Getting small internal threading bars in a hurry

[TGTool]

I'm probably in the crusty old fart category. Back in the late 70's when I was in the toolroom they had a Deckel grinder and I think they still had the pantograph but they no longer used it. Same with the rotary head mill. With changing times and shop specialization they farmed out that kind of work. But they'd kept the little cutter grinder and it was nice to have for the occasional special job (some of them Swiss Navy projects). IIRC I still have the little dovetail cutter for an indicator holder that was one of those projects. There certainly is some satisfaction in knowing you can pull something off if you have to rather than feeling completely stymied because you have no good way to get something unique you need right now. Now I've got Quorn benchtop T&C grinder and a special form cutter coming up.

 

[implmex]

Hi TGTool:
There ain't no "probably"...if you can grind a custom cutter, you definitely fall into the "crusty old fart" category, even if you are neither crusty, old, or smelly.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[50BMG DUDE]

Hi 50BMG DUDE:
Yeah, I' saw that video once upon a time years ago.
Thanks for the reminder.
I recall thinking..."what a brilliant idea!"

Then I bought a wire EDM with a rotary axis.

Now I can make some pretty crazy cutters if I need to...BUT:
It's a right royal pain in the ass to set it all up for one simple threading cutter so I went back to grinding them on the Deckel SO and the little home made cutter grinder I built for myself back when I had more time than money.
That was forty years ago...how times have changed.

Back then you had to know how to make form cutters if you were going to be a moldmaker, so I learned the skill along with just about every other toolmaker of my generation.
What I want now is a fantasy...walk up to the machine, program for 2 minutes from a canned menu, load the blank, push the green button, and PRESTO...a beautiful shiny cutter, dead nuts accurate, for almost no effort.

When I can force myself, I can still make a respectable tool...but almost no other shops can do it...they no longer have the gear or the crusty old fart who knows how to work it.
So it's a stumbling block for pretty much anyone who wants to get into the sort of work that I do.
I know of a few guys who went back to "old school"...eKretz has a Monoset (I'm still jealous) so does TKassoc (I'm just as envious), but that's not the norm these days.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

I've got 2 Sodicks in the shop and have made some custom inserts and such, but I'm not good at cutting tapers on them. (I hand code or use the onboard CAM for the wire) - no rotary, that sounds like a treat! -

I have a KO lee T&C with all the goodies and am still learning many of them, especially the radius grinding attachment. It really is cool to be able to make the tooling you need, when you need it.

I'm in far North Idaho up in the mountains, and there are no tooling suppliers within 3 hours drive. I kinda miss being able to jump in the truck and 5 min down the road get whatever I needed in Phoenix.

 

[implmex]

Hi again 50BMG DUDE:
Regarding cutting custom tooling on the wire; here's my experience.
Turning tools are pretty easy compared to milling cutters.

I do have the benefit of having a seat of wire EDM CAM software (Mastercrap) that helps tremendously.
On that subject...it was WAY too expensive for what it does...a friend who posts on here uses an older version of Bobwire and does amazing work with it.
I doubt he paid a tenth of what that seat of Mastercam cost me.
As others (on a different thread) have pointed out, I was stupid!

So, to wire a turning tool:
I first model it in Solidworks with all the clearances modeled in.
Then I pull out a Parasolid and import it into Mastercam.
I prefer to program it using a strategy called "Complex Upper and Lower" whereby I program the upper contour, program the lower contour, put them together line by line with semicolons, and run the code.
This is only for tools where the relief is different on the trailing edge compared to the leading edge...weirdo threading tools are the best example.
Normal form tools just get cut with a single profile and a simple taper command.

Most wire CAM programs can run these complex shapes using a slightly different strategy that makes huge amounts of G01 code, but if your machine can handle it...who cares.
I learned my habit from when I was programming the paths in Mastercam Mill (all I had at the time) and it just stuck.

I'm an old fart who won't change my ways...I still don't know how to text message on an idiotphone, and I won't learn!
My Lovely Wife laughs at me.

Milling tools are more complex to make because ideally you want to wire the secondary clearance too and that involves rotating the tool and running different code for the secondary relief cuts so you don't booger the cut you made to establish the primary cutting edge and relief.
It varies as your profile changes...the relief that's parallel to the axis is different from the relief at right angles to the axis... if you just make them all the same you hack into your primary profile as you transition from radial to axial relief.

So the screwaround factor is immense compared to a lathe tool.
Additionally it makes a crappy cutter compared to grinding if you're making carbide cutters.
The reason is cobalt leaching at the cutting edge, so the carbide grains are not as tightly bound as they should be, and they crumble away early in the use of the cutter.

So I use it only when I must... to get me out of a jam.

On a last note:
I encourage you to take the trouble to get fluent with taper cutting on the wire...I've found it to be a real bacon-saver in the work I do.

In service to that, a CAM system has been of great benefit to me, and although I choked a bit at the price, ultimately it was worth it.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[50BMG DUDE]

Marcus - Thanks for the response!

I've been looking at Esprit, I do have a seat of Solidcam for the mills, and use it daily. I'm thinking about buying a swiss (used Tsugami 20mm) for my next machine purchase. Esprit is supposed to be pretty hot for the wire and also has swiss moudules. I just don't know if I can make myself learn ANOTHER cam package. I just turned 50 and have learned Surfcam, Pro-Manufature, Gibbs, Powermill, and Solidcam. Never been down the mastercam lane though.

As far as the cobalt leaching, is there a tech setting that minimizes this?

Thanks!

Chris

 

[eKretz]

I was going to mention that also Marcus. I've had a few odd contour form tools cut with wire, but didn't care for the tool life one bit. Finish produced on the part wasn't super either. Went back to grinding.

 

[implmex]

Hi again 50BMG DUDE:
Esprit is very widely respected in the wire EDM community, and as with all software, you will learn to overcome whatever shortcomings it does have.
So your choice is solid.

Regarding mitigating the consequences of cobalt leaching, there are two ways I'm familiar with.

One is to kiss the top surface of a form tool with a diamond wheel on the surface grinder AFTER wiring the profile...this will improve the performance of the tool quite a bit.
0.001" to 0.002" is plenty.
I use a fine wheel... 320 grit, resin bonded, 100 concentration.(It's what I happen to have)
For these kiss cuts I often just run it dry (bad practice, I know)

The other is to run oil as the dielectric instead of water.
Vendors specializing in making form tools in carbide and PCD do this.
Some punch tool manufacturers do it too.
Sadly, so far as I know, these are specialized machines with a corresponding price tag.
They are also very slow.

eKretz...I hear you loud and clear.
I had great expectations when I splashed the cash for my first wire.
I was sorely disappointed and don't make form tools for outside customers anymore, because the complaints got to be more than the whole thing was worth.
Whenever I can, I grind too, but your setup with that Monoset is just drool worthy compared to what I can currently muster.
But what I really really want is an Anca or a Walter.
Can you tell, I'm not thinking straight?

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[TGTool]

Wow, there's a poke from the wayback machine. Not long after I'd moved from the toolroom to tool engineering the company decided they needed a wire EDM. And of course they needed the programming and they bought into software that started in France with the US rights having been bought by a couple of the grad students. So we learned to program the wire to match tool designs, mostly dies. Computer hardware was an HP 9825 desktop with a one line display and mini cassette storage. And we paid a couple thousand extra to get the upgrade to 64k memory. How things change.

So Daniel, one of the principles, taught us how to define geometry and then pick the wire path around all the lines and circles. Besides just learning the technicals I learned something about teaching from Daniel. Toward the end of training as he was putting everyone through their paces I noticed there was a tendency to look to Daniel for confirmation before pressing the last button, and at that point Daniel would be gazing up toward the ceiling, giving nothing away, and forcing the poor guy to commit to his decisions. Good lesson. And the software subsequently became Esprit.

 

[Limy Sami]

I'm the opposite, I only bought tools I couldn't make!

 

[implmex]

Hi Limy Sami:
I used to be similar to you...I would default to making something to solve most of my problems, that would include odd sized reamers and all sorts of things I no longer do.
For me the calculus changed when the internet started to make odd tools and custom tools more accessible to anyone.
Now there's not much I cannot buy if I'm willing to wait for it and pay for it.

So my "Make vs Buy" philosophy has changed too:

If I can make a perfectly adequate tool in half an hour (like a miniature stubby boring bar for example) it's not worth it to me to do the whole "logistics thing" I can make it better, faster and cheaper than I can buy it.
I can also get just what I want and I can make one instead of buying three...I don't need to cover my ass against misadventure in the same way.
I can just make another if I bust one.

As soon as I need several to be identical, I always buy...I can get specials from AB Tools that are the same within tenths, and I cannot hope to compete with a "roll your own" solution.
But I have to plan for them and I have to wait for them.
I hate planning...I like making!

I never try to make things that are a single simple phone call away...stock milling cutters are a great example.
Yes I can spiral grind and I know cutters well enough to knock out something that will work, but I can't buy the carbide blanks for what I'd pay for a 1/8 endmill.
Now if I need it to be right hand cut left hand spiral and 1/2 degree back taper, or some other weirdo, sure, I'll set up the gadget and spend the half day it takes.
But obviously this is not the normal case.

Sometimes I'll fake it with a custom I'd never let out of the shop because it's too weird or too crude to expose to the public...my Go To example of that is a two tooth tap and driver I made for a double start 3 mm acme thread.
Here it is:



(My apologies to those who have seen this before and are getting bored with it)

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[eKretz]

Here's a good way to look at it, I think: If the job is for a paying customer and making the tool costs you more at your hourly rate than it does to buy the tool outright, then buy the tool and pass on the cost. If the job is for myself or a friend, I might grind the tool myself, might buy one. At this point, I am mostly working on projects I find fun or interesting, so I'm more inclined to work on grinding a tool myself just for the enjoyment of using my own tools.

 

[farmersamm]

I live about 2hrs from the nearest tooling supplier. Damn right I grind cutters!!

I do mostly one-off's, and it's crazy to buy expensive tooling for one particular application............if you can find the tool you need.

Working with nothing harder than Fatigue Proof, I have no need for carbide threading tools. And, given the low horsepower, less than rigid, lathe I own...........carbide threading tools are just plain stupid. Crappy results.

Same with boring tools. I grind the odd ones that I need.

A drawer full of HSS blanks, from where I buy them(WTT) is the cheapest way to come up with the tooling you need. Whether it be for the boring head, or lathe.

 

[Limy Sami]

I admit to being a bit cheeky, back when I was working full time I'd often price ''special tooling'' in on the job - at about what it would cost (aka plenty) then make the tools in the evenings aka my ''free time'' ...... and trouser the coin.

I worked hard for my skiills and experience, so like the working girls used to say ''don't give it away honey'' and I didn't.

P.S. the tool firms somehow still made enough with out me.

 

[50BMG DUDE]

Marcus,

Love the pics you post of the stuff you do. I used to work in medical equipment design and can appreciate the small little pain in the ass parts.... I'd always try to give the guy that was going to make them the best shot, but I always said "man, I'm glad I don't have to make that"

 

[50BMG DUDE]

The company I worked for made heart stents, and they made all of their own equipment in house, design and build. It was a cool job, for awhile...

 

[cngbrick]

I'm not sure if this is relevant to your case, but about 18 years ago I needed to grind a profile on a carbide boring bar "right now" so I made a mount to attach a toolpost grinder to a knee mill and used a rotary table and the mill table to grind my profile. The DRO gave me position. It was slow but got the job done accurately. I used a diamond wheel and reshaped an old Micro 100 boring bar.

In theory, this approach could be replicated on a CNC mill but you'd have to be careful about grinding dust.

RT

(Oops, just saw 50BMG DUDE posted something similar earlier!)

 

[trevj]

Good morning All:
I had to grind a single point bar for an M2 x 0.4 internal thread that needs to be single pointed to keep it as concentric to other features as I can.
I know you can sometimes buy stuff like this if you're willing to wait for it, but sometimes I'm not or I need something weird that I can't get.
So this bar is 0.058" across the tip (it'll go into an 0.058" hole).
View attachment 379519
It took a long time to make because it's so small and I can't see well enough anymore even with a 10X magnifier to be sure I got the geometry right, so I grind a bit, shadowgraph it, grind a bit more, scope it, etc etc.
Each time it needs to be picked up on the grinder again...a royal and time wasting PITA.

Almost 3 hours to grind this bar...that's a pricey bar but I need it this week and I got it today (nutso customer deadline...the purchaser forgot to include the part this tool was made for, in the order...now there's a crisis)

My question to all of you...if you can't buy one from the store in a reasonable amount of time, what do you do?
Turn down the job?
Bodge something together like I've done?
Make the customer wait?
Pressure a vendor to drop everything and make you a special?

I look at CNC cutter grinders popping out cutters like pancakes and I am green with envy and want one so I can do it too.
But under almost every circumstance, it's a stupid idea for a prototype shop to invest in something like this.

My way still kinda works, but it depends on me...I doubt you could hire this capability anymore, and most shops don't have the gear anyway.

So what do you guys do?

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

Don't let it go to your head, but I think that is fucking awesome!

I very much wish I had someone of your skill level, to teach me along the way! In all seriousness!

 

[50BMG DUDE]

Amen! - I've learned a lot from your posts over the years Marcus! I really appreciate that you share freely.

Lota old crusty machinists never share anything (think that is to preserve their mystic abilities)

I love sharing tricks and methods I've learned with someone who can appreciate WHY it's cool. So much stuff is lost on people today that have NO idea how anything is made or done.

 

[tdmidget]

Micro-100 has them in stock with a 60 degree tip ( UN threads )
But the Metric 55 degree tip does not stock that small.

Can you use a 60 Deg in a pinch?

Micro100

www.micro100.com

There are no 55 degree metric threads. The BSP and BSPP threads adfopted by the ISO are still Whitworth threads. Metric ( SI ) are the exact profile as UN. The old Systeme Francaise was different in having a radius at the crest and gullet but otherwise identical.