Tap size for 70's / 80's receiver screws?

T

Timm357

New Member
Hey guys / gals:

More of a lurker than a poster but thanks again for all the info. I have a Kenwood KR-4070 receiver from the late 70's / 80's and was lucky enough to find a mint condition stock wood cabinet for it. My issue is that the four mounting holes on the chassis inside the metal cabinet to mount the box's original screws are not threaded. I know I could take the screw in and compare until I find the right one at home depot or something, but I figured you knowledgable DIY'ers may have a recommendation. Thanks a lot. :beerchug::beerchug:
 
They will be metric. If you have calipers or a micrometer, or you can probably eyeball it close enough with a ruler. Metric hardware is mostly on whole multiples of 1mm. The screws are usually listed by the letter M followed by the outside diameter of the threads, 3mm would be a M3 screw. For electronic hardware, the thread pitch is the same for all screws of a particular diameter. So if you can determine the diameter, you can probably find the right tap and screws.
 
They don't really have to be metric. If it was me, I'd just use the SAE taps and machine screws I already have on hand. Probably about #8 or 10.
Rick
 
8-32 is pretty close to 4 mm (most likely size), would work fine. But anybody else would expect metric on this unit - I'd buy a M4 tap. 10-32 is close enough to 5 mm that they can interchange if the tread isn't very long (5 mm is slightly larger).
 
I doesn't matter if you have to drill and tap it anyway, just make it a size that fits the hole nice.
 
Good grief, don't be a hack. Most of those screws are M4, which you can buy on-line easily, or even in a well stocked home/construction/bigbox store. Or Digikey. No US screw will fit an M4 properly. As Tom says, #5 and 10-32 often interchange. I've never found nice black ones, but you can paint the heads by sticking them in cardboard and giving them a spray of black epoxy appliance paint.
 
Whatever the course of action, if you break out the tap, make sure you have a good chip management plan. You don't want stray bits o' metal to spoil your nice receiver.

(On edit... Note that the OP mentioned the holes are not threaded, from the factory. In fairness to the poster below, I added this after he posted...)

Chip
 
Last edited:
ConradH said:
Good grief, don't be a hack.

Most of those screws are M4, which you can buy on-line easily, or even in a well stocked home/construction/bigbox store. Or Digikey. No US screw will fit an M4 properly. As Tom says, #5 and 10-32 often interchange. I've never found nice black ones, but you can paint the heads by sticking them in cardboard and giving them a spray of black epoxy appliance paint.
Click to expand...

My thoughts exactly. I don't want hacked gear. And any decent small hardware store has those drawers of metric fasteners. Might not get phillips head but an allen key or hex head or slotted but they have the size that FITS CORRECTLY.
 
In hindsight, "hack" was probably too harsh. I missed that the holes weren't threaded. It's just that the world is metric and we in the USA (who don't already) need to think in metric terms. It used to be a giant PITA to get metric hardware here and nobody had a clue as to what the sizes were. That's changed and it's usually not too difficult to find metric hardware and even metric taps locally. Definitely watch your chips no matter what size you go with. I usually use Philips because that's what the OEM typically used, but nice button heads or others can do fine.
 
Thanks a lot for the tips!

Being fairly new to messing with this stuff I had overlooked metal shavings. Excellent reminder - as that could be bad. I like the sound of M4 sizing. Having worked on Hondas and Japanese motorcycles forever I default to metric sizing when the tools come out. Although I consider my work decent, this is a new arena for me and I just may have "hacked" this thing up had I not asked :music:

I'll let you know how it goes. Cheers!
 
Most small screws in Marantz 22XX receivers are M3-0.5. You can get a metric tap and die set at Harbor Freight pretty cheap.

Tom
 
It may be that because the holes are not threaded ,self tapping sheet metal screws had been used. It's common on the tube gear I play with.
 
if the holes for the screws are simple holes, sheet metal screws sound like the intended. They may require a "speed nut" receiver clip, available from most threaded hardware suppliers.
Usually, if a chassis is to accept a machine screw (i.e.:m3/.5), it will have a formed/die-stamped tubular threaded extrusion. Sheet metal is a poor choice to run machine screw threading in; it is too thin and easily strips. If you do want to use machine screws, you could purchase RivNuts and the required tooling (a more sophisticated pop-rivet tool). Rivnuts are available in most polar metric and SAE/USS sizes.
They allow you to secure a threaded insert to a sheet metal panel.
 
Last edited:
Threaded inserts are the bomb. I repair stripped out holes on commercial gear that way.

That formed lip is the key. If the hole has a formed lip you can tap it with success. If not, sheet metal screws were probably intended.
 
You must log in or register to reply here.

Similar threads

CMC Guy
80's Carver separates vs. 70's Receiver
2
Replies
22
Views
2K
Roadrash
Roadrash
chosenalready
Need screws for Kappa 8's.
Replies
6
Views
251
chosenalready
chosenalready
theoman
Klipschorn 70's Vs 80's
Replies
2
Views
460
theoman
theoman
theoman
Klipschorn 70's Vs 80's
Replies
4
Views
703
capt.chaos
capt.chaos
mguy
AUDIO RACK 70's STYLE
Replies
1
Views
706
JonTee
JonTee
Back
Top Bottom