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Thread: fancy mower repair.
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30th May 2020, 06:28 PM #1Most Valued Member
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fancy mower repair.
hi every one. A MAte has this damaged reel he would like repaired.
97303671_1385008615219973_7415523441865916416_o.jpg
A woodruff key fits in the damaged slot. I think the reel is driven via the woodrufff key buy a chain sprocket.
I was thinking just cut a new key slot for key on the other side of shaft with a woodruff cutter. maybe clean up the
shaft with lathe or file.
do you think id get away with this with out repairing the damage by building up shaft??
thanks
aaron
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30th May 2020, 06:36 PM #2Most Valued Member
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the drive cog and type of mower photos.
95810726_1080080939044649_684714565480480768_n.jpg96794237_256461799064119_257341289186459648_n.png
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30th May 2020, 06:58 PM #3Mechanical Butcher
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Some weld of the damaged keyway might help strengthen the shaft, which could be weakened by more milling.
The shaft needs to be removed anyway, so cleaning up the weld on a lathe is little extra work.
It might work even if it wasn't repaired, but I suppose it would be more inconvenient if the shaft end broke off.
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30th May 2020, 07:32 PM #4Most Valued Member
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I thought while its apart fix it . A replacement reel i believe is $350.
I hadnt thought of removing the shaft from the reel. that would make it easier to mount for milling.
Ill have to think about that when i see it for reel.
I just thought id hold one end on a 3 jaw then support the damaged end with tail stock.
Plus i havnt built up shaft with an arc welder before. Shouldnt be to much drama but is it worth the effort.
reel photo.
100738889_202104080809855_2558294838910910464_n.jpg
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31st May 2020, 12:10 AM #5
azzrock,
Great looking mower. The Brisbane City Council used them to mow the footpaths when I was a kid in the late 1950's.
They cut beautifully.
A heads up,should you opt for welding. Don't weld the shaft circumferentially .Its possible that the stress created by the weld as it shrinks can create a shear fault.
Although the load upon it will not be heavy there's always the chance of fracture when the welded this way. I only mention this as I have seen a 125mm (5") steam turbine spindle shear off because of this very reason.
Undercut with the lathe or grind a groove to take out the corners of the key pocket. Reduces slag trap that occur in squared corner.
I guessing the diameter there is around 20mm so stick with 3.25mm electrodes. That way there are fewer electrodes creating less overall heat input and less chance of distortion problems. If I viewed the illustration correctly there no a lot of shaft overhang, so little or no problems with distortion at that point.
To further minimise distortion weld opposite beads as in:
12 o'clock then 6 o'clock
then
9 o'clock then 3 o'clock
back to, beside 12 o'clock then beside 3 o'clock
and follow the pattern. It balances out the distortion forces. Essentially it is welding beads opposites against opposites.
A trick I have also used is to use a marker further up the shaft to mark 12 ,6, 9 and 3 ock's so I don't lose track of what ock I am working on and weld out of sequence.
If I have forgotten something the other guys will chime in, hopefully.
Grahame
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31st May 2020, 12:43 AM #6Most Valued Member
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Another option. I had a 4 cylinder car crankshaft, that the harmonic bolt disappeared from, allowing the drive gear to rock back and forth, wearing the woodruff key slot in the crankshaft. A friend of mine whose brother runs a engine reconditioning shop, cut the keyway wider and made a stepped key for it.
KrynTo grow old is mandatory, growing up is optional.
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31st May 2020, 01:20 AM #7Most Valued Member
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Hi Grahame and Kryn.
thanks for your input.
Grahame so weld along the shaft . ok good tip . Im not sure what you mean by undercut. Is that machine out the damaged part of shaft?
what sort of electrodes would be best?
Kryn good tip as well i suppose ill deside when i have the reel in my hand.
thanks again
aaron
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2nd Jun 2020, 09:34 AM #8
Hi Azzrock
Yes machine out the damaged or corroded bits.
The term undercut was used by the fitters and turners I worked with when a shaft was cut or turned below its original diameter.
The required weld deposit was placed in the undercut.
I found a diagram that wil help
follow this link
https://www.yourarticlelibrary.com/m...-diagram/83389
Electrodes definitely 3.2mm and preferably 6013 but 6012s will do. So long as there are no inclusions a bit of a rough ripple pattern means nothing if its going to be machined.
To get the needed build up height you overlap 2/3rds over the last bead.You want to avoid any valleys between the laid down beads.
Its easy to machine off but a real PITA to remove from the lathe, reweld and place back in in the lathe and center..
Always aim to over weld by a slight margin. This was explained to me by irate fitter and turners when I had failed to reach the overbuild height and they ended up machining thin air. Grumpy sods!
Grahame
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2nd Jun 2020, 10:40 AM #9Pink 10EE owner
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I would not replace it with a woodruff key. I think industry used them in the past because they were cheaper to cut then a featherway key. But woodruff keys weaken the shaft and each one needs a special cutter.
Gold, the colour of choice for the discerning person.
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6th Jun 2020, 12:16 AM #10Most Valued Member
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7th Jun 2020, 12:17 AM #11Most Valued Member
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hi Grahame,
thanks Great info.
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9th Jun 2020, 09:37 PM #12Most Valued Member
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Grahame.
Would you recommend any sort of preheat/post extended cool down on a shaft that size?
I have a potential similar repair on my lathe, if I cant clean up the keyway and make a stepped key.
thanks
Peter
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9th Jun 2020, 10:20 PM #13
Hi Peter, Guys,
I don't think pre-heating the shaft will make a lot of difference, its going to get very hot anyway when you weld it. I would just clean it well and get on with filling the cavity. Machine it back to true and put a feather key in there.Best Regards:
Baron J.
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9th Jun 2020, 11:52 PM #14
Well I have learnt something. 2 things
1) All this mention of feather keys left me wondering what they are. Woodruff keys I had met, and crawled after on the workshop floor.
Found this document. http://www.ondrivesus.com/documents/...ather-keys.pdf
2) Graeme's guidance on building up a shaft by welding to avoid creating cracks
Thank you 👍cheers
David
------------------------------------------------
A society grows great when old men plant trees whose shade they’ll never sit in. (Greek proverb)
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10th Jun 2020, 03:02 AM #15Most Valued Member
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hi havinago
thanks for the link.an interesting read.
the guys on here are great when you ask what they think.
aaron
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