Heisler Universal & Shaft Construction I
Nelson Riedel, Nelson@NelsonsLocomotive.com
/2009, last updated 10/02/2009

The cast iron used to make the Universals is great to machine but dirty.   Bronze is about the same strength as the cast iron and can be substituted if one wants to avoid the black dust.

The first steps to fabricating the HM304 Round Shaft Us and the HM305 Square Shaft Us were to square the material and then finish the shaft ends. 

I purchased 1" X 2" and 1.5" X 2" rectangular cast iron bars from McMaster-Carr.  The rods are rough sawed and at least 1/8" oversize.   The 1" X 2" bar is slightly small to make the 1.125" diameter end of the round shaft U.  I made that end ~ 1.09" diameter.  

The first step was to saw the lengths of bar stock for two Us plus a margin for a saw cut.  

Note the 2.125" dimension on the bar sold as 2" wide.

The sides were smoothed and squared on the lathe as shown in this photo.   The two bars here will make 4 Us.  

This operation was repeated for all the required round and square shaft Us.

Once the sides have been turned smooth (and made nearly perfectly square) the bars were cut in half and the ends turned to make them square.  The  bar was also  made the correct  length in this step.

The neat thing with working with rectangles is that it is easy to locate the holes for the pins and shafts.  The photo shows  mounting the block so that the holes for the pins could be drilled (undersize) and then bored to size.

The shaft ends of all the Us were finished next starting with sawing  off the excess material on the shaft end.  Sorry that this photo is a bit out of focus. 

This a the shaft end of a square shaft U.   The inside had been drilled and then bored to 5/8" diameter.   The outside was turned to 1.275" diameter.   Material at the base of the shaft part was left so that a fillet could be machined there later. 

This is a round shaft U.  The inside was drilled and bored 5/8"  The end was turned to ~ 1.1" OD and a fillet turned where the shaft end meets the U end.   Recall that this was 1" thick bar stock that was in fact a little thicker then 1.25".  The shaft OD could be made a bit smaller if necessary. 

A 3/16" wide broach was then used to cut a 3/16" X 3/32" key slot in the shaft end of these round shaft Us.   That finished the shaft ends.   

The last step was to drill the yoke end 1" diameter to remove excess material.      Those are 1/4" holes located at the inside corners of yoke.   These holes help with a sawing operation later.  

Making the Square Hole: The big challenge was to turn the round hole into a square hole.   I looked up  square broaches and found the cheapest ones cost ~ $250 and they didn't produce a square hole ---- the sides bulged slightly because the pilot drill is 21/32".  

I could easily square up the 5/8" diameter round hole on the mill but there would be fillets the radius of the end mill in the corners.   The smallest diameter end mill that would be strong enough to take reasonable depth cuts is about 1/4".   I have a 3/32" key slot broach that did the Shay wheels and gears and also the Heisler wheels and gears and is still reasonably sharp.  I decided to try to use it to remove the 1/8" radius fillets in the corners after the sides were finished with a 1/4" end mill. 

The sleeve shown on the right was made from 5/8" square bar stock.  A 3/16" tension pin will be inserted in the hole to keep the sleeve from sliding through the hole.   
This shows the "hole squaring" tools. Normally one shim is used to broach a 3/32" deep key slot.  I had to make the brass shim that was used together with the standard shim to make a third pass.   
The hole was first squared up by plunging a 3/8" end mill into each corner
Next, a 1/4" mill was plunged into the corners and then run along the sides to produce the hole shown in the photo.
The next step was to file any rough edges off the sides of the hole so that the sleeve could be driven into  the hole
This shows using the broach on a corner.    Each corner required three passes --- no shim, one shim and then two shims.  

The pin was then moved to the other end of the sleeve so that the sleeve could be reversed and a single pass (with both shims in place) could be made from the other leg of each corner. 

This is a finished square hole --- better than the $250 broach which makes a bulging square hole. 
The holes needed to be filed slightly to remove all rough edges to get the bar to slide into the hole ---it is a tight fit as we want for the slip joint.



The milling vise was rotated 45 degrees so that the sides of the square shaft ends could be milled flat as shown in the photo. 
Note that material was left in the corner where the shaft end meets the U end. 
This shows plunging an end mill into the corner to make the fillet. 
This square shaft end looks pretty good.  It was further smoothed using a 1/2" diameter sanding drum in the rotary tool.  


This shows the finished shaft ends of all the Us ---- note that I made an extra of each type --- in case I ruined one in the fabrication process. 

The description of finishing the Us and fabricating the other universal parts are described in the Universal Construction II page.



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