PM-1660TL

[Jim F]

I was all ready to buy a Morse Taper #7 dead center. I planned to use the part of the dead center that has the exact same outer dimensions as my reducing sleeve, but cut to length to allow for a 60° nose at an appropriate working length. The idea here is to just have a solid dead center (i.e. no reducing sleeve). Not that there’s anything wrong with reducing sleeves!

However, I took a close look at the dimensions of the reducing sleeve, and I saw that a 7MT dead center would only be able to be pushed in (to the spindle nose) for only 1/2” until the dead center reached the point where it couldn’t go in any further.

I HAD thought that the supplied reducing sleeve may have been a shortened “MT7 outside and MT4 inside” socket (or collet). This is NOT the case because the smallest diameter of an MT7 (2.7500”) can only be pushed in to the spindle nose for a distance of 1/2”.

I now believe that the outer dimensions of the reducing sleeve supplied with the PM-1660TL do not correspond to a shortened 7MT shank. It MAY have the same ANGLE of taper as an MT7, but most of the length of the reducing sleeve has a diameter that is too small to be found on a #7 Morse taper.

I just bought a 12” length of 3” diameter cold rolled 1018 ($66 delivered), and I will attempt to make a dead center. I will copy the outer dimensions of the reducing sleeve and then extend that taper angle out several inches to a 60° tip. Not my first choice of material, but it fits my budget.

Cliff Notes version: This lathe appears to have a spindle nose with custom dimensions, perhaps because in order to obtain a 2.55” spindle through hole, 6MT is too small and 7MT is too big.

Maybe PM made a 6 1/2 taper, also........

 

[erikmannie]

Maybe PM made a 6 1/2 taper, also........

I have all but concluded that the taper in the spindle nose is larger than an MT6 and smaller than an MT7.

It is just a good thing that I have a lathe so that I can make my own dead center! I think I can handle cutting a taper, especially when I have the part that I am trying to reproduce in my possession.

I have been watching YouTube videos on this, and it looks like once I have the taper set correctly it will go quickly to knock out a few of them.

Maybe I can have a side hustle selling Morse Taper 6 1/2 reducing sleeves & dead centers. I gather that there is very little competition.

 

[Jim F]

I have all but concluded that the taper in the spindle nose is larger than an MT6 and smaller than an MT7.

It is just a good thing that I have a lathe so that I can make my own dead center! I think I can handle cutting a taper, especially when I have the part that I am trying to reproduce in my possession.

I have been watching YouTube videos on this, and it looks like once I have the taper set correctly it will go quickly to knock out a few of them.

Maybe I can have a side hustle selling Morse Taper 6 1/2 reducing sleeves & dead centers. I gather that there is very little competition.

Make a 5 1/2 taper, also.

 

[erikmannie]

Make a 5 1/2 taper, also.

And so I shall: the niche business of MT 5 1/2 and MT 6 1/2 reducing sleeves, blanks and stubby dead centers.

 

[Larry$]

Eric, good reason to buy a surface or cylindrical grinder. They look like great things to have for the Never complete" hobby shop.

The practice of making non-standard spindle noses bothers me, alot. I understand why it is done. It sells more lathes to be able to claim a larger bore. It would cost more to provide a headstock with the room for and cost for he bigger bearings otherwise required.

 

[erikmannie]

Eric, good reason to buy a surface or cylindrical grinder. They look like great things to have for the Never complete" hobby shop.

The practice of making non-standard spindle noses bothers me, alot. I understand why it is done. It sells more lathes to be able to claim a larger bore. It would cost more to provide a headstock with the room for and cost for he bigger bearings otherwise required.

Maybe after several years these non-standard Morse Tapers will become standard to a point where one would be able to buy a dead center, reduction sleeve or extension socket off the shelf.

It would appear that these non-standard sizes are a result of manufacturers’ desire to attain a large pass-through. That trend is not going away!

Like I said above, I don’t see that chuck manufacturers are aware of this insofar as providing chucks with larger center holes keeping up with larger pass-throughs.

For the people reading this who bought a lathe with a “larger than normal” pass-through, was the center hole of your chuck this diameter or larger?

 

[erikmannie]

Another important point (which I mentioned once above) is that the outer diameter at the small end of the reducing sleeve is larger than the pass-through diameter.

In other words, I would not be able to slide any tapered shank (say, for example an MT 6/12 dead center) fully seated into the taper of the spindle nose because the 2.55” pass-through is too small.

The included reducing sleeve is crucial for seating a dead center when using a face plate or dog driver.

 

[Downunder Bob]

@erikmannie I'm late to the discussion (I think I've read it druing it's early posts) my apologies if I've repeated another post.

I use a machined centre in my 3 jaw instead of a centre in the headstock taper. I just chuck up a piece of steel in the chuck and turn it to 60 degrees. every time I need it again I just re-cut the 60 degree by a few thou. It must always be perfectly concentric with the rotation, unless your headstock is very loose.

This process takes about a minute each time - less time than it takes to remove the 3 jaw chick...

Yes, I were taught to do this as an apprentice, much quicker and more accurate. Alyhough these days I rarely use a head stock centre.

 

[erikmannie]

Yes, I were taught to do this as an apprentice, much quicker and more accurate. Alyhough these days I rarely use a head stock centre.

This is a fast way to do it, and with no drawbacks that I can think of. One just has to buy or cut a straight shank dead center and have bent tail lathe dogs to lay in front of a chuck jaw. Easy peasy.

 

[Downunder Bob]

That is exactly the way we were taught as apprentices some 60 years ago.