# Off centre machining



## malmac (May 3, 2018)

I wanted some custom spacers for the saddle on my old motorbike. However the stud was not central to the space. So I offset my work piece in the 3 jaw chuck using a piece of metal, drilled the hole off centre, then re centered the piece to machine the main body and then to get the slightly oval end result, placed it back in the lathe off centre again and machined off one side. I have not used that approach before and it was much quicker that changing over to the four jaw chuck.     Enjoy your workshop    Mal


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## FOMOGO (May 3, 2018)

That's using the old noodle. What sort of motorbike do you have? inquiring minds, and all that. Cheers, Mike


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## malmac (May 3, 2018)

I have two early 1960's BMW twins. One is up and running and the other is still in parts. Lots of fun times ahead of me.

here is a pic of the one that is together and running.


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## thomas s (May 4, 2018)

Good job on the spacers. Nice looking bike.


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## chips&more (May 4, 2018)

Just did the same thing today. Needed a 0.005” offset hole. Took a 0.007” shim in one of the three jaws to do it. The internet has formulas to find the proper shim. But I have found that there are too many variables to get the perfect offset from math and or set-up. I trial and error or close enough kinda thing. Only takes a few minutes. And like said, another reason I hardly use a 4jaw chuck…Dave


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## malmac (May 4, 2018)

chips&more said:


> Just did the same thing today. Needed a 0.005” offset hole. Took a 0.007” shim in one of the three jaws to do it. The internet has formulas to find the proper shim. But I have found that there are too many variables to get the perfect offset from math and or set-up. I trial and error or close enough kinda thing. Only takes a few minutes. And like said, another reason I hardly use a 4jaw chuck…Dave



Dave, I had never tried it before - it worked well. However I also have a job coming up, to cut some acme thread into some square brass stock - think the 4 jaw will be the go for that job.

Mal


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## RandyWilson (May 4, 2018)

I specialize in offset machining. I just need to learn how to control which way and how much.


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## chips&more (May 4, 2018)

malmac said:


> Dave, I had never tried it before - it worked well. However I also have a job coming up, to cut some acme thread into some square brass stock - think the 4 jaw will be the go for that job.
> 
> Mal


Mal, maybe the 4jaw maybe not. I typically sleep on it. Then the next day I usually have a plan that is different than the day before. And is faster, easier and more accurate. Keeping your project machining steps simple can be challenging, but can yield your best results. When you think there is only one way to do it, try sleeping on it…Dave


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## FOMOGO (May 4, 2018)

Nice bike. Always had a soft spot for the older ones. Mike


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## malmac (May 4, 2018)

chips&more said:


> Mal, maybe the 4jaw maybe not. I typically sleep on it. Then the next day I usually have a plan that is different than the day before. And is faster, easier and more accurate. Keeping your project machining steps simple can be challenging, but can yield your best results. When you think there is only one way to do it, try sleeping on it…Dave




Totally agree on the sleeping bit. I also hand write a step by plan - if things are bit complicated. It helps me look for a simpler way of solving the problem. So much is about the thinking before the turning.

Mal


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## tjb (May 4, 2018)

I usually figure out the right way after having done it the wrong way a time or two.  Works every time.


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## brino (May 4, 2018)

chips&more said:


> When you think there is only one way to do it, try sleeping on it.



...or ask here.
You will get such varied opinions and methods that'll you'll have to read the thread several times to get all the nuiances, and then you can design a custom process using the best parts of every other method.
-brino


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## malmac (May 20, 2018)

tjb said:


> I usually figure out the right way after having done it the wrong way a time or two.  Works every time.




Yep did that the other day. Made two brackets for my new ute tray. One I measured worked perfectly, but the second one did not allow for the fact that the tray builder did not put the under tray gussets in exactly the same spot. Bugger - so now I have to make a second bracket that is slightly modified. Did I learn a lesson, well maybe not, I am sure I will many more such unnecessary mistakes in the future. Attached is a photo of the bracket that fitted correctly.   That is our slide on camper which sits on the tray of the vehicle.    Cheers    Mal


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