[Fishin_Rod]

I am new here and would like to thank everyone for their knowledge and info.

I am also new to machining, self taught / youtube.

I am having trouble pressing an aluminum 6061 reducer into an aluminum 6061 tube, and keeping it square. The tube is 1.5" od x 1.361" id +/- 0.004" . The reducer I have been turning down to 1.363" OD x 1.25" long reduced to 1.009" OD x 1.25" long with a 0.8125" ID and attempting to press it into the tube. The tube is 15" long, but the reducer only needs to press into the tube 1.25" until it is flush with the edge of the tube.

I have tried turning the tube on my lathe, to square up both ends. Then pressing the reducer in on my 10 ton c press. This ends up being a couple hundreths of an inch out From one end of the tube to the other.

I also tried to press the reducer into the tube and then turn it down to the 1.009", but I must not have had my steady rest set up right. Because, the cut was out of round.

I am looking for any advice on getting this squared up or tricks for pressing it together. I can post pictures later if that would help.

I have also thought about turning down a piece of solid aluminum to 1.353" x 16" long. This way I could press the reducer into the tube a little past flush. Then flip the tube over and stick the reducer through the hole on the press plate. Next place the solid 1.353" down the tube and press it tight against the plate. I have not tried this yet.

thank you for any advice.

[klaymonster]

heh i dont know about maching and stuff but i was just workin on the balljoints on my car and havin trouble pressing them in and what i was told was chamfer the edges of both pieces and stick the cap part of it in the freezer for a good while and let it shrink up some. after that the parts should go together like ...well two things that go together well
:wee:

[amplexus]

Dip the inner piece in liquid nitrogen it will slide right in, no press needed.
Amplexus Ender

[Geof]

Aluminum is tricky to push into aluminum because it tends to seize up and that makes it difficult to get things straight.

Are you doing several of these? It may be worthwhile making some fixturing so the tube and the reducer are held parallel and concentric as you start pushing them together. Also do use lubricant such as Never Seize or a moli grease.

Another little trick is to machine the leading edge of the part you are pushing in slightly smaller than the ID it is entering. This gives a lead in that gets things lined up and it also prevents the lubricant being squeegeed ahead of the insert.

[Fishin_Rod]

Here is one already pressed into a 1.25" tube.



Here is another example of one. This was a full length piece of aluminum round pressed into an aluminum tube. the full length pieces square themselves up as they press through the tube. The short 1.25" pieces is where I am having trouble.

[Fishin_Rod]

Yes, I will be making several of these.

I do not use any grease, I actually spray the parts with brake cleaner first to remove all grease / oils. Once these parts are pressed together they are used on an airgun and under high pressures. I do not what them to separate under pressure.

I do knock the edge/corner off the reducer before pressing it in. I have not tried to turn down the front edge though first.



This is a shorter model installed on my pellet gun.

[Fishin_Rod]

Do you think this would work instead of liquid nitrogen.

[ame="http://www.youtube.com/watch?v=d11TFkeqbwY"]YouTube - Poor man's "Liquid Nitrogen"[/ame]

I thought you posted it as a joke but if it will quick freeze it, it would work great. Would this weaken the aluminum? I have tried to freeze the aluminum in my home freezer (20 f) and it does not seem to shrink very much.

[amplexus]

Try your local dairy farmer most of them have a liquid n2 tank for ai. Household freezer is not cold enough, dry ice and alcohol might work it will freeze mercury. Adding heat within reason to the outer piece will also help. Check handbook of chemistry and physics for coefficient of expansion for aluminum
Amplexus Ender

[harryn]

Hi, Dry Ice is not nearly as cold as LN2, but it is still much colder than a normal freezer. It might be cold enough for your project.

Unlike the author of that video, do not handle dry ice with your fingers. There is something fishy going on in that video - dry ice will stick to your fingers and cause nearly instant frost bite. He was handling it with his fingers - just crazy. That would only be at all feasible if the dry ice had become coated by condensation and frozen it, providing some insulation.

Your parts are small enough that you could just stick them in a cooler on top of the dry ice - skip the alcohol - until you are finished with the machining.

[Fishin_Rod]

I was not for sure why he was touching the dry ice with his fingers. I had noticed that also, but thank you for the warning and advice.

How long would dry ice last in a home freezer? If this would work, I could have several tubes and reducers ready to do at one time.

[Geof]

.....How long would dry ice last in a home freezer? If this would work, I could have several tubes and reducers ready to do at one time.

Dry ice sublimates at around -80 degrees C, it does not turn into a liqiud it turns straight into a gas; carbon dioxide. It is not cold enough in a regular deep freeze to keep dry ice and it can be very dangerous to put dry ice in a regular freezer.

In a chest type freezer the carbon dioxide gas fills up the freezer and stay there even when the lid is lifted because it is heavier than air. If someone leaned into this freezer to get something they could become unconcious within a second or so and dead not long after that.

Even in an upright freezer it is dangerous depending on how good the door seal is. It is possible the freezer will become full of CO2 and when the door is opened a gush of CO2 flows out onto the kitchen floor; could be bad news for your kitty. In addition because a large quantity of CO2 is released into the room quickly it can mix and raise the overall level of CO2 in the air high enough to give respiratory problems.

Many people recognize the finger freezing hazard from dry ice but I have found not many people are aware of the dangers from the CO2 gas that it produces.

[Fishin_Rod]

I did not know about the co2, it makes perfect sense though. I am glad you said something. I will keep it in a styrofoam chest, like I have seen others do.

side note/story (I use to work for the millwright union):

A while back they talked about changing the gas chamber from cyanide to co2 as a more humane gas.

It was discovered how well it works to kill someone on a job site. The job site would fill large machinery / crank cases with co2, (I believe to prevent rust during construction), over night and on weekends. There was a worker who did not ventilate the case before crawling inside. That worker fell over/colapsed, and two other workers who seen this happen went to give aid. They both almost made it to the unconsious worker before they fell over. The others then decided to isolate and deny entry until they discovered what was going. Come to find out the co2 was the cause. It is in our enviroment everyday, so you do not notice anything different until you go unconsious and suffocate in your sleep, very quickly.

Thanks for the warning geof.

[Fishin_Rod]

here is a picture of the reducer I pressed in and then back out.


This is my small work bench in the corner of the garage. Everything is compacted but usable. I just wanted to give everyone an idea of what I am working with.

[amplexus]

Actually one breath of co2 will not kill you, it takes about 5 minutes with no oxygen to die and a couple of minutes to pass out (how long can you hold your breath?) your cats are also pretty safe, otherwise there would be no co2 fire extinguishers. it is only a serious risk in a sealed container.
Amplexus

[klaymonster]

how about the chamfered edge idea have you given that a shot?

[Fishin_Rod]

klaymonster, how about the chamfered edge idea have you given that a shot?

I have not been home from work yet, to try any of the advice given. I am on a 72hr shift, and get of work tomorrow morning.

[Cruiser]

.oo3 interference fit is a lot for an ambient press. I used a lot of dry ice and heat for this type of job and could actually increase the interference. Use dry ice in ice chest with newsprint. You can get it from ice cream store and many other places, then use butane torch to warm up the tube till it is just too warm to hold, don't get it too hot. Aluminum goes away at 1000 to 1025 deg. Use a good set of welders gloves to assemble the parts and have a block of wood and dead blow mallet to give them a thump when needed as ice will form on the cold piece and get in the way at times. It might be a good idea to put the inner piece on block and place tube on from top just in case it wants to fall into hole and get too deep. After cooling the two pieces will be as one and the machining lines will interlock and molecular attraction should make it impossible to separate the two parts. you could measure the parts before and after the heating or cooling and calc a new interference, but don't get too carried away here too or it will be the same thing as what you got now. Don't polish the machined surfaces, leave tool lines there ! they form what is called a phonographic interference seal.

[SCzEngrgGroup]

I am new here and would like to thank everyone for their knowledge and info.

I am also new to machining, self taught / youtube.

I am having trouble pressing an aluminum 6061 reducer into an aluminum 6061 tube, and keeping it square. The tube is 1.5" od x 1.361" id +/- 0.004" . The reducer I have been turning down to 1.363" OD x 1.25" long reduced to 1.009" OD x 1.25" long with a 0.8125" ID and attempting to press it into the tube. The tube is 15" long, but the reducer only needs to press into the tube 1.25" until it is flush with the edge of the tube.

I have tried turning the tube on my lathe, to square up both ends. Then pressing the reducer in on my 10 ton c press. This ends up being a couple hundreths of an inch out From one end of the tube to the other.

I also tried to press the reducer into the tube and then turn it down to the 1.009", but I must not have had my steady rest set up right. Because, the cut was out of round.

I am looking for any advice on getting this squared up or tricks for pressing it together. I can post pictures later if that would help.

I have also thought about turning down a piece of solid aluminum to 1.353" x 16" long. This way I could press the reducer into the tube a little past flush. Then flip the tube over and stick the reducer through the hole on the press plate. Next place the solid 1.353" down the tube and press it tight against the plate. I have not tried this yet.

thank you for any advice.

In addition what others have mentioned, that is a HUGE interference to be trying to press. You really need to either get better control of the dimensions, or custom machine each plug to each tube. A more appropriate interference would be about 0.001". That said, you *should* be able to make them go together easily by using temperature. Rather than cooling the plug, heat the tube. With aluminum, the parts will just slip together with no pressing required. I would suggest you put some kind of a "stop" in place on the plug, to keep it from going in too far, and to hold it at the proper depth until the tube cools off. I once put a press-fit wheel onto a pulley - both steel. The diameter of the interface was about 5". Cold, there was a 0.005" interference, and they would not even begin to go together. After heating the wheel to 350F in a kitchen oven, it just dropped in place. Once cooled, my 12 ton press had difficulty removing it.

Regards,
Ray L.

[Fishin_Rod]

I made it home and was able to try some of the advice I had received. I made a mandrel and placed the reducer on the dry ice. The reducer shrank .003", just from the ice alone. I then heated the tube to where it was warm to the touch, and the peice almost dropped all the way in. I had about 1/16" that had to be pressed in. I also left a collar on the reducer and faced the piece of tubing.

[Fishin_Rod]

Do you think the reducer would hold bettter/stonger if I cut some shallow wide threads on the piece before freezing and dropping into the tube? This way when it expands back to normal the cuts/threads would grip the inside of the tube.

I forgot on the last post to thank everyone for the advice!