tool to use in boring head
|Peter Peters||15/01/2019 04:30:42|
|1 forum posts|
I'm designing and building a ball turning tool which will drop onto the Myford topslide tool clamp stud and tighten down. The intention is to enable a finish cut from the lathe centreline right round to parting-off a complete ball - no doubt with a small pip. The tool-bit I intend to use is a 35deg. diamond shape carbide insert in a home made holder. The bit is VCGT-VP1-PC 8115 .
Right in the middle of the design work I became aware of contributor Nobby's use of a boring head to turn a ball and wondered if I could do the same but couldn't see how to grind the tool-bit. What's more would it part-off at the end of its final cut? Can anyone help.
|Bill Pudney||15/01/2019 09:13:53|
|414 forum posts|
I recently made a couple of three ball handles for a small carriage and cross slide I've had underway for a while. To avoid the making of a ball turner, which would probably only be used twice, I adapted Guy Lautards method in one of his books. The process went something like......
1/ Draw the required handles in CAD, in my case TurboCad. Identify the max ball diameter as a datum.
2/ Draw a line parallel to the datum, 0.5mm away from it, record the diameter, and enter the number on a chart.
3/ Repeat stage 2/ until end of circle, thus creating a set of co-ordinates
4/ Set up dial indicator on carriage to measure diameter reduction
5/ Using a sharp, rigid parting tool, line up left side of cutter on the part datum, move slide towards tailstock by the appropriate amount, in my case 0.5mm, and plunge in the amount indicated. Repeat.
6/ Using a well chalked, sharp file remove the steps produced and polish with oily wet and dry.
7/ Repeat for the other balls. There are a LOT of little steps.
This is obviously a vastly shortened version of the real process. But I was able to make my two three ball handles in a morning. The CAD work and developing the process took a while though.
I will ask the Chief Photographer to provide a couple of pictures of the finished handles.
|Paul Lousick||15/01/2019 09:39:19|
|1149 forum posts|
Refer to previous article posted on MEW "Simple ball turning attachment for the lathe"
and Youtube video: https://www.youtube.com/watch?v=-n6o6hrtbmE
Edited By Paul Lousick on 15/01/2019 09:42:59
|Martin Kyte||15/01/2019 09:39:28|
|1471 forum posts|
I made the Hemmingway version last year.
This is essentially a boring head style device mounted in the toolpost. The cutting tool moves in an arc in a vertical plane along the lathe spindle axis. (up and over the work) so cuts at the top of the work and not the side as in normal turning. To imagine the cutting tool required if you consider a normal knife tool rotated 90 degrees so it is positioned over the workpiece you will get the profiles of the cutting edges required for the 'end' of your tool. It will be more akin to the diamond tool as advertised by eccentric engineering but with the body of the tool square on to the work so all the clearence angle have to be generated by grinding.
The parting off requirement may be a little more challenging as the clearences start to disappear as you swing round to the headstock end of the ball. A deep wide groove machined in the blank helps but to get right round to parting off position really needs a cranked cutting tool.
15988 forum posts
If you are looking at turning to a minimal stub or parting off teh ball have a look at the way teh Turnado works as that goes down very fine.
|Tim Taylor 2||15/01/2019 15:35:51|
|66 forum posts|
While the concept used is not new, the way EE has designed the Turnado is pretty slick.I particularly like the way the tool holder is designed - with the front of the supporting foot well in front of the tool all the force is directly down and there is very little chance of the work grabbing the tool and flinging it somewhere. Also, the rake angle on the tool should be neutral (0 deg) for the same reason. With minimal additional fixturing you could turn some pretty accurate and repeatable decorative shapes, tapers, etc.
I have seen videos where a conventional tool is hand held on a riser block for doing free hand machining, and I think the Turnado idea is much safer.
The only real drawback for me is that EE is located in Australia, and the shipping costs to the US would be prohibitive. They sell the tool holder as a separate item, and I might just order one of those - the rest can be easily fabricated from raw materials obtained locally
Edited By Tim Taylor 2 on 15/01/2019 15:36:28
|John Reese||16/01/2019 21:56:59|
|772 forum posts|
There is a You Tube video by Doubleboost showing the use of the boring head for turning balls. Check it out.
About 3 minutes in.
|88 forum posts|
I have also made the Hemmingway version. Martin described the cutting tool but if using a boring bar it is quite springy so only very light cuts in harder material is possible. Haven't tried parting off with it as I can't see that it would be easily achieved.
27 forum posts
Hi, one of the problems with boring bar versions is the sharpening of the toolThe following U tube video would seem to have found a very good solution to the problem.
I hope this is of interest to those that have built boring bar versions of ball turning tools.
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