Pm1440GT one piece spindle bore dead center

[NortonDommi]

I know it's not a MT 6 because the BV I had was a MT 6 and the dead center I kept from it is considerably bigger.

So you bought a MT 5 and it is too small, a MT 6 is too big and PM state that the taper is a MT 5.5 which is not a thing as far as any listings anywhere that I am aware of but then I know only what is listed by some sources. Apparently grade 9 bolts are a thing now too.
If you are going to make one you will still need to accurately measure what you have. A MT 5 would not pass 2". IF some taper has been made and called a MT 5 1/2 is it a 'stub' taper? Regardless it would be nice to know and think how many people you could help! A MT 4 1/2 & a MT 7 are the only ones with the same taper so there is no way out of measuring it.
At least then you will be able to compare your measurements with all known standard tapers.

 

[Tozguy]

Maybe email PM and ask them for the dimensions of the new MT taper they made ?

Please let us know if someone finds 'official' dimensions for an MT5 1/2.
It would also be interesting to know if this taper shows up on other brands besides PM.

 

[Lonewolfgun]

I sent Precision Matthews a message to find out more info on this taper.

 

[mksj]

It really doesn't matter what the internal taper of the spindle is, all these lathes come with an adapter for a spindle adapter for the spindle to use a dead center, on the 1440GT per above it is a MT3, on the TL series it is a MT4. They also should have come with dead centers in the tool box. If you read the manual and the description they describe this. No need for fairy dust to determine the sizes.

The 1440GT Manual States:
Spindle:
Chuck/faceplate attachment D1-5 Camlock
Internal taper MT5-1/2

TL manual states that the spindle is a MT6 and the site description states:
Spindle:

• Spindle Mount D1-6 Camlock Quick Change
• Internal taper of Spindle is a MT 6 (With included reducing sleeve) MT 4
• Spindle bore 2.55” in. diameter (will pass a 2.500″ piece)

 

[erikmannie]

I sent Precision Matthews a message to find out more info on this taper.

If you ever do make your own (“one piece”as in the title of this thread) dead center (the tail of which will have the same outer dimensions as your reducing sleeve), you can tell when you have the taper angle cut perfectly as follows:

Imagine two (very clean!) identical reducing sleeves laying up against each other, but facing different directions. The sides farthest away from each other will now be truly parallel, and you could measure this accurately with an outside micrometer.

I was measuring my tapered sleeve, and I used dial calipers. An outside BLADE micrometer would have been better. If and when you do you like the above (and have two identically tapered shafts up against each other facing different directions), you can use a standard outside micrometer.

 

[erikmannie]

It really doesn't matter what the internal taper of the spindle is, all these lathes come with an adapter for a spindle adapter for the spindle to use a dead center, on the 1440GT per above it is a MT3, on the TL series it is a MT4. They also should have come with dead centers in the tool box. If you read the manual and the description they describe this. No need for fairy dust to determine the sizes.

The 1440GT Manual States:
Spindle:
Chuck/faceplate attachment D1-5 Camlock
Internal taper MT5-1/2

TL manual states that the spindle is a MT6 and the site description states:
Spindle:

• Spindle Mount D1-6 Camlock Quick Change
• Internal taper of Spindle is a MT 6 (With included reducing sleeve) MT 4
• Spindle bore 2.55” in. diameter (will pass a 2.500″ piece)

Oh, I get it now. The spindle bore of a TL, being a straight 2.55”, will pass a 2.500” piece. The spindle NOSE, however, has an MT6 taper. Looking at the dimensions below, it looks like an MT6 taper cannot pass a 2.500” piece:

I have a 1660TL and I can pass a 2.500” piece through the (tapered) nose spindle of the D1-6 camlock mount. If I were to buy an MT6 dead center, I would be able to pass this dead center all the way through the spindle (spindle nose and all) and out the other side.

Maybe a good product idea for PM is to offer “one piece” dead centers that have the same tail dimensions as the reducing sleeves, but extend out to a 60° tip. Never mind the fact that the diameter of such a dead center would not pass through many of the center holes in the chucks that we use.

The pass through diameter is one of the big selling points of a lathe, but if the smallest diameter of a dead center must be greater than this pass through diameter (explanation below), the taper on the dead center makes for a diameter that is even larger where the dead center is to pass through the center hole of the chuck in use. None of the center holes in my chucks are big enough for that. Such a dead center would also stick out very far! When you use the reducing sleeves that PM provides, the tip of the dead center ends up right where you would want it.

In order for the paragraph above to make sense, you have to understand that the reducing sleeve bottoms out when you put it in (or at least this is the case with my 1660TL and D1-6 camlock). I.e., the internal diameter of the spindle nose taper is at all points larger than the diameter of the straight walled spindle. This is not advantageous if you’re trying to use an off-the-shelf dead center.

The reducing sleeve is critical if you want to use a dead center at the headstock end!

 

[Tozguy]

Does anyone know where to find a one piece MT5-1/2 that'll fit the spindle bore?

Not so far it seems.
A more common approach would be to buy a center that fits in the adapter sleeve that was provided with the lathe (as already mentioned above). Since standard procedure is to skim turn a fresh point on the center everytime it goes in the headstock then it should not be made of hardened steel.
Solid centers dedicated for use in the tailstock are often hardened or have a carbide point so you have to keep them well identified.
BTW technically a live center is one that revolves with the work. A dead center is one that does not revolve with the work. So a solid center in the headstock would be a live center. But that does not prevent many of us from thinking otherwise.

 

[erikmannie]

Maybe the OP is looking for something like this. This is currently for sale on eBay (title is Morse Taper 7 MT7 Heavy Duty Dead Center for Lathe), but the dimensions are wrong for the OP.

Note how it is stubby and the tip has been reduced so that it will get through the center hole of most chucks.

Compare that profile to a dead center in a reducing sleeve:

 

[NortonDommi]

It really doesn't matter what the internal taper of the spindle is, all these lathes come with an adapter for a spindle adapter for the spindle to use a dead center

No need for fairy dust to determine the sizes.

Absolutely a great need for "Fairy Dust" to be sprinkled upon this matter.
It absolutely matters what taper is in a lathes headstock as it is not just a LIVE centre that may be fitted, a collet holder immediately comes to mind as one such. Nice to know if you wanted to fit a boring head for milling as well.
Without knowing for certain what the taper is one cannot source or make something that will fit properly. What happens when the reducer/adaptor sleeve is misplaced/lost/damaged? This is the reason that there are for sale items that use other tapers than Morse.

 

[mksj]

You have a spindle adapter that fits a standard dead center, that was the question, and that is the answer to this thread. I see no other question of fitting anything else. Almost every new lathe in this size comes with these types of adapters. If you want to fit something else like a 5C collet closure, that is different story, but that was not the question. The spec's on the PM lathes are spelled out in the site description and the manual, might be worth reading the manual if you do not believe that it is a MT 5 1/2, if you need the dimensions to make an adapter then measure it.