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View Full Version : Made some insert holders last night.



terry_g
10-25-2009, 12:40 PM
Someone had given me a box of Kennametal triangular inserts. I can't read the part number on the box but they are negative rake inserts. I made these insert holders from 5/8" keystock last night. I angled the insert down at five degrees.I tried one out on some mild steel they seem to work quite well.
Can a good finish be achieved with this type of insert?

Terry

http://farm3.static.flickr.com/2520/4043242986_17d3268dd6_o.jpg

http://farm3.static.flickr.com/2667/4043243424_ca0b70554c_o.jpg

Black_Moons
10-25-2009, 02:58 PM
yes good finishs can be achived with those inserts and metals given the CORRECT SFM (really fast usally.. like 300+) and cutting depth and feed and a good day. Till the insert gets a microscopic chip anyway.

HSS is usally easyer to get good finishs with for hobbiests.

Small warning: Any 'slack' around the insert can allow it to suddenly rotate a few tenths of a degree and start cutting at a diffrent depth/position.. though iv only experianced this myself when doing facing cuts and the insert passes the center point of the work.

beanbag
10-25-2009, 04:24 PM
If the insert has a tapered screw hole, perhaps you should use a screw with a taper as well.

Black_Moons
10-25-2009, 04:57 PM
Or put a taper on your screws. Iv seen that done before in a lathe.

tattoomike68
10-25-2009, 05:47 PM
Unless you make them hard they wont hog off anything, the inserts will push metal and twist them up.

They will work fine for light fast aluminum cuts and and plastic work. They wont hold up to turning steel like a real tool will.

If you want the project to go farther then learn to case harden them then they will perform better anyway. thats a cheap way to make them better.

good luck, harden them up and you have some good tooling. :)

JoeFin
10-25-2009, 10:05 PM
Are you guys kidding ?

I've been making my own insert holders for years and they Hog metal just fine - 303 stainless, Inconel as well as Al. Never had any of the problems you guys are decribing. I do how ever harden the metal and then run it through the surface grinder. I couldn't imagine trying to get an HSS bit to hold up under those conditions

http://i198.photobucket.com/albums/aa83/Freakindj/inserts008.jpg

Pictured above is Prehardened Stainless Steel being turned down on a Shop made tool holder with a A2000 grade insert

John Stevenson
10-26-2009, 05:25 AM
I do these commercially and the difference between home made and commercial is very slight.

http://www.stevenson-engineers.co.uk/files/lathetools1.jpg

These are full pocketed ones, i.e. supported on two sides.
Where they differ is they are milled in this case with a 10 degree tapered cutter to match the insert.
The pocket is slightly less than the insert depth so the unused edges don't get rubbed on the tool.
There is also a relief pocket in the corner, again to protect unused tips.

These have a bridge and clamp fixing but if using a central screw drill and tap the hole very slightly off centre and towards the back edge.

This has the effect of pulling the inset back onto the edge when tightening instead of locating around the screw which may give a bit of slack.

J&L sell tapered cutters in different angles off the shelf.

These then go for case hardening to 25 thou and hot blacked.

No reason at all to make your own holders but make sure you either buy 3 or 4 packs of tips or that they can be obtained cheaply before you start, nothing like investing time into a holder that's too expensive to feed :D

These tools go out on hired boring machines and when they come back they are always missing, they are charged for as consumables but the hire company got fed up of spending 55 to 65 per hire on a small piece of what is basically square steel.

.

beanbag
10-26-2009, 06:46 AM
but if using a central screw drill and tap the hole very slightly off centre and towards the back edge.

This has the effect of pulling the inset back onto the edge when tightening instead of locating around the screw which may give a bit of slack.


.

Nice work on the toolholders, and thanks for the tips.
If you make the hole slightly offset, doesn't that stress the insert?

Black_Moons
10-26-2009, 09:34 AM
awsome looking holders.
I thought the flexability of steels was more or less the same?
Should'nt the only way a mild steel holder fail is possabley the insert denting the insert holding area itself?

lazlo
10-26-2009, 10:15 AM
I thought the flexability of steels was more or less the same?

That's right -- the modulus of elasticity (the rigidity) of all steels is nearly identical, and heat treating makes virtually no difference in rigidity.

But it's nice to case-harden toolholders to minimize the set screw bites...

beanbag
10-26-2009, 02:06 PM
modulus of elasticity is the same, meaning that the materials have the same "spring constant". But as you harden, the yield strength goes up, meaning that it takes more force before the material takes a permanent set. However, brittleness goes up also, meaning that the chance of catastrophic failure increases also.

So to summarize, the difference between a hardened vs non-hardened toolholder:

small forces: they behave the same
medium forces: The hardened toolholder springs back while the non hardened one takes a small set
large forces: non hardened one is bent and hardened one is snapped

case hardening is a good way to go

PS: I'm not a mechanical engineer, I just made all of this up right now

I've made tool holderes out of non hardened steel, and a crash will take out both the insert, as well as jack up the pocket of the holder. I'd like to try a hardened tool holder, in the hopes that a crash will only take out the insert.

digger_doug
10-26-2009, 02:32 PM
John,
Those holders are very nice.

Could/would you sell them to us ?

J Tiers
10-26-2009, 10:29 PM
I think the issue with case hardening is nothing much to do with either bending OR breaking of the shank.

It would be about the insert pocket.

A soft metal pocket will be hammered until it isn't flat anymore, by interrupted cuts, variations in materiel, etc, etc, etc. Eventually, you may snap inserts because the support is bad, or get problems from the insert wobbling.

The insert pocket on a hardened holder will not be hammered out of shape, and so it will last better.

dp
10-26-2009, 11:04 PM
The insert pocket on a hardened holder will not be hammered out of shape, and so it will last better.

They can be replaced in 30 minutes. Probably not that big a deal if they're not hardened. None of mine are and they're doing fine. And when they're beat to death I'll saw the ends off and remake them. If I'm still around.

J Tiers
10-26-2009, 11:10 PM
They can be replaced in 30 minutes. Probably not that big a deal if they're not hardened. None of mine are and they're doing fine. And when they're beat to death I'll saw the ends off and remake them. If I'm still around.

No quarrel with that (surprise...... ??). Just commenting that the original matter of hardening talked of case hardening.... which doesn't necessarily affect the bulk properties, just the surface.

It's the only thing I can think of that is legitimately different in an important way for case hardening. Surface is not as easily deformed

Don't forget..... YOU are away chasing hackers and goofy users (assuming you are in IT, as I think I recall) or are otherwise employed while most machinists are busy making chips, maybe 2 shifts, on larger machines than either of us has. That puts a tiny bit more wear and abuse on their stuff ;)

dp
10-26-2009, 11:55 PM
No quarrel with that (surprise...... ??). YEAH! :D


Just commenting that the original matter of hardening talked of case hardening.... which doesn't necessarily affect the bulk properties, just the surface.

I suspect that's why they invented the insert anvils. They take the brunt of abuse. While it's Shirley possible to make anvils I think I'd just buy a bag.

ldbent
10-27-2009, 12:30 AM
Where can one buy the anvils and Torx screws(the ones with the underside of the head contoured) in small quantities?
What is the proper way to replace an insert when it has the center post as well as the strap clamp?
Thank you,
Larry

beanbag
10-27-2009, 05:09 AM
Where can one buy the anvils and Torx screws(the ones with the underside of the head contoured) in small quantities?
What is the proper way to replace an insert when it has the center post as well as the strap clamp?
Thank you,
Larry

Some guy on ebay sells insert screws

Glenn Wegman
10-27-2009, 05:43 AM
MSC sells replacement parts, but I'm not sure about enco.

Look through the Indexable Tooling section and you'll find them.

I've never seen a case hardened tool holder. Through hardened to 40's RC, yes, cased, no.

Black_Moons
10-27-2009, 08:30 AM
I wonder how well non hardened + store bought anvil holds up vs hardened.

J Tiers
10-27-2009, 08:41 AM
I've never seen a case hardened tool holder. Through hardened to 40's RC, yes, cased, no.

Exactly... case hardening takes longer, and isn't as 'good". For a large item like a gear, it makes sense to reduce the cost, and more importantly, reduce hardening problems, but the steel in an insert toolholder is relatively insignificant.... hardens fine, quick process, no hassle, and arguably "better".

Someone up-thread mentioned case hardening, and it would work.

As for the anvil, might or might not make a difference. it's the same stiffness, and the same area, more-or-less, and you'd not think it would be a lot different from just an insert.

I frankly don't know why the 'anvil" so-called, exists at all. Maybe someone can explain.

lazlo
10-27-2009, 10:17 AM
I wonder how well non hardened + store bought anvil holds up vs hardened.

Depends on how much you crash. The commercial toolholders have carbide anvils. They take all the impact, and will crack on a good crash. I know :)

Glenn, how do you know that the shanks are through-hardened? I can tell they're at least casehardened by how they resist the set screw, but I've never bothered to cut one open and stick a Rockwell tester on it :)

Glenn Wegman
10-27-2009, 11:23 AM
Hello Robert,

I've cut a couple (Valenite, Kennametal) down from 3/4" shank to 5/8" shank. Used an HSS end mill!

I'll Boink one on the hardness tester after lunch and get a real number as it was just a guess.

lazlo
10-27-2009, 11:28 AM
I'll Boink one on the hardness tester after lunch and get a real number as it was just a guess.

I wasn't taking you to task Glenn, I was just curious how you knew... :)

Glenn Wegman
10-27-2009, 11:32 AM
Didn't take it that way at all Robert, I'm a little curious as to the hardness too, now that you brought it up! :)

Glenn Wegman
10-27-2009, 12:53 PM
Boinked a Dorian and a Kennametal and both were exactly 44RC, so I did not bother with any others.

John Stevenson
10-27-2009, 06:12 PM
The anvils exist because you can fit tapered anvils to take advantage of certain inserts to increase / decrease rake angles for optimum use in a commercial shop.

lazlo
10-27-2009, 06:41 PM
The anvils exist because you can fit tapered anvils to take advantage of certain inserts to increase / decrease rake angles for optimum use in a commercial shop.

John, I have several insert anvils, in lathe tools and in facemills, and they're all flat.

John Stevenson
10-27-2009, 06:50 PM
It's not the only reason, changing because of damage is another but the tapered ones are used a lot on threading as one insert can be setup for different materials.

This is a question that would be better posted on PM.

I don't have any experience of them as none of my tools use them but I do remember reading about them, wasn't on Google as it's always too buy to get on :D

lazlo
10-27-2009, 06:59 PM
It's not the only reason, changing because of damage is another but the tapered ones are used a lot on threading as one insert can be setup for different materials.

I don't have any experience of them as none of my tools use them but I do remember reading about them, wasn't on Google as it's always too buy to get on :D

Sadly, I don't have any cute Google quotes, but I did crash my Sandvik RA-245 facemill shown here, and two of the carbide anvils cracked (and the inserts shattered), but the facemill was otherwise unharmed:

http://i164.photobucket.com/albums/u15/rtgeorge_album/IMG_1641_edited-1.jpg

I found replacement anvils at CarbideDepot.

Using the anvils to tweak the rake angle on a lathe tool sounds pretty cool though.

PaulT
10-27-2009, 08:44 PM
Exactly... case hardening takes longer, and isn't as 'good". For a large item like a gear, it makes sense to reduce the cost, and more importantly, reduce hardening problems, but the steel in an insert toolholder is relatively insignificant.... hardens fine, quick process, no hassle, and arguably "better".

In some cases case hardening is better. For example where you want contact areas on the part to be as hard as possible to avoid getting distorted from local pressure but in the event of an high overload you would prefer the part to bend and stay in one piece rather than to fracture into two.

Paul T.