FishBiscuit

I'm prepping a 1970s Raleigh frame for painting or powder coating, and I was wondering if anyone here knows the best non-destructive method for removing the chrome thimbles (or dimples, or indents, or whatever they're called) from my thimble crowned fork. I did a few searches on this forum and on the internet in general, and I couldn't find any answers.

And if I do end up accidentally destroying the thimbles, does anyone have a lead on a supplier for replacements?

Thanks!

Ex Pres 

Can't you just mask them off for prep and powder?

Amesja

I don't know what the correct method would be but this is how I'd personally go about it without any other clue.

Since the paint is already in bad shape and you are going to repaint anyhow I'd attack it with a hammer -no really! I'd tap very lightly and gently on the top of the crown just above and behind the thimble area being VERY careful not to hit the crown and bend the very thin sheet metal. I'd tap with the flat edge of a ball-peen hammer lifting the head just about an inch or two off of the metal and fairly rapidly -two to four times a second. I wouldn't be surprised that this would vibrate the heck out of the crown area and that thimble would pop right out short of it being somehow glued in with some very good LONG-lasting epoxy that hadn't dried up over the years. My guess is that it is just pressed in.

Once you get one side out the other side can probably be pressed out from the other side so try the other side if the attempt on the first side isn't successful after 30-40 seconds.

But I'm sure this isn't the correct way to do this and someone will come up with a better/correct way to get them out (hopefully). I'd be very leery of trying to pry them out with a tiny screwdriver as I'd be afraid that it would bend that delicate flange and booger it up.

thenomad

I masked it off and then painted. I was able to scrape the excess off the edges of the thimble just fine and it looked as it should. Funny enough, I also then had to hit the fork with another coat of paint and I just decided to paint over it. Then I took q-tips with nail polish remover and swabbed till it was all gone. Also looks factory.
So having tried two methods I'd say either will be fine.
Looked too thin for me to try and pry out. I really doubt they are an item that is "in stock".

FishBiscuit

Interesting theory. Thanks for the suggestion, but I'm leery of hammering on any of the tubes on the frame. I would think if the the thimbles could simply vibrate out, riding the bike down a typical city street or unpaved trail would have done them in a long time ago. They're in there pretty good, and I'm pretty sure that they are just pressed in there. It's probably easier and cheaper to find a replacement for the thimbles than the the fork (since the thimbles were a generic part, and this fork pretty much only goes with this frame).

Unfortunately, the steerer tube goes through the fork crown and would prevent access to one side from the other.

The only other suggestion I've found online since posting the question is to heat the fork in an oven at 200 degrees, drop an ice cube into the thimble (to shrink it, I suppose), and to wedge a thin blade into the gap and pry it out by working your way around it. Somewhere I've got some utility blades. I'll try that first, as I don't think the blade can harm the thimble before it breaks itself. Just need to find those blades...

FishBiscuit

Keeping them in there and painting around them is definitely my other option. If I'm paying buku bucks for a paint job, though, I'd like to approach the problem in the most anal retentive way possible.

USAZorro

If you're spending a lot, I'd expect the painter would deal with it. My guess is it would just get masked off.

Amesja

Maybe instead of a metal ball-peen hammer a Big Rubber Mallet might be what is needed. That'd be what I would try next. A big 2lb rubber bonker hitting the top of the crown just hard enough to flex the round shape of the crown top horizontal tube (but because it is rubber not permanently dent it). This flexing might be enough to cause the round insert to be pushed out as the tube is made slightly (and temporarily) ovaloid.

These are both techniques I've actually used at work when trying to disassemble similar assemblies. You'd be amazed at how hitting something with a hammer will cause something to come apart (or at least loosen slightly) -and in a non-destructive manner. I've done very similar things to try and get a concrete core out of a $600 core-drill bit without damaging it or the delicate diamond cutting teeth on the bottom. Those cores get VERY stuck very easily sometimes. The thimble is metal -but it is a similar concept.

As for why it is not popping out while being ridden, I would imagine the kinds of shocks/vibrations that a hammer capable of transmitting directly to the area are several orders of magnitude greater than that which would be experienced while just riding down a very bumpy road. And even so when hitting it in a non-destructive manner. Metal flexes -let it flex just enough to do your bidding. It's not brain surgery or rocket science here...

sailorbenjamin

When prying with a knife, USE SAFETY GLASSES. You probably already knew that, though.
What about compressed air? I like the heat and the ice, but then maybe seal the fork up somehow and blow them off?

Amesja

IF a knife is going to be used then use the RIGHT knife for prying -such as one of these designed for watch case back removal.

IF you can get it in there -be very careful not to ruin the thimble as it'll be hard not to bend the stamped metal brim. It doesn't look nearly as hearty as a watch back (I am an amateur horologist in my spare time and have opened a few cases over the years). And yes, like sailorbenjamin said, use safety glasses as knives are made of hardened tool steel and can and will crack and shatter when you pry on them and pieces can fly out at eye-popping speed...

sailorbenjamin

The solution just dawned on me. Drop an M-80 down there and shove a cork in it.
Oh yeah, wear safety glasses.

FishBiscuit

You guys are all awesome! Great suggestions. The M-80 suggestion sounds great, but I think I save that as a last resort. The space behind the crown thimbles, as far as I can tell, is isolated from the rest of the fork- there's no other outlets to blow air in from.

Thanks for the link the the watch case opener, Amesja! I think heat + ice + something like that will be my first attempt. And yes, I always wear safety goggles when dealing with razor sharpened metal that is prone to breaking. I've ended up with shards in my eye in the past, and it's no fun at all!

Grand Bois

Fill the thimble with CRC freeze off. It will shrink and you'll be able to pop it right out.....maybe.

https://www.autobarn.net/freeze-off-super-penetrant.html

cudak888 

Work a razor blade around the edge, carefully prying it out. Swap to thin screwdriver if you get it out far enough. Make sure to go slow and apply minimum pressure so as not to distort the thimble.

-Kurt

sailorbenjamin

In 25 years of wearing safety glasses they've only saved my eyes 3 times.

Thumpic

glue a "puller" (PVC, dowel rod) of some type into the thimble.....let it cure completely and try to pull it out.......I can't imagine it's so tight it would not pull.......

or.....

plug all the holes; fill it with water and freeze it....they'll act like freeze plugs and pop right out.....