Rotary table conundrum!

[pmdevlin]

Be gentle chaps, I have some very basic questions on the way....

first one!

I have treated myself to a second hand 4" rotary table to use with my sieg xl mill. I don't really do much, mainly model boat parts, and the odd easy project for friends. Don't have any scales, so its all done by eye and basic digital rulers etc, so you get the picture!

So in its very basic form, lets say I want to cut a disc from a piece of Brass. I understand centring the rotary table under the stock, but now how do you centre the work, lets say its 3" square, on the rotary table? Easy if there is a central hole, but if there isn't what do you do?

What sort of clamps for securing the work to the rotary table are recommended as I don't have any, and is it just a matter of making some 90 degree clamps to secure the table to the bed?

Many thanks

Paul

 

[Nick Hulme]

I understand centring the rotary table under the stock, but now how do you centre the work, lets say its 3" square, on the rotary table? Easy if there is a central hole, but if there isn't what do you do?

Having centred the table leave it there and use a pointy tool in the mill to position a scribed or drawn centre mark on your stock ;-)

- Nick

 

[purpleknif]

An indicator would be my 1st choice .

 

[Toolguy]

I would use an edge finder. Quick, easy, cheap.

 

[pmdevlin]

as easy as that Nick, now I feel stupid!

Guys, don't now what indicator or edge finders are, I'm a novice here!

Please elaborate

Thanks

 

[petertha]

Maybe the 3x3 square is just an arbitrary example, but just an FYI visual, this dimension actually overhangs the 4" table. Depending on your T-slot configuration, meaning the count (3 vs. 4 slots) and width, you may not have a much room left for the outboard support of typical T-slot type clamps (pic attached), so that's a consideration. You could possibly make yourself a larger diameter sub-table that clamps to the existing 4" table (with countersunk screws), but accommodates larger work stock. This somewhat depends on how your RT turn handle comes off the body & locking levers etc. interference wise.

Another option I've seen by builders is they glue the part stock on to a sacrificial piece of hardwood, maybe like MDF which is pretty flat & smooth. Then machine the part, then remove the metal from wood. On thicker metal stock I've seen epoxy used as adhesive, then removed with heat. This might not be appropriate for thin stock, so maybe double sided transfer tape assuming you have pre-tested it & can be de-bonded with thinner or something?

Another consideration, rather than machining the square piece precisely to 3x3 beforehand & then dealing with the fiddly setup of 1) centered to RT axis 2) square to the mill X,Y axis 3) possibly also rotationally registered to some angular division setting on the RT, you could just plop down oversize rough stock on the RT, pre-zero the RT dial & then end mill machine the square shape in-situ. That way the dimensions & zeroing & squaring is done with everything pre-aligned & you can carry on with RT operations. This only works on simple shapes. If you have a pre-machined part, you need some form of registry to align it to the RT.

 

[petertha]

There are probably lots of rotary tables setup pics on the forum to give you ideas & reference. But I suspect fewer specific to smaller size like your 4" diameter tables. I really like this locomotive build showing how smaller tooling (Sherline in this case) was used to create a 'larger scale' model with lots of interesting setup configurations. Many RT operations are using mounted chucks which is not your specific question/example, but anyway some reference material to absorb.

http://www.homemodelenginemachinist.com/showthread.php?t=23204&highlight=locomotive&page=5

 

[Cogsy]

Guys, don't now what indicator or edge finders are, I'm a novice here!

Please elaborate

Thanks

Indicator is a dial indicator - here's a random YouTube video. A must have if you do any 4 jaw work (and very useful for all sorts of other stuff).

[ame]https://www.youtube.com/watch?v=ZvD7kTneFJA[/ame]

For centering round stock, or picking up the centres of holes under the mill, a coaxial indicator does a nice job - here's another youtube video.

[ame]https://www.youtube.com/watch?v=kETFbWFvoq8[/ame]

An edge finder is mounted in the spindle (I use mine in a drill chuck for ease) and spun. It will wobble around some but as you approach the edge of the work it becomes more and more steady. As you get directly over the edge of the part the end of the finder will 'kick out', indicating a found edge. Stop and retract the edge finder then continue to advance the spindle 1/2 the diameter of the edge finder's tip and the center of the spindle is directly over the edge of the part. They're super cheap (like less than $4 for a chinese one that works) and very handy. They can also be used to find center of round stock easily too. Here's a listing from ebay for a cheapy...

http://www.ebay.com.au/itm/1pcs-Mec...268753?hash=item2a6f14ecd1:g:QwwAAOSwLpdW-fZ8

 

[rodw]

The coaxial indicator in the last video is an awesome tool for centring your mill over either a central bore or a punch mark (with the right tip fitted). The problem you will have is having the room to use one on your small mill. That said, I only have an SX3 mill and use mine.

It is also great to centre the rotary table. I have a taper that suits my RT and start by fitting it and placing the other end in the drill chuck. This gets me close but not perfect. The coaxial indicator finishes it off.

 

[SmithDoor]

If I had this size I would just mount a 6" 4 jaw chuck to the 4" table
For some work about 5% 3 jaw will work not worth the time to change back and fourth .
Note if your 4 jaw does not have tee slots you will need to tap the face the 4 jaw for hold downs (use on tall work).


Dave

Be gentle chaps, I have some very basic questions on the way....

first one!

I have treated myself to a second hand 4" rotary table to use with my sieg xl mill. I don't really do much, mainly model boat parts, and the odd easy project for friends. Don't have any scales, so its all done by eye and basic digital rulers etc, so you get the picture!

So in its very basic form, lets say I want to cut a disc from a piece of Brass. I understand centring the rotary table under the stock, but now how do you centre the work, lets say its 3" square, on the rotary table? Easy if there is a central hole, but if there isn't what do you do?

What sort of clamps for securing the work to the rotary table are recommended as I don't have any, and is it just a matter of making some 90 degree clamps to secure the table to the bed?

Many thanks

Paul

 

[petertha]

If I had this size I would just mount a 6" 4 jaw chuck to the 4" table
For some work about 5% 3 jaw will work not worth the time to change back and fourth .
Note if your 4 jaw does not have tee slots you will need to tap the face the 4 jaw for hold downs (use on tall work).

Timely you mention this, I was just mulling over some chuck/RT improvement options. Four jaw chucks better accommodate drilling hold down through bolts to make them like commercial 'front mount' chucks if say 4 holes are equi-spaced 90-deg between the jaws avoiding the worm screw mechanism area. But also need to consider what RT you are marrying it to now or in future. If you have a 3 or 6 slot RT table, the bolts must engage RT slots at potentially different phasing, 90-deg chuck vs. 120-deg RT in this example.

Drilling typical 3-jaw scroll chucks in this manner requires some careful inspection because the scroll typically occupies majority of this space depending on type/size. Drilling into that component would be a bad thing.

This brings up a general purchase consideration that doesn't get much coverage. If you happen to get RT table with 3 or 6 slots & you choose a chuck system with 3 FM holes (as opposed to integrated backplate chucks or rear screw chucks), potentially you could economize & bolt the 3-hole chuck directly on RT with no inter-plate fuss & lowest overall stack height. And potentially still use the exact same chuck on your lathe with appropriate spindle adapter. I wish I would have clued into this when I was first buying this stuff.

 

[pmdevlin]

I really like this locomotive build

beautiful, I can only drool over that sort of work, must have cost a fortune to have all that brass

the 3x3 square was just am example, nothing specific at this stage, thanks for all the links and info, the edge finder looks interesting,, I'm going to see if I can find some videos in action!

 

[10K Pete]

One of the handiest things you can make for yourself is a pointer. It's nothing more than a piece of regular steel rod with a point on it. A simple lathe job.

If you put your pointer in the chuck of the mill it can then be used to center your rotary table and then pieces on the table.

We're not talking super precision but with a sharp point and a magnifier you should be able to get within a few thou of correct position.

If the rotary table has a hole in the center then make your pointer bigger than the hole. Then you can use the pointer to hold the RT while you bolt it down. If the hole in the RT is big then make your pointer with a big point and a smaller shank.

Pete

 

[Nick Hulme]

An impressive range of complex solutions for cutting a disc from a plate ;-)
KISS
Now if the question had been how to mill a hole in a precise position on a plate then out comes the metrology equipment, but indicating? Just to cut a disc out of a square bit of plate? Honestly?

ROFLMAO

- Nick

 

[Cogsy]

His question was how to accurately centre something on his new RT as he didn't know how. The example given was just as an example for illustration only, not a job that he needed to do and was specifically asking about. He now has the info he was actually after and the piece of plate is irrelevant. Telling him not to bother as it's only a disc from a piece of plate wouldn't have been overly helpful.

 

[Nick Hulme]

His question was how to accurately centre something on his new RT

Ahh, there we are then -

Be gentle chaps, I have some very basic questions on the way....

first one!

I have treated myself to a second hand 4" rotary table to use with my sieg xl mill. I don't really do much, mainly model boat parts, and the odd easy project for friends. Don't have any scales, so its all done by eye and basic digital rulers etc, so you get the picture!

So in its very basic form, lets say I want to cut a disc from a piece of Brass. I understand centring the rotary table under the stock, but now how do you centre the work, lets say its 3" square, on the rotary table? Easy if there is a central hole, but if there isn't what do you do?

What sort of clamps for securing the work to the rotary table are recommended as I don't have any, and is it just a matter of making some 90 degree clamps to secure the table to the bed?

Many thanks

Paul

"basic form" - look it up!
Over-complicating basics is a very basic error and a great way ton waste time and under-achieve in the workshop ;-)
Assuming someone needs the most complex solution possible for a simple task is... well, you tell me

- Nick

 

[goldstar31]

Ahh, there we are then -



"basic form" - look it up!
Over-complicating basics is a very basic error and a great way ton waste time and under-achieve in the workshop ;-)
Assuming someone needs the most complex solution possible for a simple task is... well, you tell me

- Nick

Actually Nick is right. All that a rotary table is a faceplate tilted at 90 degrees. Solve one- solve the other!

Simple?

Norm