Crank pin replacement OPS .90
- Thread starter dwilfong
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Hi David,
I have actually tried repairing a couple of vintage engines in my collection where the disc drive pin was worn. I ground off the drive pin and center drilled a hole in the crank pin on a milling machine. I then pressed in a drill shank of the same diameter. It has worked well as I have tested the engines this past summer.
I actually posted a thread on it. Martin Hamilton responded to my post and he suggested to use needle roller as it is much harder than drill blank. I am sure he will chime in.
kez
I have actually tried repairing a couple of vintage engines in my collection where the disc drive pin was worn. I ground off the drive pin and center drilled a hole in the crank pin on a milling machine. I then pressed in a drill shank of the same diameter. It has worked well as I have tested the engines this past summer.
I actually posted a thread on it. Martin Hamilton responded to my post and he suggested to use needle roller as it is much harder than drill blank. I am sure he will chime in.
kez
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Hi David,
Wish you had posted this a few days ago, I have a broken crank back up north that I'd have brought down and given to you. I've made complete cranks out of O-1 oil hardening drill rod (Carpenter is the best I've used) and also S-7 shock resisting tool steel. I like the S-7 best if you have a source to heat treat properly.
John
Wish you had posted this a few days ago, I have a broken crank back up north that I'd have brought down and given to you. I've made complete cranks out of O-1 oil hardening drill rod (Carpenter is the best I've used) and also S-7 shock resisting tool steel. I like the S-7 best if you have a source to heat treat properly.
John
dwilfong
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I can heat treat it here at home if the recipe is not to involved. have a small kiln with a digital controller on it.
S-7 you say, source and heat treating procedure?
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Hi David,
In the Detroit area where I taught machine shop and welding all I did was send it out with my students other project and it was done for us. I would just spec the Rock C number and material. The last one or two cranks we did I think were out of M2 & M4 which is high speed steel. We were getting off falls from one of the local tool shops and the students made countersinks and other cutting tools as well as cranks. The oil hardening tool steels were always heated in a salt melting process that the concentration of salt determined the temp and then the parts were quenched in oil. Then drawn back in tempering to what ever Rockwell we called for. You could do the heating before quench in and electric or gas funace and then temper in the same after quenching. We used the ASTME handbooks for a guide. Sorry I don't have them down here but I think the info is on line. Sorry I don't know what process they used for the S-7 or HSS materials. But again I think you can find it on line. If not let me know and I'll call up north and get the info for you. PM me and I'll give you my e-mail and cell numbers here in Sarasota if that will help.
John
In the Detroit area where I taught machine shop and welding all I did was send it out with my students other project and it was done for us. I would just spec the Rock C number and material. The last one or two cranks we did I think were out of M2 & M4 which is high speed steel. We were getting off falls from one of the local tool shops and the students made countersinks and other cutting tools as well as cranks. The oil hardening tool steels were always heated in a salt melting process that the concentration of salt determined the temp and then the parts were quenched in oil. Then drawn back in tempering to what ever Rockwell we called for. You could do the heating before quench in and electric or gas funace and then temper in the same after quenching. We used the ASTME handbooks for a guide. Sorry I don't have them down here but I think the info is on line. Sorry I don't know what process they used for the S-7 or HSS materials. But again I think you can find it on line. If not let me know and I'll call up north and get the info for you. PM me and I'll give you my e-mail and cell numbers here in Sarasota if that will help.
John
dwilfong
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I found it on line.
In my younger years I would rebuild Vickers vain pumps and after machining the parts I would put them in the oven with cyanide and sodium salts to cook them. Put a real nice case harding on the parts.
Still remember old man Florig dipping his bare hand in the bucket of cyanide to load the oven.
In my younger years I would rebuild Vickers vain pumps and after machining the parts I would put them in the oven with cyanide and sodium salts to cook them. Put a real nice case harding on the parts.
Still remember old man Florig dipping his bare hand in the bucket of cyanide to load the oven.
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David do you have a Rockwell tester to check your hardness? Also make sure you leave extra material to grind after heat, sorry you already knew that, just the old teacher coming out. On some of our extursion dies a Logghe's we would have them low temp stress releaved cryrogenicly after heat treating.
John
John
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As you can tell I can type but I don't always spell correctly, I did not teach spelling or shake a the spear!!!!!
John
John
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Hi Dave,
Are you planning to use a shrink fit for press fit the pin?
John
Are you planning to use a shrink fit for press fit the pin?
John
dwilfong
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I was thinking hot crank cold pin press fit
That is why I am asking what have some done to fit one and what thy have used for material.
Size on size or over size pin to hole.
Can go by the size that it is now for a reference?
How much heat to press the old one out?
Will this change the crank temper.
That is why I am asking what have some done to fit one and what thy have used for material.
Size on size or over size pin to hole.
Can go by the size that it is now for a reference?
How much heat to press the old one out?
Will this change the crank temper.
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Hi David,
Technically, that's a shrink fit, the size schedule goes by dia. ie: the smaller the dia. the less difference in size. I don't know what OPS used for there crank material, if it was O-1 then it will continue to draw down the temper if you go too warm, it only takes a few hundred degrees to draw down too far. I haven't unpacked my "Machinerys Handbook" yet but will do soon and check the color & temps for O-1, the HSS materials can tolerate much higher heat before drawing down the temper. Sorry I can't remember about S7. You can buy temp sticks at ceramic supplies or mill suppies that melt at given temps. Before controlled furnaces and temp sticks we used color to drawn down and temper. ie: after quenching and hardening we would clean the part almost bright by wire wheel or sanding etc.and then as we added heat with a torch and watch the color. Each color represents a different temp. From yellow to straw yellow thru to blue. It only takes a few hundred degrees and it goes fast and you have to re quench quick as you see the right color. No matter what process you use you still have to quench after tempering or drawing down. If you use O-1 it seems to me that we kept it in the Rc 46-48 range to avoid brittleness. HSS and S7 could go higher Rc 56-58. If you have a good lathe that is capable of 1200 surface feet per minute and quick change tool rest using carbide ceramic inserts, you may be able to use pre heat treated material and get a finish that almost replicates ground surface. Hope this helps.
John
Technically, that's a shrink fit, the size schedule goes by dia. ie: the smaller the dia. the less difference in size. I don't know what OPS used for there crank material, if it was O-1 then it will continue to draw down the temper if you go too warm, it only takes a few hundred degrees to draw down too far. I haven't unpacked my "Machinerys Handbook" yet but will do soon and check the color & temps for O-1, the HSS materials can tolerate much higher heat before drawing down the temper. Sorry I can't remember about S7. You can buy temp sticks at ceramic supplies or mill suppies that melt at given temps. Before controlled furnaces and temp sticks we used color to drawn down and temper. ie: after quenching and hardening we would clean the part almost bright by wire wheel or sanding etc.and then as we added heat with a torch and watch the color. Each color represents a different temp. From yellow to straw yellow thru to blue. It only takes a few hundred degrees and it goes fast and you have to re quench quick as you see the right color. No matter what process you use you still have to quench after tempering or drawing down. If you use O-1 it seems to me that we kept it in the Rc 46-48 range to avoid brittleness. HSS and S7 could go higher Rc 56-58. If you have a good lathe that is capable of 1200 surface feet per minute and quick change tool rest using carbide ceramic inserts, you may be able to use pre heat treated material and get a finish that almost replicates ground surface. Hope this helps.
John
steve wood
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i use a-2 every day,used to use a lot of s-7,not so much where i work now.have made a crank pin for an older cmb rs 45 out of d-2 and ,far as i know it's still running.of the stuff i have available to me now i would use the d-2.i can make and heat treat and grind for you,but not till i get back to work
dwilfong
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Sounds good Steve. When you get back on your feet let me know.
I will send it with the case and jug.
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The air hardening tool steels are good stuff but because they work harden so quick if new users aren't careful they'l destroy saw blades just cutting stock or do the same to cutter while machining. Both perform really well, we used a lot of D2 for die sections.
David is a case and jug some kid of code for barter trading payment?
Steve, seems like it's been awhile since your knee surgery, hope the recovery is still going well.
John
David is a case and jug some kid of code for barter trading payment?
Steve, seems like it's been awhile since your knee surgery, hope the recovery is still going well.
John
dwilfong
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No code he is going to boar out the case on a OPS 90 so I can put the 1.26 boar 1.20 P/L in it.
Building a 1.27cid eng next.
That is why I am asking what is the best material for a crank pin.
There will be a 1.26" Diameter piston pounding on it and swinging a VAC91 steel rod.
It will need to be the best I can get.
The crank is huge on this eng so it should be good to go.
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I'm interested to see what type of pressing fixture will be needed to keep it all straight with out mushrooming the end or galling the pin on the way in . JMHO but would not heat it prior to pressing it .
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Tom,
I think the hole size in the crank is larger than the pin size. I would heat first, press it in but have it over size so I could grind it to size and parallel after it is pressed in. Or what ever way Steve does it I'm sure will be just fine. "There is more than one way to remove the epidermis of the feline creature"
John
I think the hole size in the crank is larger than the pin size. I would heat first, press it in but have it over size so I could grind it to size and parallel after it is pressed in. Or what ever way Steve does it I'm sure will be just fine. "There is more than one way to remove the epidermis of the feline creature"
John
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Love it, politically correct for skinning a cat.
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