Tips for turning to an accurate diameter

[Wallace]

No harm in working to the closest tolerances you can on a one off. I spy a thread dial on the saddle, are you going to cut the threads on there too?

 

[lshigham]

Actually I meant 'expressing' in hundredths of a mm, if you can turn work to that tolerance (four tenths of a thou) then fair play to you. The thing is that the originals won't have been produced to such tight tolerances so replicating them to 'microns' isn't necessary nor practical, if the micrometer even repeats to that scale.
I didn't mean to cause you any offense, just point out that no-one uses microns as a term in regular machining.

Don't know about anywhere else but where I work thou is the most commonly heard term when machining something

 

[waddycall]

No harm in working to the closest tolerances you can on a one off. I spy a thread dial on the saddle, are you going to cut the threads on there too?

I'm planning on cutting the thread with a tap as it's an imperial lathe with an odd combination of change wheels and I can't remember the set up for an approximation of 1.5mm! On my previous attempt at making this stem (two years ago) I cut the thread on the lathe. I cut the thread first and then made a male threaded mandrel with a centre hole in it to support the part between centres. By the time I got that far I thought I was home and dry and messed up turning the diameters! Got a bit further today with the two final diameters for the Lower yoke and bearing finish turned within spec.

 

[Mr shiney]

Wow, impressive attention to detail! I cut my Can Am head stock from a length of gas pipe......

 

[waddycall]

Finished the stem this afternoon. The four important diameters for the bearings and yokes are within the 10 microns I was aiming for. Lots of spring cuts and letting it cool before finish turning helped a lot. I didn't use any emery as I found I didn't need to. Just got to hope it all fits now. Thanks for the help. Pete

 

[Pete.]

If you have copied the original to 0.01mm there shouldn't be any hoping involved

 

[Mr shiney]

Did you cut it from solid bar or tube?

 

[waddycall]

If you have copied the original to 0.01mm there shouldn't be any hoping involved

With so much attention on the diameters I probably got the length wrong!

 

[waddycall]

Did you cut it from solid bar or tube?

I cut it from solid bar but drilled a 10mm hole right through for the tank vent.

 

[Wallace]

Have you checked it for taper?

 

[waddycall]

Have you checked it for taper?

Lol. It's fine where it matters! The middle bit will have a fair taper due to the length but that's not important thankfully.