Parallel ring mandrel

[thehomeengineer]

Hi All
This again may not be of interest to all.

I have been working on the Trunk Guides for my 3" Foden steam wagon which is a reasonably complex casting to machine and hold. So to aid this process, I used a parallel ring mandrel which is perfect for this application as an expanding mandrel wouldn't work as the casting has a blind bore.

The first step as with most castings is to establish that every thing is going to fit so marking out and creating some datums.

In the case of the trunk guides I machined a datum diameter which also enabled the casting to be chucked in the 3 jaw chuck so the 1" diameter bore could be machined to size.

A piece of steel was then machined to an accurate slide fit to the 1" bores and a 1 degree taper, is then machined at the end to lock the casting in place.

The casting is lightly taped on to the mandrel and the machining of the casting can then be completed.

The photos and video will hopefully aid this explanation.

Boring casting with the aid of a fixed steady for extra support

Compound slide set to 1 degree

Taper at the end of the 1" diameter

Ready to accept casting

Casting on mandrel

Facing end of casting

Measuring overall length

Reaming


Once the casting was faced to length, the mandrel taper was machined off and a stud fitted to complete turning

I hope this was of interest and thank you for viewing
The Home Engineer