metal stock for indexable toolholder

[brunneng]

I'm going to be doing some internal threading on the lathe and decided I'd add to my slowly growing stock of indexable tooling. I bought a Carmex 08-IR/L-A60 internal threading insert with screw and wrench from MSC. I'm going to make the tool holder as this is hobby, not business and $70-$120 is a lot of $.

I have the geometry worked out in CAD for the tool holder and I was wondering about suggestions for the metal stock to use. I have seen where some people have been using key stock. Is this OK?
The tool holder will be made from 3/8" square stock (it's a small insert 48-16 TPI, 3/16 IC) and will only extend an inch at max.
I don't plan to harden it but I would like to make a holder to last years.

Would hot rolled be better than cold rolled to keep distortion down as most metal will be removed from 2 adjactent sides. Or a pre-stress releved grade? I already have a supply of 12L14, would that work well?

Thanks,
Kevin

[This message has been edited by brunneng (edited 04-01-2003).]

[Thrud]

Kevin

Generally when you get a insert for a specific tpi it is a full thread form (rounded crest and valley) rather than the universal sharp V form inserts. This is a matter of choice. If you desire the correct thread form then get the inserts for the tpi you are doing. The sharp V inserts allow you to use less inserts for a wide variety of threads, but the thread form will not have the crested profile as shown in machinery's Handbook.

As for your boring bar. 4140 (4130 would also work - both can be case hardened) is the material used commercially. A round boring bar is preferred over a square one because of stiffness and resonance. The best holder for your boring bar is one that clamps its diameter, next best is a hole with hold down screws (say, 3 in a row). If this is the method you use, then a clamping flat can be milled along the top on the bar so the hold down screws have a flat surface to bear against. Commercial bars also have a flat on the bottom milled at the proper dimension so the boring bar tip is at a standard height for that bar so it may be clamped in a tool post.

BTW - Always use an anti-sieze compound on the insert retaining screw threads! I use Jet-Jube Kopr-Kote High Temperature Anti-seize. And make sure the insert and seating area below it are spotlessly clean - no metal particles!

[CCWKen]

To keep the cost down, I'd just use a 3/8 HSS bit for the holder. You don't have to buy 3-6 feet of the the stuff and they're cheap. For your depth, they'd work great. You can drill/tap 'em and grind 'em without much trouble.

[John Stevenson]

Kevin,
I make holders up for a commercial application.
see http://homepage.ntlworld.com/stevens...iles/Tools.jpg
Four of these go out on hire with some North Sea boring rigs, when the machine comes back the tools are always missing, either lost or stolen. The company got fed up of paying out $$$ for tools so I make them now.
They are just made out of bright flat bar, what I believe you call cold rolled in the US.
They are case hardened five thou deep and blacked, we use the same holder all the while on our own machines. The blacking is pure cosmetic and the 5 thou case just stops the screws digging into the top surface. For a home shop use this isn't really nessesary.

Just go with it, it's not rocket science and I'm amazed that companys still manage to charge what they do for a holder.
I have seen some of the cheap Chinese ones but so far they haven't got the geometery right and but it's only a question of time.

John S.

[brunneng]

Thanks guys.

I wasn't sure if there was a resaon why some internal holders are round and some are square.

I suppose that I could take a square bar and cut the seating for the insert in proper alignments then chuck it in the 4-jaw and turn the area in between the insert and clamping end and offset back from the front edge for clearance. That way the flat clamping area would always set the tool correctly but I'd still have the round bar for the reasons Thrud mentioned.

I'm making it to use in my QC Holder which holds 3/8" in both square and rounds (screw type). I haven't started making my own QC holders yet but I do have the stock to start with. I even thought about making an insert holder that directly mounts to the QC itself.

JS- Yeah, I can't understand the prices some things cost sometimes. Once the machines are set-up it can't cost that much to make the holders, but I guess demand and volume sets the price. I can understand the pricing on some of the inserts with the complex grinding done on them but most of the holders are just a pocket. A couple of jigs and a home shop could produce a large quantity of them. And if you're set-up for CNC...

Ken- how do you tap a hardened HSS toolbit?

[CCWKen]

I don't consider myself an Ex-spurt, but I do know that if you can grind it, you can drill it (drill press). And if you can drill it, you can tap it. And that's with the "cheap" Tin coated drills and taps I have. At least that's the way it's been working in my shop.
I do like John's method though. Key stock is CR and cheap too. Just go with what you have or can get (make or buy). Making tools now for jobs "forever" is a lot to ask. Your machines, jobs, hobbies etc. can and will change over time. Take it from an Ex-spurt.

[SGW]

Well, *I* sure can't drill/tap a HSS toolbit....

For tool holder material, take a look at the "heat treated" 4142 stock that's sold by MSC and otehrs. I think you could do a really nice job with that. I've used it a bit and found, with sharp tools, it machines to a beautiful finish. You need to take it a bit slow and coolant helps, but I found it quite nice to work with.




[This message has been edited by SGW (edited 04-02-2003).]

[Thrud]

SGW:
Well, *I* sure can't drill/tap a HSS toolbit....

What? You want some meatloaf tipped drills & taps too?

[darryl]

Thrud, you and I can both cash in on this one! You sell the meatloaf tipped taps and drills, I'll sell the week old dirty dishes crud coated grinding wheels to sharpen them!