pressed in pins (rod temperature)

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pressed in pins (rod temperature)

Post by rewguy »

How hot does rod have to be?
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Re: pressed in pins (rod temperature)

Post by PackardV8 »

rewguy wrote: Tue Aug 20, 2019 10:53 am How hot does rod have to be?
How high is up? The temperature necessary for the rod to accept the pin depends upon the pin diameter and the interference fit between the pin and the rod small end bore.

A large diameter pin with .0015" interference would need to be hotter than a smaller diameter pin with only .0005" interference.

The temperature range is usually 400 - 600 degrees, but if one has ever stuck a pin because the rod wasn't hot enough, most err on the high side.
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Re: pressed in pins (rod temperature)

Post by Makin Scripts »

Its been along time since messing with a press-fit piston pins for me. But placing a small bit of 95/5 solder on the small end of the rod and watching for it to liquify while on the hot plate is the back woods way I was taught. Fling the solder off and work fast! Been plenty of times I wished I had just used the press from the beginning.
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Re: pressed in pins (rod temperature)

Post by af2 »

Makin Scripts wrote: Tue Aug 20, 2019 2:46 pm Its been along time since messing with a press-fit piston pins for me. But placing a small bit of 95/5 solder on the small end of the rod and watching for it to liquify while on the hot plate is the back woods way I was taught. Fling the solder off and work fast! Been plenty of times I wished I had just used the press from the beginning.
The ones I have seen done have the press next to the heater and go in good.
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Re: pressed in pins (rod temperature)

Post by Dave Koehler »

rewguy wrote: Tue Aug 20, 2019 10:53 am How hot does rod have to be?
I think we better ask what tool you are using to heat the rod end?

Tip 1: Measure the small ends. Some may be on the extreme small side which can bite you.
Tip 2: Run the hone on the small end with a back and forth swipe. Surprising how a nosee em burr shows up and makes your day go bad.
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Re: pressed in pins (rod temperature)

Post by modok »

IMO about 350 F, heated evenly will work every time for .001-.0015 interference per inch of diameter.
Do a little foreplay with a 350 temp stick to make sure it's FULLY up to temp before penetration.

Get ready to go patiently, getting the tools ready, heating it up.
but when it's time to go, GO. You do not want to be stuck halfway.
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Re: pressed in pins (rod temperature)

Post by econo racer »

Would putting the wrist pins in the freezer over night work?
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Re: pressed in pins (rod temperature)

Post by modok »

It might help a little, it's proportional. Then you only need to heat it up 280F...ok, but has that saved labor? not much. Oil I use is rather stiff at freezing, Are you going to use thinner viscocity oil then?
if it has too much interference fit, that's not good. Your going to stretch/weaken the rod, distort the pin, so it's better to get the fit RIGHT.
3 Rules of fitting a thing in a hole

1-measure the fit of the parts before trying to assemble them
2-chamfer the edges
3-lube

Of course that's very GENERAL outline,
but over the years, whenever I get into a jam, assembling any kind of press fit assembly, 9 times out of 10, it's because I neglected one of those three things. Piston pins included. Any good pin has a nice radius chamfer on the corner, but some cheapies don't.
Smart alec says.....we don't actually need to lube the pin for this...I'll oil it later....well, what if you DO get stuck halfway.....then your going to wish you has some oil on it, as that would improve your chances of getting the pin back out without ruining the piston. tools for doing that alreay set out ready to go, BTW will tend to prevent that situation from even happening. Murphy's law. Murphy strikes when you are unprepared. SO be ready, and then nothing will ever go wrong. Until you aren't, then it will.
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Re: pressed in pins (rod temperature)

Post by econo racer »

Can you heat it up with just a little propane torch?
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Re: pressed in pins (rod temperature)

Post by PackardV8 »

econo racer wrote: Wed Aug 21, 2019 9:35 am Can you heat it up with just a little propane torch?
If a hardware store hand held propane torch were the answer, would shops be paying Sunnen, Goodson, et al, more than $1,000 for their electric and propane units?

As has been mentioned here, just stick one pin and you'll be careful for a loooong time.
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Re: pressed in pins (rod temperature)

Post by modok »

It can work fine, does not matter how you heat it up.

You can make toast with a propane torch, but a toaster is more convenient.
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Re: pressed in pins (rod temperature)

Post by benno318 »

econo racer wrote: Wed Aug 21, 2019 9:35 am Can you heat it up with just a little propane torch?
absolutely.
I have done literally thousands of press fit pins with only my handheld torch. I have an electric sunnen rod heater and I prefer my torch. I just use the sunnen for the pin depth setting feature.

I use sta-lube assembly grease in the pin bores, and experience tells me that just a moment after this turns liquid, its ready to go. the rod also changes colour to a straw shade.
very occasionally it may be required to "bump" the pin if something goes wrong, the lube makes that a lot easier compared to different lube or none at all - especially to move the pin a very small amount to centralise it, if I have set the pin depth incorrectly, for instance. I always do this asap while its still warm if its ever needed.
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Re: pressed in pins (rod temperature)

Post by rewguy »

Is too hot a bad thing?
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Re: pressed in pins (rod temperature)

Post by modok »

Sometimes, depending on the alloy, heating a heat treated steel part over 400F will can cause a loss of hardness/strength, so that's why you often see specifications for between 300 and 400F, to be safe.

MOST connecting rods, the harm would be minimal. If we're talking about heat treated fancy rods, or GEARS, then I'd worry.
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Re: pressed in pins (rod temperature)

Post by rebelrouser »

I use a Goodson rod heater set to 450 degrees, and a special marker that melts at 450 degrees to verify the temp. Oven has a temp setting, but the marker just backs it up. My big deal is that if the heating of the rod leaves a blue mark, my opinion is that the properties of the metal has been changed and I have seen rods break on such a blue line. I see lots of machine shops heat rods until they are blue to press in the pins, I will not accept a blue rod from a shop. At the 450 degree temp, have never seen it leave a blue mark.
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