Top Hat Fixing Washers Name

[DMcMahon]

The wooden side panels on my Ampex ATR-700 reel to reel tape recorder are secured with fixing screws that go through white plastic top hat washers.

The original panels were rather slim white painted plywood, I have replaced these with wider solid wood panels which I think improves the overall appearance.

I would like to replace the white top hat washers with a different colour version to improve the appearance more, but am struggling to find suitable, am not really sure the correct name for part, any ideas please ?

The original fixing screws were too short with the new solid wood panels, so currently using longer screws that have an integral flat washer, the diameter of the integral washer is larger than the top hat recess hole diameter which results in the head of the screws protruding out of the top of the top hat washer, so I also need to get longer standard screws.

David

[pmmunro]

Try a search for "screw cups".

PMM

[DMcMahon]

Thankyou PMM that is a good idea.

They are not quite the same because they do not have the top hat extension skirt that fits into the countered holes in the panels, but may be OK as long as their outside diameter is large enough to cover the holes.

The original securing screws were cheesehead and the replacement screws are round/domed head, neither of which are ideal with the sloping/countersunk sides of the cup washers. Somewhere I have some brass ones, will see how they fit and try and find some countersunk machine screws.

I think the original screws were imperial and the replacement are metric which are a tight fit, as can be seen by the thread damage/wear at the end of the screw in the first photo.

David

[Uncle Bulgaria]

I'm making some assumptions here: those look like M5 roofing type screws. As Ampex was (is?) a US firm did they use UNF fixings? I assume the screws go through the wooden side panels and into a threaded hole or captive nut in the metal chassis. It could be a trick of the light, but it looks as though the tip of the screw has been scraped by being put into a hole that isn't the right thread for it.

I'd be tempted by pmmunro's idea of screw cups and raised countersunk screws (probably stainless Phillips...) as they'd be a bit more classy than plastic washers, unless you want the '70s look! If the original screws are indeed an Imperial thread form, then screw cups are available for various gauges. For example, at Bresco. Notice some are countersunk so the washer itself sits within a countersunk hole to spread the load of the screw head, while others have a turned flange that will bite into the wood.

An alternative is the turned cup washer which has a flat back so will not bite into the wood, but also sits above its surface to support the screw. Spalding have a selection of these.

If you want to reproduce the original, I think a search for 'plastic shoulder washer' will get you close. Good luck!

Edit: Ha! Looks like we had the same idea at the same time...

[DMcMahon]

Thankyou Uncle Bulgaria.

I must check the service manual to see if the panel securing screw type/size is specified.

David

[Uncle Bulgaria]

You can't go wrong with some thread gauges. I use mine all the time!

[ms660]

Originally Posted by DMcMahon

but am struggling to find suitable, am not really sure the correct name for part, any ideas please ?

Google "shoulder washers"

Lawrence.

[Radio Wrangler]

"Top hat bushes" is another term.

Likely available things won't have a relief for the screw head. You need a friend with a lathe...

David

[David G4EBT]

There are combined cups and caps available in brown like these:

https://www.trade-point.co.uk/depart...20group%20%231

Where countersunk cross-head screws are flush with the surface of the wood, there are brown caps which can be hammered onto the head:

https://www.ebay.co.uk/itm/124471417...67931512c0d5bd

Hope that's of interest.

[Silicon]

Have you considered 'shouldered recess washers'?

If time and expense were not important I would want some kind of flush fixing.

[Lucien Nunes]

If the replacement screws are M5 and they just don't quite fit, then the original screws were probably 10-32 which is a common size for US mounting hardware. I.e. 10 gauge, 32 threads per inch. You should have no trouble finding 10-32 screws of your preferred style and length in the USA, probably also in the UK.

Standard M5 screws have 0.8mm pitch or approx 30.6TPI and No.10 is about 4.8mm.

[DMcMahon]

I must try and find (if I still have them somewhere) the original fixing screws to see if they will still screw in (with side panel removed), I am wondering if the threaded holes may be damaged now after forcing in the M5 screws and therefore maybe no longer will take a 10-32

David

[DMcMahon]

Many thanks to everyone for the good suggestions, lots of ideas to check out.

David

[DMcMahon]

Found my Ampex manual, it actually is the "Operation & Maintenance" manual as opposed to a Service manual.

It is a large manual with loads of detailed information on the electrical set-ups and electrical drawings etc but no mechanical exploded view drawings and no mechanical part listings, so no information on the side panel securing screws.

David

[DMcMahon]

Originally Posted by Silicon

Have you considered 'shouldered recess washers'?

If time and expense were not important I would want some kind of flush fixing.

A quick Google look at this appears to show top hat type washers which would not be flush fitting ?

David

[Uncle Bulgaria]

Some filister 10-32s to test, sir?

[McMurdo]

I would call those nylon shoulder washers. Whether you can get them in assorted colours, I don't know, I've only seen white

https://www.raptorsupplies.co.uk/p/m...cro%20Plastics

[DMcMahon]

Originally Posted by Uncle Bulgaria

You can't go wrong with some thread gauges. I use mine all the time!

Thank you Uncle Bulgaria, yes nice gauges.

Using my inferior gauge the replacement screws (roof screws ?) check out as M4 0.7 pitch, the screw nearly fits the 8-32 imperial gauge.

David

[DMcMahon]

Had another closer look at the ATR-700 Operation & Maintenance manual and now see that there is 1 mechanical exploded view drawing with associated parts list, luckily it is for the Trim & Cabinet Assembly.

The top hat/shoulder washers are item 21 and just called "Washer, Trim".

The side panel securing screws are item 22 and called "Screw B" (various different screws are called Screw B) with further description M4 X 20 (NI). Other different screws on the listing are also Metric with various M sizes

I assume that 20 is the length in mm and NI is Nickel.

Slightly strange that on this American recorder that the screws are metric and also strange that if the fixing holes are M4 metric, why the replacement longer (35mm) M4 screws (roofing) are a tight fit.

I have one theory that may hold some water.

The ATR-700 design was closely based around the Teac A-7300. Evidently Teac did the design and manufacture of the ATR-700 under license from Ampex. Main changes were relay out of front panel controls and phono and XLR rear panel input/output connectors being changed to all XLR to suit the American market.

Do not know if the ATR-700 was manufactured in Japan but maybe the 700 got metric screws/fixings due to Teac design using metric parts.

David

[Uncle Bulgaria]

That's a very nice gauge - I have had trouble in the past with unknown nuts as it can be very difficult to identify the threads internally when small without running a die down a suitable piece of bar or finding the right 'known' screw. I think I'll have to look out for one of those...

Looking again at your earlier picture, the markings at the end of the thread do look very like those that occur when a 'quite close' thread is forced to screw up. I think it would be worth trying a 10-32. I've only got some 8-32s or 10-24s here or I'd send you one to test.

I had a long thread-based struggle last month when trying to identify a thread that wasn't quite anything. It measured very close to 5mm major diameter, and while it was just too large to be an Imperial size, the pitch was an extremely close match for 34TPI. That isn't a thread pitch that's used, but is very close to 0.75. The thread turned out to be M5x0.75, which is bizarre.