Rotary Table Questions

[Susquatch]

A few years ago, I hobbed a spur gear to repair my old mill/drill. I used a gear cutter hobb and rotary angle indexer with an er30 collet to hold the work. It worked and the gear was a complete success.

However, I had wished I had a rotary table instead. I recently made an adapter plate for a new motor for my Hartford mill. Again, I found myself wishing I had a rotary table.

I took a quick look on Ali, Amazon, BusyBee, Accusize, and KBC. They seem to come in 2" increments from 4 up to 20. All are also expensive. So I made search bots for both Kijiji & eBay and I'll see what comes up. I'm in no rush.

My questions here are looking for advice.

What size do you think is optimum?

What features are desirable?

Is an add-on chuck essential?

Are there any add-on accessories that ARE essential or at least highly useful?

 

[RobinHood]

I have an OE 12” BP for my mill. It can only be mounted flat on the table - some of the newer/other brands can be mounted both horizontally & vertically. I think that would be an advantage.

They are heavy (well, the older ones anyway). My RT is quite low profile and very accurate (It divides the circle into degrees, minutes, and seconds. Used it yesterday to set a 39.45* (39* 27”) angle either side of a ref line to bore two 24.05mm holes. Worked great.

I would get the largest RT you can afford - for your mill size 12”+. Why, because if you have an 8” work piece there are only 2” all around for clamping - that is not a lot of room for strap clamps.

I bolt chucks onto it as required. I don’t have any “dedicated“ ones. Pulled the backing plate off of an 8” lathe chuck in the past because it was the best option. I do have some “spare” chucks that I try to use if I can (4J, 3J & 3J independent).

Fixture plates are nice to have for small stuff - you can make one from a chunk of alu sheet.

 

[Brent H]

@Susquatch : I have a 12” rotary table used on my (same as your) Bridgeport mill. It is huge and can sit vertical or Horizontal- although I need to make a base mount for it so the existing slots line properly.
I purchased indexing plates for it and it came with an 8” bison 3 jaw chuck. The chuck only has the one jaw set which sucks but it would be nice to have a 4 jaw and outside jaws - then you can clamp some big parts. With the 12” table you can really mill some large pieces and secure things down. Given the mass of the table it is very solid when machining.
I have made gears and other items and it works great.
In a perfect world having the 12” table AND a smaller, say 6”to 8” indexing head would be sweet. I missed out on one at auction that included gearing to tie back into the power feed for making helical gears - bummer

 

[PeterT]

Some more points to ponder
- some but not all RT's will allow a tooling plate to be mounted to RT with through bolts into T-slots, thus buying you more available real estate. But some RT's have a ledge or casting that limits so evaluate some pictures
- ability to be horizontal and vertical isvery important in my mind, otherwise you need a dividing head
- adding chuck to RT usually involves a home brew intermediary adapter plate. I have posted some piics so do a search. But be aware the whole thing starts to stack up like a wedding cake & you may run out of vertical room depending on your mill, tooling, part etc.
- trying to make self centering chucks concentric to the RT MT hole can be somewhat futile depending on accuracy you are after. Adapting a 4J chuck vs a 3J gives you ability to dial it in regardless.
- whatever RT you buy, consider teh plates &tailstock while you're at it. Sometimes its harder to reconstruct the accessories years later
- watch Stefan video where he dissects an Asian RT. Like most things they vary in quality

 

[John Conroy]

I have a Vertex CS8 Super spacer which is basically a rotary table with a 8" chuck instead of table. I got it used for a good price but it had a worn out gear and it took a while to find a preplacement. I made a 12" table for it using a 12" brake rotor for a GM truck and a 12" round steel plate that I drilled with a pattern of threaded holes for hold downs. With the chuck mounted it weighs 175 LBS so these things are pretty heavy so best to find a way to load it onto the mill table without lifting. It can be mounted vertical or horizontal and I have the indexing plates for it. Used ones are pretty hard to find but if you are patient you'll find one.













As Peter mentioned they do fill the available vertical space between spindle and table pretty fast especially when you add a drill chuck or boring head. That was the main reason I added a 6" riser block to my mill.

 

[Susquatch]

Thanks @Brent H, @PeterT, @RobinHood, @John Conroy.

OK, the largest I can get. Preferably 12+.

Vertical & Horizontal if possible.

About the dividing heads. I have a few pieces already. See photos below. The easiest one to use is the 5C Collet Head. But the 3 jaw chuck head will do angles off the table and is slick even if it is a bit complicated.

Do they change anything?

 

[Brent H]

@Susquatch : the 5C collet indexer is great for fast machining on dimensional stock. Accurate but not super strong.

the Indexing head with the chuck - beauty! Solid, lots of options and just as fast as the collet indexer once you set things up.

your three jaw (can change out to 4 jaw) size would be my next purchase. I don’t think I would get a 5C indexer as that requires more collets and the fast operations I can handle with a hex/square collet chuck

the big rotary table will allow you to do some pretty cool things the other 2 machines cannot.

I made my own tailstock for the 12” - it is somewhere on here. Works great

 

[RobinHood]

All good points that I forgot to mention, fellows.

Apropos using up space fast even on a 12” table - here is a 200 mm hand wheel being machined. Not much room for clamps.

 

[PeterT]

Usually people buy the RT size they need & that's the end of it. But as table diameter grows, usually so does thickness. Not always depending on the model but something to check.

What I was saying about some RT's can accommodate larger diameter tooling plates (or the extending part footprint for that matter) is kind of depicted by these pics. Its hard to judge based on catalog pictures where the dial or casting upright may intercept, but anyways this is what I was driving at.

 

[Susquatch]

Thanks for all your input guys!

I found a 10" Sowa RT at a really good price in A1 condition. It's not 12", but I'm hoping it will meet my needs.

 

[Dabbler]

My 10" table is about 1/2 the weight of my friend's 12" table... Small win for the 10" table. My 8" table weighs about the same as the 10" - go figure...

 

[Susquatch]

My 10" table is about 1/2 the weight of my friend's 12" table... Small win for the 10" table. My 8" table weighs about the same as the 10" - go figure...

I am told this one weighs over 100 pounds. I'll find out when I pick it up next week.

 

[Susquatch]

Picked up the 10" rotary table enroute to Barrie. Here are some photos.

It has 4 degrees per turn of the crank and 5 minutes per division with a vernier scale to find the nearest minute of 5.

As far as I can tell, it has zero backlash but that's with no load. I'll have to test it with a load to see what it really is.

I have no idea what the knurled rings (one inner and one outer) are for. Any ideas?

Also, the dial zero and vernier are located oddly. I think they can be rotated by loosening the tiny set screw, but I'm hesitant to play with it.

Lastly, there are two screws on the outside of the crank handle. The center one is probably a retainer, but what is the outer one for? An index adjustment or a rotation stop??

It doesn't have a 90 degree stand, but I have other tools (see separate post above) for that so I'm not worried about it. If I ever need it, I can always make a separate stand.

Lastly, it seems to have this very odd crank disengagement mechanism. You loosen the little T-handle and then you roll the entire crank assembly (prolly a worm gear) out of engagement.

 

[Dabbler]

The vernier and the disengagement are on the same mechanism on both of mine. You have a typical rotary table: 90 turns per revolution, so any indexing plate set will work, once you have it mounted. (rotary indexers are 40 turns per revolution, FYI.

The disengagement mechanism is to permit it to use indexing plates.

 

[Susquatch]

The vernier and the disengagement are on the same mechanism on both of mine. You have a typical rotary table: 90 turns per revolution, so any indexing plate set will work, once you have it mounted. (rotary indexers are 40 turns per revolution, FYI.

The disengagement mechanism is to permit it to use indexing plates.

Cool! I have a set of 4 indexing plates that came with my semi-universal dividing head. Any Chance that they can be used with the dividing head? Or is all that kind of stuff proprietary?

 

[Susquatch]

The vernier and the disengagement are on the same mechanism on both of mine. You have a typical rotary table: 90 turns per revolution, so any indexing plate set will work, once you have it mounted. (rotary indexers are 40 turns per revolution, FYI.

The disengagement mechanism is to permit it to use indexing plates.

Just thinking out loud..... Why would you want to disengage the worm in order to use dividing plates? I would have thought that the plates need the worm too......

 

[Brent H]

I think you can disengage the worm so you can rotate the table without the handle spinning. - mine does the same thing - I will have to check it out.
The indexing plates typically fit standard.

 

[Dabbler]

A dividing head plate is calibrated for 40 turns per revolution, not 90, so to use one in a straightforward way... no. But on some divisions, it can still be useful with a little math - perhaps an engineer?

On a dividing head like mine I have to disnegage the clockwork to use dividing plates. On both my RT's the worm gear is always engaged, both plates and manual handle...

I think I 'spoke' poorly in my above post on the matter. Sigh. English! sorry. I think I said it backwards!

 

[Susquatch]

I think you can disengage the worm so you can rotate the table without the handle spinning. - mine does the same thing - I will have to check it out.
The indexing plates typically fit standard.

Ah yes, that makes sense. Who wants to crank around to 180° manually. Better to disengage spin and re-engage.

I will have to check my plates to see if they will fit.

 

[RobinHood]

On my BP RT, the worm needs to be engaged at any point in the circle that is divisible by 4 and the handle needs to be in the UP position. Otherwise the markings on the hand wheel and table are out of sync no matter what you set the dial to and thus the set angles won’t be correct.

Yours might be different, but there are RTs where it matters where you engage the worm.