In preparation for turning the bushes on my Metric Lathe I annotated the diagrams with metric dimensions.
The image is of the first 1/4"x40 bush made to the dimensions needed.
First time working in the workshop with my heated gilet jacket so warm
The bronze was first machined down to the outside diameter of the threaded part.
Then a centre drill used and then the correct drill for tapping drilled nearly through.
The part was then parted off and reversed and held in the machined surface. Centre drilled and then tapping drilled and finally tapper first with a taper tap held in tail stock chuck to ensure it was square and the normal tapping handle used until the tap was right through.
Then the lathe was used again with tap in tail stock chuck to run through and out to ensure clearance.
Total time to complete was 3 hours !!! Made be quicker for the next one ..
Second 1/4"x40 bush made but I checked the diameter of the tapping drill and found it was 0.1mm too small and that was the reason why the tapping was so difficult even though I was using a third tap which is tapered.
I decided to buy from Avon Engineering Supplies, as found on the internet, the correct tapping drills for
1/2"x32 - 11.9mm
3/8"x32 - 8.6mm
1/4"x40 - 5.5mm
and 5/16"x32 7mm
they should arrive by Wednesday 5 feb 2025.
I can carry on with making the blanks for the bushes but leave the tapping until later !!!
I also made a size checker for the OD on the insert of the 1/14"x40 bush to make sure the measured dimension did fit the hole !
The correct size tapping drill have arrived so I can proceed with making the bushes.
It was much easier to tap after using the correct sized tapping drill. The bush on the left side was the latest one made.
Two more bushes made making a total of 5 1/4"x40 but I may decided to make one more as one has its flange slightly under size.
Then they all need to be degreased to make ready for silver soldering in to the boiler when it is ready ...
Made to 5th bush to the correct dimensions in 20 minutes instead of 3 hours for the first one !!!
So next time it will be making a different size bush !
A suitable plastic box was found and the 5 Bushes put safely inside.
Started work on the 5/16"x32 bush but my old taps just could not cut the thread so new taps ordered.
As for the previous bushes hole drilled so that I can check diameter of outside of the threaded part.
The new taps arrived yesterday but no work in the workshop due to severe back ache but with a new day all is well and I was able to use the new 5/16"x32 taper tap to complete the first and also a second of may be 6 bushes of this size.
Today I applies my blue colour coding ( for 32tpi) to the new taps and drills.
The taper tap missing was already in use !!!
Colour coded blue to match the 32tpi of the taps and to indicate they are special sized drills..
Another, the third 5/16" x32 bush made
4th 5/16"x32 bush made today
All 6 of the 5/16"x32 bushes made.
Did a lot of reading in preparation for a next stage.