Poor Man's Rotary Table

[MozamPete]

Well I have decided I need a rotary table of some sort for my mill, but at present I'm not inclined to hand over the sort of money that seems to be necessary to acquire a new one (and second hand ones seem next to impossible to find over here).

So the plan is to build something resembling a basic rotary table from the materials I have at hand (i.e. little additional cost) as an initial tool to get me going. To this end the attached is what I have come up with as a starting concept (to be refined as the build goes along).



- Body will be from a piece of 140mm x 60mm channel
- Table will be 140mm diameter cut from a piece of 16mm plate
- Table will have either small 'T' slots or just a series of drilled and tapped holes for mounting clamps
- Most of the table bottom will be recessed so it is bearing on only a couple of rings to reduce friction when turning
- Worm gear will be cut from 12mm plate and hobbed with an M12 tap in the lathe chuck
- Worm gear size is limited to around 105mm diameter to fit in the 'flat' area inside the channel so will be either 180 or 120 teeth to give a whole number of degrees per rotation of the drive handle
- Worm drive will be M12 treaded rod and probably have some fine adjustment on the position of one end to ensure if engages well with the worm gear (or possibly an idler gear to force the threaded rod into the worm gear)
- Spindle will have a MT2 taper through the centre to use accessories (such as a drill chuck) with the table detached (I don't want the taper hole to go right through the table as that could interfere with mounting small work pieces on centre
- Some sort of clamping arrangement to lock the table in position when actually milling
- One end of the channel will need to be closed with a piece of plate to allow it to be used vertically (the distance between the channel sides is just such that one will always seem to fall into a slot on the mill table if left open)

Any suggestions / recommendations / "Why the hell are you doing it that way?"s will be most appreciated as I go along. As I said this is a concept design that will probably be highly modified as things progress, but hopefully ends up with something that is usable (although I'm not expecting it to be perfect).

So far I have cut the channel, cleaned it up and marked out the plate to cut the table.

Cutting the 140 x 60 channel for the body of the cut off saw


Rough mock up to visualise sizes


After cleaning of the body piece by electrolysis. There is some weld splatter on the channel but I will mill/face all the sides/edges once I have welded on the tabs that will become the bolting down slots and closed up one (or both) of the open faces of the channel.


Marked out plate for table. Just happened that the largest piece of scrap I had can just fit a 140mm diameter.

 

[fixit]

Well I have decided I need a rotary table of some sort for my mill, but at present I'm not inclined to hand over the sort of money that seems to be necessary to acquire a new one (and second hand ones seem next to impossible to find over here).

So the plan is to build something resembling a basic rotary table from the materials I have at hand (i.e. little additional cost) as an initial tool to get me going. To this end the attached is what I have come up with as a starting concept (to be refined as the build goes along).

View attachment 90884

- Body will be from a piece of 140mm x 60mm channel
- Table will be 140mm diameter cut from a piece of 16mm plate
- Table will have either small 'T' slots or just a series of drilled and tapped holes for mounting clamps
- Most of the table bottom will be recessed so it is bearing on only a couple of rings to reduce friction when turning
- Worm gear will be cut from 12mm plate and hobbed with an M12 tap in the lathe chuck
- Worm gear size is limited to around 105mm diameter to fit in the 'flat' area inside the channel so will be either 180 or 120 teeth to give a whole number of degrees per rotation of the drive handle
- Worm drive will be M12 treaded rod and probably have some fine adjustment on the position of one end to ensure if engages well with the worm gear (or possibly an idler gear to force the threaded rod into the worm gear)
- Spindle will have a MT2 taper through the centre to use accessories (such as a drill chuck) with the table detached (I don't want the taper hole to go right through the table as that could interfere with mounting small work pieces on centre
- Some sort of clamping arrangement to lock the table in position when actually milling
- One end of the channel will need to be closed with a piece of plate to allow it to be used vertically (the distance between the channel sides is just such that one will always seem to fall into a slot on the mill table if left open)

Any suggestions / recommendations / "Why the hell are you doing it that way?"s will be most appreciated as I go along. As I said this is a concept design that will probably be highly modified as things progress, but hopefully ends up with something that is usable (although I'm not expecting it to be perfect).

So far I have cut the channel, cleaned it up and marked out the plate to cut the table.

Cutting the 140 x 60 channel for the body of the cut off saw
View attachment 90888

Rough mock up to visualise sizes
View attachment 90887

After cleaning of the body piece by electrolysis. There is some weld splatter on the channel but I will mill/face all the sides/edges once I have welded on the tabs that will become the bolting down slots and closed up one (or both) of the open faces of the channel.
View attachment 90886

Marked out plate for table. Just happened that the largest piece of scrap I had can just fit a 140mm diameter.
View attachment 90885

You are my kinda guy!

 

[MozamPete]

Went to make a start on the spindle and thought that I should start by turning up some male MT2 tapers to make sure the top slide is set to the correct angle before starting on boring the female taper. Well the finish I was getting was horrible and with such a small angle on the top slide the handle was fouling with the tail stock and I was getting my fingers jammed.

So looked like some maintenance was in order before diving further into this project. I dismantled, cleaned and adjusted the top slide and got it operating a lot smoother. Then thought that some sort of simple power feed would be the way to go to give a consistent feed rate and get around some of the clearance problems.

What I came up with was a modified socket that fits nicely over the existing top slide handle and is driven by an air ratchet. Gives about 30 rpm which seems perfect.





I'm now getting a good MT2 taper with a smooth finish (probably also helps that I'm less likely to be greedy and take overly deep cuts as the feeding of the top slide is now less of a hassle)

So no real progress on the rotary table this weekend, but I think I'm now ready to bore the spindle taper.

 

[Rbeckett]

I found a nice 90 to 1 rotary table for right at 300 bucks and did not have to spend a lot of time making one. The rotaries off the internet are usually available pretty cheap and allow me to add to my tooling a little at a time to avoid the huge sticker shock that you are currently having. The reason I am advocating buying one is because your time has value and though it is possible to make a perfectly acceptable one at home it is not cost effective and may contain errors that will have a negative impact in the overall performance of the tool or device. IIRC the one I picked up had free shipping which was a good thing because it is a very heavy item to ship, especially if you are the one paying the bill for that, and it is dead in accurate with a warranty. The one I got is a vertex knock off and the money I saved on freight alone allowed me to buy a set of circular plates to set up gears, and flanged items with holes around an arc. You might also take a look at the Home workshop series of books and see f they have a book available that outlines the use of and how to employ a rotary table and has a set of drawings for one you can build yourself. I am sure they have one for a dividing head, but am unsure whether they do the same treatment of Rotary tables also. Definitely worth a quick look to see what is out there if you just have to build on e on your own.

Bob

 

[MozamPete]

Thanks. I do realize it would be easier and enviably end up with a better product if I just brought one - but where's the fun in that. Machining is a hobby to me so all the time I spend in the shop free (or wasted depending how you look at it). Some people play golf, I potter around in the garage learning skills that I really don't need in everyday life.
In the end I will be happy with a rotary table that is functional, if not perfect, for little outlay other than time. And i it is a total disaster I hope I at least learn something along the way.

 

[MozamPete]

Started turning down the plate that will eventually become the table - this may take some time!

 

[xalky]

Nice. I agree with your take on your hobby. I've made a few things myself that would have been more economically feasible to just buy. Sometimes I make something just for the sake of making it, because I can, because I want to, because it's my buzz and I'll get it how I want.

 

[MozamPete]

OK this project sort of stalled for a long time, but I'm on a mission to complete all my half finished projects and other project ideas that I have spent money on buying parts for but never actually built - before I start anything new.

So today I cast a blank to make the worm wheel. I roughed out a gear and hub in polystyrene a few days a go and had been painting it with a layer of plaster each night. I made it intentionally large as I'm new to casting so expected it to be pretty rough and wanted plenty of allowance to machine off.





That should do - will machine it down tomorrow if I get time.

 

[MozamPete]

Turned the lump of casting down into a blank. The casting was full of porosities but will do for my purpose. If I had known how well the casting would come out I would of put more effort into getting the mould closer to the final required size - either way better to be too big and have to machine a bit more off than too small.


Then I turned up an arbor with a bearing to attach it to my lathe tool post where I will try to free hob it with a M20 tap.

 

[Ulma Doctor]

WOW Peter!
looking good, great idea!