Topics

Tek Knob Project - scan and make


Kuba Ober
 

Two things came to my mind in relation to the tek knobs index project:

1. Instead of taking just a few photos, a larger number properly exposed photos that cover the entire part from all sides could be used to produce a point cloud and then a 3D-printable mesh. I can cover the subscription cost of the software needed - it’s not exactly cheap.

Alternatively, manual measurements could be made for OpenSCad models - I’m sure that a lot of those knobs are slight variants and easy to model.

I can offer to process 25 knobs a month using either process, resulting in a printable STL file. Over a year or two presumably we could have reproducible models of all knobs that way. Perhaps sorting the work in order of popularity/demand would be useful.

I have 0 clue about such order and would follow whatever input the group has - as long as I wouldn’t have to decide on it. In other words: send me the knobs to process and I will process them and ship them back, but don’t make me choose them :)

2. Homemade 3D prints in ABS can be vapor smoothed and look beautiful with no other manual post-processing of the print. They can also be painted.

Alternatively, various professional printing services can print those knobs nicely from various materials, for a low cost: the knobs have small volume and that’s what mostly affects the price.


Should this be of interest, feel free to message me directly for a shipping address. I will turn around 25 knobs in 30 calendar days and will cover the cost of shipping them back.

All the best, Kuba


 

A small problem with this plan is the interior of the knob, which is a METAL (aluminum) core, threaded for one or more steel setscrews. I am certain an all-plastic version would not work.

regards,
walter


Kuba Ober
 

A polycarbonate or graphene-infused PLA insert would probably work, and instead of a clearance fit a tighter friction fit would be called for. I’m of the mind that given the low cost of replacements, a friction fit is all that’s needed. A drop of ABS juice/glue is all that’s needed to retain a knob worn out from multiple removals. Or just print a new one, they would be a few bucks each from a print service, or a dime or two when printed on your own printer.

Another idea that I’ve tried and was working OK is to have a locking sleeve where the knob has two parts, top part having a tapered slotted sleeve that fits the shaft, and the bottom part having a conical seat that compresses the sleeve. A snap latch interlocks these two, unfortunately for small knobs it’d be a single use part that has to be destroyed for servicing.

Another option is, instead of a permanent latch, to have the bottom part do a twist-lock on the top part. This would allow for a few reassembles before it wears out to require replacement. That may be hard on the smallest of knobs. Probably the smallest knob this would work on is something like the 7000 plugin freestanding adjust knobs like hor/vert offset, trigger level, etc. It’d also need a slow print at 0.1mm or even 0.05mm layer height with a 0.1 or 0.2 nozzle. Regular friction fit knobs work OK printed with a 0.4 nozzle.

The biggest deal would be to have the 3D models of existing parts and then the design of replacements is a separate and a much more limited task and can be easily applied to all the parts of a given class at once.


keantoken
 

I might send you my miraculously unbroken FG504 freq stop knob. It's mechanical design is obviously flawed. What saved it is probably the fact that the motion stop, which normally puts pressure on the knob's weak points, has rounded over and ceases to function. So the varistor reaches the end of it's travel instead.

On Tuesday, December 19, 2017, 1:41:07 PM CST, Kuba Ober <kuba@...> wrote:

A polycarbonate or graphene-infused PLA insert would probably work, and instead of a clearance fit a tighter friction fit would be called for. I’m of the mind that given the low cost of replacements, a friction fit is all that’s needed. A drop of ABS juice/glue is all that’s needed to retain a knob worn out from multiple removals. Or just print a new one, they would be a few bucks each from a print service, or a dime or two when printed on your own printer.

Another idea that I’ve tried and was working OK is to have a locking sleeve where the knob has two parts, top part having a tapered slotted sleeve that fits the shaft, and the bottom part having a conical seat that compresses the sleeve. A snap latch interlocks these two, unfortunately for small knobs it’d be a single use part that has to be destroyed for servicing.

Another option is, instead of a permanent latch, to have the bottom part do a twist-lock on the top part. This would allow for a few reassembles before it wears out to require replacement. That may be hard on the smallest of knobs. Probably the smallest knob this would work on is something like the 7000 plugin freestanding adjust knobs like hor/vert offset, trigger level, etc. It’d also need a slow print at 0.1mm or even 0.05mm layer height with a 0.1 or 0.2 nozzle. Regular friction fit knobs work OK printed with a 0.4 nozzle.

The biggest deal would be to have the 3D models of existing parts and then the design of replacements is a separate and a much more limited task and can be easily applied to all the parts of a given class at once.


Phillip Potter
 

I have seen many many posts on this thread AND NOW I KNOW WHY!! ;-)

I was working with my (new to me) 7603 with 18 and 18A plugins, when ALL OF A SUDDEN, the vertical range selector knob BROKE IN HALF... HUH!  Upon close observation, I find that the knobs on my 18 (and my 18A!) have been re-glued, some more than once!  So, out came the juice/solvent/glue bottle and now there is a knob laying on the bench glued and wrapped; hoping for a better day.

Of course, I went to "sphere.bc.ca/test/tek-parts/tek-knobs.html" to find some replacements... only to find the vertical range selector knobs are out of stock, BUT when they were in stock they were $10.00 each!  Whoa...

Thank you to those members who are actively searching for a method of manufacturing replacement knobs!  I now understand the push to get something working... I wish I could help, but I am really out of my element when it comes to creation of things.  Breaking them is probably the only thing I am good at, these days.

What would you say if I have an urge to put some lube into the switch assemblies in my plugins, to lower the torque needed to turn them? Thoughts?

Thanks for listening,
Phil


keantoken
 

If you look at intact knobs, they usually have a hairline crack on one side. They will survive a long time this way as the crack releases stress in the part. But I suspect the plastic in the knobs has shrunk over time against the aluminum inserts, causing them to eventually break.

On Tuesday, December 19, 2017, 9:31:00 PM CST, Phillip Potter <p.potter@...> wrote:

I have seen many many posts on this thread AND NOW I KNOW WHY!! ;-)

I was working with my (new to me) 7603 with 18 and 18A plugins, when ALL
OF A SUDDEN, the vertical range selector knob BROKE IN HALF... HUH! 
Upon close observation, I find that the knobs on my 18 (and my 18A!)
have been re-glued, some more than once!  So, out came the
juice/solvent/glue bottle and now there is a knob laying on the bench
glued and wrapped; hoping for a better day.

Of course, I went to "sphere.bc.ca/test/tek-parts/tek-knobs.html" to
find some replacements... only to find the vertical range selector knobs
are out of stock, BUT when they were in stock they were $10.00 each! 
Whoa...

Thank you to those members who are actively searching for a method of
manufacturing replacement knobs!  I now understand the push to get
something working... I wish I could help, but I am really out of my
element when it comes to creation of things.  Breaking them is probably
the only thing I am good at, these days.

What would you say if I have an urge to put some lube into the switch
assemblies in my plugins, to lower the torque needed to turn them? Thoughts?

Thanks for listening,
Phil


Phillip Potter
 

Hi Anthony,

Yep, that is in evidence! I squeezed them as tightly as I could and applied the juice, in an attempt to shore them up, but I am not optimistic that they will last very long. The ones that had been previously re-glued were a mess and I just put the juice over the top of the former botched job.

Thanks for the reply.

Phil

On 12/19/2017 7:36 PM, Anthony via Groups.Io wrote:
If you look at intact knobs, they usually have a hairline crack on one side. They will survive a long time this way as the crack releases stress in the part. But I suspect the plastic in the knobs has shrunk over time against the aluminum inserts, causing them to eventually break.


stefan_trethan
 

The following notion might be distressing to some members, reader
discretion is advised:

If all else fails you can just use standard knobs in many cases.
I replaced the upper three knobs on an AM502 with different black ones
and it doesn't look all that bad.
You can even make stacked knobs by drilling through the larger one.

By replacing all three that were a similar design it isn't as obvious
that they are not original.
I can provide a photo, for your amusement.

ST


Phillip Potter
 

Hi Stefan,

I would be interested in your pictures, but... maybe we should take this off-list, so as not to offend; LOL!  I would like to see how you did it, but I have my doubts about my skills with reworking, since I do not have a drill press, or a vice.  I tend to be a purist but not a prude, and not easily offended.

Thanks for thinking of my amusement, however, that's very kind of you in this Holiday Season! ;)

Phil

I can provide a photo, for your amusement.

ST


Michael A. Terrell
 

Is anyone in the group near Orlando, Florida? Skycraft used to have bins full of used knobs from the test equipment that they scrapped for gold.

They also had some handles and rack mounts for HP equipment. I used to buy up all they had when I went there for parts. I was working in Orlando as a Broadcast Engineer at that time, so I went there and to the other surplus shops quite often.

I haven't been there in over a decade, and I doubt that I'll ever make that long trip just to look for knobs.

-----Original Message-----
From: stefan_trethan <stefan_trethan@...>
Sent: Dec 19, 2017 10:51 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek Knob Project - scan and make

The following notion might be distressing to some members, reader
discretion is advised:

If all else fails you can just use standard knobs in many cases.
I replaced the upper three knobs on an AM502 with different black ones
and it doesn't look all that bad.
You can even make stacked knobs by drilling through the larger one.

By replacing all three that were a similar design it isn't as obvious
that they are not original.
I can provide a photo, for your amusement.

ST



Michael A. Terrell


Chuck Harris
 

Fundamentally, the problem is the plastic shrinks over
time, but the aluminum insert doesn't. When the plastic
has shrunken enough, it cracks.

What to do...

Well, the answer is very simple. You must make the hole
for the insert a tiny little bit bigger.

Here's how...

Put the knob back together and wrap it with a small
rubber band... snug's good, not killer tight... spread
the wraps over the whole knob. Then, using a soldering
iron, apply heat to the shaft hole in the aluminum insert
in short intervals... 1 second heat, 5 seconds watch...
until you see the rubber band start to shrink the knob
back into shape, and then quickly cool the insert with
compressed air. When it starts, it goes quickly, and if
you let it get too hot, all of the knob's plastic will
melt, and the rubber band will distort the knob.

Now, the cracks will be just hairlines, and can be easily
fixed using a solvent glue, such as methylene chloride.

Don't use crazy glue, duco, silicone seal, epoxy... You
will just make a mess.

-Chuck Harris (who has done this lots of times)

Phillip Potter wrote:

Hi Anthony,

Yep, that is in evidence! I squeezed them as tightly as I could and applied the
juice, in an attempt to shore them up, but I am not optimistic that they will last
very long. The ones that had been previously re-glued were a mess and I just put the
juice over the top of the former botched job.

Thanks for the reply.

Phil


On 12/19/2017 7:36 PM, Anthony via Groups.Io wrote:
If you look at intact knobs, they usually have a hairline crack on one side. They
will survive a long time this way as the crack releases stress in the part. But I
suspect the plastic in the knobs has shrunk over time against the aluminum inserts,
causing them to eventually break.


Michael A. Terrell
 

Has anyone tried the UV cure glue that is being advertised? I bought a package of the glue and the UV LED device from Bondic, but I haven't used it yet.

-----Original Message-----
From: Phillip Potter <p.potter@...>
Sent: Dec 19, 2017 11:08 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek Knob Project - scan and make

Hi Stefan,

I would be interested in your pictures, but... maybe we should take this
off-list, so as not to offend; LOL!  I would like to see how you did it,
but I have my doubts about my skills with reworking, since I do not have
a drill press, or a vice.  I tend to be a purist but not a prude, and
not easily offended.

Thanks for thinking of my amusement, however, that's very kind of you in
this Holiday Season! ;)

Phil


I can provide a photo, for your amusement.

ST



Michael A. Terrell


Phillip Potter
 

Wow... thanks for this!  Hope springs eternal!

Phil

On 12/19/2017 8:13 PM, Chuck Harris wrote:
Fundamentally, the problem is the plastic shrinks over
time, but the aluminum insert doesn't. When the plastic
has shrunken enough, it cracks.

What to do...

Well, the answer is very simple. You must make the hole
for the insert a tiny little bit bigger.

Here's how...

Put the knob back together and wrap it with a small
rubber band... snug's good, not killer tight... spread
the wraps over the whole knob. Then, using a soldering
iron, apply heat to the shaft hole in the aluminum insert
in short intervals... 1 second heat, 5 seconds watch...
until you see the rubber band start to shrink the knob
back into shape, and then quickly cool the insert with
compressed air. When it starts, it goes quickly, and if
you let it get too hot, all of the knob's plastic will
melt, and the rubber band will distort the knob.

Now, the cracks will be just hairlines, and can be easily
fixed using a solvent glue, such as methylene chloride.

Don't use crazy glue, duco, silicone seal, epoxy... You
will just make a mess.

-Chuck Harris (who has done this lots of times)

Phillip Potter wrote:
Hi Anthony,

Yep, that is in evidence! I squeezed them as tightly as I could and applied the
juice, in an attempt to shore them up, but I am not optimistic that they will last
very long. The ones that had been previously re-glued were a mess and I just put the
juice over the top of the former botched job.

Thanks for the reply.

Phil


On 12/19/2017 7:36 PM, Anthony via Groups.Io wrote:
If you look at intact knobs, they usually have a hairline crack on one side. They
will survive a long time this way as the crack releases stress in the part. But I
suspect the plastic in the knobs has shrunk over time against the aluminum inserts,
causing them to eventually break.


Vince Vielhaber
 

Not all it's cracked up to be. It falls apart with the slightest amount of heat. I keep some around and use it, but only to glue something long enough to make a mold out of it and pour a new one.

Vince.

On 12/19/2017 11:15 PM, Michael A. Terrell wrote:
Has anyone tried the UV cure glue that is being advertised? I bought a package of the glue and the UV LED device from Bondic, but I haven't used it yet.

-----Original Message-----
From: Phillip Potter <p.potter@...>
Sent: Dec 19, 2017 11:08 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek Knob Project - scan and make

Hi Stefan,

I would be interested in your pictures, but... maybe we should take this
off-list, so as not to offend; LOL! I would like to see how you did it,
but I have my doubts about my skills with reworking, since I do not have
a drill press, or a vice. I tend to be a purist but not a prude, and
not easily offended.

Thanks for thinking of my amusement, however, that's very kind of you in
this Holiday Season! ;)

Phil


I can provide a photo, for your amusement.

ST



Michael A. Terrell


stefan_trethan
 

Not on knobs, but I wasn't too impressed since the UV seems to have a
hard time penetrating the glue itself.
I prefer Epoxy and CA glue over the UV stuff.

ST

On Wed, Dec 20, 2017 at 5:15 AM, Michael A. Terrell
<mike.terrell@...> wrote:
Has anyone tried the UV cure glue that is being advertised? I bought a package of the glue and the UV LED device from Bondic, but I haven't used it yet.

-----Original Message-----
From: Phillip Potter <p.potter@...>
Sent: Dec 19, 2017 11:08 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek Knob Project - scan and make

Hi Stefan,

I would be interested in your pictures, but... maybe we should take this
off-list, so as not to offend; LOL! I would like to see how you did it,
but I have my doubts about my skills with reworking, since I do not have
a drill press, or a vice. I tend to be a purist but not a prude, and
not easily offended.

Thanks for thinking of my amusement, however, that's very kind of you in
this Holiday Season! ;)

Phil


I can provide a photo, for your amusement.

ST



Michael A. Terrell



keantoken
 

It isn't advisable to try and force the knob back together before gluing because it has already shrunk even more after breaking and the stresses required to force it back to the original size, assuming you are successful, will for sure just cause it to crack somewhere else again. So I would either use the heat method Chuck described, or just leave the crack as it is and fill it with a suitable adhesive. On Tuesday, December 19, 2017, 9:46:24 PM CST, Phillip Potter <p.potter@...> wrote:

Hi Anthony,

Yep, that is in evidence! I squeezed them as tightly as I could and
applied the juice, in an attempt to shore them up, but I am not
optimistic that they will last very long. The ones that had been
previously re-glued were a mess and I just put the juice over the top of
the former botched job.

Thanks for the reply.

Phil

On 12/19/2017 7:36 PM, Anthony via Groups.Io wrote:
  If you look at intact knobs, they usually have a hairline crack on one side. They will survive a long time this way as the crack releases stress in the part. But I suspect the plastic in the knobs has shrunk over time against the aluminum inserts, causing them to eventually break.


Michael A. Terrell
 

Thanks for the bad news. I was hoping that it would be strong enough to repair the handle on a Fluke DVM. :(

-----Original Message-----
From: Vince Vielhaber <vev@...>
Sent: Dec 19, 2017 11:22 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek Knob Project - scan and make

Not all it's cracked up to be. It falls apart with the slightest amount
of heat. I keep some around and use it, but only to glue something long
enough to make a mold out of it and pour a new one.

Vince.



On 12/19/2017 11:15 PM, Michael A. Terrell wrote:
Has anyone tried the UV cure glue that is being advertised? I bought a package of the glue and the UV LED device from Bondic, but I haven't used it yet.

-----Original Message-----
From: Phillip Potter <p.potter@...>
Sent: Dec 19, 2017 11:08 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek Knob Project - scan and make

Hi Stefan,

I would be interested in your pictures, but... maybe we should take this
off-list, so as not to offend; LOL! I would like to see how you did it,
but I have my doubts about my skills with reworking, since I do not have
a drill press, or a vice. I tend to be a purist but not a prude, and
not easily offended.

Thanks for thinking of my amusement, however, that's very kind of you in
this Holiday Season! ;)

Phil


I can provide a photo, for your amusement.

ST



Michael A. Terrell


--
Michigan VHF Corp. http://www.nobucks.net/ http://www.CDupe.com/
http://www.metalworkingfun.com



Michael A. Terrell


stefan_trethan
 

I've sanded either the plastic or more likely the aluminium to make it
close up (don't recall).
Worked OK, even for the gears in the 7A13. I used epoxy to stick it
all back together and fill any gaps.
The heat method is more clever, no need to pull the plastic off which
can cause damage.

ST

On Wed, Dec 20, 2017 at 5:28 AM, Anthony via Groups.Io
<keantoken=yahoo.com@groups.io> wrote:
It isn't advisable to try and force the knob back together before gluing because it has already shrunk even more after breaking and the stresses required to force it back to the original size, assuming you are successful, will for sure just cause it to crack somewhere else again. So I would either use the heat method Chuck described, or just leave the crack as it is and fill it with a suitable adhesive. On Tuesday, December 19, 2017, 9:46:24 PM CST, Phillip Potter <p.potter@...> wrote:

Hi Anthony,

Yep, that is in evidence! I squeezed them as tightly as I could and
applied the juice, in an attempt to shore them up, but I am not
optimistic that they will last very long. The ones that had been
previously re-glued were a mess and I just put the juice over the top of
the former botched job.

Thanks for the reply.

Phil


On 12/19/2017 7:36 PM, Anthony via Groups.Io wrote:
If you look at intact knobs, they usually have a hairline crack on one side. They will survive a long time this way as the crack releases stress in the part. But I suspect the plastic in the knobs has shrunk over time against the aluminum inserts, causing them to eventually break.






Dave Seiter
 

That would be an interesting project.  I have a Type W plugin that has a split white DC balance knob.  IIRC, this is a common problem. I believe there is a similar knob used elsewhere that has the same problem.  They should be simple objects to print, but the set screws are really small and I don't have a hex key that will fit. (It's smaller than .05", which is usually the smallest you see on Tek gear).  I was also wondering if it would be possible to print the 7K series backplane connector covers.
I haven't tried printing with ABS yet, although my printer is capable of it.
-Dave

-------------------2. Homemade 3D prints in ABS can be vapor smoothed and look beautiful with no other manual post-processing of the print. They can also be painted.

Alternatively, various professional printing services can print those knobs nicely from various materials, for a low cost: the knobs have small volume and that’s what mostly affects the price.


Dave Seiter
 

That's a great method for repairing knobs!
-Dave

From: Chuck Harris <cfharris@...>
To: TekScopes@groups.io
Sent: Tuesday, December 19, 2017 8:13 PM
Subject: Re: [TekScopes] Tek Knob Project - scan and make

Fundamentally, the problem is the plastic shrinks over
time, but the aluminum insert doesn't.  When the plastic
has shrunken enough, it cracks.

What to do...

Well, the answer is very simple.  You must make the hole
for the insert a tiny little bit bigger.

Here's how...

Put the knob back together and wrap it with a small
rubber band... snug's good, not killer tight... spread
the wraps over the whole knob. Then, using a soldering
iron, apply heat to the shaft hole in the aluminum insert
in short intervals... 1 second heat, 5 seconds watch...
until you see the rubber band start to shrink the knob
back into shape, and then quickly cool the insert with
compressed air.  When it starts, it goes quickly, and if
you let it get too hot, all of the knob's plastic will
melt, and the rubber band will distort the knob.

Now, the cracks will be just hairlines, and can be easily
fixed using a solvent glue, such as methylene chloride.

Don't use crazy glue, duco, silicone seal, epoxy...  You
will just make a mess.

-Chuck Harris (who has done this lots of times)

Phillip Potter wrote:
Hi Anthony,

Yep, that is in evidence! I squeezed them as tightly as I could and applied the
juice, in an attempt to shore them up, but I am not optimistic that they will last
very long. The ones that had been previously re-glued were a mess and I just put the
juice over the top of the former botched job.

Thanks for the reply.

Phil


On 12/19/2017 7:36 PM, Anthony via Groups.Io wrote:
  If you look at intact knobs, they usually have a hairline crack on one side. They
will survive a long time this way as the crack releases stress in the part. But I
suspect the plastic in the knobs has shrunk over time against the aluminum inserts,
causing them to eventually break.