Rotary table size myford vmc

[BramParticipant @bram]

Hi, wondering on people's thoughts about what rotary table size for my old myford vmc mill, haven't got deep pockets but looking at used vertex 6" or poss new Axminster 8". Any thoughts would be appreciated, thanks.

Bram

[BramParticipant @bram]

[Neil WyattModerator @neilwyatt]

Hi Bram,

8" sounds a bit OTT for a VMC to me. Others might disagree,

Neil

[BramParticipant @bram]

Very possibly, initial thoughts where for 6" vertex just didn't want to pick one up and regret not going any bigger, as I say any input would be great

Ta

[John ReeseParticipant @johnreese12848]

You need to consider how much space you need for clamps. Bigger is better.

[Old SchoolParticipant @oldschool]

If you decide to go for an 8" table have a look for a second hand British one I got one from a well known auction site for £80 and it was like new no marks on the table just a dodgy paint job

[BramParticipant @bram]

Humm! Just stood in front of mill with a rule and wondering if 8" is a tad tight, it would fit but think 6" would look more to scale if you get what I mean. Without tooling it's around 13.5" height and 6" throat to centre of spindle. Bed is24 x 6.

[Clive FosterParticipant @clivefoster55965]

As John says you need to consider the space required for clamps and workpiece holding devices.

In my view an 8" table is the smallest size for which conventional Tee slot, clamp and step block methods can be considered reasonably satisfactory. Even then there can be a lot of inaccessible space. In the days when I had an 8" table and used such methods it was quite common to have to shuffle clamps around mid job so cuts could be made. Assuming the job had stayed exactly put during the shuffle could lead to unfortunate language when the assumption proved erroneous!

A grid of holes can be much more satisfactory for model size work. Say 1/4" or 6 mm threads at 1" – 25 mm or 1/2" – 12 mm spacing. Consider adding something like the Thor Labs 1/2" thick anodised aluminium breadboards here **LINK** . Not cheap but not completely unaffordable. Looks to me that the 6" Ø double density one would go really well with a 6" table. I used a square one on the built in rotary table of a BCA style mill, probably 10", and found it both durable and a great improvement on the standard three Tee slots. If you go that route be prepared to make lots of clamps.

Mine were mostly either 1/4" aluminium bar or 1/8" – 3/16" steel strips with a single lengthways slot. Blunt taper on the business end. Support end either bent over as a shallow L or threaded, tapped or weld nut as appropriate, with a knurled head to set the height finger tight. Best to have a rotating alloy foot so you don't damage test able if you forget to slip a 1/8" – 3 mm protection shim under the screwed end. Staking an alloy foot on can get interesting! But you shouldn't really be turning the screws in contact with the table. Set height and clamp down is the way to do things, not jack up with the screw.

Clive

Edited By Clive Foster on 18/10/2017 19:12:50

[Neil WyattModerator @neilwyatt]

Posted by Clive Foster on 18/10/2017 19:12:00:

Consider adding something like the Thor Labs 1/2" thick anodised aluminium breadboards here **LINK** . Not cheap but not completely unaffordable.

Their website says:

Flatness

±0.006" over 1 ft2

±0.15 mm over 0.3 m2"

For 3-thou across a 6" disc I think I could make one for the same price.

My home made rotary table/dividing head has a flange to fit my chucks instead of a table, when I need a table I can fit my 7" faceplate which has lots of clamping alternatives.

[Clive FosterParticipant @clivefoster55965]

Neil

The smaller Thor labs ones I had in the lab were much flatter than that. Big ones not so much so but it is only 1/2" alloy so not super strong.

Indeed not too hard to make but probably best to start with tooling plate which erodes the price advantage rather and hand tapping all those holes will take a while. I think tapping heads are great! Major advantage of buy over build is that the Thor Labs anodising is very hard.

As ever the make or buy thing all boils down to your personal time / cost / capability equation. For me it was always easier to go out and earn a bit more money to buy in that sort of thing. But back in those days proper material was harder and more costly to obtain in small quantities although scrap and surplus much easier although it was take what you get terms. Things have changed in manner old codgers like me don't always understand.

Clive.

[Ian Skeldon 2Participant @ianskeldon2]

Oh they do look useful, thanks for the link Clive.

[BramParticipant @bram]

Thanks for all replys, breadboard does look useful. Still dithering about table size, understand clamping issues of Smaller table but little concerned about depth available if I go for 8" and I think it would be generally cramped. Vertex one I've seen has four slots in table and I already have a spare slim 4 jaw chuck that looks like it would go straight on so leaning that way unless advice suggests otherwise, then I'll bang my head against the wall a bit more and see if I can make an educated desision!!!

[MWParticipant @mw27036]

Posted by Neil Wyatt on 18/10/2017 14:09:26:

Hi Bram,

8" sounds a bit OTT for a VMC to me. Others might disagree,

Neil

Jeez. I have trouble with an 8" four jaw let alone a whole RT!

(I'd "probably" say, we enthusiasts wouldn't be looking at anything bigger than say 6 inches for a RT). 

About the limit was this monstrous cam-lock four jaw I had to lift onto a Colchester master, this was probably about 18". It used to bust my gut trying to change it.

Michael W 

 

Edited By Michael-w on 18/10/2017 23:19:03

[Mike PooleParticipant @mikepoole82104]

I have a VMC and a 6" RT, obviously an 8" RT is going to overhang the table of the VMC but I think it will not be a problem to use an 8". As long as the cutter can reach the centre and the perimeter of the work all should be well, indeed even 12" may be viable.

Mike

[John HinkleyParticipant @johnhinkley26699]

I have a Warco vmc mill and from what I read, it is about the same size as your Myford mill. I use a 6 inch RT and find it eminently suitable for the kind of work that I undertake. I occasionally have difficulty centring work due to the reduced throat clearance and have to resort to other methods rather than my preferred axial centring device. But that's all part of the fun.

When I upgraded my vice, I made the mistake of ordering a 6 inch precision one from Arc, thinking bigger was better. How wrong was I? As it turned out, very wrong! I nearly gave myself a hernia just lifting it onto the table. It dwarfed the rest of the machine and was obviously far too big. A quick phone call and 100 mile dash up and down the M1 and it was replaced with the much more reasonably-sized 4 inch version.

To some up, if it were me, I'd go for the 6 inch version and if you need a larger working area, buy or make a pallet table. You could machine a register on the back to accurately locate it on the rotary table, should you so wish. In fact, I might make one like that myself!

John.

[BramParticipant @bram]

Ok this is good thanks for replys, think I'm going with 6" last question really but have seen secondhand vertex four slots on table complete div plates and centre or new warco again complete div plates and centre. Very similar price in fact used vertex is slightly more expensive. Obviously both look identical externally but have read countless tales about internals being better in vertex, what do you think!!!!! Thanks again for replys Phil

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