Rotary Tables

Warco HV4 rotary table

Very soon after buying a milling machine I can guarantee you will be looking at rotary tables. A rotary table feels like a must have. Use it to machine:

  • arcs
  • flats on bolt heads and nuts
  • rotate a part to be drilled at precise divisions or angles
  • large circular parts that cannot be machined in a lathe
  • add division plates and use to machine gears

Lots of uses and hence, I thought I would share my experience, trials and errors.

3 inch rotary table

3 inch Rotary Table

It all started with a small 3 inch rotary table for my Unimat 3 milling machine.

The image shows the rotary table with an adapter plate and to this is mounted a Unimat 3 three-jaw chuck.

Small rotary tables such as 3″ and 4″ are ok, but unless you are machining very small parts it can be difficult to clamp parts down. A 6″ rotary table is a better size and makes clamping parts down practical. Also, a 6″ table will fit under most mini milling machines.

Small rotary tables such as 3″ and 4″ are ok, but unless you are machining very small parts it can be difficult to clamp parts down.

A 6″ rotary table is a better size and makes clamping parts down practical. Also, a 6″ table will fit under most mini milling machines. Just remember that you need to be able to machine beyond the centre of the table, check the spindle to pillar dimension on the mill.

Vertical Machining

Do you want to use the table in the vertical position? A 6″ rotary table in the vertical position may not fit under the smallest of milling machines.

master conrod on 5-cyl rotary

Here I’m machining the slot in the big end of the master conrod.

The rotary table is in the vertical position.

The difficulty here was clamping the conrod tight enough with the bolt through the centre so that it did not rotate of it′s own accord.

If I had fixed the conrod directly to the rotary table I would have had an issue getting clearance between the chuck and the table.

Fixings

The location of the table to the milling table can be a challenge. The fixing of parts and alignment to the rotary table can be a bigger challenge and you will need to spend time making fixtures…

Sometimes you get complacent.

I was in a hurry and thought for some reason that I could make a hardwood adapter.

What I just decided to ignore were the forces involved in end milling with a 12mm diameter bit and cutting speeds of around 1500rpm.

The cutter bit and jammed, nearly damaging the part beyond repair and nearly doing a lot more damage besides that.

machining the crankcase of the poppet valve engine

I quickly forgot my “quick” solution and changed to using an 8mm thick piece of aluminium.

The bolts were recessed so that the cutter would clear them when machining the second stage that would complete the round body of the crankcase.

machining the poppet valve case

An 8mm bolt was fixed into the adapter plate and points up through the crankcase, a number of washers were then used and the part locked down with a nut.

A dial gauge was then used to centre the part, rotating it back and forth whilst nudging it into location. The nut was then tightened and a second locking nut added.

Extending a Table

long T-nuts to extend a rotary table

The given size of a rotary table is the diameter of the table itself. Kind of obvious really, but you need to fix items to the table, normally using the T-slots. This means you lose a significant amount of the diameter.

I made long T-nuts to extend my HV4 rotary table.

4″ Rotary Table

HV4 rotary table

The Warco HV4 rotary table is more substantial than the smaller table I had been using.

Although it states it is 4 inches in diameter, it is actually 110mm across.

The backlash in this table was negligible and the rotary action is very smooth, a significant step up from the smaller table.

Division Plates

rotary table and division plates

Division plates extend the use of the table significantly.

I can now accurately drill steam cylinder covers, machine nut heads and cut gears.

When using the division plates you need to stay focused as even with the brass fingers you need to carefully count the rotations. This is very rewarding and very calming. Trust me though that you won’t want interruptions.

editor@glue-it.com
gear cutting

Gear cutting using the rotary table with indexing plates and an MT2 collet chuck fixed into the table.

About Nigel 338 Articles
I've been making models since I was around 7 years old and using a lathe from the age of 11, a self taught engineer with a passion for making model engines.

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