QCGB swap

[Aaron_W]

I couldn't find anything in the parts lists and diagrams about there being different leadscrews, hence my question, but I find it hard to believe it wouldn't be "plug and play" since the QCGB was an add-on option.

I guess I'll find out!

EDIT: I tried searching for that thread and couldn't find it. Let me know if you find it.

Disregard, I tried to look for it and I am combining your post from earlier this year looking at this option with another post where someone was making a similar conversion to a Logan.

This also now explains to me why throughout your Enco thread I had this thought of didn't he convert his lathe to a QCGB? Why is he looking for another lathe, guess it must have been someone else who did that.

 

[ARC-170]

Disregard, I tried to look for it and I am combining your post from earlier this year looking at this option with another post where someone was making a similar conversion to a Logan.

This also now explains to me why throughout your Enco thread I had this thought of didn't he convert his lathe to a QCGB? Why is he looking for another lathe, guess it must have been someone else who did that.

I had thought of converting my lathe, but a QCGB is $700 (as of Dec, 2020) and I'm not sure if that includes shipping and tax. Plus, I think I'd need to get a cover, which is another $100 or so, plus shipping and tax. I figured I was most of the way to a newer lathe, so why not go that route. Then I saw the one I just bought and will be able to convert mine now. I got it for a decent price and with enough extra goodies that I can sell so that I can recoup most of my costs.

 

[Aaron_W]

I had thought of converting my lathe, but a QCGB is $700 (as of Dec, 2020) and I'm not sure if that includes shipping and tax. Plus, I think I'd need to get a cover, which is another $100 or so, plus shipping and tax. I figured I was most of the way to a newer lathe, so why not go that route. Then I saw the one I just bought and will be able to convert mine now. I got it for a decent price and with enough extra goodies that I can sell so that I can recoup most of my costs.

That sounds like a good deal for you. It seems like the short bed lathes with a QCGB are much less common, but make a nice lathe for small spaces.

 

[wa5cab]

On questions of lead screw length, the same two lead screws were used on the 12"x24" and 12"x36" from the introduction of the 101.07403 in 1940 until the introduction of the final 12" versions in 1966. It was shortened at that time to make room for the slip clutch.

The lathes that required a 1" length reduction of the lead screw in order to install the QCGB were the 10F 10x24 and 10x36.

 

[ARC-170]

You will want to swap the two 48 teeth idler gears for a 52/44 combo gear. Then you can cut the most common metric threads through the gear box and imperial threads 8 tpi and finer. You lose the ability to cut the few threads coarser than 8 tpi.

You scored Jeff. Way to go.

Thanks! If I'm understanding you correctly, I would use the 52 and 44 tooth gears in place of the two 48T gears? There are two gears on the quadrant, both 48T (listed as "9-101-48A 48T Gear" on the exploded view). Are you saying replace these with a 52 and a 44? I would keep the two 44's.

The issue with cutting metric threads is that the thread dial doesn't work. The motor needs to be stopped, then reversed, with the feed lever still engaged. I don't have a reverse, so I'll have to turn it by hand.

I didn't just get the QCGB for threading, I got it to change feed rates, so this is a minor issue to me. I usually make threads using a tap or die. It's hard to get them perfectly straight, though. I use a tap guide for the taps (that usually works well) and the tailstock to keep the dies true, but there's still a small error, especially with the dies.

 

[mickri]

There is a thread on cutting metric threads on a craftsman 12" lathe. Also Robert did a threading chart that is in the downloads. I have the chart taped to my lathe for reference. You lose being able to cut threads 7.5 TPI and coarser while gaining the ability to cut the most common metric threads. If you should need to cut the coarse threads you can swap the two 48's back in. To cut metric threads you move the sliding gear to the inner position so it engages the 44 tooth gear. The 44 combined with the 52 makes the conversion to metric. The threading chart tells you where to set the qcgb to cut the metric threads.

I also use taps and dies whenever I can. My taps and dies go up to 1/2". Over that I have to use the lathe. I converted one of my tap holders to be guided by a chuck. It works really good to keep the tap going straight into the hole. I have used it in the lathe tailstock, drill presses and the mill. I plan to make something similar for dies. I think Halligan142 has a video on how to make a die holder. Should be lots of examples on the net.

 

[mickri]

You don't have to turn it by hand. You can use the reverse lever that causes the carriage to travel away from the headstock. I have cut metric threads both ways. By reversing the motor. And by reversing the direction of the lead screw.

 

[Bi11Hudson]

I have a Craftsman 101.27440 12X36. I am told there is an earlier version that does not have a QC box that is basically identical where the QC box can be interchanged. The caveat here is that there were two different lead screw pitches on one or the other machines. As long as the lead screws are the same pitch, it should be simply a matter of getting the gearing leading into the box correct. What I see is a "try it" situation. In the worst case, the swap doesn't work and you simply change it back. But, with the same lead screw and model of lathe, there is little chance of that. I say try it and see what happens. . .
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