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Rotary Table 3 or 4 slot?

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Jim Beagley18/09/2020 12:34:38
86 forum posts
47 photos

I’m about to purchase a 6” rotary table for model and hobby use and I’ve been looking at the various incarnations of the HV6 that is widely available.

I cannot decide on a 3 or 4 slot model.
i can see that a 3 slot would be easier to fit a 3 jaw chuck to, but then a 4 slot has more clamping possibilities.
Any advice?


Edited By Jim Beagley on 18/09/2020 12:35:26

Michael Gilligan18/09/2020 12:50:18
16374 forum posts
714 photos

This has been rehearsed on several previous threads, Jim

My personal preference is strongly in favour of 4 slots

... but I know that others disagree

Let battle commencedevil


Len Morris 218/09/2020 13:02:12
43 forum posts
19 photos

4 slots. Much more versatile.

JasonB18/09/2020 13:06:30
18885 forum posts
2080 photos
1 articles

Darn, I'm in agreement with Michaelwink

I find 4 slots makes it easy to mount square or rectangular work as it's easy to put two clamps on opposite sides. If you do want to use an edge finder on square or round work then you can have the grooves at 45deg so all edges can be accessed without clamps getting in the way.

Mounting 3 jaws only really work better on a 3-slot table if you have a spare one with through fixing. The ones I use on the R/T are mounted to a plate that is drilled with 4 holes. This also allows easy offsetting for eccentric work as you can slide it sideways.

Mike Poole18/09/2020 13:15:17
2745 forum posts
64 photos

I have a four slot and my three jaw chuck is fitted on a sub plate, I bored a hole in the centre of the sub plate to be a close fit on a boss that fits in the morse taper in the table so centering is easy and the boss is removable to use the through hole.


SillyOldDuffer18/09/2020 13:31:47
6329 forum posts
1388 photos

What a boring battle! A vote for 4 slots from me too.

My machines all use bolt-on chucks, not screw or clamp types, so what follows may not apply to everyone. Rather than mess around making a baseplate to fit an existing chuck I ordered a chuck sold specifically to fit the tableat the same time Much easier to mount because the rotary table chuck is drilled through for fixing from the front. Also, rotary table and lathe are often used at the same time: having to swap a chuck between mill and lathe would waste time.


old mart18/09/2020 13:48:54
1991 forum posts
151 photos

I bought a 6" Soba RT which gets used regularly. It has 4 slots, which makes attaching the 6" four jaw independent front mount chuck very easy, using tee nuts which I made to fit the slots properly. Being able to mount a three jaw chuck is also handy, and I can mount a Pratt Burnerd 5" front mount using three 8mm tapped holes in the top. If you do that, beware of the lubrication drilling if there is one. I carefully drilled the holes and was somewhat annoyed with myself, as the third one broke into the lubrication drilling which I hadn't noticed. So this top has 6 holes in it. There is enough free play in the mountings of the three jaw chuck before the screws are tightened to put a MT test bar in the top and gently tighten the jaws on it before the chuck is secured. This will give at least 0.002" tir which is ok for all but demanding work.

I would vote for 4 slots, slightly more versatile.

Thor18/09/2020 14:39:25
1276 forum posts
39 photos

My Rotary Tables all have 4 slots, so 4 slots get my vote too. A friend of mine has a RT with 3 slots and he wishes it had 4.


norman valentine18/09/2020 16:39:52
249 forum posts
35 photos

I have found that the best number of slots is on the table that I have got.

I made it, and four slots seemed logical. I haven't found otherwise. But I am sure that if I had made it with three slots I would have been equally happy.

Howard Lewis18/09/2020 18:00:36
3608 forum posts
2 photos

My Vertex HV6 has 4 slots giving an extra 33% of choice if needed.

I tend to use a small 4 jaw chuck on a Myford/2MT adaptor when the face of the table is vertical, but bolt to the table when the face is horizontal..

To my way of thinking, the most important feature is the ratio. The higher the ratio, the greater accuracy that can be achieved i e any error in moving the Handle is decreased to a 90th as opposed to a 40th or a 36th..

Others may feel free to differ. Purely my choice.


Clive Foster18/09/2020 18:03:26
2375 forum posts
76 photos

Clive figures that the number of slots matters not as a grid of tapped holes sub plate is much more appropriate than slots on small rotary tables given the size of the machines and workpieces they are appropriately used with. M5 or M6 in five spot dice pattern on 25 mmm or 20 mm centres works well enough with suitably small clamp bars et al.

I consider conventional clamping gear, such as the import kits of stout bars,Tee nuts, studs and step blocks, frustratingly cumbersome on tables below 10" / 250 mm diameter. 8" / 200 mm is marginal. I've not made a sub plate for my 8" (yet!) but my go to table is a 10" one and I also have a 12" in reserve if need be. Pretty sure that if the 8" was the one and only it would be wearing a grid of holes plate.

On model engineering size jobs its not the holding power against cutter forces of a beefy clamp that matters. Its more the ability of the job to withstand the cut and also not distort under clamping loads that is important. Not to mention the distressing common issue of clamps needing to go where you want to cut.

Far quicker to drop 5 or 6 small, less sturdy clamps where they fall using a grid of holes plate and temporarily remove the one thats in the way of the next cut than to spend ages plotting the exact positions where a bigger clamp affixed via aTee slot won't be in the way. In the days when I had my little BCA, which did have a grid of holes plate, I'd sometimes cut straight into a shop made clamp that was a bit in the way rather than bother to remove it.

Not as if I was going to be lovingly attached to a bit of 3/16 steel hammered into an L shape with strategically placed hole for the screw or a simple strip of 1/4 alloy wearing a similar screw hole with the non business end propped up on a pile of offcuts.

Model Engineers as breed seem reluctant to accept the value of sacrificial tooling et al. We are far too protective of our ever growing boxes of oddments. But this pot admits he is just as bad as any kettles. Buying a new piece of hefty alloy bar because the same size bit in stock purchased for a job that never happened was "too nice to use" may lead to legitimate concerns over sanity. Especially as the second job was also abandoned when the customer pulled out so I now have two pieces "too nice to use".



Edited By Clive Foster on 18/09/2020 18:04:07

Edited By Clive Foster on 18/09/2020 18:04:32

Edited By Clive Foster on 18/09/2020 18:05:18

Jeff Dayman18/09/2020 18:35:37
1895 forum posts
45 photos

Jim, it really does not matter which type of table you buy, because you can always make a separate fixture plate to mount on it, if need arises. It can have as many holes, slots, grooves as you need, in any pattern. I have several of these makeshift plates made for various custom jobs done over the years. Just food for thought.

Nicholas Farr18/09/2020 18:43:14
2441 forum posts
1193 photos

Hi, mine has 3, and it is very often a nuisance and would prefer 4, but I bought it off a neighbour several years ago for a song and it wasn't that old or used much, just to say he offered the price so who was I to refuse. Go for a 4 slot I say.

Regards Nick.

Jim Beagley19/09/2020 14:09:58
86 forum posts
47 photos

Thanks very much for all the comments. 4 slots it is then.
cheers all.

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