So my Tommasini had a frozen quill stem when I bought it. I had to cut it of to be able to tap it out. I'm looking for a new one. I have a 25.4 bar with a 1"stearer. Here are my three questions

Can I get a 26 and think that if I take out the shim it will clamp down tight enough?
Is there some shim material to build up the bar?
Some say if you have a smooth bar you need a smooth surface inside the bar clamp area and if you have a groved bar the inside of clamp you need to match that with groved.

Please advise

Yes, you can get a stem with a 26mm clamp and use a shim to mount 25.4 bars. You can get shims on ebay or make your own.

I've never heard that about smooth / grooved. I doubt it is a real issue.

congratulatiosn on being able to tap the old stem out.
You can shim a stem with a 26mm clam to work with 25.4mm bars, but you can find 25.4mm-clamp quill stems easily enough, especially if you're willing to go for a used stem. There are tons of road quill stems with 25.4mm clamps out there. I'd do that if you're able. What stem shape are you looking for (in terms of length and angle)?

If you can locate a stem with a 25.4 clamp that would be preferable. I have had difficulties keeping shimmed bars from creaking. You might be able to wick some Krazy-type glue between the bar and the shim, NOT between the shim and the stem, to quiet things down. But avoiding shims is best.

you can also use a quill to threadless adapter , then use a threadless stem .. which are more abundant , now.

there are 25.4. (inch) 26 and a oversize (1.25"), and shims machined to convert any of the larger sizes

back down to any of the smaller ones.

I've used Loc-Tite Red on shim interfaces


of course you can buy a lovely Nitto nickel plated lugged stem ,
and hire one made by anyof a number of custom frame builders.