HP scopes knobs removing

[DmitryL]

Hello, everyone.

I scored recently more or less working HP1740A scope. Need to clean it, replace some failed tantalum electrolytics, etc.
The problem is that I need to remove knobs from the front panel. What screwdriver size should I use for this ?
I tried gently Torx T4, it looks a bit too small and screw grubs have hex. holes.
I think that Tek scopes have the same grubs.
Any ideas ?

[Fank1]

They are probably "ALLEN" so you need a set of ALLEN Wrenches.
Some military stuff used spline sockets, but probably not this.

[nctnico]

On my HP gear I used a 0.05" allen key.
I got a set like this from Ebay: http://www.ebay.com/itm/197-Hex-Key-Allen-Key-Set-S-A-E-0-028-to-7-64-Blue-/200940134343

[calmtron]

I have a HP1742A scope that I have restored. It uses fractional-inch-sized allen set screws as nctnico says, 0.05" and one other size that I can't remember.
Some of the screws on my scope was completely stuck - ruined two different sets of allen keys before shelling out for some Bondhus ones that managed to take the punishment and get most of the screws loose. Had to drill out the last screw though.

[Stray Electron]

  Keep in mind that some people use TWO allen screws per hole.  The second one helps prevent the first one from loosening up and the knob or other part from slipping or falling of of the shaft. Remove the first allen set screw and if the knob doesn't loosen up then check for a second set screw in the same hole. Many knobs also uses two set screws but in two holes that are 90d apart.

   HP uses several sizes of allen screws depending on the size of the knobs. 1/16" is common as is .050" but I have seen them down to 0.020".

[DmitryL]

Thanks for the reply.
Does anyone know how to unscrew some really stubborn grubs ? Yes, I used WD-40, put a few drops and left it for a day or two.
I may try heating these screws with soldering iron, maybe thermocycling help, but I'm not sure.

[nctnico]

What do you mean 'stubborn'? Just buy a good quality allen key and use (the) force.

[DmitryL]

What do you mean 'stubborn'? Just buy a good quality allen key and use (the) force.

"Stubborn screws" here means that:
- they got stuck
- someone already worked on them before me and inner hex slot has become bigger, so that allen key simply doesn't have good grip

I found a way and removed all these screw grubs, maybe that will help someone. To do this:

1. find am appropriate TORX screw driver, its tips is conical and has sharp edges.
2. grind the end of the tip, so it becomes thicker and shorter until it can hardly get into the inner hex hole of the screw.
3. _force_ this screw driver into the hole, its edges will cut into the hex slot
4. turn it, applying pressure to the screw driver, trying not to  break the knob
5. enjoy

[Kilgore]

Sometimes left-handed drill bits help, but you will need a set with small sizes.

http://www.harborfreight.com/13-piece-left-hand-drill-bit-set-95146.html

[tggzzz]

1. find am appropriate TORX screw driver, its tips is conical and has sharp edges.
2. grind the end of the tip, so it becomes thicker and shorter until it can hardly get into the inner hex hole of the screw.
3. _force_ this screw driver into the hole, its edges will cut into the hex slot
4. turn it, applying pressure to the screw driver, trying not to  break the knob
5. enjoy

I'm having the same problem as you.

Not knowing anything about TORX screwdrivers, do you have any information about the size you (started with and) used?

I think "5." is unlikely

Thanks.

[alex.forencich]

  Keep in mind that some people use TWO allen screws per hole.  The second one helps prevent the first one from loosening up and the knob or other part from slipping or falling of of the shaft. Remove the first allen set screw and if the knob doesn't loosen up then check for a second set screw in the same hole. Many knobs also uses two set screws but in two holes that are 90d apart.

   HP uses several sizes of allen screws depending on the size of the knobs. 1/16" is common as is .050" but I have seen them down to 0.020".

We got a new Thorlabs Nanomax positioning stage a few months ago.  The stop set screws are set up like this - long one for the stop, short one behind it to keep it from backing out.  Except some dolt put THREE set screws in one of the axes.  When we installed the micrometers, the axis didn't move because the linkage was pushed in farther than the travel on the micrometer.  Took a while to figure that one out, but at least we didn't have to send the stage back.