Shrink fit

[Charles Lamont]

One of the most impressive events to be seen at the steam railway workshops where I volunteer is the fitting a of cylinder liner. A cast iron cylinder liner, about 20" diameter, 3ft long and 1/2" thick, is lowered into a bath of liquid nitrogen. When cold, it is lifted out with a fork-lift, over the side of the bath, and put down, white with frost, on slides or rollers fixed to the front of the cylinder, unhooked, and shoved down the hole by hand (with special gloves). The liner already has ports cut out in the end, so it has to go in at the right angular position. The only thing is, the guys need to concentrate on the job, so spectators are not welcome.

Here, a valve liner has just been fitted:
http://www.4930hagleyhall.org.uk/images/210120_-097-copy_600px.jpg

 

[bobm985]

Methyl Ethyl Ketone Peroxide is the explosive substance. It's also used as a hardener for polyester resin; like Bondo and fiberglass repair kits. MEK is the solvent of choice in the aviation biz because it's slightly less volatile than acetone. It will wash the crud off the workpiece instead of just shifting it to another area before it evaporates like acetone.

 

[bluejets]

I am trying to shrink fit a steel cylinder into an aluminum sleeve. Drawing called for .001 to .002 press fit. I put the aluminum sleeve in my toaster oven at 200* but it was still a very tight fit. I think that the temp was too low. Any input on temp for shrink fit.

Gordon

When you think about it, the liner doesn't really need to be a shrink fit as the head holds it in place as do all the OS style commercial engines so a slip fit would suffice.
Avoids things like the liner getting distorted when shrunk in and having to do heaps more work to get it straight again.

If water cooled jackets are involved, my normal approach is 2 slightly different exterior sizes, maybe 5 thou.
It allows the liner to be installed to perhaps 95% and the last bit is pressed in by hand and sealed in place with a few drops of loctite.

 

[davidyat]

Cogsy,
I remember a lot of guys having Elsinore 250's racing in the desert. I just couldn't understand these guys racing in the desert with big rocks and their expansion chambers slung UNDER the chassis with no protection from those rocks which you were going to bash on!!!

 

[William May]

I used to use dry ice and alcohol to shrink install the horizontal stabilizer pin in Learjets. There is only one pin, that holds the entire tail together. It was about 15" long. We let it chill for 4-5 hours. Once everything was set up and aligned, the cooler box with the pin was brought to the aircraft. We used cloth gloves to handle the pin, to keep warming to a minimum. The pin came out of the solution, and we had 10 seconds to have it installed and driven home with a rivet gun. Failures were rare.
So handle your parts with cotton work gloves or paper towels.
In aviation, we used MEK for ALL solvent uses. It was one of the few that left absolutely no trace after evaporation. Now they are trying to switch to MPK (Methyl Propyl Ketone) instead of MEK (Methyl Ethyl Ketone) but we have noticed that there IS a residue with MPK, and it has a greasy feel to to. MPK DOES NOT clean as well as MEK
Another chill material to use is liquid nitrogen. This is available at any welding supply place. It boils off quickly, so you can't just put it in a bucket. What to use?
An ordinary thermos.
You will only need a small amount. Buy a pint, or maybe a quart. Have them put it in a thermos bottle. DON'T SEAL THE BOTTLE!!! In fact, drill hole in the lid!, I made a plywood case to carry a 3 gallon Dewar flask. It was made of glass, so it needed a surrounding housing to carry it around and keep it upright. I made it out of plywood. The cover was another piece of plywood, and I DRILLED A 1/4" HOLE IN IT FOR VENTING PURPOSES. Liquid nitrogen will boil off continually from when you first pout it into the thermos. Put your part on a piece of wire, and lower it into the liquid nitrogen. Give it 10 minutes or so, and it will be as small as it can be shrunk to. Remove it from the nitrogen when you are ABSOLUTELY READY for everything to be assembled. Once again, cotton work gloves work very nicely to manipulate the part. Slide it off the wire and put it in position, and you are done. There is no pressing involved. When we put wheel bearing races in Lear wheels, we just dropped them into the cavity and they went in with a "Clink". Other parts were a similar "Drop In" fit after being chilled in liquid nitrogen. When we put strut axles into aluminum strut forgings, you had about 10 seconds to have the axle in place and aligned. We slid the axle into place and instantly used an alignment rod to put it in the right position. (There were holes drilled in the axle that allowed the anti-skid wiring to exit the axle at the strut area. These had to be in the proper place, or the axle would have to be hydraulically pressed out again, and the process repeated. ) We used welding gloves for the axles. Clean cotton work gloves for all the other small parts.

 

[Richard Carlstedt]

There is always a concern about getting the Aluminum part Too Hot
a easy thing to do is to make a mark on the part with Magic Marker
When heated to 400-450 F the mark goes transparent so you know
you are 300-350 F over ambient temp (room, temp) for your calculations
In this case, a 1.000 hole will be ( 350 x.000013 x 1 ) = .00455 " larger

Added benefit this technique for Aluminum is also that the stress relieving point is reached
and that means brittle aluminum sheet can then be rolled / bent with a radius.
We have all bent Aluminum sheet and had it crack at the bend. !
Draw a straight line with magic marker where the bend will occur.
Take your pencil torch and only play it on the line---when it disappears , you bend it
Rich

 

[SmithDoor]

Here is a chart on heat shink

Dave

PS: It does have copyright but it is ok to post per copyright holder.

 

[Steamchick]

When I was a teenager..... in the 1960s - one of my "Saturday morning" jobs was to press fit liners into the engine blocks of Diesel (truck) engines. It was pretty easy, 2 blokes put the upside-down block on the press (I wasn't big/strong enough to be considered "Safe"!) then I aligned the block under the press ram, inserted the drift (machined to slide in the bore of the old liner, and clear the OD size), the pump the hydraulics to press the old cylinder out. The new cylinder was the revers, but had to have everything spotlessly cleaned and a wee drop of light oil put on the bore of the block so the liner would slide-in easily, without "seizing" and needing excessive force to fit it.
Then the block was taken to the boring machine, where I bored it, before finish honing on the vertical honing rig.
Surely normal appropriate fits will enable you to do the same process? - and with a model, the pressing loads should easily be within the capabilities of a good vice - if you haven't got a press? (Who has?).
K

 

[awake]

Who has a press? Why ... I do. I made a 20-ton press - it works quite well, though I doubt it can actually get all the way up to 20 tons. The main thing was acquiring some heavy steel c-channels; that came courtesy of a friend. I also borrowed his radial drill to make it easier to drill the holes for adjusting the table height. After that, just a welding job and a 20-ton hydraulic jack.

 

[Steamchick]

Lucky You! But I don't, and I don't know anyone who does have a press of that sort of size. Most model assemblies need so little pressure to press fit anything, that I use my 3in vice. A lot of pin-to-rod-eye fittings I can assemble using the Drill press, as barely a few pounds of force are needed. Well withing the capability of that tool, and lots of control. Just fit a blank rod in the chuck and the job on the bed and the regular alignment of the drill-press is good. But people - probably you? - who make bigger models may need something bigger. Well done! (Actually, the 6" ram press I used as a lad was almost too big for pressing piston pins into press-fitted piston/rod assemblies! - The weight of the handle of the pump was almost enough to fit a small pin into the con-rod, so we removed it and used a large ring spanner for better feel! But occasionally we used it with a good heave of the handle on larger - I.E. 10~20" diameter - press-fits.).
Cheers!

 

[Steamchick]

Withing? Where did Spell-check get that one? Sounds like a village in Suffolk or somewhere? e.g. "Much Withing in the Bind" - But it actually means making something with Withies! - You learn something every post!

 

[Steamchick]

One of the most impressive events to be seen at the steam railway workshops where I volunteer is the fitting a of cylinder liner. A cast iron cylinder liner, about 20" diameter, 3ft long and 1/2" thick, is lowered into a bath of liquid nitrogen. When cold, it is lifted out with a fork-lift, over the side of the bath, and put down, white with frost, on slides or rollers fixed to the front of the cylinder, unhooked, and shoved down the hole by hand (with special gloves). The liner already has ports cut out in the end, so it has to go in at the right angular position. The only thing is, the guys need to concentrate on the job, so spectators are not welcome.

Here, a valve liner has just been fitted:
http://www.4930hagleyhall.org.uk/images/210120_-097-copy_600px.jpg

Interesting! But "from my engineer's seat"... I wonder at the corrosion from the trapped condensation between the liner and the bore of the housing? - I would expect this to rust with time so getting the liner out after decades of use will be a bit of a B#1"£$%^&r! But it is obviously manageable, or people would learn not to do it.
THANKS!
K

 

[Cogsy]

+1 on the press for me. Similar to Awake, it's a home made affair although I did get the legs already pre-drilled from a scrap yard so it made it easy. Very handy for things like changing wheel bearings or just making things come apart that don't want to.

For model-size jobs I use my 2-ton arbor press for most things. I might use my vise on occasion but I wouldn't consider using my mill or drill press.

 

[awake]

K, just to be clear, my post was meant in the spirit of, "if I can do it, anybody can." (You didn't suggest anything different, but I just want to be sure I didn't come across as boasting or anything of that sort.)

Al, I have a little arbor press - 1/2 ton, maybe? 1 ton at most - that handles most of the pressing needed for models. I'd love to pick up a somewhat larger arbor press, but haven't found the right deal yet. Meanwhile, the 20-ton press mostly gathers dust ... but when I need it, it is sure nice to have it!

 

[SmithDoor]

The only time I have a 20 ton is bending steel plate.
Today I have a 4 ½ ton arbor press that does everything.
It is sized to broaching.

Dave

K, just to be clear, my post was meant in the spirit of, "if I can do it, anybody can." (You didn't suggest anything different, but I just want to be sure I didn't come across as boasting or anything of that sort.)

Al, I have a little arbor press - 1/2 ton, maybe? 1 ton at most - that handles most of the pressing needed for models. I'd love to pick up a somewhat larger arbor press, but haven't found the right deal yet. Meanwhile, the 20-ton press mostly gathers dust ... but when I need it, it is sure nice to have it!

 

[awake]

Oh, a 4.5 ton would be nice ... even better if it has a ratcheting handle!

 

[SmithDoor]

The one I have had ratcheting handle.
Great for brochures

Dave

Oh, a 4.5 ton would be nice ... even better if it has a ratcheting handle!

 

[Steamchick]

Hmmm. I have simply not needed such big tools for my models. But I haven't needed to broach anything, or use a present as a press-brake for bending or folding big stuff. But I am "jealous" that you have such fun! Do post more stuff, it's interesting! (Or do I nod a frontal lobotomy?). I'll have a ride on the Guzzi for my fun.
K