Reducing diameter of existing chassis hole?

[doveman]

I know I've seen something somewhere to use when reducing an existing hole. I have a larger hole that I would like to reduce and install a pot. I know I could use washers but I think I've seen something with a step sized for the original hole.

Anyway ... I'm betting somebody here has been there before.

[Milkmansound]

what about a metal plate that covers up the hole with a proper diameter hole in it? Screw it on with a couple 4-40's and some keps nuts.

a large shim washer might also cover it up - one on each side, but thats not a great mechanical connection

[prspastor]

what about a metal plate that covers up the hole with a proper diameter hole in it? Screw it on with a couple 4-40's and some keps nuts.

a large shim washer might also cover it up - one on each size, but thats not a great mechanical connection

Yep, this is what Mike Zaite does with his amp chassis. He uses the same chassis for different amps and has plates that are fit over large square holes. That way, he can fit 6v6, KT66, or EL84s on the same chassis. Brilliant!

I bet you could cover it up as milkmansound suggests with the proper diameter holes.

[Phil_S]

I've recycled a few chassis that had the wrong size holes. I install a plate from the inside and drill a new hole secured by a couple of #4-40 screws. Make sure the placement of the screws won't get in the way of other stuff. Then, I find a washer that will work on the outside of the plate to make it approximately level with the rest of the chassis. Sometimes, I can't find the right thickness washer, in which case I might leave it out. Sometimes the washer can be "modified" to work. You can improvise with an extra nut on the outside if you need to. It is imperfect, IMO, no matter how you do this, as there is really no good way to make a hole smaller!

I've attached a couple of pictures of a marginally satisfactory job I did. The particular needs forced some compromises I didn't like but decided to live with. Check the second pot from the left. Ugh!

OTOH, there are plates manufactured to reduce and octal socket hole to accept a noval. I think those are just as butt ugly and have never bothered to get one. I put a plate on the inside and drill a new hole for that, too. This can be tricky with respect to the retaining screw placement, as well.

Good luck!

[doveman]

Thanks for the ideas guys. My situation is not nearly as big. What I am considering is putting a pot in the second hole (black plug is unused hole) from the right. This is a Dr Z amp and as mentioned above there are several plates and plugs on the chassis. The hole is a bit bigger although I haven't checked the size yet.

I was thinking that I had seen something that would sit flush with the inside and have a step (height would be the thickness of the chassis) in it the size of the original hole with a smaller hole in it the size of a standard pot. I think I've seen one before but I don't recall where ... internet search has not uncovered it either. It might have been a simple washer with a step in it.

[IMG:635:349]http://i104.photobucket.com/albums/m168 ... 66back.jpg[/img]

EDIT: Hmmm ... "might have been a simple washer with a step in it" ... maybe a search for a "step washer".

[IMG:267:189]http://i104.photobucket.com/albums/m168 ... Washer.jpg[/img]

This was what was in my mind ... now to find one the right size ... I will be measuring and searching.

[M Fowler]

http://www.mcmaster.com/#catalog/118/3261/=htxcmu

[Phil_S]

There is an Ace Hardware near me that has loose parts bins and sells nylon shoulder washers like that. Sorry, I have a big-hole imagination!

[rp]

get yourself a decently stiff scrap of metal to span from the fuse holder to the IEC edge. Drill for the IEC screw and the fuse holder hole and use those two points hold it in place (on the inside of course) then drill your new pot hole (pothole?) Maybe a touch of silicone btwn plate and chassis to avoid any rattle. As for a shim, why bother with such a miniscule thickness? The knob ought to totally hide the kluge.

[M Fowler]

Send me that Dr Z Route 66 and I'll send you my clone that you can drill holes on.

Mark

[rock_mumbles]

Keystone has fiber shoulder washers ... I use them to mount and insulate Switchcraft metal 1/4" jacks in holes drilled for Cliff jacks ... I have some of the #3069 they fit in a 1/2" hole and have a 3/8" hole inside

http://www.mouser.com/catalog/catalogusd/645/2017.pdf

If that would work and you don't need other parts from Mouser I could mail a couple to you ...

[rp]

OP BTW how about a few detailed pics of the innards - pretty please.

Hey Mark, that clone would have fooled me, at least from the rear.

[doveman]

Keystone has fiber shoulder washers ... I use them to mount and insulate Switchcraft metal 1/4" jacks in holes drilled for Cliff jacks ... I have some of the #3069 they fit in a 1/2" hole and have a 3/8" hole inside

http://www.mouser.com/catalog/catalogusd/645/2017.pdf

If that would work and you don't need other parts from Mouser I could mail a couple to you ...

Very generous offer ... I took the plug out ... it's 5/8" (.625) and the pot is probably going to be 3/8" (.375). Thanks anyway.

[BobW]

I have filled chassis holes successfully using JB weld or a strong epoxy.

Place a piece of packing tape taut (no dips or wrinkles) across the hole from the outside, then fill the hole from inside the chassis using JB weld or epoxy. Allow a small overlap of the fill to help adhere to the inside chassis. Let it dry overnight then mark and drill your new hole. For larger holes, I've placed a small piece of window screen into the hole then filled.

When it's dry, simply pull the tape away from the chassis. Some minor dips, if any, may need refilling if air pockets were allowed to form when initially filling the hole.

HTH

[amplifiednation]

why don't you just get a pot with a 5/8" shaft?

[doveman]

The ganged pot came with the VVR3 kit ... didn't really think it'd be hard to find a washer to insert into the hole. Still think i can find one. Right now I have a 5/8" nylon washer (the same thickness as the chassis) with a 3/8" hole ... snug in the hole then held into place by the flat washers on either side. It should hold forever, but I'll find what I'm looking for ...

[IMG:639:423]http://i104.photobucket.com/albums/m168 ... C_0299.jpg[/img]

See my VVR thread on the project ... works great by-the-way.