What method do you use to find center height for your lathe bit?

[VicParticipant @vic]

I made a simple tool.

[Clive FosterParticipant @clivefoster55965]

I'm a great fan of the optical type. Simply made by fitting a suitably thick peice of perspex on a base and scribing a line at centre height on both sides.

If space is tight you can look through it rather than at it. Lines on both sides of the perspex allows you to compensate for any parallax issues. When the line looks thinnest you are looking straight on. So you can observe from a distance if need be.

Made a mirror for mine so I can look down rather than across. Also put extra lines on it so I can use it off the cross slide as well as the bed. Along with other lines for non lathe jobs.

Would have been better with 10 mm or 12 mm perspex than the 6 mm I used. But it was what I had and is good enough.

Article in one of the early MEW magazines describes one that I used as a basis. Darned if I recall the authors name tho'.

Clive

[Nigel Graham 2Participant @nigelgraham2]

I'm not sure if the back-cloth is for the same purpose, but putting a sheet of white card or similar behind the lathe helps setting anything optically, too.

[ChrisHParticipant @chrish]

I use an otherwise redundant vernier height gauge set at centre height. Keep it right by the lathe. Centreing tools is all it's used for. For me it's quick and easy and, due to being kept in a "specially for it" place by the lathe, always on hand.

[Phil WhitleyParticipant @philwhitley94135]

I eyeball it to a centre in the tailstock, but I also use the 6" rulle method. First job you do turning is to face off, so you will know if you got it right or not, or you could face off a bit of scrap bar……………but what counts as scrap in the home workshop? surely it's all metal you haven't decided a use for yet?

[Former MemberParticipant @formermember19781]

[This posting has been removed]

[HollowpointParticipant @hollowpoint]

I usually chuck up something with a point and then eyeball the cutter up to it then I chuck up a piece of stock and face it making fine adjusments with th QCTP.

I've always found a badly centred tool gives poor finish.

Edited By Hollowpoint on 27/06/2019 19:15:52

[Bill PudneyParticipant @billpudney37759]

I have an optical centering scope, it's primary use is to locate centers on the mill, but another major use is to stick it in the tailstock and adjust tool height as indicated. Guaranteed within a small range. Very quick and easy, and having a second use for a bit of kit is always a good thing!!

cheers

Bill

[thaiguzziParticipant @thaiguzzi]

All Heavyweight Stainless Steel.

Edited By thaiguzzi on 28/06/2019 05:57:00

[Neil LickfoldParticipant @neillickfold44316]

I now use a piece of plastic strip. Can be made from plastic shim, or cut from a lid of an ice cream container.

I changed to plastic, as it wont damage a pcd or cbn insert. It works quite accurately for both internal or external tools or stock in a drill press or mill.

[John RutzenParticipant @johnrutzen76569]

I made a double ended centre height gauge, one end faces up and the other down. The refinement I have in mine is a powerful magnet fitted in the base. I got the magnet out of an old microwave oven.

[Peter SpinkParticipant @peterspink21088]

Posted by Vic on 27/06/2019 13:00:53:

I made a simple tool.

Vic, nice toolholder – what is it?

[EmgeeParticipant @emgee]

Posted by Neil Lickfold on 28/06/2019 07:25:11:

I now use a piece of plastic strip. Can be made from plastic shim, or cut from a lid of an ice cream container.

I changed to plastic, as it wont damage a pcd or cbn insert. It works quite accurately for both internal or external tools or stock in a drill press or mill.

Neil, is the method as others where the strip is between the tool and workpiece, a set on centre tool gives a vertical strip ?
Can't imagine how you use it for an internal tool unless at the back of the workpiece ?

Emgee

[Ian McVickersParticipant @ianmcvickers56553]

I use the scribed line on my tailstock.

[Howard LewisParticipant @howardlewis46836]

Pedant Alert!

My method is:

Place a bar of known diameter in the chuck ( I use silver steel )

Measure the eccentricty with a DTI or Finger clock (depending on how confident you are in your chuck ) I use a Vernier Height Gauge., but an adjustable pillar with ends faced square is quite acceptable, to measure off the Bed or the surface of the Cross Slide.

Note the reading.

Deduct (Half the eccentricity + half the bar diameter ) from the reading. Here "eccentricity" means the MAXIMUM .

THIS figure is your Centre Height from the Bed or Cross Slide. By whatever means you choose, Slips / Height Gauge and Clock / Adjustable pillar, (Adjusted with Micrometer, Calliper ) set your Centre Height Gauge to this dimension.

For tools mounted in the Front Toolpost, the underside of the blade should be set to this dimension.

For tools mounted in the Rear Toolpost, the tip of the tool should be set to the upper surface of a blade.

The Upper surface of a Lower blade sets the tools in a Rear Toolpost. The Lower surface of the Upper blade sets tools in the Front Toolpost. .

The time spent on this procedure, saves a lot of setting up time, and unless something moves, no pips when facing!

Howard

WHY do I only spot the errors AFTER hitting "POST"?

Edited By Howard Lewis on 28/06/2019 22:06:12

[Neil LickfoldParticipant @neillickfold44316]

Posted by Emgee on 28/06/2019 09:15:02:

Posted by Neil Lickfold on 28/06/2019 07:25:11:

I now use a piece of plastic strip. Can be made from plastic shim, or cut from a lid of an ice cream container.

I changed to plastic, as it wont damage a pcd or cbn insert. It works quite accurately for both internal or external tools or stock in a drill press or mill.

Neil, is the method as others where the strip is between the tool and workpiece, a set on centre tool gives a vertical strip ?
Can't imagine how you use it for an internal tool unless at the back of the workpiece ?

Emgee

Yes when vertical is on centre. And for internal is at the back of the work piece. If you have lots of holders and don't have to change tools during the making of a part it becomes not needed as they can be set from skimming the end face of some solid stock.

[Peter SpinkParticipant @peterspink21088]

Posted by Peter Spink on 28/06/2019 08:59:11:

Posted by Vic on 27/06/2019 13:00:53:

I made a simple tool.

Vic, nice toolholder – what is it?

Sorry, ignore that – have found the thread. Nice job!

[jimmy bParticipant @jimmyb]

I use a cheap "thickness" gauge.

Works pretty well.

JIm

Edited By jimmy b on 29/06/2019 07:43:11

[Danny M2ZParticipant @dannym2z]

For final finishing I have found this tool quite handy, especially on 'difficult' materials. Shear tool

It is not picky regarding height as it is automatically on center due to the design. Indeed, I raise and lower mine with the QCTP to present a fresh edge for the final finishing cut.

Notice that I said "Finishing Cut" – only good for the last 0.001" or so but what a lovely finish.

If I had the time it would be interesting to experiment with the cutting angle for various materials. I have noticed that brass with a finely honed HSS edge can appear as a mist of tiny motes when the light is right.

* Danny M *

[Blue HeelerParticipant @blueheeler]

Danny thanks mate for the link to the shearing tool.

[Nigel McBurney 1Participant @nigelmcburney1]

I use a length of aluminium round bar faced off at each end,the length is the centre height of the lathe (bed to Centre) at the top end I have an offset steel penny washer secured with a small screw the washer overhangs the ally bar by about half an inch on one side, To set a cutting tool the top tip of the tool just slides under the washer,I used alloy bar so that if dropped or knocked over it does not damage machined surfaces of the lathe, I got this idea from my first job,a similar tool made from steel was used to set tooling on a Ward capstan, to set the rear toolpost tools the top of the bar just slid under the rear tool . Simple !!!

[colin hawesParticipant @colinhawes85982]

Estimation followed by adjustment if necessary. Colin

[John RutzenParticipant @johnrutzen76569]

That shearing tool works on the same principle as a skew chisel in woodturning. Hard to use woodturning to avoid a dig in but that wouldn't happen here. I'll have to make one because I find it difficult to get a good finish. Thanks for the post.

[Neil WyattModerator @neilwyatt]

Posted by Danny M2Z on 29/06/2019 08:40:17:

For final finishing I have found this tool quite handy, especially on 'difficult' materials. Shear tool

It is not picky regarding height as it is automatically on center due to the design. Indeed, I raise and lower mine with the QCTP to present a fresh edge for the final finishing cut.

Notice that I said "Finishing Cut" – only good for the last 0.001" or so but what a lovely finish.

If I had the time it would be interesting to experiment with the cutting angle for various materials. I have noticed that brass with a finely honed HSS edge can appear as a mist of tiny motes when the light is right.

* Danny M *

Thanks Danny, I read about those years ago and still haven't got round to grinding one up.

Neil

[thaiguzziParticipant @thaiguzzi]

And this is what a shear tool does on a shaper;

[Author]

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