Boss volume pedal repair -- which machine screws?

Stuckfast

I picked up a Boss FV-500H volume pedal cheaply because it is mechanically faulty. There's no resistance to foot pressure and it flops back to full volume as soon as you remove your foot. On opening it up it's obvious why this is happening. There should be two machine screws that connect the treadle plate to the axle and both are missing. I've been through my pile of random bits and bobs and can't find one that fits, and neither can I find a service manual online. Does anyone happen to know what the size and pitch of these machine screws should be? Or a spare part number from Boss/Roland? 

ICBM

It’s certain to be a small M series, but which size and what length I don’t know without one for comparison. I don’t have a FV-500 unfortunately.

Stuckfast

It seems to have a conical upper section and then a fairly short threaded section, so might be a custom part I fear.

jasonbone75

Just checking mine now @Stuckfast they are crosshead countersunk but need to pop one out to measure. I may have something compatible in the maintenance screws stock at work but am off sick today.

jasonbone75

OK, they are threadlocked so rather not break that and have to clean them up to re-apply. My guess is they are M3 countersunk from head size. They won't be custom though. I'll see what varieties I have when I'm in the office and if necessary can send a few options in the post for you to try.

jasonbone75

I suspect these will do it but can't recall if I have that short in my stock:

http://https//www.westfieldfasteners.co.uk/Bolts_Screws_Metric/Machine_Screw_Phillips_Countersunk_M3x4_A2_Stainless.html

Stuckfast

Thanks Jason, that looks very plausible!

Stuckfast

Just tried some M3 bolts and they are too small, so I'll try to get hold of some M4 ones.

SteveRobinson

M4 screws are quite a size up and unlikely I think. They *might* be M3.5?

The screws that hold your household light switches to their back box are M3.5 if you want to try the thread for size.

Stuckfast

Oh cool, I didn't know M3.5 was a thing.

jasonbone75

Good shout on the light switch screws Steve.

@Stuckfast I have just returned to work today and I only have two options one of which you have already managed to eliminate. I have M4x6 CSK as well as M3x5 as shown. If you struggle to find anything to try I can post the M4s to you.

(EDIT: I do have various M3.5 as well but nothing countersunk)

Stuckfast

Thanks Jason, that's very kind. I'll try some light switch screws first since I can probably find some!

Mike58

Just to say, I love a forum as useful as this. I may never ever require an M3.5 countersunk machine screw but it’s fascinating just to know this stuff. Hope the repair works out.