# Making eccentrics with help from the miller



## Bogstandard (Aug 27, 2007)

First off turn up your eccentric blanks in the lathe







Then mount your blank onto the miller, either into the RT or the vice (if you have a backstop on the vice, use it then you can repeat the op by just dropping it in), and centre it to the spindle.






Offset by the required amount using your X or Y indexing handles and lock the table up. Then just drill your holes. If you are doing more than one just drop the new one in and drill away.






Either make up a mandrel to fit or just a bolt in the lathe chuck and mount up the drilled eccentric and gently turn the boss to the required size (this pic shows it being done in a 4 jaw self centreing chuck not a 4 jaw independent).







Job done.






John


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## Bogstandard (Sep 9, 2007)

That looks very good Kevin, it certainly makes a slicker looking eccentric.
Might have a bit of trouble cutting the inside groove on some of the smaller ones, but just might give it a go.
Definitely one for where you are stuck for width, this would fit the bill perfectly.

John


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## compound driver (Sep 10, 2007)

Hi John
The eccentric is the same as is used in full size practice on most if not all traction engines and many stationary engines. The other advantage is the single center shoulder helps prevent side play on the strap.
Some time this week or next im machning up the last strap for the traction engine il post a few pictures as I do. Again this ones from cast iron with a MS sheave.

Cheers Kevin


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## compound driver (Sep 10, 2007)

eccentrics from the two inch. 

The sheaves are machined 1.250 with a .125 shoulder. The straps are bored 1.249 and the grooves .135 deep.

Threads in the straps will be drilled and reamed for 5BA bolts after teh last machining job. 











Cheers Kevin


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## Bogstandard (Sep 10, 2007)

Lovely work Kevin, it could be classed as heavy engineering against some of the work we do.
As I said before, I will give this a try when I design my next little engine, but the limitation as I said is the groove in the inside of the strap. Maybe if I cut the groove first, then make the sheave to fit.
The max width of the groove would be 1.5mm
The only prob that I see is that I design and make my engines so that a raw beginner can also make them with a bit of instruction, I am just wondering if it would be outside their scope as a first build, compared to the usual way we do them.
I gather the crank in the background is built up, otherwise there would be a lot of wasted material.
Have you seen the pics from the Malpas show, I bet you have seen all these engines before.

John


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## compound driver (Sep 11, 2007)

Hello John

Yes the crank is built up but not in the way most are done. The seperate parts are the counter weights these are bolted to the square section of the crank web.

The big problem I could see would not be so much the machining but the tool grinding to make the grooves. the tool I used was ground from stelite (probably Super Hydra). Most of my tool steel came from APV just as it was closing down.
The important thing is to put some relief on the flanks of the grooving tool maybe a few thou in the reach. With out this the groove will be taper sided.

As long as you know the width of the tool and the width of the eccentrics its a reasonable job to use the compound slide to set the tool in the middle of the strap.

Boring the cast iron does need a degree of care as the iron dust tends to stick on the surface of the bore and give a false indication to the machined size. Thats also true during reaming on cast iron but not so much of a problem. 
With the Mehanite cast iron and a sharp tool .0005 should be managable but not in any way required. A few thou either way is fine on most steam engines.
Tool wise HSS is a good option on cast iron and a mile better than carbide.

Im just starting drawing the next engine talking of size. Its a 5 inch to the foot Foster rope hauling engine from around 1901. These were used in Argentina on the huge field systems there. It has one forward gear chain drive and no reversing, should tip the scales at around 5.5 hundred weight. The last one I looked at was a real stunning engine.
I also have a Fowler A7 in the building stage and a Burrell gold medal both in 2 inch to the foot. So not a lot of spare time to cut the grass. Thank god for steam LOL

Cheers Kevin


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## Bogstandard (Sep 11, 2007)

Hi Kevin,
I have no trouble machining anything and if I am grinding very small tooling I do it on my surface grinder, let the machine do the work, I can get within 0.0002" using my grinder.
I always wanted to make one of the larger engines, maybe a 3" but because I can only really use one arm now (I have trouble holding my camera in my right hand just to take pictures) I just wouldn't be able to handle any of the heavy stuff.
I have great admiration for people who build these large models. I was talking to some of the builders at the steam fair and they said that a lot of it is passed down thru the family, in fact one young girl (aged about 12) said that when her grandfather eventually snuffs it, she is taking over the running and maintenance of his 4" traction engine.
I will just have to be satisfied with my little engines, unless you have a spare one you wish to donate F.O.C.

John


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## compound driver (Sep 11, 2007)

Hi ohn
Now thats part of the problem I have as I get older the bits get heavier and harder to move around. I cant even shift the 18 inch rotary table now with out a mate to hekp.

I have a feeling that when this generation of ME's passes on it will be all but finished as a hobby. The Modelworks engines will take over and the likes of them. 

Oh well I suppose all good things come to an end 

cheers kevin


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## Bogstandard (Sep 13, 2007)

They look really good Kevin, very slick looking.
As I mentioned before, to make very small ones just might be a bit much for a beginner, but if I can use this method on my builds I will. A much neater solution.

John


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## AllThumbs (Jan 18, 2008)

A little weed helps with the process a little I see.


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## DICKEYBIRD (Jan 18, 2008)

AllThumbs  said:
			
		

> A little weed helps with the process a little I see.


Like woah dude, I'm not like sure I could do any like machining stuff while blowin' weed! Like, far _out_ dude, lookit all them shiny curly things. They're like SO p-r-e-t-t-y. ;D


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## AllThumbs (Jan 18, 2008)

I only mention it because of the joint in the first picture reply #9


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## compound driver 2 (Jan 18, 2008)

Its a roll up hop head!  been roling my own smokes for years much cheaper than buying packs of smokes. Even rolled my own when i lived in Boston, used to get interesting looks from the police LOL

Cheers Kevin


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## rake60 (Jan 18, 2008)

Huh..
Here a roll up is a tortilla shell filled with eggs bacon and cheese that is
guaranteed to clog up your arteries over night.

Now Gentlemen I believe the topic here is about machining...

Rick


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## AllThumbs (Jan 18, 2008)

My bad. Back on topic.


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