Bending 12mm square mild steel bar

OK.

But the shank on my Diamond toolholder is about 12mm square but the head that holds the cutter is 23mm deep.

Yes Paul, I can get a depth approaching the longer measurement having bent the 12mm bar to achieve this.

It won't be an exact copy but hopefully something near enough. Time will tell.

John

There have been at least two designs published for Tangential Turning Tools.

The first involved milling at compund angles, the second milled the shank at an angle, after the slot for the tool, had been milled.

Bother mwere for 1/8" toolbits.

In addition to making one , a second one was upscaled to take 5/16" toolbits.
Both produced very satisfactory results, comparable to the Diamond Tool marketed by Eccentric Engineering, (which sees a loit of use )

Howard

Ah ha. Penny just dropped. Had not realised a diamond tool holder was in fact a tangental tool holder, ala Eccentric Engineering etc. Thought it was to hold a diamond dresser on a grinder etc.

In that case, to hold a lathe tool bit, you will be far better off to machine a 90 degree V slot in two pieces of steel and bolt them together as a clamp, as Eccentric does and as many of the designs on the net also do.

Bending a piece of 12mm bar at 90 degrees is not going to give you the clearly defined smooth 90 degree surface you need to grip the tool bit that machining will give.

And cutting the 12mm bar ends at 45 degrees and silver soldering together to form the 90 degree groove is unlikely to last for very long. Clamping force applied by the clamping screw, plus the cutting forces transmitted through the tool bit will eventually break the silver solder.

Stick with the tried and true two-piece method with the machined grooves. If you don't have a mill I am sure it could be done in the lathe with the end mill cutter held in the chuck and the job mounted on the toolpost or cross slide with a bit of jury rigged clamping.

EDIT: BUT reading back through this thread, it is unclear whether you are wanting to bend the 12mm bar to make the square hole that the tool bit slides into for clamping, or are you wanting to make the bend in the main shank of the holder than drops the head down below centre height where the tool bit is clamped?

A sketch of what you want to do would be helpful.

Edited By Hopper on 27/05/2023 12:18:00

Hopper, I want to drop the head down so the tool bit is at a suitable height as per the Eccentric holder.

I have made a holder using the square hole method I described and it is fine. The problem is the tool bit is really too high leaving no room for adjustment. I really should reduce the shank thickness but unfortunately this holder does not have the off-set angle that the Eccentric diamond holder has.

Adding a drawing or photo isn't possible just now.

John

The shop made tools clamp the toolbit in a slot, so that it can be set to centre height, jjust like the Eccentric Engineering one. Like the "Diamond" tool, the toolbit slot is angled relative to the body.

The published designs would make life much simpler for you, rather than trying to imitate the Eccentric Engineering forging.

If you want, no doubt some kind soul will tell you nwhich issue of MEW contained the two designs.

Howard

Howard, Thanks for your input. A slot might be possible but it would have to suit the tool bit dimension while a V does not require a sized slot drill. I have tried to avoid a slot design for this reason.

Having tried various mock-ups it has become obvious that I can not make what I want from a 12mm square bar. I shall have to do as Jason suggested and cut the shape from a piece of 12mm thick strip.

Thank you all for this discussion, it has really helped me to understand what I am trying to do.

John

Either that or cut the shank and weld it at the required angle. Welding will be strong enough, where silver solder would not be. Local welding shop might do it for you for a few beer tokens.

Thanks Hopper, I now have a better idea of what I'm trying to do.

John

Michael Cox tangential tool holder. MEW 179. I made both left and right handed versions.

Michael, thanks for the photo. It is a much simpler version from what I first had in mind.

It is obviously the way to make it.

John

Hi,

It's true what they say about a picture.

Bear.........

Hopper, I took on board your advice that a silver soldered joint would not be strong enough to withstand the forces involved in cuting especially intermittently. So I made a joint between two bits of 1cm square mild steel bar. Putting one end in the vice and a lever on the other end, I could feel the bar flexing but the joint remained sound. I couldn't apply enough force to break or bend the bar or joint.

So I'm going to continue with my approach in the knowlege that it will produce a strong tool holder.

John

I on the other hand thought a silver soldered joint would be fine, glad to be proven right

Tony

That's good. See how it endures over time under repeated shock loading. If not used all day every day it probably should do the job for hobby use.

I do tend to be a bit of an industrial-strength belt-and-braces kind of guy. I blame it on years of riding vibrating, bone-shaking, ground thumping old Harleys. As Mr Harley famously said to Mr Davidson "Nothing too strong ever broke".

Edited By Hopper on 02/06/2023 09:56:23

Edited By Hopper on 02/06/2023 09:58:19

Hopper, I can understand where you are coming from. Belt and braces is often a good maxim but I think this time it is a bit too cautious.

This is a rather rough tool holder made roughly as I have been describing.

It is not very pretty but it cuts mild steel like magic. I think because I wanted to prove my idea that I rushed making it not as refined as I would have liked. Machining the V grove was a difficult set-up because of the combination of three angles. The only way I could do this was to machine the grove before bending the holder, this removes one of the setup angles. Another point I would do differently next time is to have the bolt head on the other side of the holder.

Hope this inspires others to have a go.

John

Good stuff, well done. A lick of paint and it will look as good as a bought 'un .

I think a polish up would make a lot of difference.

Quite a complicated machining procedure as I only have a mini-lathe with a milling crosslide vice these days. Still it was an interesting experience.

John

It is amazing just what can be produced with limited resources but plenty of skill and imagination!

Howard