# 1236 Crash



## Blackhawk (Mar 8, 2015)

did something stupid and crashed my lathe a few weeks ago, looked it over and thought I got lucky, nothing broke. What happened was I turned it on and the 4 jaw hit the cross slide and left two gouges.

I'm now trying to cut off some ballscrews and need to go in reverse, at first it would work but on the second one I was cutting it became intermittent. Now on the third ball screw it does not work.  I never used the reverse before so I don't know if the crash did it or not.

Any thoughts

Lanham


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## darkzero (Mar 8, 2015)

Can you clarify reverse? Reverse on the spindle or power feed for the carriage or cross slide?


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## seasicksteve (Mar 8, 2015)

You might have a shear pin on the drive for the apron Im not sure if that lathe has a separate drive or if it uses the lead screw but I would look for a shear pin. Could have been hanging on but gave up the ghost when you changed direction


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## Blackhawk (Mar 8, 2015)

Here is a video of the issue


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## tmarks11 (Mar 8, 2015)

This is an electrical issue; the motor isn't even starting.  Could be lose wiring or a microswitch that needs adjustment.  Worst case scenario is you need a new reverse contractor ($20-30).

Not a mechanical failure. Nothing to do with your recent crash.

The trick is to track down where the problem is.  I would start at the microswitch that is engaged by cams on the spindle on/off control rod.  It might be misadjusted (although I think I heard a click when you moved the lever to "reverse").  There are two microswitches; one for forward and one for reverse.  Make sure you adjust the right one. 

That microswitch is located in a compartment in the right bottom of the QCGB, where the spindle on/off control rod runs. It is part #331 shown below, accessible behind plate 328.  YMMV, as this is a Grizzly schematic, not the PM1236, but it is probably similar. Taking the QCGB facia off might help.

If this is not easily accessible, it might be easier to take a multi tester to where the control wiring from the spindle reverse microswitch connects to the reverse contractor in the electrical cabinet.


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## darkzero (Mar 8, 2015)

Agreed, as said that's an electrical issue. The switch is located under the gearbox knobs. If you peak up you can see them. Probably easier to remove the knobs & the gearbox face plate to fully diagnose that area.

But why cut the ball screws with a cut off like that? I would cut with a badnsaw, etc, then face the end(s) in the lathe.


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## Blackhawk (Mar 8, 2015)

Thanks for all the replies, I will check the switches.

My bandsaw just bounced off the ballscrews. 

Lanham


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## darkzero (Mar 8, 2015)

Ah I see. Please keep us updated on what the problem was.


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## Blackhawk (Mar 8, 2015)

The other issue besides it bouncing off the bandsaw was I had to turn down the outside diameter for the bearing. It was getting softer as I cut away the outside so I just threw it on the bandsaw and it cut right off, thank the lord cause the other two I did took a day. Now on to the electrical issue.

Lanham


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## Blackhawk (Mar 8, 2015)

Mission complete, thanks for the help






Lanham


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## hman (Mar 12, 2015)

Glad to hear you found the problem, and it should be an easy fix!

Slightly OT ...
I have a vintage Grizzly 12x24 (old enough not to have a motor control lever on the carriage) and experienced a nasty crash a while back.  A lever on the carriage selects either lengthwise feed or cross feed.  I was doing a lengthwise feed cut (at kind of a high speed), and when I got to the end I accidentally moved the lever *past* the center detent and jammed it into power cross feed.  The QCTP ran into the part.

Given the noise it made, I was sure I'd be faced with some nice shattered gear teeth.  But it turns out there's a spring-loaded safety clutch on the shaft!!!   Of course, it took about an hour's worth of disassembly to discover it ... but finding out that all's well was definitely worth the time and effort.  Plus I learned a few things about the apron, etc.

I've since figured out a swing-away stop that will keep the select lever from going past the center detent.


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