what you are looking at is the result of a (post) mid life crisis, in which the woefully inexperienced OP (me) purchased from eBay a nasty looking de Rosa frame...and then over the next several months purchased parts that he thought might fit the frame.

at some point, he took the frame (beautifully stripped and repainted, sans decals) and several cartons of parts to his LBS for assembly. A week later he returned, and the mechanic rolled out the de Rosa. We ooo'ed and ahhh'ed and then he pointed out with great pride that the brakes I had brought him were not appropriate for the frame and forks. To make them work, he reversed them (and had to modify the front spring, IIRC) to install them.

"They're a little squeaky, but they should quiet down when the shoes seat in," said the mechanic.

well, the rear brake is quiet and strong, but the front brake is worse than ever. it begins to squeal with the slightest touch, and gets progressively louder as more pressure is applied. Yesterday, the OP noticed one of the pads working its way out of its shoe--on investigation, it was apparent that there are tabs on the shoes to prevent that--but they are now pointing the wrong way.

It's easy enough to reverse the brake shoes, but could it be that there is something in the position of the brake arms and spring that is causing the squeal? If so, why isn't the rear brake squealing?

Well, for one thing you need to swap sides on the brake shoes, for probably both front and rear I imagine. If not they could shoot out the front several feet, leaving you with no brakes at all. Not surprising a younger wrench would have NO way of knowing this, however. I imagine the shoes are also toed out now, which will cause the squeal. They need to invest in a Park Tool BT-3, and learn how to work on bikes before they hurt someone, IMHO.,,,,BD

My point being since the brakes are reversed, they're now toed opposite of what they should be. A BT-3 allows the brake arms to be tweaked to a level, or slightly toed in position. It also wouldn't hurt to clean the rims with alcohol, and sanding the surface of the brake shoes a little. That should help as well.,,,,BD

i don't understand what the mechanic did. "he reversed them"? what does this mean? he put the front on the rear, and vice-vera? it's important to know exactly what he did in order to correct it. if the brakes did not fit the rims and frame, you should have purchased those that did.

i'm still working out the kinks on my new build ('80 grand jubilé) with both front and rear squeak. they're new kool stop pads, and they really scream upon initial use unless the arms are nearly perfectly adjusted to the rim. two tips to follow are immensely helpful: first, the pads should mirror each other perfectly. if the front of one pad hits the rim first, then the other pad should do exactly the same. if the pads are perfectly mirrored and still squeak, then the front of the pads should be toed in so the rim hits the front of the pad first. if that still doesn't work, you might need to clean the surface of the rim, file (scuff) the slightest bit off the pads, or purchase new pads.

also, make sure the arms have no play in them when pulling them away from the fork, toward the front of the wheel.

The "mechanic" released the bike to you in that condition? I think you should have the entire bike checked out by a competent mechanic.

New brakes have to be oriented the same way or else the pads too can be ejected. That's a little scary.

More than a little scary.

So he put the rear in front and the front in back, and forgot to switch the pads around? I'm guessing it was because you handed him recessed brakes to put on a nutted mount frame? He must have also drilled out the fork crown from behind, then? I've done that, but I'd never do it to a customer's bike without asking/explaining...

They're also a LOT more noticeable being backwards, being tapered from front to back. They also have screws holding them in. Still, yes a little scary.,,,,BD

In Southern California, a customer would have let the brakes fail, and obtained a nice out of court settlement.

The front to back swap is not that difficult, but as others have said required a bit of additional work, no idea why the springs were involved. My guess is the rear brake has a fixing nut and the front has an allen key nut and was drilled out to accept that.
There are other ways to do this, but it should function. If you swap the pad/holders around so the open end faces aft on both the current front and rear brake you should be good to go. I have found that some rims cause squeal more than others, same calipers and pads.

1) order compatible Kool Stop brake pad replacements and replace old pads.
2) re-install shoes/pads in the proper position
3) toe in the pads/shoes
4) go over rim braking surfaces with brown Scotchbrite pad
5) return to shop and give dope slap to so-called mechanic
6) leave shop, never to return

dope slap? is that like an old fashioned duel challenge swipe across the face but using a bag of weed in place of the white glove?

well, make sure you use a ziplock.

Very bizarre situation. I am sure that the problem can be solved rather easily, however the actions of the mechanic are incompetent.

To elaborate on what Bikedued said: You want the leading edge of the brake pad to contact the rim ever-so-slightly before the trailing edge does so. This will eliminate squealing and shuddering. The ends of the calipers where the slots are located for installing the brake pads may have originally been bent slightly to achieve this. But since this bending occurred the brakes have been reversed from front to back and vice-versa. So now the calipers are bent in exactly the wrong direction. (As Whatwolf points out, this also caused the pads to oriented backwards so that they can slide out when the brakes are applied.)

The Park tool that Bikedued mentions is for re-aligning the calipers. If you are careful this can also be done with a very small crescent wrench clamped on to the flats of the calipers.
Brent

And the cable length adjuster isn't set up correctly. Incompetent mechanic - and I'd really worry about other screw ups, too. The components are probably twice his age, at least. Maybe try the Bike Pro Shop in Georgetown.

You can see the slight toe-in and the brake block holder tabs in this picture.

Hey, at least the Gatorskins are facing the right direction. ,,,,BD

I would probably take both brakes apart and swap the center bolts between them rather than bending them again to achieve proper toe-in. Or get the correct brakes (I assume nutted is what you need). Not sure why the "mechanic" would have needed to do anything to the springs?

In the 2nd pic, you can see that one of the brake blocks is already trying to escape

I've had better luck with the one in Alexandria than in Georgetown. I basically was laughed out of the one in Geogetown back in '03 when I brought a Raleigh 3 speed in. "That's not a real bike" was the sum of the attitude I dealt with at that time. Maybe it's better now. I've had no problems with the one in Alexandria this year. The Revolution Cycles in Georgetown was good to me though. There's also a new shop dealing in vintage/older bikes in Arlington that has good reviews, though I've not been there yet. There's also the co-op in Alexandria/Del Ray.

The co-op in Del Ray could work out well as the owner is competent, at the same time, the people working there are bike lovers that volunteer their time, some do and some don't know vintage parts. Maybe worth a try even though they are on the other side of town. Haven't been able to get to the one in Arlington yet. The one time I went they were closed, but I have heard good things about the owner.

I certainly feel your pain....currently working up an OLD Torpado...with Mafac Racers....back brake is quiet and works OK, front.....screams like a banshee! Been working the toe-in, a bit of sanding on the pads...which may be my big problem, old, HARD rubber....have to see if I can find something newer that will fit. Not always easy with old, outdated brands.

Was the "mechanic" a younger guy? Say in their 20's or 30's?

I go by a certain rule at the LBS: don't hand over anything to a mechanic unless said mechanic is at least 20 years older than what they will be working on.

There's no excuse for the improper brake shoe fitting though...that's just lack of common sense

It shouldn't be hard to find Kool Stop pads for your Racers. They make them in black snd salmon.