Recommendation for Tool and Cutter Grinder

I'm looking at buying a tool and cutter grinder for shaping 6mm HSS Lathe tool bits. My first question regarding this is how long does shaping take? I can find lots of guides but no one seems to give a time schedule. The tool below in the most complex thing I need to make (not drawn to scale).

I noticed Grizzly make a tool grinder for £1700 (not cheap) but then I noticed the U3 by some Chinese company is next to identical. You can see the comparison below. Grizzly is to top one. Every bolt and lever are in the same place. I have a bit of a reservation about buying a bit of precision equipment made in China when I have no reviews.

So can anyone recommend a good tool cutter and grinder to make 6mm HSS lathe parts?

Chris,

With the best will in the world, I think that you'd be asking a great deal to produce a tool such as you have intimated in your drawing with the Grizzly - or any other such T&C grinder. I drew the proposed tool (to scale) and to my mind that is a minute size to aim for. You'll need a microscope as well! Look at this:

That's seriously small and I doubt it would last very long. What exactly are you trying to acheive? There's got to be an alternative way to get the desired effect.

I assume that, quoting Grizzly machines, you are located in North America. Those machines are available in various colours and flavours from a number of retailers at varying prices. All seem to do a pretty good job for what they intended to do. See Stefan Gotteswinter's sie and YouTube channel, for example.

I have no experience of them and not much experience of tool grinding in general, but someone who knows will doubtless be along soon to say I'm wrong and tell you how to do it!

John

That shape would be a challenge, and I don't think the grinders illustrated are in any way suitable. A better solution would be a surface grinder, or a T&C grinder like a Clarkson, plus a universal vice and a way of wheel dressing fancy shapes. Altermatively mill the shape.

It's all moot as I agree with John in that the first cut in metal will probably result in the tip going ping. If the width at the top of shape is 0.35mm then the base must be less than 0.2mm, along with a sharp corner as a stress raiser. If the shape was a rectangle and cuts were straight plunges you might get away with it. Easier to make as well; I'd use a mill.

Andrew

We featured a similar grinder in MEW 282/283. Supposedly they were originally intended as universal sharpeners for engraving cutters. Graham Sadler's article covers some modifications to make it more versatile.

You may be better off looking at something like the Worden, which is a pretty quick-build kit and much cheaper while probably being more versatile.

The tool you illustrate looks too thin to be practical, unless you meant 3.5mm? A cutter made from a hacksaw blade would be more practical.

If its 3.5mm modifying an off the shelf parting tool on an ordinary bench grinder with the help of a decent support and a card template would save you about £1680 of your £1700...

Or allow about 10-15 minutes grinding time from a square blank, most of which will be waiting for it to cool down (don't dip it in water as it may crack).

Neil

Edited By Neil Wyatt on 09/09/2019 10:56:22

I'd start with a Minithin or similar insert and see if I could thin that down and angle the corner on a grinder with diamond wheel, thinnest they do is 0.5mm. Even then the angled face if it is being used like a parting tool will want to bend the cutter sideways and it will snap far faster than you can grind up a new one.

.

I have to ask, Chris

[ 'though you may not be at liberty to tell me ]

What would you be doing with a tool like that ?

MichaelG.

Does the tool have to be made in one piece? If the 6mm dimension is to fit the toolpost and is not itself a cutting edge, why not make the tool from a piece of tool steel mounted in a holder. It would be quicker and much less wasteful. Perhaps even mount the toolbit tangentially to increase its strength.

Brian

Miniature buttress thread maybe

Edited By JasonB on 09/09/2019 13:21:02

Don't see how that works? The toolbit as drawn has an internal acute angle on the left, but a buttress thread is simply a lop-sided Acme thread where both angles are obtuse.

Andrew

Depends what buttress threads you look at, I think there is a BS for a 0/52deg buttress thread as well as 7/45deg. The left hand side of the tool would give clearance on the zero degree face. Also a DIN one

Edited By JasonB on 09/09/2019 13:53:08

But that would give a rather rough finish on the flat face, dependent upon the number of passes and infeed increment. Given that the flat face is the important one it would seem sensible to make sure it is smooth and perpendicular to the rotational axis while being less worried about the angled face.

I suppose we'll have to wait and see if the OP enlightens us as to what he is hoping to do.

Andrew

I think I made the shape to complex. Basically, I need to make a mine parting tool because I’m working with small screws. When you make a screw there is a small part of the shaft that is left unthreaded. This means that when the screw is screwed into the hole that the head will not rest against the part instead the unthreaded portion will jam.

So to solve this if I make a mini parting tool I can cut the unthreaded section to the minor diameter of the screw so it fits in the hole perfectly. Gravers don’t really work for this. This is why I need a grinding tool because I can’t buy tools like this. I’ve attached pictures for clarity.

Ah, that's easy. Just one pass with a milling cutter leaving an outstanding rectangle on the left edge of the tool. Presumably the width and depth of the rectangle don't need to be large. No need for a grinder. Have you looked at the tooling mentioned by Jason? What constitutes a small screw? I normally just lightly countersink the mating part, but I rarely deal with anything much less than M3/6BA.

Andrew

The screws are from M1.2 to M0.9. Will a milling cutter cut HSS?

Could be done quite easily with a graver Gravers don't need to be square in section use a lozenge one

Roy

Edited By roy entwistle on 09/09/2019 14:36:59

Yes, although it needs to be carbide. Here's an involute shape milled on the end of a piece of 1/4" square HSS for use in cutting an internal gear:

Excess material and relief was added by hand on a bench grinder prior to use.

Andrew

I suppose I would call that an undercutting tool, just what I use my Mini-thin cutters for but usually when there is more cross section so you don't end up weakening the part too much.

The other solution depending on the depth of the threaded hole is to drill a small way in clearance size so the bit of the shank under the screws head can enter the hole.

As for grinding a tool I would go for something more like this with the end ground across to the desired width as it will be far more robust. You will only be using the tip of it so the rest can be wider, could easily be done an a bench grinder and the flat end stoned on.

Edited By JasonB on 09/09/2019 15:20:59

This is what I use to grind small lathe cutters and carbide tips. I could make a small cutter like you would use by roughing it out on the offhand grinder then finishing it on the diamond wheel. 10 to 15 minutes max.

I can adjust to suit any angle. It was a engraving tool grinder and cost £26.00 on the net. I just had to make the tool plate rest.

David

Can'y you just put a very small countersink in the hole? I always do this when using capheads as they have a radius twixt head and shank. For very small screws like yours, just mount a countersink cutter in a file handle and do it by hand.

Given the size of the screw the projection of the grooving tool only needs to be minute, a few thou.

Starting with a standard parting tool (or one made from a bit of hacksaw) a diamond file, a steady hand, a guide rest, and a microscope and have a go. Each time you get it wrong the parting tool can be got back to square in a few seconds with a regular grinding wheel.