Member postings for Niels Abildgaard

Jouke

Interesting,but why so much tilt on toolbit if You can make it to any diameter,as I asume You can from the photo?

Your Emco spindle has what I ,after much consideration and not much expirience, consider the best way.

Three or four screws through chuks to front of spindle.

Very short ,strong,safe and fast to change.Whats not to like?

What lathe do You have?

It could be fun if someone will try and compare with my homemade.

There is an old thread that have pictures etc.

I tried 6mm carbide and allwent well untill 2.5mm depth of cut.Then lathe was not really up for more.It was therefore reasonable that a 3mm tool should be able to do 2.5mm wide also from a lathe power viewpoint.

That might have been the case put cutting was not possible.Noise was unpleasant,swarf curled wrong and it had to stop.

Doing 1.5mm and down it was pure music

Round tangential tool limits

There is a picture of sharpening here and stone is a carborundum or silizium carbide and not expensive,but diamond in some form is better.

Tangentials

You aint seen nothing yet

It has tasted a 12.9 screw and chatters at lower work rate than my 2times 2 square versions.

The distance from front bearing to work area is far to long.

Bigger spindle and shorter overhang before making final verdict.

Edited By Niels Abildgaard on 08/06/2020 18:47:19

My toolslip have always been a caused by brain failure.

Forgetting to tigthen up after a regrind.

I experimented quite a lot with different screw head forms,differential screws and worse.

After making my screws like picture there have not been any slips caused by screw.

M8 with 0.5mm pitch.

Edited By Niels Abildgaard on 08/06/2020 06:07:55

Edited By Niels Abildgaard on 08/06/2020 06:15:02

Hello Diogenes

Do we have a race?

I have speculated very hard for years how to make the first part of the slitting nice and today I saw the ligth.

I use my very good (and rather expensive) Iscar parting off system and can easily go 10mm in with a width of 1.4mm.

Rest of the way will be hacksaw and is OK.

Concerning round tangential toolbits.

It was tried with 3,4 and 6mm round carbide and flat top on mild steel.

It worked very well until depth of cut was equal to radius of toolbit ,that is 1.5 and 2 and 3mm.

The cutting edge was much more robust than any of my homebrewed square things.

Interupted cuts,cast iron skin etc

For our small lathes there is no reason to opt for bigger toolbits as 1 to 2mm depth of cut is power limit anyway

Concerning angles of tangential grinding.

As said for round toolbits horizontal flat is as good as anything else and does not dig in in brass or some of the nastier bronces.

For square toolbits it is another case.

If You lean it 15 degree in as the Australian Diamond Tool and grind top horizontal there will be around 89 degrees between the two cutting edges and this is next to impossible to adjust with old mens eyes if you want cutting and facing with same toolsetting.To ease it toolbit is ground in a rather obscene angle with a jig,but this makes cutting tip less robust.

For my 2 and 3 mm square carbide sticks I did it otherwise.I bougth a swing grinder from Swindon and modified one face so that the cutting corner was 85degree and that was enough for my brain and eyes at that time.Today I wish it had been 80 degree and I have at least twenty modified 2 times 2 (almost) 60mm long and that will last me out.

I once made a set of holders for a Myford that has only about 16mm from base to center and they looked wrong.

The mentioned 737 captain proposed a sligth change and it looking something like this.

The grinding of the carbide top is not difficult.

Make it more or less horinzontal and it works very well

I tried 5 degree downward and that worked but 10 degree neative did not.

Edited By Niels Abildgaard on 07/06/2020 09:36:04

Edited By Niels Abildgaard on 07/06/2020 09:38:35

Hello DiogenesII

The way to machine the cheeks can be seen here

Old pictures

I have never been very at ease with slitting saws and You just use one a little more than a mm thick?

What is Your centerline distance from compound slide top?

Edited By Niels Abildgaard on 07/06/2020 09:20:26

Good morning

A picture showing combat area from below and one showing going in a 90 degree corner.The angle between the cheecks can be 90 degree of course,but is difficult to set by eye.Have tried 85 degree but prefer 80 to day.

Machining of cheecks is last operation as it has to be done reasonably controlled relative to toolbit.

This has shown me that carbide can cut carbide.

I am impressed by Pauls tantool with a 2mm round toolbit.

How is the flexibility slit cut?I have tried with a hacksaw and was not impressed.

Edited By Niels Abildgaard on 07/06/2020 06:41:44

Manufacture can now start and I like to do it in the fourjaw and using most modern rocket science angle measuring equipment to get 12 degree toolbit angle.When i took the last picture I had to realise it was a scrapper.The future toolbithole was 3 mm from centerplane.Old men shall not calculate in head anymore.

Will start a new tomorrow.

The next picture shows that deciding distance from clamp stud to cutting point is not trivial and length of virgin toolbit is not either.

I have broken more than two turning compound slide back.

Edited By Niels Abildgaard on 06/06/2020 21:03:10

Interleaving text and photos is not easy.How do I put a phto from album some text a new photo etc?

Edited By Niels Abildgaard on 06/06/2020 20:56:26

It is my plan to make a tangential holder for 3mm round carbide that suits my 250 lathe..

It was once measured by a Boing 737 (old model) captain that I could decide to stop,remove toolholder ,regrind.put back on lathe and start cutting again in less than two minutes.

This is somehow due to having upper surface of holder exactly on lathe centerline when underside sits firmly on compound slide.

It has been nessecary to measure that precisely and I did it this morning

I did it by turning a scrap piece of alu so that it could go over compound slide.

A toolbit and a feeler gauge of 4.08mm could just pass under the 39.68mm round.

39.68 divided by 2 is 19.84mm plus the stack of 4.08 mm gives a centerheigth of 23.92mm over compound slide surface.

The he next turning was made 47.84mm and a single layer of kitchen alu foil can go between.Two certainly not.

Foil is very close to 0.01mm.

My centerline is 23.93 or 4 mm over compound slide.

Edited By Niels Abildgaard on 06/06/2020 20:50:33

Succesfull way to make a chuck unstuck for me was a spindle holding tool copied from this australian picture.

I used oak instead of aluminium for the two blocks.

Chucker unstucker

When I first got the lathe the 3 jaw were really stuck and I sepparated it from backplate and machined plate away.

One hour work and a new backplate was 15£.

Second time the shown tool copy did it in a second.

I found a picture of my Boxford when space was not a problem

1.1kW six pole

If You have the space do like this.

SuperBox

Motor was a 1.1kW 6 pole and the inverter had fallen of a lorry.

Sell the backgear parts (You do not need them anymore) and You end up with a usefull lathe and cash in hand.

In my Boxford days with VFD I found that a 1.1kW 6pole motor with a 60mm V belt taper lock on motor and the existing one (ca 90mm) on spindle would do anything in cooperation with a HuanYang 2,2 kW inverter.

I only used back gear for spindle locking while changing of chucks.When I forgot to release, (more than once) motor would turn and belt slip.The combination enabled a 3mm wide parting of tip on 100 mm mild steel.