REPORTS ON A 1914 HUMBERETTE RESTORATION

[JV Puleo]

No need to harden the nuts and I'm guessing that even EN8 is overkill. See what is available in hex stock. You may have to make a threading fixture first - something to screw the nut on to to face the ends. You can use the original nut as a gage, make the fixture then make a new nut to fit the fixture. I'd look for a tap but it may be too expensive for a one-off nut. You can always single point it... a little more work but cheap to do.

[Mike Macartney]

1 hour ago, Roger Zimmermann said:

You had a lot of work and trouble to attach something with these 6 screws and turn the flywheels. What is the purpose of all that?

 

Roger, the problem I found was this

 

 

 

On both halves of the crankshaft assembly, when I split the two halves to remove the connecting rods that the two pistons are fixed to, I found that the main shafts to the clutch/gearbox and the front shaft to the cranking handle/valve gear were loose, allowing the flywheel to move on the shaft flange where the rivets were. This movement had worn away some of the metal from the cast iron flywheel. This wear was uneven over the surface. Apparently, the engine had never run since it was taken off the road in 1926. The first person who bought this car in 1995, after its long term storage, must have taken the engine apart. I believe that he had found the loose rivets, from my inspection of the rivets,  it looks as if he just tried to tighten the rivets by 'bashing them' with a hammer and chisel to try and tighten up the rivets.

 

 

This is the only photo, that I can find at present, of the two flywheels when I spilt them apart. You can just see the tops of the 'hammered' rivets on the flywheel on the right of the photo.

 

 

These two photos shows the rivets a bit clearer.  I am sure it would have not left the Humber factory looking like this!

 

,

 

This is a photo of the recess where the shaft flange fits into. The darker areas are where the cast iron had worn away making the surface uneven. Joe suggested, that rather than machining the surface, I lapped the shafts flanges into the recess in the flywheel with grinding in paste. His suggestion worked well.

 

I hope that helps you understand the problem that I found and the way the problem has, hopefully, been overcome.

 

[JV Puleo]

Here's my nut making procedure...

1. Make a holding fixture by threading the end of a piece of bar to fit the original nut. It is a good idea to make this with an area turned round but not threaded. It can then be checked with an indicator. As long as the unthreaded part is done without removing the piece from the lathe before threading it will be concentric with the threads. Wince you are using a 3-jaw I suggest marking both the fixture and the jaws so it can always be returned in exactly the same spot. Drill a hole through the end of the fixture for a tommy bar... you may need it.

2. Take a piece of hex stock (longer than the nut is thick). In the 3-jaw chuck, drill, face and bore to the hole size for the thread then single point the thread using the fixture to check it. If necessary, you can lap the threads using the fixture.

3. Put the fixture in the lathe with the nut flat side to the back then face off the other side to the desired thickness and chamfer the edges. This should give you a perfect nut with front and back parallel.

[Mike Macartney]

Thanks for the information Joe. I am still trying to get my head around what this thread actually is; the 18 tpi gauge nearly fits the thread, but so does the 1.5mm metric thread gauge nearly fit (the 1.5 is from my memory, as I saw your message when I came back to the kitchen for a cup of tea and I had left my note book in the garage). When I have checked threads on nuts and bolts previously it is normally fairly obvious what the thread is. The profile seems to be 55 degrees, rather than 60 degrees. I have been checking the thread in between final finishing the faces of the cast iron flywheels to try and get them the same width. If I still can't work it out this thread size, I will post a drawing of the thread dimensions to see if you have any ideas.

[Roger Zimmermann]

Thanks for the explanation! Of course, the flywheels must have an axle to be able to turn, it was what I did not see. Sometimes my brain is limited!

[Terry Harper]

Mike,

 

Are you planning to check the straightness of the connecting rods as well? With these headless motors its common to find

connecting rods that were bent when the cylinder blocks were installed.

 

Lot of fine work you have done! Best of all you did all yourself, learned a lot of new stuff and saved a ton of machine shop costs!

 

T.

[JV Puleo]

55-degrees is what I'd expect. That is the Sir Joseph Whitworth profile. I doubt it's metric though that isn't impossible. It is going to be something that could be cut on a period lathe and I'm not certain how many metric calibrated machines were in use in the UK in 1914...probably not many. Worst case scenario, make an 18tpi nut as close as you can and see if it works. You may have to lap it to get a good fit because sometimes, in these larger sizes, they weren't as precise as we'd expect today.

 

Oh.. I can't imagine they'd cut a 55-degree metric thread.

Edited August 5, 2019 by JV Puleo (see edit history)

[mike6024]

 

The nuts look OK from a functional perspective to me. The threads are OK and they appear to retain the bulk of their strength despite the chisel marks. The corners are good enough for a socket or box wrench to grab them, aren't they?

 

[Bush Mechanic]

4 hours ago, mike6024 said:

 

The nuts look OK from a functional perspective to me. The threads are OK and they appear to retain the bulk of their strength despite the chisel marks. The corners are good enough for a socket or box wrench to grab them, aren't they?

 

 

And it has 'patina'. 

[Mike Macartney]

3 hours ago, Bush Mechanic said:

And it has 'patina'. 

 

'Patina' I like. 'Butchery' I'm not to keen on!

[Mike Macartney]

8 hours ago, mike6024 said:

The nuts look OK from a functional perspective to me.

 

You are correct. I suppose pride comes into it. In years to come when somebody takes the engine apart they may think like me -"The last person who worked on this engine couldn't be bothered to get a socket or spanner the correct size to undo this nut - I wonder what else he bodged!"

[Mike Macartney]

16 hours ago, Terry Harper said:

Are you planning to check the straightness of the connecting rods as well?

 

Thanks for your kind words Terry. Yes, my next job after the flywheels/crankshaft is to check the con rods. From my motorcycle experience I know that you can quite often find bent rods. The smaller of the two conrods (the secondary conrod) is long and slender. Not knowing the history of the engine it is worth me checking the rods while I have it apart. I will need to make mandrels for both the big ends as they different sizes. I have a glass surface plate that I hope is big enough to check the conrods on.

[Mike Macartney]

16 hours ago, JV Puleo said:

Worst case scenario, make an 18tpi nut as close as you can and see if it works.

 

At least it will give me a bit more practise at threading on the lathe. To date I have not tried threading on the large lathe, only on the smaller Myford lathe.

[Mike Macartney]

17 hours ago, Roger Zimmermann said:

Thanks for the explanation! Of course, the flywheels must have an axle to be able to turn, it was what I did not see.

 

When you have not had experience of vintage motorcycle engines it can be confusing, when compared with car engines. It was probably my fault for not explaining better in the first place.

[Mike Macartney]

Machining the two flywheels to the same width. I had a problem!

 

 

I checked that the cutter would traverse the face before machining and decided to cut the metal from the inside out. When the cutter had got to the outside diameter of the flywheel, I stopped the lathe,  it looked as if the cutter had gone blunt about a third of the way across the flywheel and had been rubbing rather than cutting!?!

 

This was the tool I was using.

 

 

I don't know if the angles were wrong or why it went blunt so quickly.

 

As this was going to be my last cut on the flywheel I decided to resort back to a tool with a carbide insert. The lathe tool was actually too tall for the tool post but, as the face to be cut was far enough out from the centre of the flywheel, I gave it a go.

 

 

Luckily, it worked OK. I can now get on with separating the conrods and see what problems I have there.

 

 

[Mike Macartney]

Separating the V-twin engine conrods to see if there are any problems.

 

As the secondary conrod was ''floppy' from side to side when the main conrod was held I knew there would be a problem with either the phosphor bronze bush or the 'small' big end pin.

 

 

Just in case I could fit the small conrod the wrong way around, I marked both conrods on both sides with masking tape, noting where the other rod fitted. In the above photo at the 'big end' of the small conrod you can see that there seems to be a locating peg. As there is no way of removing this the pin must slide out on this side.

 

The first job was to remove the split pin on the other side that seemed to be holding the pin in place. I think it would be best to replace this split pin with a roll pin when I put the engine back together.

 

 

I hoped that by straightening the other end of the split pin I could tap the pin out a little to grab hold of the split pin head as the head seemed to be recessed in.

 

 

Luckily the pin moved easily when the other end was straightened and the pulled out easily, even with these 'cheapo' pliers. Seeing the 'hammer marks' on the main big end makes me wonder why they are there?

 

I think a new pin is needed, there is a lot of wear.

 

 

As yet I have not measured the shaft, even before measuring you can see that it is very worn. The ridge is unusual, it must be due to the wear being uneven due to the motion of the secondary conrod around the movement of the main big end? The bush seems to have very little wear.

 

 

The two rods apart, with the connecting pin back in the large conrod and the rather small split pin sticking out of the end of the large conrod.

Edited August 8, 2019 by Mike Macartney
Added a bit more (see edit history)

[JV Puleo]

That is a lot of wear, exaggerated by the fact that the split pin kept it from turning so all the wear is on one side. Is there room in there to make the pin longer and put circlips on the ends so the pin floats? I'm guessing there isn't but it would be worth checking. I think that I'd make an oversize pin, then ream and lap the holes so it was a light press fit.

 

Another thought... if there is enough material, you could counterbore either end of the hole the pin is in so that just enough projects to add a C-clip

Edited August 8, 2019 by JV Puleo (see edit history)

[Mike "Hubbie" Stearns]

Mike, could the wear on the shaft and/or bushing account for the difference in the Conrad length ?

[mike6024]

Can I request some measurements, out of curiosity?

 

1. center to center, Master rod big end to wrist pin.

2. center to center, Link rod

3. Center of big end to center of link pin.

 

Wonder if they add up. That is, if measurement #1 = #2 + #3

 

 

[chistech]

11 hours ago, JV Puleo said:

That is a lot of wear, exaggerated by the fact that the split pin kept it from turning so all the wear is on one side. Is there room in there to make the pin longer and put circlips on the ends so the pin floats? I'm guessing there isn't but it would be worth checking. I think that I'd make an oversize pin, then ream and lap the holes so it was a light press fit.

 

Another thought... if there is enough material, you could counterbore either end of the hole the pin is in so that just enough projects to add a C-clip

I was thinking the same thing. It looks like there’s at least .375 on each end which should leave enough for a clip with a shorter pin.

[mike6024]

No I wouldn't do that. Yes it looks like it would be possible. Not advisable. That would be load bearing material you would be machining away.

 

The original design is the link pin is fixed. The crank end of the link rod has a bushing in it. The force is transferred from the link rod to the master rod where that link pin is tightly fitted into the master, and fixed with the cotter pin. if the pin were allowed to float or rotate, you'd have another friction interface, but without any bushing. If you know what I'm saying.

 

[Mike Macartney]

18 hours ago, JV Puleo said:

I think that I'd make an oversize pin

 

Does this mean you think I could make a replacement pin with the equipment I have? I had thought that this maybe a specialist job that would need hardening and a ground surface?

 

I doubt very much that there is any room for circlips, or the like. I will do some measuring today.

 

I will reply to the other posts this afternoon, after I have spent some time in the garage this morning. 

[Terry Harper]

Hello Mike,

 

If you need a ground surface for the pin I would look for or borrow a tool post grinder.

I borrowed one when I did the valves and lifters and it worked great. You could probably even

cobble one together with a bit of scrounging.

 

T.

[Mike Macartney]

14 hours ago, Mike "Hubbie" Stearns said:

Mike, could the wear on the shaft and/or bushing account for the difference in the Conrod length?

 

It is possible. The considerable wear on the shaft is not going to help the difference in compression heights.

[Mike Macartney]

12 hours ago, mike6024 said:

Can I request some measurements, out of curiosity?

 

1. center to center, Master rod big end to wrist pin.

2. center to center, Link rod

3. Center of big end to center of link pin.

 

Wonder if they add up. That is, if measurement #1 = #2 + #3

 

 

 

I do not have a Vernier caliper that will measure the rod lengths so I had to measure it with a steel rule.

 

BIG CONROD = 9-1/32" + half the small end diameter + half the large big end diameter

Therefore = 9.0313" + 0.2575" + 0.4875" = 9.7763" Nominal 9.75"

 

SMALL CONROD = 7-15/16"  + half the small end diameter + whole of the big end diameter + distance from large big end

Therefore = 7.9375" + 0.2575" + 0.515 + 0.5625 = 9.2725" Nominal 9.25"

 

I must have gone wrong somewhere! I'll check tomorrow when I am less tired.

[Mike Macartney]

5 hours ago, Terry Harper said:

You could probably even cobble a tool post grinder together with a bit of scrounging.

 

I did in fact make one a few years ago for my Myford lathe. I make it out of a brand new bench drill press that I won in a raffle. It was a failure; it ran too slow and I used the chuck to hold the grinding wheel. I thought I had sold it on, but I saw this morning it is in my bottom shed where my Myford is!

 

I have managed to get good surface finishes, after turning, by using emery cloth with the lathe chuck spinning at high speed.

[Mike Macartney]

12 hours ago, chistech said:

I was thinking the same thing. It looks like there’s at least .375 on each end which should leave enough for a clip with a shorter pin.

 

8 hours ago, mike6024 said:

No I wouldn't do that. Yes it looks like it would be possible. Not advisable. That would be load bearing material you would be machining away. The original design is the link pin is fixed. The crank end of the link rod has a bushing in it. The force is transferred from the link rod to the master rod where that link pin is tightly fitted into the master, and fixed with the cotter pin. if the pin were allowed to float or rotate, you'd have another friction interface, but without any bushing.

 

I agree with Mike, the width on each side of the large conrod, where the smaller conrod fits, is only around 0.310" on each side.

[Mike Macartney]

Here are some photos of the bottom of the V-twin conrods with some measurements. I'll put some text in tomorrow. My brain is a bit 'muddled' with all the measuring and calculations I have been doing!

 

 

 

 

 

 

 

 

[alsfarms]

Hello Mike,  I took a couple of minutes to inquire as to how both the main rod and secondary rod get the flow of lubricating oil.  With the wear noted, I suspect that an oiling issue is one of the causes if not the main cause for the serious wear.  How straight are your rods?  Do you have any literature that calls out the RPM's this engine should run?  How are the small ends of both rods?

Al

[mike6024]

So the diameter of this worn pin is .506 inch or 12.85 mm or about 13 mm. I think it does need to be hardened, high carbon

 

 

I think you could use one of these to make a new pin. It is a shoulder bolt (again!). D13 and 12.9. Where the 13 means the shoulder part is 13mm diameter, and 12.9 means the hardest, highest quality bolt. metric bolt grades being 8.8, 9.8, 10.9, and 12.9.

 

I'd suggest buy one of these, they're cheap, Price:US $4.35   -  http://www.ebay.com/itm/D13-M10-x-1-5mm-Socket-Head-Shoulder-Bolt-Stripper-Screw-High-Tensile-12-9/132444483292?

 

 

Edited August 9, 2019 by mike6024 (see edit history)

[Mike Macartney]

17 hours ago, Mike Macartney said:

I must have gone wrong somewhere! I'll check tomorrow when I am less tired.

 

Checked my calculations of the length of the conrods this morning. I had made a mistake.

 

The large main conrod is 9.775" long and the effective length of the secondary conrod is 9.760" long. So they are virtually the same length.

[Mike Macartney]

14 hours ago, alsfarms said:

How do both the main rod and secondary rod get the flow of lubricating oil.  With the wear noted, I suspect that an oiling issue is one of the causes if not the main cause for the serious wear.  How straight are your rods?  Do you have any literature that calls out the RPM's this engine should run?  How are the small ends of both rods?

 

Al, The lubrication system is by splash lubrication, not ideal. The drillings for the lubrication to the big ends look clear with no blockages. I will try and take a couple of photos. I am about to check the rods for straightness. I am about to make some mandrels to check the straightness of the rods. I have no literature that shows the RPM of the original engine. Both the small end bushes and piston wrist pins look good with no noticeable wear. Mike

[Mike Macartney]

14 hours ago, mike6024 said:

I think you could use one of these to make a new pin. It is a shoulder bolt (again!)

 

Thank you for the link. Would the shoulder bolt be hardened? There is no room to bolt it in position as the big end is between the two flywheels. If the shoulder bolt is hardened I would not be able to drill the hole for the locating pins. I think I need to machine a new pin, drill the fixing holes and then harden it by heating and quenching. Do you think I would then need to temper the steel to a light straw colour?

[alsfarms]

Hello Mike,  Does the rod assembly simply have a hole in the bottom of the rod assemble that is dipped into the oil as it rotates?  How much level is help in the crankcase?  Do you have room to afix some form of a "dipper" (like an old Chevrolet 6 cylinder engine uses) to scoop up and force a slug of oil into the rod big end with each revolution?

Al

[JV Puleo]

I doubt the pin was hardened but you could test it by trying a file on one end where it isn't worn. Unlike today, cranks weren't hardened in 1914. I also doubt it was ground although that would be nice to do. Cylindrical grinding came rather late to Britain where the "turners" - the lathe men - were very suspicious of it, believing it would leave tiny bits of abrasive in the surface. But, I think I would go for a ground pin the closest size larger than you need regardless of whether it's metric or imperial. The split pin was not a bad idea. It cannot come out where a roll pin or a tapered pin might. Dowel pins would be very difficult to drill and I don't know what you have in the UKfor ground rod but something must be available. Having replaced the pin, you could then replace the bushing, lapping it to fit the pin perfectly. There is always a temptation to do it wildly better than the original - I certainly suffer from that but sometimes it's not worth the effort. Even if a floating pin would be better, we have to think of the effort involved and whether it will make any difference at all over the long haul.

[mike6024]

 

That 12.9 shoulder bolt would not be hardened. It would just be a high carbon, high tensile strength steel. But these are from China, so there is a question there about quality.

 

The reason I suggested it is that it should be like a nice, uniform, 13mm with a smooth ground surface, so all you would need to do is cut the head off, and cut it to length, and drill your hole in it. 

 

So really no different than a high carbon, 13mm steel rod. Just the shoulder bolt is a nice short rod. Buy one a little longer than you need, you can pick the length.

 

You do not want mild, low carbon steel.

 

SAE bolt grades are 3, 5 and 8. You use 8 where quality and strength are important, like bolts for suspension and steering.

 

Metric grade 12.9 is high grade comparable to SAE grade 8.

 

http://www.boltdepot.com/fastener-information/materials-and-grades/bolt-grade-chart.aspx        -   Bolt grade links

 

Grade and Material    Mechanical Properties
                                                                                                         Min. Tensile Strength
Class 8.8 Medium carbon steel, quenched and tempered    830
Class 10.9 Alloy steel, quenched and tempered                     1040
Class 12.9 Alloy steel, quenched and tempered                     1220

 

 think if you then want to harden it, you (heat and) quench it, but not temper it. The tempering is heating again after the quench to reduce the hardness, and reduce the brittleness to lessen the chance of cracks developing. hardened steel can be more brittle, but it depends on the thickness. It should be hardened on the outside surface but the inside, tough. If you hard a thin piece of steel you could quench it, hardened all the way throughout, it would be expected to be brittle and break.

 

Hardened steel. The term hardened steel is often used for a medium or high carbon steel that has been given heat treatment and then quenching followed by tempering. The quenching results in the formation of metastable martensite, the fraction of which is reduced to the desired amount during tempering.

 

I took just one material science class back in college, don't remember much, but hardening was mentioned, and we did do some hardness tests in the lab using a Rockwell machine which tells you how hard based on how deep a dent a pin puts into the steel. When you quench, some of the carbon atoms remain "outside the matrix" because it cools too fast, making it hard. You change the steel grain structure.

 

So, in summary, I'd say just get one of these 12.9 shoulder bolts and make your pin, and don't try to harden it or anything. Maybe you can tell how hard it feels by filing on it. it should definitely be harder than just a common mild steel rod.

 

 

Just my opinion. You can make the rod any way you like, but if you buy some steel rod I think you should get a high-carbon alloy, not just any rod.

[mike6024]

Carbon Steel

Carbon Steel can be segregated into three main categories: Low carbon steel (sometimes known as mild steel); Medium carbon steel; and High carbon steel.

Low Carbon Steel (Mild Steel):  Typically contain 0.04% to 0.30% carbon content. This is one of the largest groups of Carbon Steel. It covers a great diversity of shapes; from Flat Sheet to Structural Beam. Depending on the desired properties needed, other elements are added or increased. For example: Drawing Quality (DQ) – The carbon level is kept low and Aluminum is added, and for Structural Steel the carbon level is higher and the manganese content is increased.

Medium Carbon Steel: Typically has a carbon range of 0.31% to 0.60%, and a manganese content ranging from .060% to 1.65%. This product is stronger than low carbon steel, and it is more difficult to form, weld and cut. Medium carbon steels are quite often hardened and tempered using heat treatment.

High Carbon Steel: Commonly known as “carbon tool steel” it typically has a carbon range between 0.61% and 1.50%. High carbon steel is very difficult to cut, bend and weld. Once heat treated it becomes extremely hard and brittle.

 

Difference between 1018 mild steel and 1045 medium carbon steel - http://www.capitalsteel.net/news/blog/1018-vs-1045-steel-comparison

 

.You see the 1045 has more carbon, is stronger and harder.

 

	1018	1045
Iron, Fe	98.81-99.26%	98.51-98.98%
Carbon, C	0.18%	0.45%
Manganese, Mn	0.60-0.90%	0.60-0.90%
Phosphorus, P (max)	0.04%	0.04%
Sulfur, S (max)	0.05%	0.05%

 

	1018	1045
Tensile Strength	64,000 psi	91,000 psi
Yield Strength	54,000 psi	77,000 psi
Elongation in 2"	15%	12%
Reduction in Area	40%	35%
Brinell Hardness	126	179

Edited August 9, 2019 by mike6024 (see edit history)

[Mike Macartney]

On ‎8‎/‎8‎/‎2019 at 6:22 PM, alsfarms said:

I suspect that an oiling issue is one of the causes if not the main cause for the serious wear.

 

Al, Yesterday I forgot to take photos of the bottom of the smaller conrod showing the oil holes. I made a note in my book to take them, but then got involved in machining the mandrels, for checking the straightness of the conrods. This morning I managed to remember to take the photos. I don't think the big end actually dips into the oil. I think that just the flywheels are in contact with the oil, which causes an oil mist inside the bottom half of the engine, but I may be incorrect in my assumption.

 

This a photo of the oil holes for the lubrication of the main (big) conrod.

 

 

You can see there is a oil hole each side of the conrod.

 

This is a photo of the bottom of the secondary conrod 

 

 

On one side of this conrod is an oil hole.

 

When you look on the other side.

 

 

There is no hole for the oil.

 

Looking inside the bronze bush.

 

 

You can see an 'oil trough' has been cut along both sides of the oil hole. I am now wondering to myself, if the ridge in steel pin has been caused by the ridge getting lubrication and the area either side of this ridge, not getting enough lubrication and wearing away the steel pin? Next time I go up to the garage, I'll check the position of the ridge in relation to the 'oil trough'. Yet another thought; the power force of the cylinder firing on this conrod is going to directly travel along the line of the conrod. The 'oil trough' in the bush is nearly inline with conrod, maybe this is why it has worn a ridge on the pin? Perhaps a spiral cut, in the bronze bush, would be better for wear than a straight cut?

 

It maybe a good idea to drill an extra oiling hole on the side of the conrod that does not have a hole. What do you think?

 

Looking at the photo above I can also see a groove around the inside of the bronze bush by the oil hole. I'll also examine that to see if it is a wear mark, or, was meant to be there.

 

 

Here is a different view.

[Mike Macartney]

On ‎8‎/‎8‎/‎2019 at 7:05 PM, mike6024 said:

I'd suggest buy one of these, they're cheap, Price:US $4.35   -  http://www.ebay.com/itm/D13-M10-x-1-5mm-Socket-Head-Shoulder-Bolt-Stripper-Screw-High-Tensile-12-9/132444483292?

 

Mike, I have saved it in my eBay. I will have a look and see what length I need. It seems a reasonably cheap way of buying a ground shaft.

[Mike Macartney]

18 hours ago, JV Puleo said:

I doubt the pin was hardened but you could test it by trying a file on one end where it isn't worn. Unlike today, cranks weren't hardened in 1914. I also doubt it was ground although that would be nice to do. Cylindrical grinding came rather late to Britain where the "turners" - the lathe men - were very suspicious of it, believing it would leave tiny bits of abrasive in the surface. But, I think I would go for a ground pin the closest size larger than you need regardless of whether it's metric or imperial. The split pin was not a bad idea. It cannot come out where a roll pin or a tapered pin might. Dowel pins would be very difficult to drill and I don't know what you have in the UKfor ground rod but something must be available. Having replaced the pin, you could then replace the bushing, lapping it to fit the pin perfectly. There is always a temptation to do it wildly better than the original - I certainly suffer from that but sometimes it's not worth the effort. Even if a floating pin would be better, we have to think of the effort involved and whether it will make any difference at all over the long haul.

 

Thanks Joe for that information. I'll try a file on the pin tomorrow.

 

Is it OK to lap in a bronze bush using grinding paste? I had the same thought as those suspicious lathe men. I do realise that it would need a really good clean up after lapping. 

 

What I was thinking of instead of the split pin was a spiral roll pin like this.

 

 

At least it would hold the pin tight. The problem being with the split pin is that the big end pin could move slightly and wear away at the split pin and possibly break it or wear through it. A "belt and braces approach" could be to use the spiral roll pin with a split pin down the middle of the spiral roll pin.

 

I think a floating big end pin would be out of the question, as the sides with the pin holes would have to be bushed, the amount of metal surrounding these holes, for the small big end pin, looks to me as the weakest part of the big end assembly.

 

The hexagonal bar arrived this morning for making the big end journal nuts. Will now be able to try out your nut making method.