Help! Trying to build up my new frame, first time I’ve done this and I’ve inevitably stumbled upon my first problem!

I’m trying to install my Shimano external BB, drive side went in a treat by hand and tightened up with the tool. Opposite side however will only go in about 1 turn before it gets stuck. I’m scared to get the tool on it as it may knacker the threads.

Any tricks to help it in or do I need to visit my LBS?

Read this – excellent source of info
Yes you are right to consider hand tight as being the best way to start the BB going on – be VERY careful with directions of threads! A wire brush can be useful to clean up threads and you must use copper slip to install IMO.
Is all else fails, get LBS to chase threads for you. Strip them and you may be fubared.

Are you sure you are turning them the right way? The 2 sides have opposite direction threads. Look for arrows on the cups.

Yeah I’m defo turning the right way, as per the arrows on the cups.

I’ve cleaned everything and tried again, it’s gone about half way this time with some moderate force. The other side didn’t need the tool until the very end.

Shall I use the tool, I’ve backed the cup out and it doesn’t seem to be damaging the threads. Would it be obvious if it was?

Take the other side out and try it then. it may just be the rubber seal on the internal tube engaging?

Have tried that but it didn’t help.

Darn it.

just try the bbkt that came out again, and that usually cleans the thread, clean it all up and grease it.

It’s a brand new frame and brand new BB, so no old one to play about with unfortunately.

Flap over, I backed it out and back in many times and it freed up a little, I then finished the last bit with the tool and it all looks good.

Phew! 🙂

OP – you were smart to be cautious. Its easy to strip the threads, or the drive splines on older type BBs.

If it doesn’t go in by hand don’t force it. Stop. Take it to a bike shop for facing and to have the threads run through with a tap.

Once done it will be fine.

One thing I do when replacing an external bb is to run a pick around the thread after cleaning it with a toothbrush and degreaser. Then rinse and dry thoroughly before using copper grease.

Not failed yet!