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quadrod
05-08-2015, 08:11 PM
Ok, what do you call metric acme thread and what do you call the taps?

PixMan
05-08-2015, 08:32 PM
30 Trapezoidal Thread

Juergenwt
05-08-2015, 08:36 PM
Look here: http://www.gewinde-normen.de/en/trapezoidal-coarse-thread.html

oldtiffie
05-08-2015, 08:55 PM
Why not start off by having a look at a McMaster-Carr" (sp) on-line catalogue - or Birmingham Gears - both in the USA.

https://www.google.com.au/?gws_rd=ssl#q=mcmaster-carr

https://www.google.com.au/?gws_rd=ssl#q=birmingham+gear

https://www.google.com.au/?gws_rd=ssl#q=Metric+acme+thread

mike4
05-08-2015, 09:05 PM
How long is the part , could you not cut it in a lathe?

Michael

quadrod
05-08-2015, 09:18 PM
I have a 13 south bend lathe that does not cut metric threads. I need to cut a 3mm thread pitch on 80 mm diameter stock. I have a bright ( well may be not so bright ) idea to tap the center at 10mm or 12mm trapizoidal and put a length of trapizoidal shaft in the tail stock and let the tail stock pull the apron along as the shaft feeds into the stock while cutting the 3mm thread pitch on the stock.

PixMan
05-09-2015, 12:44 AM
Get the change gears for cutting metric threads on your lathe and never worry about that again. My lathe isn't as common as a South Bend, but I made the blanks and had the gear teeth cut for my own gears because my lathe (Victor 1640) was bought used and didn't come with them. I have done dozens of metric threads lately, in 1.0, 1.25, 1.5 and 1.75 pitch.

I have a dividing head now and would make my gears complete if I had to do it all over again.

CalM
05-09-2015, 01:03 AM
I have a 13 south bend lathe that does not cut metric threads. I need to cut a 3mm thread pitch on 80 mm diameter stock. I have a bright ( well may be not so bright ) idea to tap the center at 10mm or 12mm trapizoidal and put a length of trapizoidal shaft in the tail stock and let the tail stock pull the apron along as the shaft feeds into the stock while cutting the 3mm thread pitch on the stock.


the "Lead Screw" you propose only needs to be 3mm pitch. the Acme part is not a requirement.

You can still cut an acme thread on the work even if the drive screw is Whitworth 55 Degree. As long as it's 3mm pitch.

quadrod
05-09-2015, 09:34 AM
CalM that is correct. A bolt with 3mm thread pitch is about an inch or 24mm in diameter but you can get trapezoidal threaded shaft in 10 and 12mm diameter leaving a smaller hole in the middle of my working stock. I need a hole in the middle anyway so this would work with my project. For about $30.00 I can get the tap and shaft off ebay, a set of metric gears for the south bend if i can find them is around $500. I do have a mill and rotatory index table and some day I may make the gears myself.

CalM
05-09-2015, 10:03 AM
CalM that is correct. A bolt with 3mm thread pitch is about an inch or 24mm in diameter but you can get trapezoidal threaded shaft in 10 and 12mm diameter leaving a smaller hole in the middle of my working stock. I need a hole in the middle anyway so this would work with my project. For about $30.00 I can get the tap and shaft off ebay, a set of metric gears for the south bend if i can find them is around $500. I do have a mill and rotatory index table and some day I may make the gears myself.

You have done your homework it appears.

I hope your project comes out as you anticipate.

The Artful Bodger
05-09-2015, 04:00 PM
It is really not that hard and it is a most satisfying achievement when you cut your first gear!

CalM
05-09-2015, 04:39 PM
I single pointed a replacement nut for the cross slide of my first Logan lathe.

Getting that acme nut fitting just so also was a very satisfying feeling.

janvanruth
05-09-2015, 09:09 PM
trying to tap 12mx3 tra. might be a challenge
as the ficture will only used once to make the intended o.d.thread i would make the i.d. of the hole you are to tap as big as possible
my guess is that 30% engagement of the tra. thread should suffice and save you some trouble tapping

CalM
05-09-2015, 10:12 PM
IF.. I were tapping such a hole, I would single point "rough it out" (9TPI?) 3mm is .118" so even 8 TPI would work for a short thread.