Help in making simple split bearings.

[Gas_mantle]

Hi,

I'm wondering if someone can help me in trying to make some simple split bearings for a small engine I'm making.

I need to make 4 all the same and am trying to make them from 3/8 steel and brass without much success - I'd like if I can to have feet either side of the bottom for mounting to the base and radiused sides turned on my lathe, something like this very crude hand drawn picture.



At the moment I've tried lining the parts up then drilling and securing the them with bolts and trying to turn the edges the same and perpendicular to the base but I'm having trouble getting everything to line up to the lathe centreline. They way I'm doing it I can get the top running ok by using the tailstock centre but with the base mounted in the chuck I can't seem to position it right so the end result is square.

Clearly the way I'm trying to do it isn't a very good method but I can't think of any other way, can anyone please suggest a better way or at least tell me how I can improve on the method I'm using.

Any help would be great, thanks.
Peter.

[Jasonb]

I'd say you are juggling two mant bits of metal at once.

Treat the top, bottom and bearing as 3 separate parts.

First soft solder the bearing halves together.

Now machine them to a length just over your turned dia, machine the caps to the same length and finally the bases to the finished length over the feet.

Now set up in the mill and drill clearance holes in the bearings and caps, note which side is against the vice fixed jaw and if you use some form of stop it will allow you to do the 4 caps and 4 bearings at equal settings. Add a small BS0 ctr drill hole to the middle of the bearing caps as you do them.



Now drill and tap the bases and also put in the holes for the feet.

The bearing can then be lightly held in teh 4-jaw to be drilled & reamed



With that done assembe the three partsand screw together making sure that the faces you had against the vice fixed jaw are all on the same side.

Set up in the 4 jaw with packing behind to give a level surface to rest the base against, and set the ctr drilled hole to run true. Bring up the tailstock centre for support, remove packing and turn your outer curved surface, this is a longer part but same setup.



The ctr drille dhole can now be extended with a 1/16" drill so it breaks through the top bearing half for oiling. Mark all 4 bits of metal so they go back together the same way before taking apart to deburr and melt the solder apart

 You will just have the base rather than a conrod

[Gas_mantle]

Thanks Jason,

I wouldn't have ever thought of doing as you suggest but now you've shown me I can see how it's a far better method and I'll give it a go tomorrow.

I don't yet have a mill but think with care I ought to be able to get round that problem in my drill press, as for the soldering will Loctite 638 be a suitable substitute ? I know it's really a bearing retainer but presumably it will hold for what I need.

You wouldn't believe how many attempts I've made at these parts, I even had to order more materials yesterday in order to have another go 

Peter.

[sssfox]

Peter,

If you plan on bolting (or screwing) the final parts together, you can clamp the pieces in a small vice by the ends that will be cut off, then clamp the small vise rotated 90 degrees in a larger vise, so you can drill pilot holes all the way through.  Then, separate the parts, drill the pass through holes, thread the bottom part and screw everything together.

You can still loctite everything together so nothing shifts.

Just another way of doing it.  Any way that will keep the parts from shifting will work.

Steve Fox

[RayW]

Hi Peter,

Having just made the split big end bearing for my Otto engine, I would go along with Jason's suggestion of soft soldering. As long as you ensure that the mating faces are good and flat before soldering, the two halves should hold together without any problem and are easy to separate with gentle heat once machining is finished. It is then a simple matter of cleaning off the soldered faces by light sanding on a flat surface.


Ray

[Gas_mantle]

Hi Steve,

Thanks for your reply, the problem I was having in the last few attempts was that by drilling through all the parts together no matter how hard I tried with my simple drill press the holes did wander slightly then after bolting everything together to turn the sides in the lathe I was having difficulty picking up the centreline to mount accurately in the chuck. The way I was doing it by dialing the edges of the foot in the chuck to centre the base proved difficult to get spot on - although I do accept most of that is probably my inexperience.

This is the first attempt I made and as you can see it's like the Leaning Tower of Pisa !



What I've decided to do tomorrow is vastly reduce the height by cutting slots in the base plate to lower the crankshaft, by doing that I can use the steel sideways to gain more width and thereby allow me to make protruding feet at the sides and also by keeping to the metals width the 2 untouched sides will form the bottom and the surface the brass will sit on.

I'm hoping by reducing the height, widening the base and making it the way Jason suggests I can achieve greater accuracy.

If nothing else a shorter wider bearing will look more in proportion anyway.

Hope that makes sense, it's difficult to describe what I mean - I post a pic of the finished results in a day or 2 

Cheers
Peter.

[Gas_mantle]

Thanks Ray, you replied just as I posted my last message - as you can see above that's what I'll do but without any soldering gear it will have to be Loctite.

Cheers
Peter.

[Gas_mantle]

Hi,

Thanks for the helpful replies, just thought I say I got one of the bearings done and the other 3 roughed out. The picture isn't great but you can see it's a vast improvement on the first attempt, I used Jasons method modifying it slightly so I could do it on my bench drill.



Cheers
Peter.