Tender Trucks

Making the Bolsters

These are fun to make. Lots of layout lines to pay attention to but not too complex. Two sizes of brass square stock make it simple to size up the basic starting blanks. This is a good place to make a mention of the strange sizes that Kozo calls out for some of the parts. The thing to remember is Kozo is building in metric dimensions. He calls out what is the closest in fractional sizes for U.S. builders.

For example, the upper bolster seen in the photo below is called out at 3/4" x 19/32". (The 19/32" is very close to 15MM) Available stock can be purchased at 3/4" x 5/8". I don't consider the 1/32" oversize a critical dimension, so I am not going to mill 0.031" off to make it exactly 19/32".

There is a 3 degree taper called out in the milling cuts. A great chance to put my sine vise to use!

I used the lathe to square off and size the bolsters to the proper length. Light clamping in the four jaw left no tooling marks in the brass. The thinner lower bolsters are small enough to actually go back into the spindle bore for even better clamping.

Here the sine vice is flat and I am going to mill the slot to the proper depth. I did all the flat work first before setting up the vice at the 3 degree angle.

My favorite "stop the action" trick. The mill is running but the strobe flash stops the motion.. This is the final pass at the desired depth.

Open WIDE! I have cleaned the base of the vice of chips and have placed the sine blocks. The sine of 3 degrees is 0.052336. My bars are 4 inches apart. 0.052336 x 4" = 0.209344". (0.209" is the target.)

I selected two disks. The sizes are: 0.108" and 0.101". Stacked together I have the 0.209" I desire. This is far more accuracy than required!

The side view of the sine blocks in place. There is a slight angle in this photo so be assured the blocks are directly under the sine bar.

All prepped for the drilling. This shot is not posed. I just grabbed a quick photo as I was closing down for the evening. Man! I just love this kind of work...

Drilling done, bolsters finished through initial clean-up. Parts came out nice. I am again feeling the size this model is going to be when I see the size of these bolster parts.

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