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Rotary table and chuck problem

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jamie hanby21/07/2014 20:28:46
5 forum posts

I got a rotary table and a chuck for it. I need something so I can center the chuck on the rotary table.

RDG told me I needed a back plate but didn't say witch one http://www.rdgtools.co.uk/acatalog/Finished_Back_Plates.html

Suppose I need an adapter too, again no idea witch one to get. http://www.rdgtools.co.uk/acatalog/Rotary_Table_Adaptors.html

Any help would be really appreciated.

Nigel McBurney 121/07/2014 21:19:54
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966 forum posts
3 photos

Be care careful with threaded adaptors, the chuck may start unscrewing when taking milling cuts ,its ok just to drill or spot holes but not adviseable to mill . industrially a chuck would be secured to a plate with socket head cap screws and plate in turn bolted to the rotary table.

Oompa Lumpa21/07/2014 22:07:50
888 forum posts
36 photos

Welcome to the forum Jamie. From what I can see, that chuck you have linked to is front mounting with three bolts. All you need are three bolts and three T nuts for the slots in the table, position the chuck over them and bolt it down. Very straightforward.

The Vertex four inch table looks quite cute actually and if it's as good as the six inch you are onto a winner.

graham.

jamie hanby21/07/2014 22:14:19
5 forum posts
Posted by Oompa Lumpa on 21/07/2014 22:07:50:

Welcome to the forum Jamie. From what I can see, that chuck you have linked to is front mounting with three bolts. All you need are three bolts and three T nuts for the slots in the table, position the chuck over them and bolt it down. Very straightforward.

The Vertex four inch table looks quite cute actually and if it's as good as the six inch you are onto a winner.

graham.

I have t-nuts and bolts but I can't center the chuck. Thought there might be an easy adapter that you put on first to center the chuck and then bolt it on.

Its a nice lite table for the price, haven't had the chance to use it yet so I can't comment if it is any good.

Thanks for the help.

Oompa Lumpa21/07/2014 22:21:39
888 forum posts
36 photos
Posted by jamie hanby on 21/07/2014 22:14:19:
but I can't center the chuck. Thought there might be an easy adapter that you put on first to center the chuck and then bolt it on.

Thanks for the help.

There will be an adapter as soon as you make it. Welcome to the world of engineering.

Just get a suitable morse taper blank arbour, stick it in the lathe, bore a hole at the blank end the same diameter you have a piece of bar (preferably Silver Steel) and stick the bar in the arbour with loktite. Put the taper end - check which taper is in the table before purchase - lower the chuck over it, tighten the jaws then you can bolt it to the table. Close enough for most everything.

graham.

(could someone perhaps draw this?)

jamie hanby21/07/2014 22:36:22
5 forum posts

Just had an idea, I could get a http://www.rdgtools.co.uk/cgi-bin/sh000001.pl?WD=22mm%20mt2&PN=2-MORSE-TAPER-28MM-DIA-BLANK-END-ARBOUR-3-8-bsw-DRAWBAR-THREAD--5757999.html#SID=493

Rotary table is mt2 taper and the chuck is 22mm.

Robert Dodds21/07/2014 23:07:00
305 forum posts
58 photos

Jamie,
Well spotted and yes , thats the right way to go.

your dilemma now is whether to go for 3/8 whit or M10 tapping in the shank of the arbor. That depends on whether metric or imperial threads dominate in your existing kit. you will need a screw or studding to secure the arbor to the RT

Good luck with it

Bob D

jamie hanby21/07/2014 23:19:24
5 forum posts
Posted by Robert Dodds on 21/07/2014 23:07:00:

Jamie,
Well spotted and yes , thats the right way to go.

your dilemma now is whether to go for 3/8 whit or M10 tapping in the shank of the arbor. That depends on whether metric or imperial threads dominate in your existing kit. you will need a screw or studding to secure the arbor to the RT

Good luck with it

Bob D

Don't think I have to worry about the drawbar thread because I don't think I need to secure the arbor unless i'm missing something. All Ill do is drop the arbor into the RT and then place the chuck over the arbor & then bolt down the chuck.

Thanks for all the help really appreciate it.

RJKflyer22/07/2014 10:34:04
49 forum posts
3 photos

All I have is an 12mm thick aluminium backplate that bolts to my chuck with 4 cap screws, and the ali backplate has a raised centre spigot (only about 5mm) which fits snugly into the hole in my rotary table.

The backplate overhangs the chuck by about 10mm and has four holes in it to allow bolts to drop through to the T-slots in the RT.

Isn't this easiest, and possibly best? No risk of anything unscrewing, self-centring and no intrusion into chuck or table.

Clive Foster22/07/2014 11:14:51
2993 forum posts
105 photos

Don't overthink things. I start by mounting a co-axial indicator in the spindle and centralise the rotary table working off the centre hole. With the chuck loosely fitted the table and roughly centred by eye a straight round bar held in the spindle can be bought down in to the chuck aperture using the quill. Tighten the chuck up on the bar to pull it central and clamp down. Replace bar with cutter and have at with no central obstructions till you get to the table bore. If you haven't got a a coaxial indicator make an alignment spigot by turning the end of an ordinary morse taper blank end arbor down to a suitable size to grab in spindle collet or chuck and use that to centralise the loosely mounted rotary table in exactly the same manner as described for the chuck.

A spigot is faster than using an indicator but I have three rotary tables with different sized centre holes, 2 plain, one morse, and can't be bothered to make up three spigots.

Could use an ordinary indicator to centralise the rotary table but I figure life is too short to faff about with the usual mirror and contortions to see whats going on round t'back. Not to mention getting my right and lefts uddled up between back'n front readings.

Clive

Ian Parkin22/07/2014 11:50:54
avatar
995 forum posts
235 photos

I use a MT 2 test bar when fitting the chuck

knock the test bar into the hole.... place chuck over test bar... tighten chuck onto bar... fasten chuck to RT

knock out test bar from behind

Ian

Neil Wyatt22/07/2014 12:15:37
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Moderator
18899 forum posts
734 photos
80 articles

Lock the mill table slides in a fairly central position.

Fit a centre to the mill and drop the head so that you can use this to centralise the rotary table. Fix table in place.

Fit a collet to the mill with rod in it. Place the chuck of the rotary table and then tighten it onto the rod. Mill axis, chuck and rotary table are now in line. Secure chuck to rotary table and then zero all readouts. Remove rod and get to work.

Neil

Clive Foster22/07/2014 12:42:53
2993 forum posts
105 photos

Neil

Although the often advocated "push a centre in" alignment method frequently works its bad practice and should never be used save perhaps as a quick and dirty way of rough setting. I often use it so as a first step when setting things up in a four jaw on the lathe. Not only is it insufficiently robust but it also relies on perpendicular line contact between unmatched surfaces which are not inherently defined for such purposes during manufacture.

If you want to align something you have to use properly defined axes either directly parallel to the desired axis or, as with a taper, explicitly designed and accurately made with respect to that axis. Dropping a centre down relies on a clean, round edge or accurate chamfer on the table and a centre accurately ground right out to its shank or taper junction. Rotary tables normally have a chamfer or tapered edge to the central bore to protect it which is normally "just made" rather than accurately specified. Manufacturing methods ensure that it should be close but there is no tellings exactly where the centre will touch.

Given how little trouble it is to make a proper MT alignment spigot its silly to rely on a potentially iffy method. Even it it almost always works. The almost bit is guaranteed to turn up at the most inconvenient time when a mistake is most irretrievable!

Clive

Who isn't paranoid. The shop gremlins. Lawyer Murphy and the Custard Pie God really are out to get him at every opportunity!

Neil Wyatt22/07/2014 13:07:56
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Moderator
18899 forum posts
734 photos
80 articles

Hi Clive,

You are no doubt right, but I suspect the limit on accuracy in this case will be that a 3-jaw chuck is being used for workholding.

Neil

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