#### Re: Metric [1 Attachment]

fwhite913

So if I had ( for example ) a 100/127 tooth transposing gear set installed and a 36T stud gear, what would the QC box settings be?   To get .25mm pitch, I would set the QC box to what TPI setting?  How accurate would that be?

Would you please provide a table of settings for 0.25 to 1.25MM pitches.

On 04/17/2018 01:58 PM, vtsblogan@... [SOUTHBENDLATHE] wrote:

[Attachment(s) from vtsblogan@... included below]

I think this is pretty well known. It pays to learn gear ratio formulas of course- Martin Cleeve's book explains this well, and though he is talking about change gear lathes, as long as you allow for the QC it works.

There are several metric pitches that can get pretty darn close with standard English overlaps.

Once you insert the transposing gears- I use 37/47 because it's more convenient and I don't cut metric much- it really is close enough for virtually all work, but of course you need the 100/127 for perfect match.

I'm using gears from my Logan here, because I have it right in front of me, but the same holds true for the SB lathes (stud gear may change though) With transposing gears in place, and a 36 stud gear I can cut pretty much any .25 metric multiple- .25, .50. .75, 1, 1.25 etc just by changing the QC lever- because a lot of the QC halves itself (or other ratios as well) as in 20tpi setting and 40 tpi setting etc are just like adding in an extra set of compound gearing into the mix. I.E. the QC at 8 TPI is 1:1, QC at 16TPI is 1:2

Compare that to the change gear lathes  I think you would see that the QC is hardly "extremely limited"

Hope I'm making that clear.

On Tue, 17 Apr 2018 13:04:12 -0500, "913fred@... [SOUTHBENDLATHE]" wrote:

>>In addition, you can cut Metric threads very, very closely with but one gear change

On 04/17/2018 10:49 AM, vtsblogan@... [SOUTHBENDLATHE] wrote:

palciatore@... not to sidetrack your discussion, or open a can of worms, but to call a QC gearbox "Extremely Limited" is silly. In additionto all but therarestEnglish threads, you havethe ability to instantly change your feed rate- something that isfar more valuable. In addition, you can cut Metric threads very, very closely with but one gear change, and you can cut all of the same Metric threadsas the Model C since you can also use the Metric Conversion gears on the Model A as well. And you can still instantly change feed rates with the Metric gears in place if you need to do a non- threading operation on a part.

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