Narrow grooving

[Humph7ey]

I am making a set of pistons 2.65" dia and need to cut ring grooves 0.85mm (0.334") wide and 3.8mm (0.150")
for the top rings.
What sort of tooling would you use? The material is aluminium.
I am using the lathe as a tool grinder but the hss tools that I am making keep breaking. Is carbide the better option?

 

[tim]

hss should be fine as your only cutting aluminium i would try with some wd40 as a lube but really should be no problam

 

[BaronJ]

Hi Humph,

I'm shocked that you are breaking grooving tools. Sounds like you are not grinding them properly.
Please can you post a picture of your tool and the way that you are using it.

 

[Jasonb]

Can you also confirm the width as 0.85mm is very thin for a piston of that diameter and 0.334" very large and neither is the same size?

If you mean you are cutting an 8.5mm wide groove then that is very wide for a single cut do it in several goes with a 2 to 3mm wide tool.

 

[goldstar31]

From what little information is given, I would suspect the parting tools which you are trying to make-- on a lathe(grrrh!) are incorrectly formed and that the better choice of lubricant might- be lard oil. That is traditional stuff.

Flying in the face of those who know better- or who believe that they are, I would suggest that you get a copy of George Thomas's Model Engineer's Workshop Manual and make the rear parting tool which inverts the parting tool and projects it at an angle - downwards, has a vee of 140 degrees along the top( which is underneath really) and sufficient clearance is given to the flanks of the tool not to bind( and break).

The design of the suggested tool allows a continuous ribbon of swarf to be narrowed and then fall out of the way.

Hemmingwaykits in the UK actually sells a couple of kits designed for two sizes of lathe.

Believe me, Thomas thought it out carefully and developed the device from yet another expert's thoughts i.e Ian Bradley, author of many books and part of the Duplex team with Dr N.F. Hallows.

Of course, there are other ways and as you have found out, decent blades are expensive to replace. You pay 30 quid or so for the book, make it, learn a helluva lot and forget it. My parting tool and its holder have been on many lathes - for the last 40 or so years.

Maybe, you could try to make up a decent tool and cutter grinder. I might have helped Noah to build the Ark- but I still use a grinder.

Hope this helps you

Norm

PS
Just a thought or two. The inverted system of cutting actually can compensate for a worn or badly adjusted lathe.


N

 

[goldstar31]

I was looking for something else on GadgetBuilder.com site and was reminded that John Moran gave a lot of information about tool grinding and how he used two very easily constructed jigs.

There is a lot of other useful stuff for most of us.

I'll leave it for you to enjoy

N

 

[lennardhme]

Hi,
You must have a broken hacksaw blade . Make a holder, grind to a tooth, & to width if required.
If it goes blunt, move to the next tooth.
cheers,
Lennard.

 

[WOB]

According to my info, the rings should be approx. 0.060" (1.5 mm) wide for 2.65" pistons. I grind my grooving tools from HSS cut-off blades with about 3 deg. side rake and zero top rake. WD-40 or regular alum tapping fluid works well to prevent swarf from jamming . I have grooved lots of 1" dia. 6061 alum pistons with 0.023" wide grooves with no problems using that tool geometry.

WOB

 

[SmithDoor]

I use a cut off tool bits
You can shape as need
In your case just flat

Dave

FYI
If you not find a cut off tool just use a thinner tool bit and take two cuts

I am making a set of pistons 2.65" dia and need to cut ring grooves 0.85mm (0.334") wide and 3.8mm (0.150")
for the top rings.
What sort of tooling would you use? The material is aluminium.
I am using the lathe as a tool grinder but the hss tools that I am making keep breaking. Is carbide the better option?

 

[doc1955]

I have just used part off blades before ground to the width needed and I have also used old broken endmill shanks and also have taken an circular saw blade with carbide and cut it up to make grooving tools. They have all seemed to work ok. I would guess you are either not grinding them correctly ot your tool isn't on center in the lathe.

 

[Anatol]

@ doc1955
"have taken an circular saw blade with carbide and cut it up to make grooving tools."
love it, brilliant idea.
Love the 6" scale tool height trick too!

@lennardhme
great idea! Someone just broke my metal cutting bandsaw blade so I have lots! I was wondering what useful things I could do with it. Browsing KN Harris on model boilers I saw he made tools out of bits of saw blade. But he assumes everyone can anneal and harden.

 

[BaronJ]

Hi Guys,

That tip with a scale is a very very old one ! FWIW It is also useful when drilling holes in round work pieces.
With care you can easily get within a thou.

 

[doc1955]

Hi Guys,

That tip with a scale is a very very old one ! FWIW It is also useful when drilling holes in round work pieces.
With care you can easily get within a thou.

That is correct it was taught to me at least 40 years ago and I know it goes back a lot farther.
Just another little tip the smaller dia you have in the lathe the more accurate it will be. And yes I have used this to drill a hole through center on the mill also and usually gets me pretty darn close.

 

[Timehunter]

+2 on post#9.
Long flat tip screwdriver tips.
Cheap!
Grind in back rake, plus width, plus side clearance ….
Mess up ….try again......you did not lose much.
Real limited use,..but it works!

 

[Cogsy]

I only ever use parting blades, both for grooving and even carving out one piece crankshafts, although the grind is different for the crankshafts. So far I've never had one break, even with tiny ring grooves ~ 0.035" wide.

 

[goldstar31]

I've been having a further thought or two about breakages.

I don't have the problem but a few points arise. The first is that as your lathe is old, so you might have wear or bad adjustments or are you parting off without a tailstock support or a fixed steady?

All my lathes have steadies.

As an aside, your Pontiacs seem to have old number plates- my eyes are poor and the photo isn't sharp- so could it be 87? I was in Limoges last month.

My son is flying out on Thursday to a nice little village called Varaignes. Lots of ducks and turkeys!

Regards

Norm

 

[Ghosty]

This is one I ground for .025" wide rings, and a T/C 1mm slotting cutter that I use for "E" clips

 

[Blogwitch]

I have never had any trouble with grooving or it's mate, parting off. No matter what material I always use ground up HSS tools.
For small stuff, I don't even bother with side clearances.

These grooves were around 0.040" with varying depths. Notice that the tool is left as wide as possible and only the very tip is to size and depth required. This is to give maximum support to the critical tip.

Just showing the actual size of the cylinders.

And lots of 'em.

John

 

[Hopper]

Use good quality HSS to grind your grooving tools out of. Some of the cheaper stuff available is not that strong when ground down to small cross-sections.

 

[tornitore45]

But he assumes everyone can anneal and harden.

Anyone with a propane torch can anneal and harden up to 3/8" stuff, more with patience and a few extras.

Propane is OK MAP is better
You need quenching oil or water can
At least 3 fire bricks to make a hearth to reflect the heat instead of blowing it away, only for heavier parts.

You can grind HSS but if you need to machine a cutter is easier to use drill rod and harden afterward.