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I've got a couple scopes and plug-ins that are missing the knurled thumb nuts from some of their ground binding posts, and I've been searching for replacements for a few months.

The binding post is a 1/4-28 thread, and the nuts are about 3/8 inch outer diameter, and 3/8 inch tall (there are shorter nuts for some TM500 and 5000-series plug-ins that are only 1/4 inch tall, but those are not the ones I'm interested in).

I've found one reasonable replacement (not a good cosmetic match, but very close to the same size, and still looks pretty good on the instrument). It's an "internal wrenching allen nut, 1/4-28" and there are a few for sale on eBay (I am not affiliated with the seller), but I'm sure you can probably find these from regular distributors (e.g. Fastnell) with the proper specs in hand.

I'm also looking at some 1/4-28 threaded brass inserts as possible replacements, but those have not arrived yet (taking, as they say, a slow boat from China). I will report on their suitability when they arrive.

-- Jeff Dutky

Jeff:

The threaded brass inserts you mention work fine on all my Tek plug-ins here: Chinese brass inserts 1/4-28 x 7.5mm. They are easily tightened down by hand and lock down snugly.

Now, the colour does not match the original part, but I think a close approximation could be accomplished with an appropriate rattle-can paint and bake process.

Shaun M

Greetings,

FWIW explore McMaster Carr.

Couldn’t hurt.

Ken

Unfortunately, McMaster Carr chooses not to do business with individuals in Canada so we northerners must look elsewhere. Interestingly enough, I ordered from them when working for a large company in Canada, but cannot do so now having left the organization.
That said, our American friends can certainly use McMaster Carr.

Shaun M

Shaun,

I'm not too concerned about the color, I just wanted something that was close to the right length and outer diameter, and that had some kind of knurling. The nuts that I ordered are black oxide, which is nice and understated on the instruments, but is still quite different than the original thumb nuts. I see on Amazon that similar "internal wrenching allen nuts" are available in stainless steel finish, which would be a much closer match to the original, but I haven't found 1/4-28 in stainless steel finish, and the prices on Amazon are absurd (or maybe that's just the quantities that are absurd).

I fully expect the brass inserts to work perfectly, but they will certainly stand out with respect to the rest of the instrument face. I've seen some "restored" oscilloscopes on-line where the BNC connectors have been replaced with gold plated ones. The brass inserts will look almost as silly.

I am frustrated, however, that I was not able to find exact replacements for the Tek binding post nuts. I found lots of diamond knurled thumb nuts, but most were too long, and/or their outer diameter was much too large. Most were also made of aluminum, which I am scared to have in direct contact with the steel binding post (maybe that fear is misplaced? The binding post is already in direct contact with the frame and face plate, both of which are make of aluminum in most, if not all Tek instruments).

I purchased a handful of NOS Tek binding posts with thumb nuts, of the smaller size for TM500 plug-ins, on eBay, and those should be enough for my use, but I haven't found any of the 3/8 inch length nuts commonly used on 500-series scopes and plug-ins.

-- Jeff Dutky

Hi Jeff,
Did you see these, on fleabay?



Price seems ok at $1.50 each. They are stainless steel. Looks like this seller has plenty.

Keith,

Yes, I bought a set of those; they are much too long, and the outer diameter is too large. They FEEL really nice, though: sold, heavy, and the diamond knurling is very satisfying.

— Jeff Dutky

Same problem here in Germany. McMaster Carr does no longer serve private m customers. Business customers might be approved if they meet certain requirements.

Fortunately Digikey and Mouser still serve private customers abroad and even offer free UPS shipping for an order value of US $60 and up.

vy 73 Heinz DH2FA

Von meinem iPhone gesendet

I just received my shipment of brass threaded inserts and they are slightly shorter than the proper thumb nuts, but they are still more than adequate replacements. They do not interfere with nearby connections, and they are not nearly as ostentatious as I had feared they would be. Their length means, however, that they would not protect the ends of the hollow shaft of the binding post like the original thumb nuts do (which are slightly longer than the shaft they thread onto).

I have one more shipment of candidate parts coming. I will report back once they arrive.

-- Jeff Dutky

Don't forget that you could add washers under the nuts to help extend the length of threaded shaft that it keeps covered/protected.--EricSent from my Galaxy

Jeff,

These would be pretty easy to make on a small home metal lathe either from steel pipe or rod, if you had one as an example. Not sure where you are located but there might be someone near you on one of these these electronic forums that probably has a second hobby (automotive, machining, etc.) using a lathe. You could end up with a near exact match. A 1/4-28 NF tap is less common than a 1/4-20 NC but are still pretty cheap (~US$3 online).

Regards

I have added a photo album with pictures of the two replacements I have found compared to two sizes of thumb nuts from Tek instruments: /g/TekScopes/album?id=266234

I have also found another candidate in this item on eBay:

I will post pictures when the parts arrive.

-- Jeff Dutky

Jeff -
which are the originals and which are "new"?
搁别苍é别

搁别苍é别,

The "originals" are the two "steel" finish nuts with diamond knurling on the bottom. The replacements are the black oxide finish and brass nuts on the top.

-- Jeff Dutky

I have added another picture to the album (/g/TekScopes/album?id=266234) showing all six candidates I have tried for replacing missing thumb nuts on 500-series scopes and plug-ins.

The picture shows seven nuts, labeled A-G. The nuts are:

A: An original Tek thumb nut, full height, as would be used on a 500-series scope, plug-in, or binding post adapter for a 465 or 475.
B: "316 Stainless Steel Knurled Thumb Nut 1/4-28 Thread" from eBay (
C: "M5 Precision Knurled Thumb Nut" from eBay ()
D: "M5 Steel Leveling Knurled Thumb Nut" from eBay ()
E: "OEM by Bosch 50534 1/4-28 Knurled Steel Nuts" from eBay ()
F: "1/4-28 Internal Wrenching Allen Nut Alloy Steel Black" from eBay ()
G: "1/4-28x7.5mm(L)x10mm(OD) Metric Threaded Brass Knurl Round Insert Nuts" from eBay ()

My evaluations are:

(A) are, of course, practically perfect in all particulars. I'm still surprised and saddened that I can't find a source for them. Were these custom made for or by Tek?

(B) has very pleasant diamond knurling, at least as fine as what Tek used, but is about 1.5X the outer diameter and about 3X as tall. It is only threaded half way through on the flat end, which makes it hard to use the female banana jack with this nut in place. While it is larger in diameter than the Tek part, it looks like it will still leave enough clearance on something like a CA or D plug-in to use the UHF or BNC connectors, but it may be too large for use on some TM500, 5000-series, or 7000-series plug-ins.

(C) is the wrong thread, closed at one end, and too short, so it will not properly clamp a wire inserted through the binding post. The knurling is very nice. It's a shame that these are otherwise unsuitable.

(D) is the wrong thread, and the outer diameter is much too large for even the relatively roomy 500-series plug-ins. The nut is also about 1.5X the height of the Tek part. The knurling is coarser than the Tek part, and is not diamond knurling, but I think it's still pleasant. They are entirely unsuitable to the task.

(E) is the same outer diameter as (B) but only slightly taller than the Tek nut. The knurling is much coarser than either (B) or the Tek part. Like (B) this seems to leave enough room for the probe inputs on 500-series plug-ins, but may be too large for some TM500, 5000-series, or 7000-series plug-ins.

(F) is almost perfect; only slightly taller than the Tek part, it does not interfere with the use of banana plugs, and looks very nice on a scope or plug-in. The knurling, while not diamond, is very fine and pleasing. I liked these so much that I ordered several more bags of them in case of future need.

(G) is slightly shorter than the Tek part, which means that it leaves a little bit of the threaded shaft/banana jack cylinder exposed to damage. The brass doesn't look nearly as odd on a scope or plug-in as I feared it would, and even though the knurling is very coarse, it still feels nice on the fingers. These have the singular advantage of being very inexpensive (I got 15 pieces for under $9, and could probably have paid even less if I were willing to buy larger quantities).

(F) and (G) are my favorites, but (B) and (E) would do in a pinch.

-- Jeff Dutky

Thanks for your research, Jeff. I archived those auction pages since eBay will eventually delete them.

Dave Wise

From: [email protected] [mailto:[email protected]] On Behalf Of Jeff Dutky via groups.io
Sent: Wednesday, July 21, 2021 4:43 PM
To: [email protected]
Subject: Re: [TekScopes] Binding Post Thumb/Head Nut Replacements

I have added another picture to the album (/g/TekScopes/album?id=266234</g/TekScopes/album?id=266234>) showing all six candidates I have tried for replacing missing thumb nuts on 500-series scopes and plug-ins.

The picture shows seven nuts, labeled A-G. The nuts are:

A: An original Tek thumb nut, full height, as would be used on a 500-series scope, plug-in, or binding post adapter for a 465 or 475.
B: "316 Stainless Steel Knurled Thumb Nut 1/4-28 Thread" from eBay (<>
C: "M5 Precision Knurled Thumb Nut" from eBay (<>)
D: "M5 Steel Leveling Knurled Thumb Nut" from eBay (<>)
E: "OEM by Bosch 50534 1/4-28 Knurled Steel Nuts" from eBay (<>)
F: "1/4-28 Internal Wrenching Allen Nut Alloy Steel Black" from eBay (<>)
G: "1/4-28x7.5mm(L)x10mm(OD) Metric Threaded Brass Knurl Round Insert Nuts" from eBay (<>)

My evaluations are:

(A) are, of course, practically perfect in all particulars. I'm still surprised and saddened that I can't find a source for them. Were these custom made for or by Tek?

(B) has very pleasant diamond knurling, at least as fine as what Tek used, but is about 1.5X the outer diameter and about 3X as tall. It is only threaded half way through on the flat end, which makes it hard to use the female banana jack with this nut in place. While it is larger in diameter than the Tek part, it looks like it will still leave enough clearance on something like a CA or D plug-in to use the UHF or BNC connectors, but it may be too large for use on some TM500, 5000-series, or 7000-series plug-ins.

(C) is the wrong thread, closed at one end, and too short, so it will not properly clamp a wire inserted through the binding post. The knurling is very nice. It's a shame that these are otherwise unsuitable.

(D) is the wrong thread, and the outer diameter is much too large for even the relatively roomy 500-series plug-ins. The nut is also about 1.5X the height of the Tek part. The knurling is coarser than the Tek part, and is not diamond knurling, but I think it's still pleasant. They are entirely unsuitable to the task.

(E) is the same outer diameter as (B) but only slightly taller than the Tek nut. The knurling is much coarser than either (B) or the Tek part. Like (B) this seems to leave enough room for the probe inputs on 500-series plug-ins, but may be too large for some TM500, 5000-series, or 7000-series plug-ins.

(F) is almost perfect; only slightly taller than the Tek part, it does not interfere with the use of banana plugs, and looks very nice on a scope or plug-in. The knurling, while not diamond, is very fine and pleasing. I liked these so much that I ordered several more bags of them in case of future need.

(G) is slightly shorter than the Tek part, which means that it leaves a little bit of the threaded shaft/banana jack cylinder exposed to damage. The brass doesn't look nearly as odd on a scope or plug-in as I feared it would, and even though the knurling is very coarse, it still feels nice on the fingers. These have the singular advantage of being very inexpensive (I got 15 pieces for under $9, and could probably have paid even less if I were willing to buy larger quantities).

(F) and (G) are my favorites, but (B) and (E) would do in a pinch.

-- Jeff Dutky