Stew Hart's Simpson and Shipton Short Stroke

[sshire]

The Alliterative Engine
Simpson and Shipton Short Stroke

Episode 3

With the plates completed, I wanted to get on the columns, the bases and the rotunds.

There are 12 fluted columns, 12 bases and 24 rotunds to make,

First up, the fluted columns. My first thought was to setup the dividing head on the Bridgeport.
On second thought, this seemed like a good opportunity to sort out the CNC rotary axis.
Setting the steps per degree in Mach 4 took quite a long time until I got it bang on and then indicated.







After that, not much to do but watch it make 4, 6” long columns.

<a href="https://www.youtube.com/watch?v=tJv1Nqgp3Zk" target="_blank">http://www.youtube.com/watch?v=tJv1Nqgp3Zk</a>




These were later parted into the 12 columns on the lathe and powder coated. In addition, each column is drilled and tapped 6-32 ate both ends.









The Rotunds

The rotunds are made with a form tool. I began with a piece of tool steel and milled a semi-circle into one end. Using a tapered cutter give a nice relief angle to the hole.





To create the relief angle, on the front edge, I used the surface grinder and sine vise.



The tool was heat treated and then diamond honed.








On the lathe, 24 rotunds were turned.







It’s quite important that the columns, the bases and the rotunds are the same height. If not, the plates will rock, twist and other bad things.

First, each of the 24 rotunds went into a 5C collet on the surface grinder and, on the recommendation of Norton, a black silicon carbide wheel was installed to machine the brass. With the mini-cool running, the wheel did not load up and gave a very nice surface finish.



So, one side flat. The reverse was done in groups with the rotunds fixed to a ground flat with double-stick tape. All 24 were within .0005. My backup plan, if the coolant was causing the tape to fail, was





The bases were cut from a 1” brass square bar. I wasn’t happy with the thought of parting them off on the lathe or the bandsaw as I’d turn as much of the brass into chips as the part thickness. My solution was to face them on the Bridgeport and use a thin slitting saw.





One face was flattened with the face mill and then the final dimensioning was the same as the rotunds: double-stick tape and surface grinder.



Returning to the plates, I neglected to show the pre-powder coat finishing.

Flattening



Chamfering





Finally, the obligatory family shot.



Thanks for watching.

[sshire]

Bill
I actually haven't been out of the shop. it's just all the non-engine stuff that gets in the way

Kirk
They are high temp silicon powder coating plugs.
All things powder coating here
https://www.amazon.com/Powder-Pro-Coating-Supply/b/ref=bl_dp_s_web_14105410011?ie=UTF8&node=14105410011&field-lbr_brands_browse-bin=Powder+Pro+Coating+Supply

[gerritv]

That is a seriously good looking base!
Great that you can grind brass, will keep that in mind.

Gerrit

[b.lindsey]

Stan, what is the Bosch head attached to the mill? Why did you use that rather than the mill spindle? Ir did I miss something?

Bill

[sshire]

The max rpm on the LMS mini mill with the speed up kit is 5000 rpm.
The Bosch 1hp trim router is 30,000 RPM.
Feeds rate and surface finish (with carbide end mills)all benefit.
Also, much improvement on engraving ops.

[Tennessee Whiskey]

Excellent documentation as always Vern. The powder coating looks great 👍. Seems like you are getting on well with the CNC. Keep it coming   

Cletus

[sshire]

Thanks Bill, Gerrit and Cletus.
Much appreciated.
I may just PM the build to you guys. Secret build log.

[b.lindsey]

Stan, I am also curious as to how well the powder coating sticks to sharp corners or in this case the edges of the flutes. Does it tend to recede away from them in the curing process or cover them as well as flatter surfaces?

Bill

[Dave Otto]

Looks great Stan!

I would be worried about scratching it up during the rest of the build.


Dave

[sshire]

Bill, there doesn't seem to be any issue with sharp corners. After reading Powder Coating forum posts, the issue with problem corners seems to be either burrs or VERY sharp corners. Of course, good prep is essential. I'm pretty sure that my rubdown with ScotchBrite, then bead blasting, then acetone and (in the case of the columns) a run by the ScotchBrite wheel on the bench grinder, has knocked off the burrs and slightly rounded the edges.
The issue I had with inside corners on the old gun (HF) was a Faraday Cage effect. (Powder not being attracted to inside corners)  The Redline gun has a continuous KV adjustment so that issue is gone. The ability to vary the Kilovolt setting in an analog manner is superior to the Eastwood dual voltage gun - only 2 settings.

[sshire]

Thanks, Dave.
It's plastic wrapped now and will remain so for part fitting. I'll just be real careful.
Since I got the new gun, the dogs are hiding for fear of becoming Super Mirror Black. I keep looking for stuff to powder coat.

[kvom]

My friend, who does powder coating for automotive parts, does a clear coat first, then a color coat.

[sshire]

Second coats are difficult unless you have a $1000 gun.
That's what I understand. I may give that a try. Nothing to lose.

[Dave Otto]

My friend, who does powder coating for automotive parts, does a clear coat first, then a color coat.

That seems backwards, what is the reason he does the clear first?

Dave

[10KPete]

Corners....

Pete