Building a 7" rotary table

[Firebird]

Hi

Getting popular these rotary table builds aren't they

Not too much to report on my effort this week, just one little job completed. I need to cut a 8mm thread on the end of the hand wheel spindle. Its fairly hard steel so I decided to have a go at screw cutting the thread. I have screw cut a couple of threads before but its not something I'm confident at. My trusty old myford is imperial but with the right gears it is possible to cut metric threads.

Heres the gear set up



I did a test cut on a piece of 8mm mild steel bar, the threads not bad but not really good enough. On closer inspection I could see that the cheapo brazed TCT tool I am using has chipped right on the point, you can just see it. I am going to have a go at grinding a tool myself and see how that goes.



Cheers

Rich

[Firebird]

Hi

Well I had a go at hand grinding a tool and didn't get on too well, theres more to it than I thought  A quick search on google  led me to a youtube video by Tubal Caine which shows how to make a jig for grinding. Now I could spend a long time acquiring the skills to hand grind or I could spend an hour making a jig that will get it right every time,    bit of a no brainer really.

So a lump of scrap ally in the rotary table has two 1/4" slots milled. Turn the table 30° one way and mill the slot. Return to 0° then turn 30° the other way and mill the second slot.



Stamp 60° to identify



While its set up turn it over and mill two slots for 55° by turning the rotary table 27.5° each side of 0°



Drill and tap 6mm each side and make a clamp



My home made disc sander has a tilting table. I tilted the table a little to give some side relief to the tool.




About an hours work and well worth the effort. I can now grind tools quickly and easily evry time.  Tubal Caine







The tool cuts the thread very easily. Not a very good photo here but theres a better one to follow.





The spindle in the mill having a 1/8" key way slot cut



After cutting the key way slot. This photo shows how nicely the screw cutting tool has cut.



I'm beginning to think that I put too much faith in TCT tooling. Its nice but very expensive. Having had a lot of success with my home made tangential cutter, which leaves a superb finish, I'm now leaning more towards grinding my own tools. The jigs are quite easy to make and ensure constant results.

Cheers

Rich

[NickG]

That jig is good Rich and has made a good thread, I recently had same trouble hand grinding for a thread. sure I've seen people put a grind wheel in lathe and set compound slide to desired angle though you'd need some wedge shaped packing (I guess) to get the relief? Lathe may not be fast enough really for grinder either so jig is better esp with your sander. I always poo poo'd tct for hobby work as I've had better results in the past with hss. However with my myford I've been using the tct tools I got for xmas one year and had good results. This is more for convenience as they fit nicely in the QCTP and can't be bothered to grind a big set of tools!

[Arbalest]

I can grind most lathe tools by hand but struggle with thread cutting bits. I saw that jig a little while ago so it's very much on my "to do list". Thanks for reminding me!

[arnoldb]

Looks great Rich 

The finish on the sharpened edges of a screw-cutting tool makes a huge difference, and your disc sander leaves a nice smooth finish.  I just finish-hone my own ground bits on the fine side of a trusty old whetstone.  Just a suggestion if I may: round the tip of the "V" on the toolbit ever so slightly - otherwise it easily breaks of, normally damaging the cutting edges further back in the process - especially if your bit's been ground a bit hot like the one you showed.  Don't ask how I know that 

Kind regards, Arnold

[Firebird]

Hi

Thanks Nick, Arbalast and Arnold.

Arnold, it got a bit hot from my hand grinding efforts. When I get some spare time  I'm going to grind up a set of cutters ready to use and I'll try honing and rounding the tip.

Cheers

Rich

[Firebird]

Hi

I have bolted the frame and top plate together, hopefuly for the last time, and mounted it upside down on the mill. A light skim all round was all it needed.



I am using a piece of 4mm thick ally plate for the base/cover. Steel would be better but I don't have anything suitable so ally it is. Drill tap and countersink for 5mm countersunk socket head screws.



Cheers

Rich

[Firebird]

Hi

I had a good day in the shop today, its bank holiday Monday and as usual it rained so we decided not to go anywhere. I set the base up in the mill and cleaned up all the sides with a fly cutter.



The handwheel is recessed for the nut.



I was going to make a handle for the hand wheel when I came across this very nice chrome plated one. At less than £5.00 it wasn't worth making one.



Drill and tap a 6mm hole



And try it



I have bored and reamed a .5 hole through the centre of the table for locating things so I have now drilled and tapped 6mm the centre of the spindle which will be useful for bolting things down



The table is mounted in the mill and has all the degree markings applied, this took about an hour



Then stamp in some numbers. I did this free hand in the end. I pondered for a while on how to make a jig to hold the stamps but decided it wasn't worth the effort.



And finally today I started on the table clamps. A bit of 25mm X 15mm steel bar is machined down to fit in the table groove. It needs a radius so I gestimated this and did it on my 6" grinder.





Cheers

Rich 

[Don1966]

That' some nice work Rich. Still following you bud.


 

Don

[Firebird]

Thanks Don.

I do believe I'm getting somewhere now with the end in sight

Cheers

Rich

[Firebird]

Hi

I finished making the two table clamps now I needed two bolts. I have used two 5/16 whitworth socket head bolts cross drilled 3/16. To make the handles I cut two lengths of 3/16 stainless steel. To make the ball ends I have used two 3/8 steel balls. These are soft not hard like ball bearings and can be drilled and machined easily. They are used as catapult ammunition.

Held in a 3/8 collet drill 3/16 just over half way.







In the brazing hearth the two balls are silver soldered to the bar



After a clean up the parts are blacked.



Drill and tap two corners 5/16 whitworth.



Make a key way for the spindle.



And press in



The spindle is assembled with hand wheel, worm gear, eccentric, two bearings and a thrust bearing



finally today I have given the base a lick of paint on 3 sides. The side which is used to mount the rotary table vertically I have left unpainted.



Cheers

Rich

[ths]

  They are used as catapult ammunition.

As much as I've loved following this thread, and as impressive the just about finished product is, I really need to see this catapult.

But seriously, fantastic work.

Cheers, Hugh.

[Firebird]

Hi

Thanks Hugh but sorry no catapult. You can buy these steel balls off ebay really cheap. These were £3.89 for 100 including postage.

Well its time to start assembling the rotary table. Fit the eccentric bush and pack the bearing with grease.



I have made a large washer from plastic to cover the bearing, it sits around the spacer washer



Followed by the adjuster nut. Adjust until there is no play and tighten the clamp bolt.



Fit the key into the keyway



Followed by the gear and its locking nut, then slip in the spindle, eccentric and worm gear.



Turn it over. The table had 4 6mm tapped holes which were used for mounting to the face plate when turning. Drill them right through 1/4" and fit 4 button oilers.





Things are rolling along nicely............UH OH  take it apart again. I forgot to drill and tap a hole in the eccentric  for the lever.

Drill and tap 3/16 X 40



Thread a bit of 3/16 stainless steel round bar 3/16 X 40 and screw in.



Everything turns well and freely, no tight spots.

Cheers

Rich

[Don1966]

That' nice work Rich and you have something useful and you built it. Isn't it a good feeling? Are you putting T slots in it?

Don

[Firebird]

Hi Don

Yes I intend to put T slots in. I figured a size that will take 8mm studs looks about right. Then I looked round at what I have. My X1 mill uses 6mm studs, a bit small, and my X3 mill uses 10mm studs, a bit big.  I think I will go with the 6mm as I already have all the T nuts and studs that I need. I can always open it out to a larger size later if I have to.

Cheers

Rich