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reverse tumbler

Posted: Fri Aug 31, 2012 9:01 pm
by wally318
Anyone here ever put a reverse tumbler for the leadscrew on their 3 in 1 ?

Re: reverse tumbler

Posted: Sat Sep 01, 2012 8:21 pm
by Torch
I personally have not (came with) but many people have. It's well documented on the Yahoo 3-in-1 site.

I think you have to be logged in to access it, but two slightly different approaches in the photos section are under "lead screw reverse" and "G9729 reverse". I think the first is a modification of Steve Bedair's design
(http://www.bedair.org/Tumble/Tumble1.html). The second is a little less sophisticated and probably not quite as convenient for cutting threads, but will reverse the leadscrew with minimal investment of time.

Re: reverse tumbler

Posted: Wed Nov 21, 2012 5:32 pm
by wolframore
I'm definitely interested in the ability to reverse my feed also whether it's for powerfeed away from the chuck or to reverse thread. I've been researching and finding a lot of info related to other lathes but have not found anything with a 3 in 1 yet. I think the Smithys have reverse tumblers but not sure how it works...

Also wouldn't it matter what the gear ratio is if you want to thread? You would need at least two that matched the output out of the spindle.. Please share thoughts as I'm trying to puzzle one together.

Re: reverse tumbler

Posted: Wed Nov 21, 2012 9:12 pm
by Torch
You don't need to worry about ratios just for reverse. All you need to do is insert a gear, any gear, any number of teeth, somewhere between two other gears anywhere in the train. If you insert gear X between gears Y and Z, the ratio of Y:X / X:Z = Y:Z. So the ratio is the same, just the direction is reversed. So if you are cutting a left-hand thread, you use the same change gear set as for a right hand thread of that pitch.

My reverse is between the gear train and the lead screw itself. Most tumbler reverse schemes are in the gear train though.

Re: reverse tumbler

Posted: Thu Nov 22, 2012 9:09 am
by wolframore
Torch thanks for the explanation... that's what I've read but haven't been able to get the concept. The Ratio formula makes sense... thank you. The input gear changes the one in the middle but the middle gear changes the output gear back so all it does is change direction... finally get it.

Torch did you put your reverse in or is it OEM? Which machine do you have?

I've looked on Yahoo's 3 in 1 group and all they have is a jpeg of a pinion gear set up with a dog clutch... it seems more complicated than just a tumbler gear. The dog clutch is a neat idea for a mechanical stop to be placed on the cross slide with an automatic reverse.

Re: reverse tumbler

Posted: Thu Nov 22, 2012 4:35 pm
by Torch
Mine's OEM. I have an HQ800V, by Chizhou Household Machine Tool Company in China. They actually make the majority of 3-in-1 machines sold under various brand names like Grizzly, HF, Craftex, etc. Their machines are modular and different manufacturers can order them with different options to customize the end product. I ordered mine direct with the features I wanted.

Re: reverse tumbler

Posted: Wed Nov 28, 2012 12:45 pm
by wolframore
wish i had a smaller list of must do's for the machine. This is definitely a high priority for making tooling. This is definitely do-able. I'm gonna tackle this one for my machine.

Re: reverse tumbler

Posted: Wed Nov 28, 2012 7:57 pm
by Torch
I believe your machine has a lever to disconnect the lead screw drive between the change gears and the lead screw. Mine has a quick-change gearbox in place of that disconnect. It incorporates the reverse gear. You could probably modify or replace yours with a reverse gear:
quick-change_gearbox.jpg

Re: reverse tumbler

Posted: Wed Nov 28, 2012 8:38 pm
by ken572

Re: reverse tumbler

Posted: Fri Nov 30, 2012 3:10 pm
by wolframore
Torch wrote:I believe your machine has a lever to disconnect the lead screw drive between the change gears and the lead screw. Mine has a quick-change gearbox in place of that disconnect. It incorporates the reverse gear. You could probably modify or replace yours with a reverse gear:
quick-change_gearbox.jpg
Torch... that's the one area I haven't opened up and looked into, I will be taking a look in there this weekend! Would be nice to have a drive - disengage - reverse there! Torch could you possibly take some pictures of the mechanism in there? Is it dry or spinning in oil???

Re: reverse tumbler

Posted: Fri Nov 30, 2012 9:33 pm
by Torch
I'm not at home for a few days and you can't see in there very well anyway because the change gears are in the way. However, it is open to the bottom and can sort of be seen with use of a mirror. Here is the best I can offer right now (ignore the red circle, this old shot was showing some play in the shaft mechanism which has long since been fixed). You can see the floating gear and the shoe that moves it, but that's about all.
shaft_end.jpg
Here's a parts diagram of the entire gearbox:
gearbox.jpg

Re: reverse tumbler

Posted: Wed Dec 05, 2012 4:03 pm
by wolframore
Torch, thanks for the pictures... I looked at my machine and it won't work there. There's a set of clutch gears that lock together with fingers. One sides rotates freely until engaged in the key and clutch. I don't see an easy way to reverse this mechanism here. Will go back to the drawing board... most likely in the change gear area.