Threading on Shoptask Gold Machine

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asallwey
Posts: 202
Joined: Sun Dec 31, 2006 6:49 am
Location: N. Virginia

Threading on Shoptask Gold Machine

Post by asallwey »

I have an '89 Shoptask Gold machine. Do any of you have this machine and if so do you thread??? How do you do it?

I've been trying to thread again, my yearly exercise it seems. I have the 4 light accessory that Shoptask/JT sold where each light indicates a full spindle revolution. I use a zero point on X to start each pass, overtravel then return to remove backlash, keep X engaged, align the chuck with a light manually, then throw the spindle lever and start cranking. It does work, but it so easy to miss a step or something and mess up a thread. It's a slow process with a number of steps.

People have said they can thread under power using it. Apparently my coordination is lacking as I've never been able to flip the spindle lever just as a light comes on and thereby miss the critical 'on' spot.

The other day I tried plunge threading from the rear, upside down tool, motor in reverse, cutting toward the tailstock. I manually align the chuck to the start spot, then hit the power. Runs to the end nice as can be. Then I shut the motor off (to stop the spindle), return, align, and press Go again. A few less steps so a bit quicker, and I had good threads. I would prefer to work on the front of the machine using the compound. And less stress on the tool.

Just wondering if anyone with this machine has any suggestions.
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Torch
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Re: Threading on Shoptask Gold Machine

Post by Torch »

I don't have that machine, but wonder if you would have better luck not disengaging the carriage at all? It requires a reversible lathe motor of course, but timing becomes a non-issue.

Run the pass, stop the motor at the end of the thread, back out the compound, reverse the motor, wind past the start, wind in the compound to the next pass depth, put the motor in forward and repeat until the thread is complete.
asallwey
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Joined: Sun Dec 31, 2006 6:49 am
Location: N. Virginia

Re: Threading on Shoptask Gold Machine

Post by asallwey »

Yes, that is what I do, X never disengages. We have a hi/neutral/low spindle lever that, when shifted to neutral, is used to disengage carriage movement. It changes, disconnects, the X-axis drive gears. I've tried power threading toward the chuck, but stopping is not like on typical old American iron. That's why I tried cutting from the back, took all the scare and worry out of the equation. Backlash contributes to the effort (mentally) because all movements have to be at least 1/2 dial turn beyond then return. It's the old "did I" question that pops up after a number of passes. I have cut some ok threads, I just don't do it enough to be confident. Kind of hard to explain, the machine is rather primitive in this capacity.
Torch
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Location: Muskoka

Re: Threading on Shoptask Gold Machine

Post by Torch »

Before actually cutting the thread, if you cut a groove, slightly wider than but the same depth as a thread, at the end of the thread it provides a fudge factor to compensate for timing differences when stopping.

But cutting from the back works too.
asallwey
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Location: N. Virginia

Re: Threading on Shoptask Gold Machine

Post by asallwey »

Thanks Torch, I do that. The problem is initiating the cut. Words just don't describe the process on my machine, but try this.

The attached pic shows the X-axis lever on the bottom, in the forward or to the chuck direction. Once set it is left engaged for the full threading process.

The upper lever controls engaging the spindle with the X-axis, low/neutral/high. Neutral allows the spindle to rotate but no X travel. The spindle does not stop rotating, just the gear train to the X-axis is changed. The little lights to the left of the spindle handle come on for each revolution of the spindle. The objective is to engage the spindle lever when a light just comes on. Slightly late or early, and we are talking fractions of time here, and the tool will be in a slightly off track. Early and you cut some of the last crest side, late you may put a cut down the center of the crest. At any given attempt the gear teeth may not mesh and grind, so a light hand is in order. Cutting on the back side lets me align the tool with the start point easily since there is no movement. Hit the power and the thread is cut.

I think the newer Shoptask machines improved on this system, but not to the extent of half-nuts. Seems cnc became the answer. Some of the early owners of the Gold (and White before) worked through this process. I was just wondering if any were here.
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Torch
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Location: Muskoka

Re: Threading on Shoptask Gold Machine

Post by Torch »

I think I see your problem: The lathe is standing on end, try laying it down so the bed is horizontal... <lol>

Sorry, couldn't resist.

It really sounds similar to engaging/disengaging travel based on a threading dial with numbers. You have lights instead of watching a dial rotate and waiting for the same number to come up each time. And you are engaging a gear train in the headstock instead of a half-nut in the carriage.

If that is so, then I don't understand why you can't leave both levers engaged throughout the entire threading process. No risk of getting out of time by hitting the wrong tooth on the gear if you never disengage the gears. The only trick is figuring out exactly when to either stop the motor, or quickly wind the tool out of the cut.
asallwey
Posts: 202
Joined: Sun Dec 31, 2006 6:49 am
Location: N. Virginia

Re: Threading on Shoptask Gold Machine

Post by asallwey »

"I think I see your problem: The lathe is standing on end, try laying it down so the bed is horizontal... <lol>"
That's another one of my frustrations, no matter which way I hold the phone I can't seem to control if it turns vertical or horizontal.

If both levers are engaged I would have to have the strongest muscle man around to crank X anywhere. You're right, the lights are similar to the 'half nut' dial. O yea, the motor doesn't stop on a dime by any means. It takes practice to win on this machine sometime. I appreciate your thoughts, I think I'll go hit it again tomorrow.
Torch
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Location: Muskoka

Re: Threading on Shoptask Gold Machine

Post by Torch »

You don't crank the x (ie: lead screw, left and right) by hand, just the Y (crosslide or compound, in and out). Let the motor crank the lead screw to move things left and right. Set the depth of cut (y). Use the motor in forward to cut the thread from right to left at the front. Stop the motor and withdraw the tool from the cut (ie: wind y out). Put the motor in reverse and run it so the tool moves left to right and clears the end of the work. Set the new depth of cut (ie wind y in) and put the motor in forward for the next pass. Don't disengage any levers until the thread is complete.

What am I missing?
asallwey
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Location: N. Virginia

Re: Threading on Shoptask Gold Machine

Post by asallwey »

"What am I missing?"
Standing in front of my machine. All the things you have said are spot-on, and most of them I employ. But it's very difficult to put into words the challenging aspect of using my machine for this task. For instance, I switched my motor to 3-phase and a vfd, but the vfd doesn't have a convenient reverse button (like I have on my Doall). So I have to turn the vfd off, switch to reverse, turn it on, then turn on the motor. Never been a problem till I tried threading, and too big a chore to switch vds.

I really appreciate your suggestions and advice. I waffled about posting because I was afraid I would get into this kind of dialogue. I could post the ~20 step procedure I use and it would track all you have said. I think my situation is one that requires practice, and I was faintly hoping a Gold user would toss out a tip that would bring it all together.

My problem here is trying to present how my machine works and I work. Think of trying to explain to a new driver how to drive a 1910 car. Explain a non-syncro trans and double clutching, long braking distance, etc., or for a more modern example, explain how to drive drywall screws with a corded drill, all with words and no person-to-person instruction.

Please take no offense, but how about if we end this. I've transposed some of your comments into my notes for checking against my procedures, so your comments have not been in vain.

Thanks again,

Alex

PS I'm hobbiest of course, for just over 20 years now. I've enjoyed making a lot of things on my machine, even if it has shortcomings. No space for a better machine, but I did squeeze a Millrite in. Never had a chance to thread on a machine with half-nuts.
toddalin
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Re: Threading on Shoptask Gold Machine

Post by toddalin »

See below:
Last edited by toddalin on Wed Dec 30, 2020 5:16 pm, edited 1 time in total.
toddalin
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Re: Threading on Shoptask Gold Machine

Post by toddalin »

Here you go:
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Torch
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Re: Threading on Shoptask Gold Machine

Post by Torch »

asallwey wrote: Wed Dec 30, 2020 9:52 amthe vfd doesn't have a convenient reverse button
Ok, there's the part I'm missing.

Good luck and take care.
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