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Author Topic: Broken vfo shaft repair question (FT-102)  (Read 10102 times)
NB1U
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Posts: 33




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« on: July 19, 2013, 01:27:53 PM »

Hello all,

I was given a Yaesu FT-102 that has a broken vfo tuning shaft.  It's snapped where it enters the tuning knob.  I would like to reattach the broken piece to the rest of the shaft and am looking for recommendations on how to repair this.  J-B Weld, super-glue, brazing, gum?  Other than the broken shaft the vfo seems to be working fine.  Thanks for your input...

73, Mark  NB1U
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KE4DRN
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Posts: 3714




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« Reply #1 on: July 19, 2013, 03:15:14 PM »

hi Mark,

J-B Weld it! 

Not a lot of surface area to work with, the super glues will hold for a while,
but the J-B will hold up a lot better.

You can try to apply some J-B with an artist brush to the area and also
on the outer surface of the shaft to cover the break.

73 james
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WB6DGN
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Posts: 590




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« Reply #2 on: July 20, 2013, 08:25:52 PM »

Well, I've always been accused of finding the most difficult way to accomplish anything so take this for what its worth.
If you can remove the entire shaft, I'd take it to a small machine ship and ask them to make you a replacement; then on to a plating shop to have it cad (if you're lucky) or iridite plated.
I never seem to have much luck with glues of any kind, try as I may to make them work and this would stand up better to the bumps and knocks of ham use.  BUT, it won't compare with a successful glue repair in terms of cost.
Just for what its worth.
Tom
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W8JX
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« Reply #3 on: July 20, 2013, 08:44:21 PM »

Hello all,

I was given a Yaesu FT-102 that has a broken vfo tuning shaft.  It's snapped where it enters the tuning knob.  I would like to reattach the broken piece to the rest of the shaft and am looking for recommendations on how to repair this.  J-B Weld, super-glue, brazing, gum?  Other than the broken shaft the vfo seems to be working fine.  Thanks for your input...

73, Mark  NB1U

If you can remove shaft so you can use a torch I would braze it and it will last forever. When fluxed and done right braze will flow into joint and you can file outside as needed. Braze has a yield strength of about 45000 psi, JB weld is 2500 or 5000 depending on fast or slow dry. When you consider the very small surface area of shaft face relative to a square inch JB weld would be very marginal.
« Last Edit: July 20, 2013, 08:48:18 PM by W8JX » Logged

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K5RT
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Posts: 126




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« Reply #4 on: July 21, 2013, 01:31:29 PM »

How did it get broken in the first place?
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NB1U
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Posts: 33




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« Reply #5 on: July 22, 2013, 07:26:15 PM »

Thanks for all the responses.  I think Plan A will be to try J-B Weld.  If that proves inadequate I may attempt to pull the shaft and have it brazed.  A replacement vfo may end up being the most cost and time-effective solution but we shall see. 
I was told the radio was dropped on the tuning knob which is consistent with scrapes and the fractured shaft.
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NB1U
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Posts: 33




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« Reply #6 on: July 25, 2013, 01:08:03 PM »

Ok. On to Plan B.  W8JX called it correctly.  The second I attached the tuning knob to the repaired shaft it came apart.  I spoke with a friend of mine (auto mechanic) and he thinks he can fix it.  Will let you all know...
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KE3WD
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« Reply #7 on: July 25, 2013, 03:10:43 PM »

Broken shafts respond very well to an old machinist's trick called, "spin welding"...

A savvy machinist with a metal lathe should know what I'm talking about.  

But really.  I would be looking for someone parting out the same rig and still has the needed part for sale. 


73
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W8JX
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« Reply #8 on: July 25, 2013, 03:47:34 PM »

I have repaired a few obsolete parts with brazing over years and it is quite strong. I once brazed a broken cast iron 3 point hitch lift link on a old tractor and it surprised me that it held fine for many years until i got rid of tractor
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KE3WD
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« Reply #9 on: July 26, 2013, 07:15:01 AM »

The thing about brazing this shaft is that one would have to first come up with a jig to hold both pieces in perfect alignment. 

Spin welding in a lathe, the alignment issue is avoided entirely. 
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K8AXW
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« Reply #10 on: July 27, 2013, 09:16:26 AM »

I had to Google "spin welding" and learned that this was spinning a PLASTIC type material in a lathe or drill. press and using friction heat to fuse the two ends together.

Then some are suggesting "brazing" which is used for certain types of metal.  Someone please explain.

If the spin welding is an option, which means the shaft must be removed, why not just have a new one fabricated?i
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KE3WD
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« Reply #11 on: July 27, 2013, 04:25:40 PM »

I have personally used spin welding on Stainless Steels, Carbon Steels, etc. 

Here's a youtube showing the spin welding of a steel banjo axle for a truck: 

https://www.youtube.com/watch?v=-NIVUnk2kyw

Of course, for this size shaft we are talking about here, a small lathe or even a drill press could be used, but you are correct in that whatever is attached to the back of this shaft *may* have to be removed.  But maybe not.  If you could hold the rear portion stationary, you would only have to spin the broken off shaft part against it. 

But I wouldn't bother in this case, as I said up there earlier, surely there are some F-102 Hangar Queen Parts Monsters around and the first thing I'd try to do in this situation would be to purchase an existing and working control for the rig. 


73
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W8JX
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« Reply #12 on: July 29, 2013, 09:27:46 PM »

The thing about brazing this shaft is that one would have to first come up with a jig to hold both pieces in perfect alignment. 

Spin welding in a lathe, the alignment issue is avoided entirely. 

It is not that hard because braze flows into cracks and weld does not. Also welding warps metal and will cause it to go out of alignment required a spin weld setup to hold it in alignment. Braze does not warp metal and if alignment is not perfect merely reheat and reflow as base metal is undamaged. With a weld if you screw up part is toast.
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K8AXW
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« Reply #13 on: July 30, 2013, 09:49:30 AM »

WD:  Thanks for the link.  This one is new to me. 
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K5LXP
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« Reply #14 on: July 30, 2013, 12:47:33 PM »

Given the complexity and practical limitations of the aforementioned methods (spin welding?!?) I would offer that if there's enough remaining shaft sticking out of the radio, to simply epoxy a metal tubing/sleeve to it and duplicating the original length of the shaft.  Then drill out the knob a few thousands to accommodate the thicker OD of the tubing, place it on the tube and call it done.


Mark K5LXP
Albuquerque, NM

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