Thread: Workholding in 4 jaw chuck

mate 16 year olds do know it all ! its all us older guys that have have to learn things ! seems like its educating every one , though some have different interests . cheers bob

Originally Posted by Grahame Collins

The best idea I could could come up with - among the assorted calls for various assistance from other kids - was to turn a 16mm stub which I threaded and stuck the other end in the Jacobs chuck.

A similar way would be to have a M16 stub with a portion turned but untapped, mount it in the material as you have done but after roughly mounting it via the tailstock chuck take the accuracy a little further by using a clock guage on the unthreaded portion. I know this is overkill for a hammer, but it is a good demonstration for the students. Also, the best and most accurate way to make yourself this tool would be to make a hammer head as normal and without taking it out of the chuck fit your M16 mandrel and give it a light skim to ensure that the unthreaded portion is spot on concentric with the threads. Make it about 6" long and put a centre drill in the end so you can use the tailstock for initial support.

To give you some further ideas of mounting in chucks or faceplates, research "boring buttons". All quality lathes are supplied with them from new (so Hercus don't ) and they are without a doubt the most accurate way you can mount anything in a chuck.

0.5mm tolerance? Hah! As a 17 YO apprentice I was hand filing to a tolerance of +- 0.01mm. I'm only 40...... Mind you, if I could go back in time and meet myself as a 16/17 YO I would probably feel it necessary to beat myself severely. On an hourly basis. For the good of the nation.

Originally Posted by Chief Tiff

To give you some further ideas of mounting in chucks or faceplates, research "boring buttons". All quality lathes are supplied with them from new (so Hercus don't ) and they are without a doubt the most accurate way you can mount anything in a chuck.

Got a link? Google, Wikipedia and H&F have never heard of em.

To research boring buttons you'll probably have to go to a library and pick out a book or two on lathe operations.

But, briefly, a boring button is a finely ground hardened cylinder of a specific diameter, usually 10, 15, 20 or 30mm (plus the equivalent Imperial sizes) and around 10-20mm high. The cylinder is hollowed enough to allow a bolt to pass through with lots of clearance for position adjustment. You loosely bolt this roughly in the position of the hole you wish to bore in your workpiece, then adjust it until it is perfectly positioned. You then place the workpiece in the chuck or faceplate and align it with a clock gauge, Remove the button, start boring.

For example;
You have a 100 X 60 X 20mm thick rectangular block of steel and you need a 40 mm dia hole boring along the centre line and with its CL 25mm from one end. You ink up and scribe the hole position and drill and tap an M8 hole where the centre of the hole needs to be. You loosely bolt a 30mm dia button in position, then using a surface table, angle plate and slip gauges you position the button exactly 15mm from the long side (giving you the centreline position from 15mm radius + 15mm= centreline at 30mm) and 10mm from the short side (15mm radius+10mm=25mm). Tighten up the bolt, recheck position then place workpiece in 4 jaw chuck or clamp to faceplate. Centre the workpiece using a clock gauge, then remove the button. Drill a hole large enough to allow access for the boring bar then bore away as normal.

This method gives phenominal accuracy on a lathe and can also be utilised on milling and boring machines. Buttons can be set up so quickly using slip gauges it's almost unreal.

Now, who doesn't know what a slip gauge is?

Many would and many may not,I not sure as too the amount of members on this forum who would have at there dissposale a Surface Plate or Slip Gauges.

The alternative to boring buttons is to centre punch the position of the hole you wish to bore, mount it in the 4-jaw as usual and use a pump centre with the point end located in the centre punch dimple and the other end held in a centre located in the tailstock.

You can then use the dial-indicator method to fine tune the centering - using the DTI on the pump centre close to the work.

A pump centre is a good project for the kids in any case.

Here is but one of many examples,

Shop Made Pump Center

Originally Posted by pipeclay

Many would and many may not,I not sure as too the amount of members on this forum who would have at there dissposale a Surface Plate or Slip Gauges.

A reasonable surface plate can be made from a piece of marble or granite; kitchen workbench suppilers often have small sections left over. Agreed, proper slip gauges are a bit hard to come by , but once again adaption is the key. 1-2-3 blocks, shim stock and feeler gauges are available, tool steel comes in very precise sizes, even glass plate and acrylics can be pretty accurate. It's also not too hard to learn some new skills and make these items.

At the end of the day however, I only mentioned buttons in this post as a suggestion for Grahame so he could look at alternative ways for aligning, and that this information may be useful to him, and that he may feel it worth passing on to his students, some of whom might actually become machinists. Knowledge is there to be shared, every now and then knowing a different way comes in useful.

Carbatec have small granite surface plates for $60,

Granite Surface Plate : CARBA-TEC

Hi Guys,
Many of my students have never worked a lathe before let alone come to grips with the complexities of a four jaw chuck and other operations which are described above.
What I am trying to do is get the kids exposed to as wide a range of machining experiences as possible.

You have to remember, this cohort are the instant gratification group who have no idea of what planning and preparation and patience are new concepts for them.

Too many schools are satisfied with just setting up their lathes with carbide tooling and running three jaw chuck projects.given my groups are given 2 full 9 to 2 days per week for 2 years ,I am tying to get a meet the course descriptors to the fullest extent.

Its a learning curve for yours truly as well.What I have learned that the kids will only respond to projects that have something for them in it.
To that end I try to stick with work that involves tools they can still use when they leave me.

The soft soft faced hammer http://www.projectsinmetal.com/free-...-faced-hammer/
and the scriber are 2 such projects
to cover the basics such as

• Facing off
• Center drill usage
• Parallel turning-turning to .1mm tolerence
• Drilling for internal tapped threads
• Static tapping
• Cutting external threads with a die
• Knurling

Single cutting edge thread cutting is something I'll leave to the employers or Tafe, as most kids won't or can't manage the maths.

If I can get a couple of projects that involve 3 & 4 jaw work and the mill under their belt ,then I'll be happy.
The kids are wrestling with sharpening their own lathe tools for now and that is making them a bit more responsible with them. It tends to make them a bit careful with lathe spindle speeds, tool angles ,tool center heights are selected .In year 12 they can go over to carbide inserts which are a whole new ball game .



Four jaw chuck work is new to me so I am asking and looking through the web for insights into what is and is not possible.
Thanks to all that have corresponded.

Hi Grahame,

Great thread!

As an aside the 'kids' I teach are a little older and a totally different topic but sometimes the same attributes - makes you wonder why you do it, but every good one makes up for the others - oh and and thats also why we have a shed.......

I also found this article interesting in setting up 4J which is indeed an art that requires practice. It may also present a small project?

Centering Work in the Four Jaw Chuck

project: Shop Made Pump Center

Now about those slip gauge things- love to hear more about them and how they work if anyone has a moment?

Cheers

Ian

I have never been able to get a 3 jaw chuck to hold wood accurately.
Four jaw is what you need. Being a machinists tool, you might encounter situations that do not exist with those chucks made specifically for wood. But, I am confident you can make it work.

A basic description of using slip gauges.

Slip gauges or Joe blocks as I was taught to call them (they are called Joe blocks after the guy who invented them )are precisely ground pieces of metal of different dimensions that are used with a sine plate or bar to calculate and set precise angles on marking out tables.
They are so flat that you can "wring" them together to create a stack of an exact size ,(They actually stay adhered together)So when they are placed under the roll of a sine plate they set the plate at an exact angle .
You need to work out the dimensions of the stack using trigonometry using the set center distance between the two sine bars and the height of the stack of Joe blocks
Sort of like engineers Lego .

Slip gauges are available from a few sellers on Ebay .
Incidently if you leave them stacked together long enough you wont be able to get them apart.
I remember using them at trade school ,the instructors always checked and double checked that we had separated the blocks and oiled after we used them ,they obviously were a very expensive bit of kit. Nothing worse than a rusty finger print to wreck expensive accurate measuring equipment.
Rough sketch attached.
Kev.

Hi a pic of a turned hammer after we oil blued it.

One soft face is not completely screwed in as the student put a burr on the all thread when it was held in the vice without soft jaws.

Hi,
First up a pic of a turned hammer after we oil blued it.

There were just 2 kids out of 13 turned up.One day after after the show holiday and 1 day (Friday) before the semester break

One soft face is not completely screwed in as the student put a burr on the all thread when it was held in the vice without soft jaws.

The other pic is what one of my female students has turned.She has taken to turning like a duck to water.There are a few little flaws ,but prior to this year,this student had not been in a metalwork class since year 8.

Grahame