Building a 7" rotary table

[Firebird]

Hi

I'm not happy with the way the eccentric works/feels so I'm trying something else. I have bored out the eccentric which I will now screw to the frame making a more solid bush. I'm then going to make an inner eccentric that is a good sliding fit in the bush. That should be much more rigid.



The boring bar I use is home made, very easy to make. A length of round steel bar is drilled and tapped 1/4" for a grub screw and cross drilled 3/16". The shank has 3 flats milled to fit into the tool holder. The 3/16" round tool steel is ground using the tangential cutting tool jig (see my post on making a tangential tool).





It cuts beautifully and leaves a very good finish.

Cheers

Rich

[Firebird]

Hi

After boring out to 1.125"



A piece of scrap ally turned to 1.125" and a 8mm hole drilled with .125" offset







Thats better, more rigid. I can make a steel one now the same length as the bush which should result in virtually zero play.

cheers

Rich

[Firebird]

Hi

Started turning the new eccentric tonight, its a straightforward turning job of little interest to you experienced guys  but it occurred to me that not too long ago I was a newbie to all this and keen to learn  so I thought I'd show it for the benefit of all current newbies. I have to turn a piece of 55mm dia steel down to around 28mm. I always try taking a cut at the lathes slowest speed and if there is any sign of chatter I switch to an even slower speed by using the back gear. Takes a while longer to get there but the cuts are nicer and there is less strain on the machine. I am using my home made power feed and home made tangential cutter.

<a href="https://www.youtube.com/watch?v=30OV-7P5SBE" target="_blank">http://www.youtube.com/watch?v=30OV-7P5SBE</a>

Cheers

Rich

[zeeprogrammer]

Very helpful to see videos of cutting in progress. Thanks.

How much were you taking off in that pass?

[Firebird]

Hi Carl

010" at a time.

cheers

Rich

[joe d]

Hi Rich

I've been following along since the beginning, and just wanted to say that I've been enjoying it.

Looking forward to more!

Thanks,  Joe

[Firebird]

Hi

Thanks Joe.

A bit more turning done and then a groove that the locking screw will locate into.



Cut from the parent material



After facing it is moved to the mill to have a centre drill mark. This time I have made the offset just 0.1"



Re centred in the 4 jaw



and drilled through 3/8"



Then a pocket machined with a 14mm end mill for the bearing, sorry no photo. Turn it round and recentre using the 3/8" drill



Then another bearing pocket, followed by a trial fit.



Centred again, I'm getting quick at using the 4 jaw. The outer part is turned true with the spindle hole.



The bush is in the mill having 2 x 4mm holes drilled and counter bored to take socket head screws. I'm a bit tight for room so I have turned the heads of the screws down a bit and used a 1/4" cutter to counter bore






Drill and tap the side plate.



And fit the bush.



A great improvement on the first attempt.

cheers

Rich
 

[Firebird]

Hi

This is the handwheel on my vertex rotary table



I need to make something similar so have started with a piece of aluminium, another turning job.



Cheers

Rich

[Firebird]

Hi

I have drilled an 8mm hole through the centre and now I need to cut a keyway. I have some 1/8" key steel so that'll do. When I got in from work tonight the wife said dinner will be a bit late I want to finish this ironing. Being the kind considerate chap that I am I said no problem I'll keep out of your way and go in the workshop for a half hour

Thats just enough time to make a keyway cutter. I can't remember where I saw this idea but its a neat little trick. Take a piece of 8mm round steel and mill a 1/8" slot 1/8" deep. I have milled the slot the same length as the bit of 1/8" tool steel I have, no need to cut it down. Drill and tap a 3mm hole at the front end.



Check the tool steel fits ok



The depth of cut is adjusted by screwing in the 3mm grub screw







The tool is used in the tail stock and wound in and out of the hole adjusting the grub screw until the correct depth is achieved



Unfortunately the ironing is finished and dinner is ready so cutting the keyway is going to have to wait.

Cheers

Rich

[zeeprogrammer]

Neat.

Unfortunately the ironing is finished and dinner is ready so cutting the keyway is going to have to wait.

Argh!

[Don1966]

Aw man that's the pits Rick!  Nice progress and I think I seen that method used before and I think it was in Ruby Kouhoupt's book. It works real well from what I've seen. Still following along.

 

Don

[PStechPaul]

I've thought about making something like that if I need to cut a keyway. But I wonder just how much material can be removed on each stroke, and where the chips will go. There seems to be an angle cut on the tip of the tool which should act as a chisel (or broach), and there may be some space in the slot to hold the chips. But perhaps there could be a larger opening, and it may be good to look at the design of the cutting edge. How much pressure is needed for the cut? Can the tool be held in a chuck on the tailstock and use that to cut the slot? Is it OK for steel?
 
Also, won't the cutting tip angle tend to dig in and raise the tool out of the slot? Maybe the cutter needs to stay parallel to the shaft. Or, perhaps cut a small notch on the tip that will follow the previously cut slot and keep it from lifting? Am I asking too many questions??   

 
I found a web page describing a somewhat different keyway cutter:
http://homepage3.nifty.com/amigos/slotter/slotting_tool-e.htm
 
Here's a video showing something similar being used on a lathe:
 
<a href="https://www.youtube.com/watch?v=7dMDOhlp0rE" target="_blank">http://www.youtube.com/watch?v=7dMDOhlp0rE</a>

[Firebird]

Hi

Thanks Carl and Don.

I can't answer any of your questions as yet Paul but you raise some good points, time will tell when I try it. One thing though its a through hole so the chips should be pushed out the other side. I'll let you know how well it works (or not)

Cheers

Rich

[Firebird]

Hi

Well the key way cutter worked well. Light cuts required not too much effort.





I would think its possible to cut steel this way as well, with light cuts.

The hand wheel is centred accurately in the rotary table on the mill.



I ground a point on a piece of 1/4" round tool steel and scribed all the marks on the dial part.



And stamped in the numbers.



The table with bush mounted in the mill and drilled and tapped 6mm for the locking screw.



The locking screw I made from a cut down high tensile cap head screw, cross drilled and a piece of 1/8" round silver steel for a bar



Finally today I got my blacking kit out and treated a few of the parts. It helps to keep the dreaded rust at bay.




Cheers

Rich

[Firebird]

Hi

Because the hand wheel is aluminium and the eccentric steel there is bound to be wear. I need to tighten the hand wheel fairly tight to reduce backlash so I have decided to fit a thrust bearing between the two. The bearing is 35mm diameter and 4mm thick. cost less than £5.00 off ebay.



Centre the hand wheel in the 4 jaw again



Machine a pocket for the bearing about 2.5mm deep.





Centre the eccentric and machine about 1mm deep



When together there is about a .5mm gap between the two



Assembled the hand wheel spins freely.



Cheers

Rich