Hi,

I have a Tektronix 475A oscilloscope. All of the rotary knobs are fastened to their shafts in the radial direction with hex screws. My metric set of hex keys goes down to 1.5mm which is just a pinch too small so those are probably 1/16". All hex screws appear to be the same size except for the one in the "Delay time position" knob. This one is smaller. Could this one be 0.05"?

Some of the screws are not so hex anymore, as if they've seen too much abuse from metric keys that don't quite fit. I'd like to replace some or all of them. Does anyone know the exact designation of these screws, thread type etc?

I'm not so versed in US customary units and associated tools, threads etc. so any help would be appreciated.

 

In the spec section of my manual it shows Setscrew #5-40 x .125"
1/16th Allen-Key.
This is N.A . designation for the thread.
https://www.boltdepot.com/Product-Details.aspx?product=8435
Max.

 

They're mostly 1/16" hex on my 466. Time delay is smaller and I didn't have the correct size handy.

I checked some 7000 series plug-ins and the set screws are the same size, so you could used parts from donor plug-ins.

 

5-40 has become uncommon in regular hardware stores and big-box stores. 4-40 is much more common, but it cannot be substituted well. McMaster Carr in the US has them: http://www.mcmaster.com/#set-screws/=11eqmjw

Not sure whether it ships internationally.

John

 

5-40 has become uncommon in regular hardware stores and big-box stores. 4-40 is much more common, but it cannot be substituted well. McMaster Carr in the US has them: http://www.mcmaster.com/#set-screws/=11eqmjw

Not sure whether it ships internationally.

John

AFAIK: the grub screws on my 465 are fractional inch.

Metric keys will sometimes work if the screw isn't tight, but an improper fit causes wear - and you *REALLY* don't want that!

 

Excellent, thanks! It seems like the required Allen keys and set screws are available on Ebay and ship to me.

Metric keys will sometimes work if the screw isn't tight, but an improper fit causes wear - and you *REALLY* don't want that!

I think the previous owner(s) found that out too. But I can probably glue in a small rod with some loctite and get it out.

 

I confirmed it on my 'scope they are as in post #2.
Max.

 

Excellent, thanks! It seems like the required Allen keys and set screws are available on Ebay and ship to me.


I think the previous owner(s) found that out too. But I can probably glue in a small rod with some loctite and get it out.

Just make sure none of the glue runs into the thread!!!