# How to determine the proper size of socket to remove old metal tube from a bore?

In order to remove an old metal tube from a cast-iron bore, i need to get a socket with the proper outside diameter and tap it on the old metal tube with an hammer until the old tube will get-out. My question is: How much smaller(in mm)should the outer diameter of the socket be than the old metal tube? For example:if the old metal tube inside the bore is 25mm(OD), should the socket be 0.1mm less?0.2mm..? What is the optimal? Thanks.

UPDATE:I added a Gif to describe what bore i was referring to.

• whatever fits and does the job is optimal Commented Nov 15, 2022 at 22:11

Why a socket?

Turn a piece of bar so that it has a square shoulder to match the end of the tube and fits closely to the inside diameter of the tube.

The socket normally will have a radius that will cause the tube to expand and get tighter in the bore.

• I have only sockets,but i understand that the round edge of the socket will cause the tube get tighter(as you said),so i maybe flat it with a file.What did you mean:piece of bar that has a square shoulder?can you add photo or a link? Commented Nov 16, 2022 at 12:01
• @xchcui If you can flatten your sockets with a file, then you need a better socket set. They should be made of hardened steel. Commented Dec 11, 2023 at 15:17

The clearance required for free movement will depend on the smoothness and concentricity of the 2 surfaces. For something rough like this, I'd start with maybe a 0.5-1mm difference between the ID of the bore and the OD of the pusher.

We can't really say without seeing how clean, smooth and accurate the parts are.

• I couldn't measure the bore ID,since the metal tube is inside,but if the metal tube OD is 25mm,which is press tight into the bore,what should be the ID of the bore?In other words-What should be the difference between the OD metal tube to the ID bore?(press tight to the bore walls)0.1mm? Commented Nov 16, 2022 at 12:20
• Don't overthink it. If the tube is 25mm, just try 24mm and see what happens. It will probably be fine.
– Drew
Commented Nov 16, 2022 at 19:11
• This is not related to overthinking.My questions are based on my experience.The closet size of socket that i found is 24.5mm(OD)and it go through the bore easily without removing the old tube,so now i need to pay for the engraver to make me special socket size(and it is not cheap).So i need to decide on one proper size that will do the job for sure.If i use the a socket the same OD as the metal tube OD(25mm),may i expect for problems like stuck socket in the bore?will 24.95mm size be a better idea?Thanks. Commented Nov 17, 2022 at 15:35
• You haven't provided nearly enough detail for us to be more specific.
– Drew
Commented Nov 18, 2022 at 4:06
• Drew,i don't have any other details.I attached a Gif,(worth 1000 words)that described the task.If you need to know ,how much clean,smooth and accurate the parts are,so lets make an assumption that all the parts are new,clean,smooth and accurate(all the part have just went-out new from manufacture).If the tube is 25 mm,what is the maximum socket outer diameter that can be used to push the tube from the bore? will 1/10 mm less(24.9mm)may be the answer?more?less? Commented Nov 19, 2022 at 17:06

I can see a lot of over-thinking going on here. The OP has been told to use a socket and a hammer to remove the tube. The reason for this is that any good mechanic will have a socket set in their toolkit. And sockets are made of hardened steel, so they can survive a bit of bashing.

So you find the biggest socket that will fit in the hole and bash it with a hammer until the tube comes free.

Nothing is measured, and you definitely don't have custom sockets made up just to hit a lump of tube with.

• Any good mechanic will have a socket set in their toolkit that is mostly for bashing out bushings and tapping in bearings and seals. Then they have the real socket sets they use with ratchets. I knocked out about a dozen bushings and bearings today, not enough to bother setting up the press. Commented Dec 12, 2023 at 3:19
• Oh, old bearing cups are real handy to match odd bore sizes. I have dozens. Commented Dec 12, 2023 at 3:21