which parting tool?

[daz]

The one I have at present is no good and is destined for the bin. It is a blade type but the tool holder itself keeps letting go of the blade halfway through an operation, not good at all. Doesn't matter how tight I screw up the blade clamp either.
I can get up to a 16.5mm shank if it helps. Would also prefer to spend a little more to get something decent that will actually work.

TIA

daz

[Arbalist]

I use two types, a Glanze insert one for hard materials and a HSS blade type like this for everything else.

http://chronos.ltd.uk/acatalog/info%5fPT0%5f%5f%5f%5f%5f%2ehtml

[awemawson]

Daz,

show us a picture of your current one. A decent design shouldn't let go so lets have a look at it

Andrew

[Stilldrillin]

Daz,

show us a picture of your current one. A decent design shouldn't let go so lets have a look at it

Andrew

Also....... What size/ type lathe are you using, Daz?

David D

[Arbalist]

Daz,

show us a picture of your current one. A decent design shouldn't let go so lets have a look at it

Andrew

If it's like this type Andrew I'm not surprised, I binned the one I had:

http://www.groz-tools.com/index.cfm?md=Content&sd=Product&ProductID=95

[Lew_Merrick_PE]

Daz,

Before you bin your toolholder, take a look at the thickness between the (reamed, I hope) hole and the back face of the toolholder,  It is a common mistake to underestimate the strength of the hinge point of such designs.  Also the top surface should have a step in it to assure that the clamping pressure is located only over the parting tool.  Way too many toolmakers ignore the realities of structural mechanics.

[daz]

Thanks for the replies guys.

Awemawson: Here is a pic from the timterweb


David: I was using it on a Clarke CL500 lathe. I have a new lathe in the workshop now, a Chester DB11GVS to be precise. My boss has also allowed me to take the old Clarke lathe home and put it in my shed  It's not the best of machines, but I have done some decent stuff with it over the years and I know it very well indeed. I will most likely get a new parting off tool for each, as well as a new knurling tool. Am currently looking at the ones from Hemingway kits.

Lew_Merrick: I shall have a closer look at it when I get it unpacked along with the Clarke lathe that is now residing in my shed.

All: The cutting blade comes out no matter the material I am cutting. It always starts off well and gets at least halfway before it starts slipping. Also doesn't matter how fast or slow I run the lathe, or the speed feed. I have tried everything and for the last while have been using the hacksaw to part off while the lathe is running. Not ideal I know, but I know the risks and am always careful. But one of these days I am going to get bitten when the hacksaw slips.

[awemawson]

Maybe I'm missing something (Marbles ?) but it's not obvious to me how the blade in your illustration is supposed to clamp. 

[daz]

There is a screw on the right hand side that is not shown. As you tighten it, it brings the clamp in from left to right. The clamp you can see right underneath the wee thingymajig you use to adjust the height of the tool.
Does that make any sense?

[PeterE]

Daz,

From what you are writing I think it behaves in much the same way as a (too) cheap parting tool I bought for my Unimat clone. My tool looks like this one in the link: http://chronos.ltd.uk/acatalog/info_PTO____.html

It starts off well, but after a very short while it starts misbehaiving like ......  I found that the single "lock" at the front acted like a center of rotation twisting the blade out of position very easily. I could confirm that by locking the blade in place with a clamp at the rear end.

The tool in your illustation also shows a single point lock that also could act as a center of rotation if the recess is too wide, and hence misbehave greatly.

Comparing that design with the one from GHT in his rear tool post design, the GHT blade is held all along its length and the blade recess has sloping edges so that the blade is forced against the bottom of the recess when put under pressure.

A blade like that should be supported at least at two points, one at the front and one at the back to stop it from rotating, that is at least what I have found.

Hope this helps.

BR

/Peter

[unc1esteve]

The pictured holder does not work because there is only one top clamping point.  It is too far from the end of the blade.  The blade moves and rotates and works itself loose.

Recent thread
http://madmodder.net/index.php/topic,9018.0.html

[Jonny]

Shame I haven't found another purpose for these toolholders, got three spare brand new plus one I only use for 1/16" shallow cut ie o ring grooves.

To tighten the things its like driving a wedge on to the top of part tool of variable distance depending on height of tool.


Never had mine work loose when had to use it, the main problem even when grinding up neutral, left hand or right hand with a bought Eclipse blade, it always veered off in direction of that Eclipse side relief. You can see the actual blade bowing plus laterally.

Used Sandvik for years then got handed a load of Iscar, Arno, Manchester, Seco part off tools rarely used on a 5 axis they came from. Got think 7 or 8 permanently setup in qr holders, need more. If you are going to buy one part off tool do your homework as there are that many styles and designs, same with the interchangeable tips not only conventional neutral, left or right hand but different cutting patterns and grades for specific materials.