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SB 10L Thread dial hits lead screw right-hand bracket

  • Thread starter Frank in W Mass
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Frank in W Mass

Guest
If you crank the apron all the way to the right, the thread dial smashes into the right-hand lead screw bracket/bearing (and I mean smashes). See example image. Then of course the dial's gear gets chewed up before it finally disengages all the way. The upper bolt holding the dial housing loosens and requires an uncomfortable amount of torque to keep the dial gear in place against the lead screw. I Can't believe the dial housing casting hasn't just snapped off. Yet.

Any ideas? I'm contemplating how to make an end stop just for this purpose but it's a crowded area.
 

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JBTR

Aluminum
Joined
Mar 19, 2020
Location
USA, Northern Illinois
I hadn't noticed that before. I guess if you're focused on what's on top of the lathe you could make that crash. The gear in the threading dial rides up onto the body of the lead screw bracket and disengages the threading dial from the lead screw. But if you keep going, the taper of the body tries to push the threading dial out farther than it can go.

I set my carriage stop in place but it would also hit the threading dial. Otherwise, without the threading dial, the carriage stop and the saddle are designed to work that way.

If you really want a mechanical solution, maybe you could design a carriage stop with an arm that is out far enough to go around the threading dial.

carriagestop.jpg
 

texasgeartrain

Titanium
Joined
Feb 23, 2016
Location
Houston, TX
My knee jerk reaction is, yeah, don't do that. Its pretty rare to power feed in that direction, so I would guess you are hand cranking that way.

The thread dial does look nice on machine, but if you are not actually threading. . . well it comes off pretty easy. But even with it off, you can still crash the saddle and apron into it.

Is the bed super short or something ? Why you moving that far down ?
 

SLK001

Stainless
Joined
Feb 8, 2015
Location
Coral Springs, FL USA
What is the reason that you are feeding left to right? And, "yes", if you do that, it will crash into the leadscrew bracket if you allow it to traverse the entire distance. Just as if you feed right to left, the carriage will crash into the headstock. If you just engage the feed and walk away, then YOU are the problem, not the lathe design, as operating machinery requires 100% of your attention.

Also, to use the carriage stop on the right, you have to remove the thread dial. There is a flat spot where it will contact and the dial gets in the way.
 
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Frank in W Mass

Guest
Well not very supportive answers. @CarlBoyd particularly makes it clear I'm not welcome here. No problem deleting account.
 

Dobermann

Hot Rolled
Joined
Jan 2, 2014
Location
North Carolina
I leave my threading dial off unless I'm threading. It takes less than a minute to put it back on if I need to thread something. AND you'll note that if the thread dial isn't there, the carriage will stop against either the tailstock or the lead screw bearing support.

I believe that some of the "Pacific Basin" lathes share this same "fault." One does need to be a little attentive when running the lathe, especially when using power feeds.
 

morsetaper2

Diamond
Joined
Jul 2, 2002
Location
Gaithersburg, MD USA
Well not very supportive answers. @CarlBoyd particularly makes it clear I'm not welcome here. No problem deleting account.

I think you are trying too hard to make "I'm not welcome here" what you get from his post. All he's saying is that you're just going to have to pay attention when down that far from the headstock.

As others have stated, and I do likewise, just keep the thread dial off the machine when not using it.
 
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Frank in W Mass

Guest
Every job I do on it is threading. Every user in the shop hits the thread dial. I never use the lead screw for anything so far out there. I am asking for help solving a problem and haven't seen any actual solutions yet. Presuming everyone in the shop is too stupid to avoid hitting the dial... I've had more than enough trolls in my life. Waiting for support to show me how to delete the account. I'm probably too stupid to find that too.
 

Dobermann

Hot Rolled
Joined
Jan 2, 2014
Location
North Carolina
I can offer two possible solutions to your issue. You're not going to like either of them.

First, there's no functional reason that you couldn't put the threading dial on the left side of the carriage rather than the right. However on my lathe (10L) anyway, the lead screw is not threaded far enough toward the QCGB to be of much use in threading much closer than about 10 inches between carriage and headstock.

This leads to the second solution which is that clearly the lathe you have is too short for the work you're trying to do. A lathe with a longer bed is necessary and I'm sure that is going to make you even more unhappy than you are now.

Of course it is theoretically possible to build a servo drive system to run the lead screw in unison with the main spindle to generate any thread you want without the use of the threading dial but for some threads you might not be able to disengage the half-nuts to repeat a cut. Even so, you'd only gain about 2 inches more carriage travel before it hits something else.

You have a difficult problem. The fact that it's a difficult problem doesn't mean you're not welcome here!!
 

mattthemuppet

Hot Rolled
Joined
Apr 22, 2016
Location
San Antonio
If you want to idiot proof that problem, the only way I can see to do it is to make a half nut lever kick out for the trail stick end of the bed. Something like a hard fixed ramp that will force the half nut lever open before the threading dial hits the lead screw support bracket.

Anything else, including bed stops, are going to cause other issues, such as stripped half nuts, broken gears and roll pins.
 

SLK001

Stainless
Joined
Feb 8, 2015
Location
Coral Springs, FL USA
Presuming everyone in the shop is too stupid to avoid hitting the dial...
If everyone in the shop is hitting the dial, then "yes", they are too stupid to use the lathe. Perhaps some training is in order. Or, perhaps a longer lathe. You still haven't answered as to what you (or they) are doing that causes a support bracket strike. Maybe with this information, suggestions could be made of alternate ways of accomplishing your goals.

Trying to make things idiot proof is a fool's errand, because no matter how well you make something idiot proof, the world will figure out a way of making better idiots.
 

BDRetz

Aluminum
Joined
May 10, 2014
Location
Ohio
I have hand fed mine into the end bearing on a 4 1/2’ bed. I was cleaning it and forgot about the end bearing. I set the rear clamp for the collet rack in about 2” from the end of the bed. Now the rear screw for the bed wiper will hit the clamp before the thread dial hits the end bearing.

It works for me as I don’t power feed out that far and am only worried about hand feeding into it. If is routinely happening in your shop, I would bolt a bar to the back of the saddle using the taper attachment mount holes that would contact the collet rack clamp with a rubber bumper or spring maybe.
750089BA-F0E4-4621-81C4-DB39AE70BC1D.jpeg
Hope this helps.

Ben
 
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Frank in W Mass

Guest
I can offer two possible solutions to your issue. You're not going to like either of them.

First, there's no functional reason that you couldn't put the threading dial on the left side of the carriage rather than the right. However on my lathe (10L) anyway, the lead screw is not threaded far enough toward the QCGB to be of much use in threading much closer than about 10 inches between carriage and headstock.

This leads to the second solution which is that clearly the lathe you have is too short for the work you're trying to do. A lathe with a longer bed is necessary and I'm sure that is going to make you even more unhappy than you are now.

Of course it is theoretically possible to build a servo drive system to run the lead screw in unison with the main spindle to generate any thread you want without the use of the threading dial but for some threads you might not be able to disengage the half-nuts to repeat a cut. Even so, you'd only gain about 2 inches more carriage travel before it hits something else.

You have a difficult problem. The fact that it's a difficult problem doesn't mean you're not welcome here!!
Good ideas :-) I think the thing to do is a small carriage stop as a safety. No one works down that end but the carriage gets down there for cleaning or having some setup room. I'll figure out a tiny stop clamped to the ways.

Though servo drive... 1955 CNC Frankenstein. Wish it had a DRO though.
 

jim rozen

Diamond
Joined
Feb 26, 2004
Location
peekskill, NY
Sorry but if somebody was abusing a machine like that in our shop we'd be tempted to zip-tie their finger (or something else) to the lead screw bracket and let 'em go to town on it.

This discussion is tantamount to saying 'there has to be some kind of lockout that prevents the operator from jamming the back gears in while the lathe is under power. Right? I mean how do we stop them from doing that?'

They do it once, they get to work someplace else.
 

MrWhoopee

Hot Rolled
Joined
Nov 8, 2017
Well not very supportive answers. @CarlBoyd particularly makes it clear I'm not welcome here. No problem deleting account.
If you're going to participate on PM you will need a thicker skin. Carl Boyd's comment was quite mild compared to some of the sh*t that gets posted around here.

From your initial post, it sounds like this crash is happening under power. I have a Heavy 10 and I'm having trouble envisioning how this happens once, let alone frequently.
 

steve-l

Titanium
Joined
Mar 2, 2012
Location
Geilenkirchen, Germany
Frank,
When asking for advice, you must be ready to receive advice you do not want to hear. Advice is subjective. Unwelcome advice does not mean you are not welcome here. In response to your original query, your problem is not a machine problem. It is an operator problem. You are trying to use a machine beyond its intended use envelope. In other words, machine abuse. You need a larger machine.
 








 
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