Vertex Rotary Table 150mm

[Martin CurrieParticipant @martincurrie]

Good evening guys

I have a Vertex 150mm rotary table and I’m a little baffled, according to the manual and certificate that came with my RT the center bore taper should be MT2.

however weak I measure the top diameter, being the widest it’s reading 23.8mm this should be MT3 at this dimension. I’m wanting to make a taper to help with alignment instead of using a coaxial indicator each time I mount it on my mill.

 

can anyone help

 

Martin 

[andy198712Participant @andy198712]

Have you got a MT dead centre you can drop in?
mines a vevor but looks oddly similar…. But I have an opening at the top that’s just round bore then it goes into a taper further down but a dead centre fits nicely and allows easy alignment

[Martin CurrieParticipant @martincurrie]

Hi Andy

Thanks for the reply to my to my post. I have a MT3 dead center but it’s too long to drop down inside. It looks to me that the center bore is stepped, perhaps the MT2 taper stated in the manual is at the very bottom of the bore.

if you look at the pics you can see what I think is a step inside the bore…

 

Martin

[Clive FosterParticipant @clivefoster55965]

Quick and dirty test is to use a pair of appropriately sized washers, one large and one small, the right distance apart to pretty much match two rings on the expected taper bore. As it’s a separating the sheep from the goats thing great accuracy of spacing isn’t needed. Locking each between two nuts on a piece of threaded rod will do.

Or you could use one at a time fitted at the end and measure the depth each one goes into.

Second method is more accurate but I’ve found it easier to set up the washers to be two points on a taper before dropping in to see how much it all wobbles.

Worst bit is figuring out what size washers make sense. Probably have to make them.

Clive

[Paul LousickParticipant @paullousick59116]

I have a similar RT and the bore is MT3

“I have a MT3 dead center but it’s too long to drop down inside”  To check if the bore is actually MT3, using your long `dead centre, turn the RT on its side and allow the centre to extend out the bottom if the hole goes all of the way thru.

[BazyleParticipant @bazyle]

Remember that MT2 and MT3 are very similar but not identical taper angles so just putting it in is not a good test. Put engineering blue on it and check the fit.

[DiogenesParticipant @diogenes]

Mine is definitely 2MT, can’t remember if it’s counterbored at the top but will go and check when I’ve had my coffee.

 

[JasonBModerator @jasonb]

Not unusual for these and the far eastern ones to have a bush with the MT2 internal taper, maybe your bush has been lost. You can also see the step that the bush fits up against which is probably the step you mention stopping the MT3 going in.

[DiogenesParticipant @diogenes]

Jason got there first, much of this probably redundant..

“Okay – my older three-slot Vertex has a plain full-length MT2 socket that extends to the table’s surface, it is 17.XXmm at the gauge line / mouth.

It looks like yours has a ?24mm ?parallel socket – arguably a better system anyway.

When I made my small R/T, a straight socket is what I used, it accepts Precision Ground Mild Steel pins which go in and out with a ‘pop’ fit, and allow various spigots / split centre etc. to be used.

Ordinary BMS can be lapped with split lap & emery to achieve the required fit.”

 

[Martin Currie]

On 4 November 2025 at 20:35 Martin Currie Said:

I’m wanting to make a taper to help with alignment

What part of the taper is crucial to helping with the alignment?

All you need is something that is a snug fit in the table, whose projecting outside diameter is concentric with the hole in the table.

There is some disadvantage to using a tapered item for this purpose: if you drop it into the hole with anything but the lightest touch, once you have done your alignment, it can be difficult to remove if the taper sticks.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, this Operation and service manual might be of interest.

Regards Nick.

[Diogenes]

On Diogenes Said:

…It looks like yours has a ?24mm ?parallel socket – arguably a better system anyway.

When I made my small R/T, a straight socket is what I used, it accepts Precision Ground Mild Steel pins which go in and out with a ‘pop’ fit, and allow various spigots / split centre etc. to be used.

+1

My 12″ (no name) rotary table has a 1″ parallel bore in the centre which is far more useful than a taper for the reason given above.

Julie

[JasonBModerator @jasonb]

I have R/T with both parallel and MT.

The MT equiped one can be lined up by holding a blank end arbor in a collet chuck in the spindle, tap the blank end so you can pull it out though the collet in the spindle usually takes care of that. Or use an edge finder as that is not bothered by a vertical or sloping face.

For small work it can also be handy to mount an ER collet chuck in the R/T as a 3-jaw can get in the way when using the table vertically for things like cutting small gears.

That same blank arbor if kept to a small dia spigot allows various rings to be slipped on when you want to line up work concentrically.

If using it like a dividing head with a drive dog then having an MT taper makes it easy to fit a dead ctr for supporting work between that and the tailstock.

I seldom use the parallel holed one.

[Martin CurrieParticipant @martincurrie]

Good evening guys

Thank you all for all your comments and suggestions to my post…

So tonight I broke out my snap gauges and measured the bore in the RT, from the top to the step half way down the bore it measured a parallel 24mm exactly.

So as Jason suggested this may have been lost at some point in the past.

Knowing that the bore is parallel and not tapered, I’ll machine a spigot to help with lining up on the mill and to assist with mounting my 4 jaw chuck on the table..

Once again thank you all for your help, it’s very much appreciated indeed!!

Martin

[old martParticipant @oldmart]

The Soba rotary table that I bought for the museum is a clone of the Vertex and works well enough, and that has what looks like a MT2 sleeve in the centre of the table. What I mean is that it is MT2, but until seeing this thread, I had not suspected that it may be removable. Is the larger bore parallel or a MT3?

If the bore is the same as Martin Currie’s one it might be possible to get a MT2 sleeve with a parallel OD and use carbide inserts to reduce the diameter of the end to 24mm, or there may be enough wall thickness in the top of the table to increase the bore to match a sleeve. I’m not back at the museum till Saturday, so cannot measure one of our MT2 sleeves until then. A sleeve could be cut carefully with an angle grinder to make an adaptor.

[John HaineParticipant @johnhaine32865]

Have a 24mm dia “slug” that drops in the bore with an accurate centre drilled in the end. Put a centre in mill spindle, bring down quill so it engages with the centre in the RT, get the table snugly aligned, then tighten it down to the mill table.

[old martParticipant @oldmart]

That is a very good and quick method which will get you within 0.001″ tir without resorting to indicators. Put a small female thread in the wall of the slug in case it prooves difficult to remove occasionally.

[not done it yetParticipant @notdoneityet]

The method of centring a chuck by this method is, at best, hit and miss, relying on the quality of the chuck.  We all (should) know that most three jaw chucks are not good for concentricity – certainly not for all diameters.  The chuck will only be centred for the diameter of the inserted post and not necessarily for other diameters.

It is one of the reasons why we do not remove and replace items, for later machining operations, when using a scroll chuck.

[Howard LewisParticipant @howardlewis46836]

FWIW, My Vertex HV6 has a 2MT sleeve which is TIGHT fit in the bore (Has only come out once)

My method, of centering under the spindle of the Mill, is a fine bored 2MT arbor in the HV6,  and a 3MT arbor in the Mill, which is a made to be a very snug fit in the bore in the 2 MT arbor.

Howard

[old martParticipant @oldmart]

Having a good Pratt Bunerd scroll chuck normally fitted to the rotary table I usually fit a test bar in the MT2 hole in the top and gently clamp the chuck jaws onto it before bolting the chuck down. The 7″ long test bar also serves to align the spindle if necessary. If the concentricity is vital, I would resort to the use of an indicator. That chuck holds all diameters with less than 0.002″ tir throughout its clamping range with both sets of jaws. Many people have never actually tested scroll chucks to find the errors and also the best key position. They also have tight registers onto the chuck backplates so that errors cannot be minimised, and then moan about scroll chucks being useless. They are also the same ones that cannot be bothered to use a four jaw independent because it takes longer to adjust.

I think I won’t be trying to remove the bush from the Soba table top, let sleeping dogs lye.

[noel shelleyParticipant @noelshelley55608]

Just checked my generic HV6 and it has a 2MT socket in the centre hole, though I’m not sure how it’s held in place – it does not fall out. Noel.

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