# A handy little jig



## mklotz (Sep 8, 2008)

I've decided to take a shot at building Bill Harris' steam roller. Since this is a big project and contains details outside my skill set, I may never finish it but, what the heck, it's always good to think big.

Since it may never be completed, I decided to start by building the engine. That way, if the rest never gets finished, I'll at least have a working engine out of the deal.

The engine has a built-up crankshaft that requires four plates to achieve the orthogonal offsets. These are roughed out as rectangular blocks of 1/4" steel, drilled for the drill rod that will form the round bits, and then need their ends rounded to a 5/8" radius in order to look "kewl".

I took a slug of aluminum left over from another job of this type (the equivalent pieces on the Poppin engine) and drilled and reamed it for a 1/4" locating pin. After milling a slot the width of the parts, I drilled and tapped for a 10-32 screw to lock the part in place after it is slid over the pin.

The slug is then chucked and the radius turned. Flip part and repeat. Total time to do all four parts was about ten minutes.


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## ksouers (Sep 8, 2008)

Gotta love symmetry ;D

You can always use it to your advantage to cut your workload (roughly) in half.


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## ChooChooMike (Sep 8, 2008)

Marv - if you only ever finish the engine, looks like you can use it to build a Shay loco !!


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## mklotz (Sep 8, 2008)

ChooChooMike  said:
			
		

> Marv - if you only ever finish the engine, looks like you can use it to build a Shay loco !!



I probably could at that but I've seen how silly those old guys look sitting on a tender behind a tiny loco. I'll stick to looking silly in more refined and more comfortable ways.


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## steamer (Sep 8, 2008)

Excellent!

That is one I will remember!

That beats a rotary table silly!

Thankyou!

Dave


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## Bernd (Sep 8, 2008)

Nice fixture you designed there Marv. Great idea for those small radii. As Dave said, beats the rotary table.

I need to design one that makes a concave curve on a 4 7/32" radius. I want to do it on a lathe on a face plate but my Grizzly only has a 7.5" face plate but a 9" swing. Perhaps an aluminum sacrificial plate?

Bernd

Here's a drawing of what I need to raduis. It's a pedestal for a truck on a steeple cab electric loco.


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## Philjoe5 (Sep 8, 2008)

Thanks Marv for showing a great fixture. I often run into a problem using my rotary table for rounding things. This looks like a good option to have in the old "toolbox". :bow:

Cheers,
Phil


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## tmuir (Sep 9, 2008)

I love that, very different.
How big is the model?


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## Metal Mickey (Sep 9, 2008)

Good tip! Stored away for the future, many thanks. Good luck with the build but where are you going to find the Tarmac to roll? :big:

Mike


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## hitandmissman (Sep 9, 2008)

Nice tip. I have that set of plans myself but never started it. Maybe some day. Please keep us informed as to how it is coming along.


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## Stan (Sep 9, 2008)

Marv: A friend of mine made that model several years ago. When he died, I inherited some of his tooling and I think I have the two gear cutters he bought to make the drive gears on the roller. You are welcome to them if you need them. Send me an email and I will dig them up and get the data of them.
Stan


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## georgeseal (Sep 9, 2008)

Stan,
Put me on the list for using the gear cutters.
I have one about half finished. (along with a bunch of other projects)
I go great guns on a project until I run into a problem and lay the project down. It may take years to resume. This used to bother me (and SWMBO). Now I have realized that I am not selling these models and it does not matter if they are finished or not. What is important is the enjoyment that I have received by working on them.

just my $0.02 worth


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## mklotz (Sep 9, 2008)

Bernd,

Another approach for your part is to do it incrementally on the mill with a ball-end mill.
Take a look at the ROUNDER program on my web site. It's designed to do just that sort of operation.

Metal Mickey,

I live in Southern California. Half of the county is tarmac parking lots.

Stan,

Thanks for the offer. I'll get an email off to you post haste.


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