# Metric thread with Quick Change



## JPMacG (Nov 26, 2017)

I just realized that the Atlas/Craftsman Quick Change gear box does not provide a means of cutting metric threads.  According to Tubal Cain, I would need to convert the lathe to a manual change gear configuration in order to do metric.  This would be too costly for me.  

Anyone know of another method?  I can imagine changing the ratio between the spindle and the Quick Change gearbox by just changing two gears.


----------



## Bob Korves (Nov 26, 2017)

Change gears to do metric threading can be used with a quick change gear box.  You just need the chart of which gears it takes for the threads you want. starting with the metric transposing gears.


----------



## Dave Paine (Nov 26, 2017)

I agree with Bob.  I have an imperial thread lead screw and QCGB.   I recently needed to single point an M16 x 1.5 pitch thread since the thread was LH and I have no LH dies or taps.

My Grizzly lathe has a few gears to change to enable machining many, but not all, metric threads or some special imperial threads.

I looked at the chart in my manual, changed one gear out and engaged with a second gear in another and I was able to machine the thread.

What is the pitch you need to machine?


----------



## JPMacG (Nov 26, 2017)

I need to do a metric 1.5 pitch thread.   I will have to go through the arithmetic and see if I can work it out with a single gear change.


----------



## Dave Paine (Nov 26, 2017)

This is the metric chart from my Grizzly G9249 lathe in case your gears match.




I may be able to machine this for you if you do not have the correct set of gears.  I am up the NE Extension, NW of Allentown.


----------



## Rob (Nov 26, 2017)

All you will need is an additional 52T gear to cut 1.5 pitch thread.  It is not perfect but close enough you shouldn't have any problems.  That is what I used to make my collet chuck for ER32 collets on my Atlas lathe.


----------



## JPMacG (Nov 26, 2017)

Thank you Rob.  LOL  That is exactly what I want to do....  cut the threads for the nut on an ER32 chuck.

And thanks for the offer Dave.  Ideally, I want to make the chuck on my lathe so that it is aligned on the spindle the way it will be used.  I work in Souderton, about 45 minutes south of Allentown.  I live near Newtown, a bit farther.


----------



## rzbill (Nov 27, 2017)

I'd say that 52T gear would work fine per the Atlas chart.  Assuming the claimed 0.05906" pitch is exact (IE 0.0590600) vs a rounded number, it would take a 300mm long screw thread to show a 0.001" deviation in thread location from the 1.5mm perfection (0.05905512......")


----------



## T Bredehoft (Nov 27, 2017)

17 pitch will be close enough if you make it a scosh undersized.


----------



## JPMacG (Nov 27, 2017)

And I only need it to work over about 1/2 inch of thread.   I plan to get a 52T gear and give it a try.  There are a bunch listed on eBay.  That same gear fits the indexing center on my mill, so it may find a second use some day.


----------



## Rob (Nov 27, 2017)

It worked great when I used it to make my collet chuck.  You might want to give Clausing a call and check their price.  Seems like it was in the high 20s when I got mine and that was for a new one and not a used one.


----------



## JPMacG (Nov 28, 2017)

Thanks Rob.   I plan to go to the Cabin Fever Expo in Lebanon PA in early January.  I will hold off on buying anything until then.  There are usually good deals to be had on Atlas parts.   Last year I picked up a carriage stop and face plate for about 30% of what they sell for on eBay.

http://www.cabinfeverexpo.com/   For anyone in the area, it is worth seeing.


----------



## rzbill (Nov 28, 2017)

Ooooh, Envy.  I went to that show when I lived in Hanover.  Great fun.  Now its a 400 mile trip to get there.


----------



## wa5cab (Dec 4, 2017)

JP, go to 

https://www.hobby-machinist.com/resources/categories/a-c-lathes-charts-tables-metric-misc-docs.518/

which is in our DOWNLOADS and download "A 30 Second Metric Conversion.PDF".  It shows how to use a 52T and 44T gear mounted in place of the two 48T gears to get metric threads from 0.5 to 7.5 MM at the expense (besides the two gears) of not being able to cut 4 TPI threads without undoing the mod.  Switching from Inch and MM is handled by moving the sliding gear to IN.  

I thought that I had already uploaded a modified to metric version of the TPI chart on your gear box but I must have gotten sidetracked before finishing it.  The chart is done except that I need to change THREADS PER INCH to something metric.  I'll try to do that tomorrow.


----------



## JPMacG (Dec 6, 2017)

Thank you Robert!


----------

