10L build ideas...

iwananew10K · Jan 6, 2016

I was collecting parts for a crazy 10L build, it was going to be a bench mount overhead drive.
I had a boatload of NOS parts, a tailstock from a 12" Taiwanese lathe( early ones had a real thick base that can be cut down to fit the 10L, are 3 MT, 4.5" travel, 1 9/16" diameter quill and are actually very nice tailstocks)

The plan was to use a wide range gearbox and incorporate a sliding gear similar to the single tumbler boxes to introduce a compound gear in the train to get the most common metric threads, notably 1mm.1.25,1.5- likely more but I never finished working it all out and everything is gone now.

Just kind of wondering of anyone ever considered such a plan regarding the gearbox?? It sure seems like it would work and be fairly easy to implement??

Random curiosity has got me wondering.

thomasutley · Jan 6, 2016

I've thought about building a metric gearbox. Would require a metric leadscrew and matching halfnuts. Probably no more effective than the metric stud gears PM member nt1953 posted a couple months ago, however, and a lot more work for the convenience of quick-change gears. His three stud gear options can be swapped out in about ten minutes and gets you scary close (within 4 decimal places of common metric pitches for most needs).

iwananew10K · Jan 6, 2016

Yeah, I have a general dislike for all metric lathes...IMO an imperial machine with a metric capable gearbox is far more versatile,and it would be sweet to simply utilize a sliding compound gear to get the most common pitches.

It would pretty much have to be with the wide range box because it includes 30 tpi...30,24, and 20 tpi represent the same intervals as 1mm,1.25,and 1.5 so a single compound gear introduced in the train could cover those.
I can't recall ever actually needing to cut any other metrics than those three.

I lost all my notes so this is just from memory.

We need kitno455 here!

stephen thomas · Jan 7, 2016

Drat, I was getting all excited reading, anticipating pictures of what you had come up with.

Kind of a letdown, Iwana :nono:

smt

kitno455 · Jan 7, 2016

Heh- yes- I have thought about this. I don't think you could do it with a simple sliding gear, but with a secondary tumbler or a pair of clutches in a pair of gears on the gearbox input shaft. I'll draw something up later today.

allan

GenePoole · Jan 7, 2016

I played around with trying to approximate metrics on my SB13, but it was just too much trouble. I finally broke down and bought a NOS South Bend transposing gear set (about $250 IIRC) and have never regretted it. It takes about 10 minutes to swap out and I can cut perfect metric threads. Here's a M27x2.0 for an AI rifle barrel:

gzig5 · Jan 7, 2016

With the metric transposing gears, do you need to leave the half-nuts engaged the whole time while cutting the thread? I seem to remember that being the case due to the imperial leadscrew.

When I get my 10L back together, hopefully this winter, I will be putting a servo on the leadscrew that will be slaved to an encoder driven by the spindle. This will give me near infinite thread/feed possibilities and should be easier to implement than additional gears in the feedbox drive-train.

iwananew10K · Jan 7, 2016

even on a true metric machine you pretty much have to leave the halfnuts engaged. The ones that have a thread dial are a screwy arrangement requiring multiple gears in the dial itself and has to be shifted around to accommodate various pitches...more trouble than it's worth for the most part and why many metric machines don't have a thread dial.

GenePoole · Jan 7, 2016

gzig5 said:
With the metric transposing gears, do you need to leave the half-nuts engaged the whole time while cutting the thread? I seem to remember that being the case due to the imperial leadscrew.

You have to maintain the synchronization. This can be attained by leaving the half-nuts always engaged (as per all the conventional tutorials), but you can disengage them as long as you re-synch them. Mark your position on the dial with a sharpie; cut the thread, disengage and retract just like you would doing regular threads. The dial will rotate again but you've got plenty of time after disengaging to reverse the lathe, wait for the mark to re-sync, then engage half-nuts again at the mark; run it in reverse until clear of the start and either stop the lathe or just make your adjustments while it's still reversing, then put it back in forward and take your next pass. Repeat. As long as you don't let the dial move too far (like several complete revolutions), you'll be able to easily maintain synchronization.

I've been thinking of making a video of this because it is really easy and makes great threads without a relief cut.

gzig5 said:
When I get my 10L back together, hopefully this winter, I will be putting a servo on the leadscrew that will be slaved to an encoder driven by the spindle. This will give me near infinite thread/feed possibilities and should be easier to implement than additional gears in the feedbox drive-train.

I've wanted to do something like this; basically make a CNC conversion, but I would need another lathe in the meantime.

SBLatheman · Jan 7, 2016

GenePoole said:
I've been thinking of making a video of this because it is really easy and makes great threads without a relief cut.

I'd like to see a video of that :scratchchin:

Ted

mdshunk · Jan 7, 2016

I disengage the half nuts making metric threads with an imperial lead screw, but I have to put a Sharpie mark in the chuck-to-spindle relationship, leadscrew-to-leadscrew bearing support relationship, and saddle-to-vee way relationship. Get all three of these back and sync and you can slap the half nuts back in and still be on the correct feed for the next pass over the threads. Works for any crazy thread type you want to dream up; not just metric.

GenePoole · Jan 7, 2016

mdshunk said:
I disengage the half nuts making metric threads with an imperial lead screw, but I have to put a Sharpie mark in the chuck-to-spindle relationship, leadscrew-to-leadscrew bearing support relationship, and saddle-to-vee way relationship. Get all three of these back and sync and you can slap the half nuts back in and still be on the correct feed for the next pass over the threads. Works for any crazy thread type you want to dream up; not just metric.

That's a lot to keep track of, but I'll admit it takes care of anything. You could probably disassemble and reassemble the lathe.

mdshunk · Jan 7, 2016

Nah, it's three sharpie marks. It takes about 30 seconds to line the three marks up between each pass. Not such a monumental feat. Jog the lathe however many revolutions to get the chuck and leadscrew both in sync, wheel the saddle back over to the mark, engage the half nuts, and proceed as normal.

kitno455 · Jan 7, 2016

Well, I'll be darned- it IS possible to do this with just a sliding gear. In fact, there are a number of ways.

If you replace the existing 80 tooth idler with another gear, it does not impact the ratio during inch threading. If you then compound that idler with another gear, and put a second gear on the gearbox input, then you can get a second ratio for metric threading. Then you need a way to select between these two gear trains. 1. Some kind of selector on the gearbox input shaft. 2. Add a second shaft to the banjo (like the single tumbler machines have) with a pair of sliding gears on it.

Possible geartrains include: 40/66/56 for inch threading, which becomes 40/66-71/51 for metric. This turns the gearbox 1.181 times faster than normal, so the leadscrew acts like it was 3.75 mm pitch. You can cut a bunch of metric threads with 0.01% error:

tumbler mmpt %error
120* 0.250025 0.010000
60+ 0.500051 0.010200
40+ 0.750076 0.010133
30+ 1.000101 0.010100
24+ 1.250127 0.010160
20+ 1.500152 0.010133
15+ 2.000203 0.010150
12+ 2.500253 0.010120
10+ 3.000304 0.010133
7.5+ 4.000405 0.010125
6+ 5.000507 0.010140
5+ 6.000607 0.010117

You can cut the same list of threads, with only 0.0005% error if you use 111/117 as the compound, and 50 as the extra screw gear.

Someone check my math, but this looks promising so far...

allan

mTeryk · Jan 7, 2016

mdshunk said:
I disengage the half nuts making metric threads with an imperial lead screw, but I have to put a Sharpie mark in the chuck-to-spindle relationship, leadscrew-to-leadscrew bearing support relationship, and saddle-to-vee way relationship. Get all three of these back and sync and you can slap the half nuts back in and still be on the correct feed for the next pass over the threads. Works for any crazy thread type you want to dream up; not just metric.

Seems to me like it would be very bad if your chuck to spindle relationship changed during the course of threading, sharpie mark or not.

Teryk

mdshunk · Jan 7, 2016

Chuck to headstock, I should more properly say, since the chuck is mounted on the spindle. Nice catch. I know where I put tick marks. Easier to do than explain, maybe.

gzig5 · Jan 7, 2016

GenePoole said:
You have to maintain the synchronization. This can be attained by leaving the half-nuts always engaged (as per all the conventional tutorials), but you can disengage them as long as you re-synch them. Mark your position on the dial with a sharpie; cut the thread, disengage and retract just like you would doing regular threads. The dial will rotate again but you've got plenty of time after disengaging to reverse the lathe, wait for the mark to re-sync, then engage half-nuts again at the mark; run it in reverse until clear of the start and either stop the lathe or just make your adjustments while it's still reversing, then put it back in forward and take your next pass. Repeat. As long as you don't let the dial move too far (like several complete revolutions), you'll be able to easily maintain synchronization.

I've been thinking of making a video of this because it is really easy and makes great threads without a relief cut.

I've wanted to do something like this; basically make a CNC conversion, but I would need another lathe in the meantime.

Thanks Gene. That clarifies it for me. A video would be icing on the cake.
I just got my EMCO Super 11 running in the basement and cut some M22x0.5 threads to practice metric. I left the nuts engaged and would back out and turn off the spindle at the same time. I could plug reverse if I needed to with the D1-4 spindle but no need for the extra shock in this case. Now I'll be able to make Highpower/LR sights like I've been wanting to for a while.

I think the 10L will become a full CNC machine with ball screws at some point down the road. I have all the drives and motors to do it, but for now I'll keep the ACME screws and just use the servos to to automate threading, tapers, and stuff like that. I currently have six lathes (Jewelers lathe, EMCO PC, Atlas 6x18, Craftsman 12x36, SB 10L, and EMCO Super 11) so having the 10L down for conversion won't hurt me too much.

iwananew10K · Jan 7, 2016

Allan, I'm glad you understood what I was trying to say because I *really* got crap jumbled up...

You should see me try to walk...

kitno455 · Jan 7, 2016

Actually, I understood you perfectly. I see some other ways to do this now, using a second shaft on the banjo, just like the single tumbler. For instance, a 59 tooth gear compounded with the existing 80 tooth idler, and a 35 tooth gear on the gearbox, outside the existing 56 tooth gear. This cuts the same pitches as I gave above. Now, the compound can't reach that 35 tooth gear. But, with an additional shaft in between, it could. And since the size difference between 80 and 59 is the same as that between 56 and 35, the two gear trains will have common center distances on all three shafts. So, you could potentially make a sliding gear out of the middle one.

allan

lalatheman · Jan 10, 2016

GenePoole said:
......... and I can cut perfect metric threads. Here's a M27x2.0 for an AI rifle barrel:

Thats an awfully nice looking thread ... how many passes ? Whenever I single point threads without a clearance groove i might do one or two pull outs OK.... BUT Haha

Thanks
Dave Lawrence

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