Hemingway geared rotary table build

[sco]

I think it's called a pad bolt - quite a neat technique that I've seen on other designs as well.  You prep the pad bolt with a shoulder and drill it's hole first - then you fit the pad bolt and machine the second hole at 90degrees to it so that it just intersects and machines a bit of the pad bolt away.  You then remove the pad bolt and turn down the shoulder before refitting it in the hole.  It works as a very effective grip that seems quite resistant to jamming.

[Kim]

Thanks Simon,
So am I understanding right, that the pad bolt a way to lock the shaft from turning?
Kim

[sco]

Well it locks the eccentric bush in the base - the worm shaft can still turn though Kim.

I didn't like the design of the table clamp presented in the plans so decide to freestyle and come up with my own version.  First two pictures show the concave faces being machined on the faceplate and then third picture is the side faces being made radial by milling on the rotary table.  The idea was that one way up the clamp locks the table rotation and the other way up the table is free to rotate and the clamp provides the abutment for the table travel stops to bear against - last two pictures show the two modes of operation.

Next job is to graduate the table - 360 marks to make - groan!

Simon.

[Don1966]

You do some very nice work Simon. You should have no problem doing the 360 marks and actually it goes quiet fast. You do have the Dividing attachment and the stacking tool don't you? Looking forward to seeing  it done.

  Don

[sco]

Don, no dividing attachment or staking tool 

Am hoping to get the numerals laser marked at work though.

Simon.

[sco]

Today I graduated.... 359 times!  During the whole process there was a little voice in the back of my mind 'We are not at home to Mr Cock-up, we are not at home to Mr Cock-up, we are not at home to...'  Luckily Mr Cock-up didn't come knocking so the process went without a hitch.  Whilst I had the graduating setup on the mill I also drilled and tapped the 24 holes for the travel stops.

Simon.

[John S]

Simon.
If you are laser marking the numbers at work and they don't have the Thermark spray [ £100 an aerosol - no not a typo, it's a type of ceramic slurry in a solvent made from crushed Chinese Ming vases, 6th dynasty ]
Get some dry moly lube £12 from RS in an aerosol, spray that on, let it dry then nuke it. Wash the surplus off with a bit of solvent and you get a nice crisp black mark.

[sco]

Thanks for that advice John - I don't know whether they have any of that stuff or not but this is how the marking they did on another cast item came out.

Simon.

[John S]

Yup that looks like thermark, slight red edge to it.
You must work for a rich company  I can't afford it.

[sco]

They spend money like there is no tomorrow 

[sco]

Noisy and nerve racking - cutting the T slots in the table;

[sco]

Next up a fiddly job making the table travel stops, I started with a bar mounted to the face plate on the lathe to machine the outer radius and profile.  Then transferred the plate to the rotary table to mill the bolt slots.

Simon.

[Jo]

  why didn't you mount it in the lathe to turn that T slot and then add the tapered bit? I am sure that is how I did mine all those years ago.

I have just realised the side of my table doesn't have true Tee slots, the top of the slot is tapered, a much easier turning exercise 

Jo

[sco]

Jo - the geared version has a completely different style of travel stop to the non-geared table.  There is a simple groove right the way around the table that the stops slide in, then a series of holes that the stops bolt into.

Simon.

[Jo]

  I can put my stops at any position/angle, does that mean that yours are restricted to the prescribed angles    admittedly with a worm wheel you can give it a bit more "welly" when rotating it.

Jo