Quick change tool holder - what is this groove for?

Does anyone know what this machined ‘groove’ in some of the quick change holders is for / why it is there? Have seen some with and some without.

Probably an undercut to remove any radius corner made by the cutter and to allow the lathe tool to seat against the bottom and side faces.

Paul.

It makes a neat fracture line - as one of my colleagues found out when machining cast iron with a substantial cut on a Hercus 9 inch lathe!

Posted by Paul Lousick on 17/11/2016 04:21:25:

Probably an undercut to remove any radius corner made by the cutter and to allow the lathe tool to seat against the bottom and side faces.

Paul.

Thanks. Those were my initial thoughts! To create a 90 degree seat against the two faces but then was wondering why it would be included on the vee holders. Perhaps they just use the same process as part of a chain even though it’s not needed on the vee holder.

Posted by Alan Johnson 7 on 17/11/2016 04:22:31:

It makes a neat fracture line - as one of my colleagues found out when machining cast iron with a substantial cut on a Hercus 9 inch lathe!

I was worried about that two, it must technically create a weak point than one without.

It might allow sort-of indexing if a thin cut-off type blade were held

It is simply bad engineering practice that creates a classic "notch" that will certainly induce a fracture sooner or later.

Avoid tool holders with this feature.

If an undercut is required, it should be a smooth, rounded shape to reduce stress points.

Edited By Paul Lousick on 17/11/2016 08:58:25

mrbuilder,

I am not familiar with Bison tool holders and would be very surprised if had such a severe sharp undercut as the one illustrated. If they do then I hope Bison do not make any safety critical components!

Avoiding sharp corners is elementary engineering practice. There have been many catastrophic failures of structures over the years caused when this principle has been ignored.

Edited By mrbuilder on 17/11/2016 20:58:14

mrbuilder,

Well I am surprised! I sincerely hope that this holder gives you good service.

It's to make sure any sharp edge on the tool shank or swarf build up doesn't push it out of square with the holder. (otherwise why wouldn't it be on the adjacent inside corner too, clearly indicative of only applying the undercut on the tool seat?)You can see a similar feature on the seats for decent carbide tip holders. I doubt it would break it's quite thick steel. You couldn't apply enough pressure with your hand.

Michael W

Edited By Michael Walters on 18/11/2016 10:59:22

Most of my tool holders, some of which are Bison, have this 'groove'. If something went badly wrong I would rather lose a tool holder than damage the tool post or gearbox.

Probably just a result of the production process and not actually put there for a reason.

Take a look at the machining marks on the lower surface of the tool slot. Can't see it in the pics, but it looks as if the square groove has been rough machined by an end mill or perhaps a side and face mill cutter in a horizontal mill. Both these will leave a bit of an uneven surface for the toolbit to sit on. So it appears they have taken a finishing cut over the bottom face with something like a cheap and readily available dovetail cutter, using the face of the cutter to make a nice flat surface. The nick in the corner is simply the result of running that cutter a tad deep in order to make sure the corner has no step left in it that would foul the tool bit when placed in situ. Remember these are churned out by the hundreds and thousands so each one is not set up individually for milling as we would do at home. Having that nick there ensures none has a ridge in the corner without each one being set up individually to the exact correct position to make a perfectly square corner.

Production engineering, it's how things get made by the thousands. Stress point? Yah probably. But they are so cheap to produce they just give you a new one if it lets go in the warranty period.

Cracker of a stress riser ! I use Bison ones on the DSG and none are like that. I would be very surprised if the one in the pic is a Bison.

Hopper, they could stuff the replacement right up where the sun don't shine if it led to a scrapped component warranty or no.

Why have i got one dixon holder with a morse 1 socket?

Edited By Hacksaw on 18/11/2016 15:39:35

Its the exact opposite of a floating reamer holder. Its carefully designed to hold a machine reamer rigidly and perfectly out-of-line with the lathe spindle.

More seriously, I suppose it's meant to be used for drilling or even reaming but I would have thought getting it lined up will take longer than using the tailstock.

Neil

Exactly what i thought , I've got it because no one else wants it

As I said in an above post the one in the picture is a Bison T00. I have the receipt, the box it came in and a picture of the part number on the front - perhaps I was really fooled! Another member above said they have Bison tool holders that are like this. Yours may be a different size, from a different era... Designs can change over time.

While this makes sense for standard holders, why would it be on their vee holders? Apart from maybe a production process that Hopper mentioned. Or if perhaps if guys use vee holders occasional to hold square tools as well (which I have seen occasionally)...