PM-25MV delivery and setup pictures, power feed issue.

[erikmannie]

I called PM, and they said that they may have a spare bracket at their facility. If not, then we will see how to move forward.

More interesting yet is that as of Sept. 2019 there is only one limit switch used for all power feed kits. The limit kit bracket (or mounting plate), however, may vary. As such, the customer may need to trim the mounting plate provided.

It would also be very easy to machine a limit switch bracket to the desired specs. This would be a steel plate with six holes in it. One could use the oversized mounting plate provided as a template for these bolt holes.

They also said that the T-nuts should have been tapped, but any T-nuts would work (of course).

I am starting to ask myself why I didn’t just machine the replacement part for the cast aluminum bracket that I broke.

PM also said that not using the limit switch is too risky to consider.

 

[WyoGreen]

Your PM25 power feed setup looks just like my Pm30 setup. I didn't like how the supplied mounting plate clamped over the existing end plate, so I made a new replacement end plate that the power feed bolts to. The power feed seems to run much smoother and quieter now. If I remember right, my limit bracket didn't fit right either. I seem to remember turning the bracket over or some such thing. I'll have to go look. I think I posted some pictures of my new end bracket on here, so a search should turn that up.

Oops, gotta go to lunch, Steve

 

[mikey]

PM also said that not using the limit switch is too risky to consider.

They might be looking at it from a liability standpoint, their liability. I assure you that your mill will not blow up if you use power feed without a limit switch. You will find the hard stops to be far more useful.

 

[erikmannie]

PM is sending me the cast aluminum power feed bracket that I cracked, free of charge. It already shipped out, and they provided me a tracking number. Very nice of them. PM said that those do, in fact, crack if one overtightens them.

PM confirmed that they sent me the right limit switch with the power feed kit. Again, I was informed that they use the same limit switch for all of their power feed models, regardless of what milling machine it will go on. I will make a custom limit switch mounting plate which maximizes the area for the x- and y-axes stop levers and keeps the limit switch under my vise.

I am also leaving my mind open to not even using the limit switch (again, so that I have plenty of room for the x- and y-axes stop levers). I understand that PM was mostly thinking about safety and liability; I will probably make the conservative choice and put the limit switch on there.

I bought some extra T-nuts for a 1/2" slot on eBay. The T-nuts that I bought accept 3/8" studs. The 52 piece clamping kit that I got from PM (when I bought my PM-25MV) included 3/8" studs and nuts, so I am trying to have 3/8" female threads on all of the T-nuts in the shop.

I wonder if I will have to grind down the 1/2" T-nuts to fit in the 12mm T-slots in the PM-25MV. Most of the T-nuts that I saw online were for metric fasteners. I saw a lot of 12mm T-slot nuts in M8 and M10. I will report back here how the 1/2" T-nuts fit in the 12mm dovetail slot.

I had to grind down all of the T-slot nuts that were provided with the power feed kit; the instructions said that one often has to do so.

I bought a 20 piece TiN coated end mill set from Little Machine Shop. I followed the recommendation of Blondihacks on YouTube. She chose the exact same mill and lathe that I did.

 

[erikmannie]

Just for the record, the thread pitch in the PM 52 piece clamping kit is 3/8"-16.

I took my T-nut down to the hardware store, and of course neither an M8 or M10 would thread in.

 

[erikmannie]

Your PM25 power feed setup looks just like my Pm30 setup. I didn't like how the supplied mounting plate clamped over the existing end plate, so I made a new replacement end plate that the power feed bolts to. The power feed seems to run much smoother and quieter now. If I remember right, my limit bracket didn't fit right either. I seem to remember turning the bracket over or some such thing. I'll have to go look. I think I posted some pictures of my new end bracket on here, so a search should turn that up.

Oops, gotta go to lunch, Steve

Steve here nailed it. The limit switch mounting plate needed to be taken off, rotated 180 degrees and reinstalled. So it was the correct part, but the factory installed it incorrectly. All good now...

 

[mcdanlj]

Like @WyoGreen, I have the PM-30.

If I used this limit switch, the locking levers for the x and y axes would have very little room to maneuver

That's spot on. I have the limit switch in place, adjusted to just barely allow full X travel, but it definitely cramps my style with the X gib locks.

I have not found a great way to route the limit switch cable. In practice, it occasionally snags.

I used the mill to cut down the T-nuts rather than filing or grinding them. They weren't hardened steel...

You'll find that a lot of folks have made power lifts for the PM-25 and a few for the PM-30. I used a drill on the nut in the Z wheel to lift the head before I made my Z power feed out of lots of re-purposed bits.

Using a drill:

PM-30 Z-axis power feed?

That video shows lower left for PM-727, as does the site for the PM-727, PM-932, and PM-940. The PM-833T has lower right. PM-25 and PM-30 are upper right. I don't see any PM bench mills that have Z crank on upper left; that seems to be the only option that is not used! ☺ I'm guessing that the...

www.hobby-machinist.com

You can buy a pre-made PM-25 Z power feed:

Pm25 power z axis

Welcome! Little Machine Shop sells a power lift for their bench mill that might work. The LMS 5500 and PM-25 share very similar column and crank layouts. https://littlemachineshop.com/products/product_view.php?ProductID=5657&category=2122081966

www.hobby-machinist.com

My recycled hack:

PM-30MV for mcdanlj

The nylon locking ring in the nut didn't quite engage the threads, so I bored out another 0.1" and now the nut now tightens securely: While I was at it, I added some bevels. The innermost bevel makes threading the nut more comfortable. The large outer bevel just makes it a slightly better...

www.hobby-machinist.com

Enjoy the mill! ☺

 

[erikmannie]

So after I talked to PM I forgot that we didn't resolve the matter of the wedge nuts supplied not being tapped (for what needs to be M8 X 1.25 (M8 coarse)).

M8 wedge nuts are readily available in the UK and India, but I definitely couldn't find any in the US. These are also called Vee Nuts, V-Nuts or Vee Wedge Nuts. I guess they are common over there, but not here.

Here is a picture of what one would use to mount something (e.g. a limit switch or stop of some kind) in the front dovetail slot of a PM-25MV milling machine.

If anybody knows where to get these in the US, I would be interested to know.

Looks like a good beginning milling project!

A lot of people would probably just grind down a T-nut.

Anyway, I found it odd that these were not readily available.

 

[erikmannie]

The closest that I could find was the items pictured below, and I will grind them to fit. I would have also expected to grind the one pictured above.

 

[mcdanlj]

So after I talked to PM I forgot that we didn't resolve the matter of the wedge nuts supplied not being tapped (for what needs to be M8 X 1.25 (M8 coarse)).

In one of your earlier pictures, it looks like a bolt is threaded into the v-nuts.

How are they not tapped? Is it that they aren't tapped through? I would expect PM to be happy to drop some replacements into the mail if so. (Also, and incidentally, an M8 tap isn't that expensive, and I'd think that for bike frame building you'd want a metric tap set anyway?)