against each other)

    [​IMG]

    As you can see; the gears for high speed are mis-matched on height when they are engaged. This isn't operator error but a design flaw. It means that the stress on the teeth is offset leading to a possible shear if there is too much resistance on the spindle. And that is exactly what happened...

    Bugger

    I am now humbly ordering a replacement gear. This means that any further updates on my 'Bulleid Light Pacific' thread in the 'Work in Progress' section may be a little quiet for a while. I will keep updating it every Sunday but don't expect any real engineering for the next week or two.

    I'm off now to do this for a while: :wall:
     
  2. Jul 29, 2014 #2

    gus

    gus

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    DIY C.I. or M.S. Spur gears would about last for ever. My Japanese Sakai Lathe and Mill have plastic gears too. But Japanese Quality Gears have very good gear life. Lathe and mill are about ten year old by now.

    Been cutting DIY gears but mainly Modular 0.8 and 1.0 for engine timing gears.
     
  3. Jul 29, 2014 #3

    BaronJ

    BaronJ

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  4. Aug 1, 2014 #4

    syrtismajor

    syrtismajor

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    I think that you two have the best way forward in replacing the gears with metal ones; especially with what happened next...

    Today the replacement gear arrived, all shiny and new in a plastic bag:

    [​IMG]

    That was carefully fitted about an hour ago followed by re-assembling the mill.

    The next test was to see if it all worked... that was followed by another sound and more expletives.

    I ripped the assembly apart again thinking that it was the complementary gear that had some unseen damage. After a good inspection I could see no damage.

    After scratching my head for a while and considering completing a drop test with it out of the first floor window, I finally found the source of the problem... The drive gear:

    [​IMG]

    There may not be anything in that photo that is obvious but I can assure you that there is. What happened is demonstrated with my next crap-o-cad:

    [​IMG]

    The little locking strip had been mashed into the nylon gear as the whole thing had slipped during the initial gear crash. This left the gear in a sort of egg-shape that kept placing un-necessary pressure on the next gear at one point during each revolution.

    As the last image says: bugger (a uniquely British way of saying 'dammit' without using unacceptable language)

    The next replacement gear is on order. It seems that the nylon ones will have to do until I can source some suitable metal replacements :(

    I feel that I have learned my lesson now from damaging an expensive piece of kit. Does that now officially make me an engineer? ;)
     
  5. Aug 1, 2014 #5

    BaronJ

    BaronJ

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    Hi,

    This is where I sourced my new gears from !
    I have nothing but praise for the people at HPC, The guys bent over backwards to make sure that I had the right gears to do the repair to mine. Its a different machine now. Not only is the finish better but the motor runs much cooler as well. Cost wise ignoring my time spent doing the repair, it worked out at less than half what I would have had to pay for replacement plastic gears.

    http://www.hpcgears.com/

    DISCLAIMER: I have no connection with HPC nor do I receive money from them. I'm just a very satisfied customer.
     
  6. Aug 2, 2014 #6

    velocette

    velocette

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    Hi
    A couple of web sites for the supply of X1 Mill Drill spares
    The first one I have used to obtain spares into New Zealand.
    Postage and handling a bit pricey but well worth it.

    http://littlemachineshop.com/products/product_view.php?ProductID=2249&category=1057823482

    http://www.arceurotrade.co.uk/Catalogue/Machine-Spares/X1-Mill-Spares

    The second one I know of only by reputation due to excellent report of their service on this and other forums.
    What about a "Poly Vee Belt" drive instead of noisy gears that sometimes break.
    Yes I am a "Poly Vee" fanatic machines all over my workshop have them fitted so I am totally biased.
    Had a quick look at the exploded drawing and if you got creative-destructive with the gearbox housing and built mounting for the motor on top of part No 21.
    With gears for the quill drive removed and a two or three step "Poly Vee" pulley fitted with a pulley fabricated and fitted to the motor.
    The motor pulley made from aluminum can be loctited to the shaft quick and dirty but totally effective. I did it with the first belt drive conversion on an X2 mill
    Just some random rambling to maybe set someone to have a go
    Eric

    View attachment X1Parts.pdf
     
    Last edited: Aug 2, 2014
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  7. Aug 3, 2014 #7

    Wizard69

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    This is important, plastic gears can be very durable given proper design and materials. In a mill they save on the need for lubrication which can't be ignored with cast iron or steel.
     
  8. Aug 3, 2014 #8

    Wizard69

    Wizard69

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    Poly Vee belts are just the nuts if you ask me, like you I often find myself recommending them. This especially in the case of a retro fit of old machinery.
    I will admit that finding Poly Vee pulleys is a pain. However they are easy to make, certainly easier than making gears, timing belt pulleys and the like. As for aluminum, that would certainly work but you could also make use of plastic to prototype or even in some cases as a runnable part.
     
  9. Aug 10, 2014 #9

    syrtismajor

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    All seems to be okay!

    I sourced my replacements from Arceurotrade as previously suggested. I have never dealt with them before but I must say that I was very impressed with their rapid response. I was also amazed by the wealth of their spare parts. Before purchasing the Seig I was advised against it as getting spares was quite tricky. It seems now that they were either:

    • A - Na├»ve
    • B - Biased
    • C - Not aware
    • D - Being annoying
    Anyway, the mill is up and running again and hopefully will not fail like this again. I also probably will not invest in new gears as I feel that they would not be cost effective as I can source spares so easily.
    All in all, many thanks you lot for the help and suggestions :D
     
  10. Aug 11, 2014 #10

    BaronJ

    BaronJ

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    At least you got it fixed.

    I thought that the manufacturers replacement gears for mine were expensive which is why I went the way that I did.
     
  11. Aug 31, 2014 #11

    kwoodhands

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    Instead of plastic gears have you seen the pulley and belt systems that LMS sells and some members have built themselves.The two step pulley is aluminum and the belt is a vee belt if I recall.
    I replaced my geared mill with the pulley and belt 5 years ago. So far I have replaced one belt and have had no problems.I run the mill in low . If I made this system for myself I would not bother with a two step pulley. One step for low speed is all I need.
    mike
     
  12. Sep 1, 2014 #12

    Alchymist

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    Believe that is the same as the Harbor Freight micro mill - 47158. Yep, the plastic gears are the weak link. First to go was the drive gear on the motor - stripped out the key. Next was the larger driven gear - both failures looked identical to the pics above. Now on it's second set of gears - and one new set in reserve. Little machine shop purchases.
     
  13. Sep 1, 2014 #13

    gus

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    If I may add on. The quality of the plastic gears from China is questionable. The Plastic Gears on my Japanese Sakai Mill is still good after last 8 years. Due to over-tight belt tension,the bearings gave way but this is after 8 years. The belt is a bit thin but still good.

    IMG_1475.jpg
     
  14. Sep 10, 2014 #14

    GVH

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    Hi...I agree 100% with both your Crap O CAD illustrations. The Key drive has been poorly designed/implemented. I have had the same experience..twice. I plan eventually to make a metal gear (Aluminium) for the motor drive gear, however, I needed to get my X1 running, so I increased the size of the key and inserted metal washers either side of the gear (the front one located in a counter-bore 3 mm deep into the gear). I joined the two washers together through the gear with two pins and filed a key way slot using the plastic gear slot has a guide. I also eliminated the rear cir-clip due to excessive play along the shaft, and inserted a nylon bush between the rear of gear and motor. This interim solution has been very successful, due to increasing the drive area of the key-way and the fact that the drive is going through metal (washers) as well has the plastic gear.

    I have kept the machine in low gear until I get around to resolving the design/implementation issue identified in your second Crap O CAD illustration.

    Geoff
     
  15. Sep 10, 2014 #15

    GVH

    GVH

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    Baron,

    Do you have the HPC Gear Part Numbers for the gears you replaced? If might adopt your solution.

    Geoff
     
  16. Oct 3, 2014 #16

    BaronJ

    BaronJ

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    Hi Geoff,
    Sorry for the late reply, I've not been in circulation for the past five weeks.
    I'll have to dig the invoice out to be able to give you those part numbers. Or it might be quicker to have a look at the web site on line catalog since your gears may be sightly different. You need to know the number of teeth, module and the diameter plus the thickness. HPC do the gears in plastic, aluminium and steel. One of mine was in stainless because that was the only stock gear that matched the adjoining one.

    Let me know if you want more info and I'll come back with those part numbers as soon as I can.
     
  17. Oct 4, 2014 #17

    millwizard

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    Littlemachineshop.com sells a v belt conversion for the mini mill. I have one on mine and works good and quiet. it a shame the machining quality is very poor on the ones from harbor freight. spindle is not perpendicular with the column.
     
  18. Oct 4, 2014 #18

    GVH

    GVH

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    Baron,

    Thanks for your response. The photo's you took had the gear part numbers on, so that info plus other details you mentioned will allow me to define gear if I go down that path.

    Regards

    Geoff
     
  19. Jun 1, 2019 #19

    Mickatroid

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    A big thanks to syrtismajor for his Crap-o-cad drawing. I found the same problem with my SX1. The gears don't mesh. It seemed so ridiculously bad in terms of design I was wondering if the problem could be something else. But no, they are misaligned by a wide margin for other people too. My solution to this problem is on my blog.

    I realise my first post in these forums is an act of thread necromancy. I don't have a habit of doing this I promise.
     

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