Micro insert internal threading?

Getting tired of breaking expensive, solid carbide internal threading tools and am looking at insert tooling.

Looking for the smallest minor diameter tooling possible, found the Vardex "Minipro" line:

Threading | MINIPRO | Thread Turning | Vardex | Products | Vargus

Their "Mini 3" goes down to 5.95mm (0.234") bore.

Anything out there smaller?

Have you looked at Horn Home >> Horn USA, Inc. - EXCELLENCE IN TECHNOLOGY

You are looking for a wrong tool. Instead of ”insert” look for solid carbide boring bars like shown in your vargus link.

Edit: I read the OP post hastily...well I’d then start debugging why the solid carbide bars are breaking all the time.

Limy Sami said:

Have you looked at Horn Home >> Horn USA, Inc. - EXCELLENCE IN TECHNOLOGY

Click to expand...

Thanks, never saw that style of insert before but it looks like they start at 8mm:

eShop - Paul Horn GmbH

The smaller stuff is essentially the solid carbide bars like I've been using, but with fancy holders.

MattiJ said:

You are looking for a wrong tool. Instead of ”insert” look for solid carbide boring bars like shown in your vargus link.

Edit: I read the OP post hastily...well I’d then start debugging why the solid carbide bars are breaking all the time.

Click to expand...

Not breaking them "all the time" but I have to do some deep internal threading at times and it seems if you don't breathe just right they break.

Yup, I'm threading at 29.5* and not "plunge" threading. It gets old fast.

I'm using "Micro 100" 1/4" and 5/16" shank tools:

Hi Terry:
Have you factored in the reality that small insert bars are typically even MORE fragile than small solid carbide ones?
I've had poor success with insert bars in the 1/4" diameter range...everything is so damned tiny that even looking at it cross eyed risks trashing it.

Having said that I've got to say that buying solid carbide ones is awfully pricey and I baulked at going that route too.

So I learned to grind small bars efficiently and now my problems are over.
I can knock up a single point threading bar that's exactly what I need in about a half an hour of quality un-interrupted time on the Deckel and the Cincinnatti style home made cutter grinder.
I have them all dressed up with the accessories I need to whip out a cutter quickly, and I have a Shadowgraph to check it on too.

However, one crucially important caveat...making ONE bar is a doddle; making a BUNCH of identical bars on a manual grinder is one helluva challenge if they have to be consistent within tenths...so all bets are off if you want these for production turning.

If you're doing this a lot as I do, it may well be a worthwhile investment for you too, and it's truly not rocket science; so you can get good at it with just a bit of persistence.

However if you do this kind of work only occasionally, I would just keep buying them from Harvey or wherever, and try, as MattiJ suggests in post #3 to figure out what's going wrong and why they're breaking on you.
I've turned some ridiculously small deep internal threads and I can't remember ever breaking a bar.
The picture shows two kinds of modified 6:32 threads each 0.400 deep and they were single pointed with a custom made bar

I have fucked up a fair few threads though.

Cheers

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

Terry Keeley said:

Thanks, never saw that style of insert before but it looks like they start at 8mm:

eShop - Paul Horn GmbH

The smaller stuff is essentially the solid carbide bars like I've been using, but with fancy holders.





Not breaking them "all the time" but I have to do some deep internal threading at times and it seems if you don't breathe just right they break.

Yup, I'm threading at 29.5* and not "plunge" threading. It gets old fast.

I'm using "Micro 100" 1/4" and 5/16" shank tools:

Click to expand...

I don't like that style of cutter because it is not meant to be sharpened much and has no top or back relief. In other words, it has ideal geometry for brass, not steel. I use Bokum or Komet internal threading tools, which are spiral form ground to 60 or 55 degrees so that you rotate them and grind just the top relief and you can do it many times. Bokum also makes nice boring bard that are sharpened the same way. They come in HSS or carbide tipped and the smallest ones I have can go in a 1/8" hole or thereabouts. I even have a Bokum grinding fixture to sharpen them on a surface grinder, but they are pretty easy to do freehand.

Not a very good website, but here is a link: Bokum Tool Company, Inc.

Grinding info: https://bokum.com/Files/CarbideNeckBrochureComplete.pdf

Larry

For long bores you probably want carbide shank anyways. Last time I checked the Horn carbide shanks were not exactly budget option. Wasnt able to find pricing for vardex, given its single-source speciality with prices nowhere to be found I’d expect that they ask for your kidney.

I have been using Horn superminis as these are occasionally available at home shop harry prices used&resharpened from ebay for few bucks per piece. Suprisingly I haven’t butchered single one yet.

implmex said:

Hi Terry:
Have you factored in the reality that small insert bars are typically even MORE fragile than small solid carbide ones?
I've had poor success with insert bars in the 1/4" diameter range...everything is so damned tiny that even looking at it cross eyed risks trashing it.

Having said that I've got to say that buying solid carbide ones is awfully pricey and I baulked at going that route too.

So I learned to grind small bars efficiently and now my problems are over.
I can knock up a single point threading bar that's exactly what I need in about a half an hour of quality un-interrupted time on the Deckel and the Cincinnatti style home made cutter grinder.
I have them all dressed up with the accessories I need to whip out a cutter quickly, and I have a Shadowgraph to check it on too.

However, one crucially important caveat...making ONE bar is a doddle; making a BUNCH of identical bars on a manual grinder is one helluva challenge if they have to be consistent within tenths...so all bets are off if you want these for production turning.

If you're doing this a lot as I do, it may well be a worthwhile investment for you too, and it's truly not rocket science; so you can get good at it with just a bit of persistence.

However if you do this kind of work only occasionally, I would just keep buying them from Harvey or wherever, and try, as MattiJ suggests in post #3 to figure out what's going wrong and why they're breaking on you.
I've turned some ridiculously small deep internal threads and I can't remember ever breaking a bar.
The picture shows two kinds of modified 6:32 threads each 0.400 deep and they were single pointed with a custom made bar

I have fucked up a fair few threads though.

Cheers

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

Click to expand...

I know you're right of course and have ground many HSS and carbide lathe tools but with just a Baldor 500 it can be a PITA.

Maybe if I had a T&C grinder it would be more "enjoyable" but for the few I do I really can't justify it.

That's where I'm at and was hoping to escape with some insert tooling. I've gone that route for almost everything else except small (1/2" or less) boring and single point internal threading and am very happy with the results and costs involved.

It looks like the Verdex "Minipro" is the best I'm going to do, they're 4mm IC threading and boring inserts can work into bores of 0.240" & 0.230" respectively.

https://www.vargususa.com/portals/0/Docs/catalogs/eng/VARGUS-MiniPro Catalog inch.pdf

Now i just hope they don't cost me a kidney like Mattij says!

L Vanice said:

I don't like that style of cutter because it is not meant to be sharpened much and has no top or back relief. In other words, it has ideal geometry for brass, not steel. I use Bokum or Komet internal threading tools, which are spiral form ground to 60 or 55 degrees so that you rotate them and grind just the top relief and you can do it many times. Bokum also makes nice boring bard that are sharpened the same way. They come in HSS or carbide tipped and the smallest ones I have can go in a 1/8" hole or thereabouts. I even have a Bokum grinding fixture to sharpen them on a surface grinder, but they are pretty easy to do freehand.

Not a very good website, but here is a link: Bokum Tool Company, Inc.

Grinding info: https://bokum.com/Files/CarbideNeckBrochureComplete.pdf

Larry

Click to expand...

Thanks, looked at Bokum and agree they're better than the micro 100 I've been using but still looking for insert tooling.

Dunno why they don't add some rake to the top of those inserts, might be why they like to grab so much...

For a one off it seems like I could take a tap and grind off three of the four flutes. Then grind off most of the teeth on the remaining flute. Good use of a worn tap since most of the wear is in the front teeth.
Bill D
If you take off all but one tooth you could cut any pitch.

Hi Bill D:
Yeah, that's a time tested approach, and for many threads it works well enough.
However, being able to make a custom bar from solid carbide quickly and accurately is what enables you to nibble out the edge-of-the-envelope projects too.

Once you get close to the limits for depth to diameter especially with smaller threads, or ACME threads or multi start threads etc etc, every tiny bit of advantage you can harness helps you disproportionately.
Sometimes just having 0.025" less stickout, or an accurate oval cross section bar just under the minor diameter is the difference between getting away with it, and failure.

You can spend hours scrolling through the catalogues trying to find the best compromise; I've been there and I'm glad I don't have to anymore.
Buying customs makes sense as soon as you need repeatability from bar to bar, and many of us can point to our favourite tool grinder as soon as we need that production capability.
However, being able to specify what works with confidence is super useful even in that case, and I find it reassuring to have actually run the bar geometry first before I commit to having a thousand bucks' worth ground up for a production job.

There was a time when every decent toolmaker could grind cutters...it was a common part of the job.
Now most look to the catalogue for all their needs.
This is the smart and most economical way forward in many cases, but the general loss of those cutter grinding skills limits us badly as soon as we can't just look up and buy what we need.

So call me an obsolete old fart, but I just can't bring myself to abandon my Deckel SO and my other grinder even in this CNC-everything world, and it makes me recommend investing and learning whenever I see a thread like this pop up.
Above all, it's not very hard to do...many otherwise really skilled guys have just never been taught how so it's not even an option in their minds.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

I don't have anything specific to add to the threading approach, but I have found with small cutters, it is all about baby steps. Slow is smooth and smooth is fast (think that is how it goes ) It is a whole different mindset than using 3/8-1/2 cutters, just as I would imagine a different skillset when using 10-12" dia shell mills.... just have to alter your thinking a bit.

Contacted Vargus USA and they have all I'm looking for in stock, they even quoted "list" pricing.

Carbide boring bars list at about US$230 ea. with the steel bars 1/2 that price.

Threading inserts are US$27.50 ea (pack of 5) and boring inserts are US$17.43.

Not cheap but obviously quality shit.

Now to see what my Kanukistan distributors come back with.

Not as bad prices as I expected but not freebies either.
Small solid carbide boring bars are sort of pricey compared to endmills considering how simple they are. Even chinesium ones cost real money when solid carbide endmill big enough for boring bar is only like 3usd per piece. Niche market compared to endmills but stil..

MattiJ said:

Not as bad prices as I expected but not freebies either.
Small solid carbide boring bars are sort of pricey compared to endmills considering how simple they are. Even chinesium ones cost real money when solid carbide endmill big enough for boring bar is only like 3usd per piece. Niche market compared to endmills but stil..

Click to expand...

Must be some wiggle room as even MSC discounts about 10%:

https://www.mscdirect.com/product/details/71973911



Any idea why my link redirects to the cookie?

It's item 71973911 at MSC.