I stripped the T-nuts on my PM-1030V compound

[erikmannie]

A little off topic, but I don’t have a whole lot of time to read for most of the year (because of working at my job and in the garage). It took me a whole month to get through the manual for my lathe.

I am going out of state to go to welding school here pretty soon, and I am taking the Machinery’s Handbook with me. For two months, I will have over 40 hours a week to spend reading it, which is a good thing because you know how many pages it has!

It has been a little challenging working on my machines without having been through that book too much. For example, I am almost entirely shooting in the dark with regard to speeds and feeds.

 

[mikey]

What I am going to do here is try the Grade 12.9 bolts. If I see any more movement, I will make a plinth. If I want to cut a taper or threads, I guess I will have to temporariliy remove the plinth.

Looking at the size of it, I would imagine that a plinth would have to be mostly aluminum If one is to remove it from time to time.

Personally, I would assess the fits of your compound on the cross slide with some Prussian Blue to make sure it has good contact. It does NOT make sense that it requires so much torque to lock it down; something is off. I would solve this first instead of using stronger bolts so you can crank down harder, Erik. Once you resolve the issue, then make a plinth. You can use the plinth for most work and then replace it with the compound for taper turning or threading. You can leave the plinth in place and feed straight in for threading if you prefer; it works pretty well, too.

Most plinths I have seen are made from cast iron or steel. Most of those are made in such a way that the tool post is fixed solidly; these guys mostly use carbide tooling.

I have a plinth half-way made and will complete it if I ever find the time. It is a solid block of aluminum very similar to the one @ttabbal made and also surfaced with a tool steel top plate. I use HSS tools mostly and even when I use brazed or inserted carbide tools I usually don't use them at the angles they were intended to be used in so my tool post has to be easily turned. I think aluminum is fine for a plinth, despite the difference in the modulus of elasticity between it and steel or cast iron. I just don't have enough power or rigidity to require a ferrous metal plinth.

 

[7milesup]

This is a super interesting thread. The depth of knowledge on here is incredible.

Erik.... One book that I have is Tabletop Machining by Joe Martin. It is geared towards the Sherline benchtop tools, but it is a very interesting read. I am assuming that you are taking a computer with (laptop, etc). I think that almost more information can be gleaned from YouTube videos and forums than books. Sad to say in way. Don't get me wrong, books are awesome and I am a prolific reader, but a video connects how the pieces go together sometimes. This old Tony, NYC CNC, Oxtoolco, MrPete222, Clickspring and Abom79 are just a few of the great YouTube channels.

 

[ttabbal]

I am saving up for a MUCH larger PM machine. I hope to one day have a machine where I don’t have to change out the gears to cut different thread pitches.

I don't bother with the compound for threading. It works fine for me. I might end up with an extra pass or two, but no big deal.

For gears, there's always this option as well..

Electronic Lead Screw

I'm going to attempt to adapt clough42's ELS to my PM1127. I figure I might as well do it publicly in case it ends up being useful for someone else. I have most of the parts now, and have the electronics and servo running on the bench. The first thing I decided to mess with is the rotary...

www.hobby-machinist.com

 

[francist]

It would appear that a plinth is a rigid spacer that is used to mount a tool post without a compound slide.

In the context here, yes, although it has much older uses primarily in architecture and components of columns

Definition of plinth

1a: the lowest member of a base : SUBBASE
b: a block upon which the moldings of an architrave or trim are stopped at the bottom
2: a usually square block serving as a basebroadly : any of various bases or lower parts
3: a course of stones forming a continuous foundation or base course

 

[erikmannie]

Because I am always striving for rigidity, I have a strong interest in building a plinth.

This is the first that I’ve heard of threading without the use of a compound; I find this to be really great news.

I would add Blondihacks to the recommended YouTube channels for machining. I watch and listen to YouTube videos a great deal. I download them on my phone and listen to them while I drive. Sometimes I wonder why I pay to go to school when there is so much exceedingly high quality material on YouTube.

I find this forum to be tremendously responsive and helpful. I appreciate the responses.

 

[markba633csi]

I have seen this before- the fit is bad between the compound and the slide:
That's one reason you needed to torque the bolts so tight
The factory really should fix that
-Mark

 

[erikmannie]

It seems to me that I caused this by abusing the factory T bolts. I have had the lathe for five weeks and used it quite a lot. As I recall, it functioned properly before I overtightened the bolts. We shall find out in a few days here when I properly install fresh hardware.

In my experience, I am rough on my tools and machines. I really should care for my equipment better. My Miller welders, however, have withstood my rough treatment so far.

 

[erikmannie]

I have seen this before- the fit is bad between the compound and the slide:
That's one reason you needed to torque the bolts so tight
The factory really should fix that
-Mark
View attachment 312502

One should note that the nuts are not tightened in all of the photos above, this due to the fact that the bolts are very stripped out.

 

[erikmannie]

I noticed that an M10 bolt is too large to pass through the compound mounting base.

The steel yard only had Grade 10.9, so I will be using Grade 10.9 M8X15 bolts threaded into an M8 T slot nut.

Earlier, I tried a 7/16” T slot nut and it was too large to fit into the T slot on the cross slide. These T slot nuts use 3/8” threads so Grade 8 bolts are readily available.

I am anxious to see if an M8 T slot nut will fit in the T slot of the cross slide. If it doesn’t, I will go back to the 7/16” T slot nut, mill it down to size, and use a 3/8” Grade 8 bolt.