# Problem With PM1340GT Compound Base Lock.



## bretthl (Sep 6, 2019)

I went to cut an external thread, set the compound at 29.5 degrees and one of the bolts would not tighten.  Removed the compound without rotating and low and behold the lock nut is positioned exactly at the insertion point.  Any ideas how to fix this?  This just happened, I have cut many threads with the compound at this position.  It is to the point where I can no longer lock the compound base anywhere near 29.5 +/- 2 degrees.


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## dpb (Sep 6, 2019)

Remove your cross slide, make a new t-nut entry hole through the bottom, and a larger t-nut.


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## JimDawson (Sep 6, 2019)

dpb said:


> Remove your cross slide, make a new t-nut entry hold through the bottom, and a larger t-nut.



Yup, that's what I would do also.

Here are some T-nuts I made for a project.  The same shape would work for your compound.  I made these on my CNC mill, but they could have been made on a manual mill with a rotary table.


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## dpb (Sep 6, 2019)

They can be the same general shape as your existing t-nuts, just larger.  Your t-nuts are sized for the existing entry hole, and to go around the corner between the entry channel, and the circular channel.  If you make a larger hole in the underside of the circular channel, you can use a much larger t-nut.


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## mksj (Sep 6, 2019)

Never seemed to have a problem with mine. It looks like the nut needs to be turned 90 degrees from it current orientation, but if just spinning in that position may have damaged the slot, then I would make a longer nut as others outlined. Alternative which I ended up doing was just using the cross slide to cut the thread and not the compound.


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## bretthl (Sep 6, 2019)

mksj said:


> Never seemed to have a problem with mine. It looks like the nut needs to be turned 90 degrees from it current orientation, but if just spinning in that position may have damaged the slot, then I would make a longer nut as others outlined. Alternative which I ended up doing was just using the cross slide to cut the thread and not the compound.



The slot is not damaged.  It is just a poorly designed location for an entry hole.  The most common orientation for a compound and they pick that for an entry hole.  It agravates me that I have to waste time messing with BS like this.


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## jbolt (Sep 6, 2019)

bretthl said:


> It is just a poorly designed location for an entry hole.



Yup, same for the PM1440-GT. One of my few pet peeves of the lathe. The T-nuts are also under designed and lend to excessive flex under heavy loads. One of the reasons I went to a solid tool post riser and only put the compound on for doing short tapers. The cross slide needs to be redesigned to have the entry hole on the bottom with a more substantial T-nut.


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## rogerl (Sep 6, 2019)

Could you put the T Nut back in the slot and then make a plug to go into the entry hole? It would do nothing for making the T-Nuts stronger but it would keep them from falling out. It would save taking the cross slide off.

Just a thought

Roger L


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## Cadillac (Sep 6, 2019)

My lathe is of same design but also has a through hole on the bottom. Always wondered why there is the hole on top if one on the bottom on mine?
I had seen acouple people end up cracking off pieces of the flange because the t bolt wasn’t supporting the underside correctly. If you look at your t-nut they are cut wrong to follow the t-slot in the carriage. The outside should be convex and the inside should be concave so it fits the slot snug. Your t-nuts are only supporting nubs in the slot.
When I went through my carriage that was one thing I did. T-nuts are as large as I could get in there and milled to follow the slot like explained. Fortunate for me my hole is at the 3:00 position and much smaller than in your pic.
The plug idea in the above post is a good one too.


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## bretthl (Sep 6, 2019)

As flimsy as this cross slide is I really hesitate to mill a slot although that would allow installation of a much larger T-nut and concave/convex as Cadi and JD mentioned.  I will try making the nut as large as possible and contour to go around the corner.  Another time wasting PM upgrade (I hate this lathe).


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## bretthl (Sep 6, 2019)

rogerl said:


> Could you put the T Nut back in the slot and then make a plug to go into the entry hole? It would do nothing for making the T-Nuts stronger but it would keep them from falling out. It would save taking the cross slide off.
> 
> Just a thought
> 
> Roger L



Ah!  I just saw this and will work it.  That will save me time, precious time.  Thanks.


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## bretthl (Sep 7, 2019)

rogerl said:


> Could you put the T Nut back in the slot and then make a plug to go into the entry hole? It would do nothing for making the T-Nuts stronger but it would keep them from falling out. It would save taking the cross slide off.
> 
> Just a thought
> 
> Roger L



This will get me by, not much T-nut engagement.  Thanks.


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## Stonebriar (Sep 7, 2019)

I wonder what the max size T-nut could be made to fit in there is. You are right that is not much holding power


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## dpb (Sep 7, 2019)

You can’t make a meaningfully larger t-nut, and still insert it using the factory entry slot.  If you make an entry hole in the back, you solve this problem.  Photo shows original, and replacement t-nuts. A replacement nut is shown, installed in the 30° location, with plenty of contact.


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## Firstgear (Sep 7, 2019)

bretthl said:


> I went to cut an external thread, set the compound at 29.5 degrees and one of the bolts would not tighten.  Removed the compound without rotating and low and behold the lock nut is positioned exactly at the insertion point.  Any ideas how to fix this?  This just happened, I have cut many threads with the compound at this position.  It is to the point where I can no longer lock the compound base anywhere near 29.5 +/- 2 degrees.
> 
> View attachment 301548


I had a problem with my 1440GS, the lock nut wouldn’t tighten after tightening it up about a dozen times.  Turned out that it could easily be stripped because of how it was made.  I called PM and got exactly the same parts that the machine came with.  I ended up making my own locknut, now all is good.


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## Stonebriar (Sep 7, 2019)

This looks like a project for my list of upgrades to my PM1440GT.


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## petertha (Sep 8, 2019)

I have a Taiwan 14x40 lathe with a similar T-nut retention system. It has some additional irritating attributes. 1) A nut can partially get bridged in the casting hole 2) the nuts can get themselves out alignment relative to the compound bolt holes & then you spend 5 minutes playing hide & seek. I made these makeshift spacers out of wood just to see if it would work. 10 years later they are still there, just a bit oilier


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## bretthl (Sep 18, 2019)

Slight improvement to the access hole plug.  Seems to work better.  Careful to ensure plug dimensions were exact.


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## dpb (Sep 19, 2019)

bretthl said:


> Slight improvement to the access hole plug.  Seems to work better.  Careful to ensure plug dimensions were exact.



Out of curiosity, how did you make that plug? I can think of a couple ways, but they don’t seem to match the tool marks I see.


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## bretthl (Sep 19, 2019)

dpb said:


> Out of curiosity, how did you make that plug? I can think of a couple ways, but they don’t seem to match the tool marks I see.



It is pretty rough but I was moving fast to get it done.  I used a super spacer on the mill and a 1/2" end mill.  With a 1" 1018 round mounted horizontal in the chuck I cut the key coming in from the end of the round.  Then I rotated the chuck and removed the remainder of the material down to 0.740" OD with the 1/2" end mill then switched to 1/4" closer to the key.  Parted off with the lathe and faced the end oposite the key to final length.  Thanks for the plug idea!


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## qualitymachinetools (Sep 24, 2019)

We came up with a fix for this a while back, if anyone has this problem please contact us directly if you are the original owner of the machine, we had that hole moved to a different spot and larger T nuts made.


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## Janderso (Sep 24, 2019)

Well done, Quality Machine Tools!!


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## jbolt (Sep 24, 2019)

qualitymachinetools said:


> We came up with a fix for this a while back, if anyone has this problem please contact us directly if you are the original owner of the machine, we had that hole moved to a different spot and larger T nuts made.


Doesnt everyone who purchased a lathe, 1340GT & 1440GT, with this particular cross slide design have the problem? 

Sent from my SM-G955U using Tapatalk


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## bill70j (Sep 24, 2019)

jbolt said:


> Doesnt everyone who purchased a lathe, 1340GT & 1440GT, with this particular cross slide design have the problem?
> 
> Sent from my SM-G955U using Tapatalk


Jay:  I checked -- after reading your earlier post -- and I do have the problem on my 1440GT.  Bill


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## bretthl (Sep 25, 2019)

So PM what is the fix?


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## jbolt (Sep 25, 2019)

bill70j said:


> Jay: I checked -- after reading your earlier post -- and I do have the problem on my 1440GT. Bill


This was a major reason why I went to a solid riser under the tool post. 

Sent from my SM-G955U using Tapatalk


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## GL (Oct 1, 2019)

I agree that everyone with a 1340/1440GT has the problem and glad that it was recognized and fixed.  The next question becomes, when did "awhile back" happen? My 1340GT is a little over a year old.  Will check next time I'm out to the shop. House taken out by tornado, shop spared, rental until we rebuild is half hour away (and I used to complain when my tools were in the other shop...across the driveway).  I guess the only saving grace is that tool pressure is down on the front of the cross slide, so chatter notwithstanding, the forward t-nut is not having to do as much work as the back one.


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## jwmay (Oct 9, 2019)

The Grizzly G4002 is similar. I made a minimally larger t bolt, which solved the problem so far.


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## wrmiller (Oct 9, 2019)

jwmay said:


> The Grizzly G4002 is similar. I made a minimally larger t bolt, which solved the problem so far.



That will work. Or in my case, I just don't swing my compound to that angle. Simple enough.


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