Tube thread straightening tool

[bojan]

This is the final design (discussed at the bottom of this thread) (https://www.iceinspace.com.au/forum/showthread.php?t=206632&highlight=tool), I think it is ready to be made...

[bojan]

Finished.. Idler is still missing a collar with groves (for threads - that will have to be made and attached for each thread pitch separately).

[JA]

Hi Bojan,
Well done on a deluxe solution employing the threaded collar. If you're making collars there's probably only two thread pitches you need to worry about: 0.75mm and 1mm, with 0.75mm being almost universally used for most small to medium sized lens threads. I have one larger Nikon lens that has a 122mm filter thread diameter with a 1mm pitch. Mostly in larger lenses now days makers use clip in lens hoods, but I'd say that 0.75 and 1mm pitch threads would do for most lenses.

Best
JA

[bojan]

Hi JA, you are right, I checked my MTO and Rubinar, they are both 1mm.
Canon 200mm (which has a small deformation), is 0.75.
So I for now I need 1mm and 0.75 mm pitch collars.


I think I can use M6x.75 and M8x1 mm taps as tools to try and make those collars, without fiddling with gears on lathe.

If this doesn't work, I will try to cut grooves, one after another (this doesn't need to be proper thread anyway).

[oska]

This Old Tony has a tutorial on YT to cut large bore threads with a tap as a cutting tool (not as a tap) and lathe, only the pitch matters not the diameter. You will have to fiddle the gearing though.

[bojan]

Here it is... 1 mm pitch groves.

Aluminium I had is not very good for machining, it is pretty soft and sticks to cutting tool despite lubricating with WD40.. but should be OK for a test.



Yep, tap, being a tap for threading has an angle.. but if I could compensate for this in holder, there should be no lathe gears involved.. because I need only groves, not a thread.
Anyway.. there are not many groves to cut so...

[OzEclipse]

Bojan,

Best lubricant for cutting/machining aluminium is ethanol. Methylated spirits will be almost as effective.

Joe

[bojan]

Thanks, I didn't know that, I will try.. however ethanol could be dangerous for me for jobs that take longer time ;-).
Generally I am using WD40 spray as lubricant (my small lathe doesn't have pump yet), and it has to be re-applied quite often as it is removed by worked part rotation.. Kerosene is also good for Aluminium..

[Leo.G]

Methylated spirits?
Thanks for the tip!
I've been using spray can olive oil as a primary lubricant on any alloy I thread on the advice of an engineer friend who said it's his go to lube for alloy and cheaper than commercial options. Plus Coles stock it, I can get it local.
That just reminded me, I have to buy 4 litres of methylated spirits from Bunnings, I'm nearly out.


Kerosene would be good for cutting but Methylated spirits is so much cheaper. Back in the 70s Kerosene was my go to car and motorbike wash, a cupful in a bucket of warm water and it would remove any grime and leave a nice shine on the vehicles. Now I just let the rain do my car washing.....