What's new
What's new

Manual tool grinder recommendations

TheGreatJon

Plastic
Joined
Dec 15, 2015
At work we have a Swiss lathe that we use for prototyping parts with a complex thread geometry (undercuts and eccentric reliefs). The implication for this discussion is that we end up breaking a lot of inserts.

I'm not the machinist (and therefore relatively ignorant in these things), but I help out from time to time when the shop is overloaded. In the hopes of cutting our own carbide inserts, I have been looking at several small manual tooling grinders. I'm currently looking at a couple of Deckels, which seem to be very compact and well reputed. I've also looked at a somewhat larger Makino C-40.

Having never done any tool grinding, I'm not sure if these machines are good options for what we want to do. Assuming that the undercuts and small sizes are the most limiting factors I've attached a neutered image of one of our smallest threads. Would either machine be capable of cutting the requisite inserts?

2.7 Thread.jpg
 
That seems a tough design to consider making any inserts. Some times one can resharpen by top grinding an insert if taking of top surface will leave the form still able to make a specification parts.
This process you run the inset about half life, perhaps a .010 wear land is the end of insert life so you pull the insert at .005 wear and take off .005 to make it sharp but still in part specification.

The other option is to consider productivity verses tooling costs. RE: if I run 10% slower will I get more parts per dollar because my tooling lasts longer.

You might show the actual insert, and what area/how you wish to sharpen. a surface grinder might be tha better choice.

QT: [we end up breaking a lot of inserts.] that is not good. hard on scrap quantity, the set up and perhaps the machine..good to make the most solid set-up and predict a target number and pull the insert before it breaks.
 
Can't really give any advice on small tool grinders other than the small deckel SO grinders are fantastically adaptable. I'm wondering what the reason for the undercut in the thread is? I'm guessing, with the reference to 2.7 on the drawing title that this might be a surgical implant?
 
Interesting thread, if inserts are available for that form, probably the way to go, it looks like alot of strain could be reduced on the threading tool if most of the material is removed first with a separate square nose tool.
The cutter grinders, the little Deckel, Gorton and other similar machines are for engraving machines, mostly useless for what you need. The Makino you mentioned I believe is a standard full size tool and cutter grinder, more in the direction I would look.
A t&c grinder with a workhead,maybe if photo bucket works,


The latest pbucket trick, out of focus. I will never pay for their service.
 
likely you will need a high quality TC grinder like the Makino C-40. or the 32 offered by Donie with perhaps1 320 diamond wheel, or a surface grinder with a 120 or finer wheel running wet for best finish.
Likely need a special vise type holder...
and very likely only able to face grind the insert because grinding the form would be very difficult.

I did run a CNC grinder that could grind the form from a carbide blank but it was in the hundred of thousands of dollars.

It seems a very odd thread and an insert or cutter would have to enter to cut one side, than travel axially and then cut the other side.

I used to do one-ups and few-ups specials with using a surface grinder.. that bit/insert would be tough to grind. The falling off due to below the cutting edge clearance would not allow much stock removal for sharpening.

If in HSS one could make it on a Royal Oak with a crusher wheel and a roll form to crush the wheel. that way the form being radially relified would stay intact with sharpening being grinding off the face only.

Then the change would be in the cutter's axial width but axial travel would be adjusted for the loss.
 
Hi TheGreatJon:
The Swiss shop in California that I worked closely with for a number of years swore by their Agathon grinders.
Another Swiss shop I worked with, liked and used Christen grinders exclusively.
Both of these brands appear to be specifically tailored for the Swiss market.
They are probably worth a closer look.

Single lip engraving cutter grinders like the Deckel SO are a bit of a pain to adapt to this application, but the Deckel S11 is a full featured very versatile and very accurate grinder.

The biggest problem with standard cutter grinders like those offered by B&S, Cincinnatti and KO Lee for example are typically set up for grinding rotary tools like milling cutters, and they're big and clumsy.
They can be made to work, but they are awkward.
An exception is the Cincinnatti Monoset...it can damned well do just about anything, but they're expensive and also a bit awkward to use for turning tools

The Agathons I have seen used most in the Swiss shops I've been in were very quick to set up for grinding turning tools and were very accurate too.

I personally use a shop made cutter grinder I built about 20 years ago.
It's a miniature universal grinder like a Cincinnatti #2 but small, so it's easy to handle.
I've built accessories for it to do most common turning tool grinding tasks, but nowadays I mostly make turning form tools with my wire EDM.
Easy fast and accurate.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
 
I personally use a shop made cutter grinder I built about 20 years ago.
It's a miniature universal grinder like a Cincinnatti #2 but small, so it's easy to handle.
I've built accessories for it to do most common turning tool grinding tasks, <..>

Oooooh, that will drive the home-shop crowd with their Quorns CRAZY!
I'd love to see some pics - says the home shop guy with the tiny TC grinder (Christen AF80)

Hans
 
Hi hansvandongen:
Here you go...pics of my shop built T&C grinder.
For scale reference, the mag chuck on it is 4" x 7".
The table runs on balls and is made of A-2 hardened to 60 RC.
Obviously, it's currently set up for surface grinding.

Cheers

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

On edit: I lied Guys; I just went back in my mind to when I was young and had time to burn on projects like this.
I built this thing in 1991... almost 30 years ago.
Man am I ever getting to be an old fart!

MC
 

Attachments

  • DSCN4953.jpg
    DSCN4953.jpg
    86.4 KB · Views: 291
  • DSCN4954.jpg
    DSCN4954.jpg
    84.7 KB · Views: 238
  • DSCN4955.jpg
    DSCN4955.jpg
    89.4 KB · Views: 190
@MichiganBuck
We only recently got our swiss machine, but it won't be used for production runs. We outsource production and our internal shop is exclusively for prototyping. So scrap isn't really an issue.

The next thought most of you will have is "You have a swiss machine just for prototyping?!!" In brief, we decided to go for it because we were paying out the nose for prototyping because a vendor would have to take their swiss off of a production run to make a few prototypes. Also, because our thread is so complicated some vendors would give up after breaking a bunch of inserts while doing the rear undercut. We hope to use our own swiss to speed up prototyping significantly, and it should pay itself off in about 8 years.

@Renardiere
Yes, we make surgical implants. The 2.7 pictured is a trauma screw for repairing bad fractures. There are a lot of benefits that go along with the undercuts, but for the implant pictured the biggest improvement is the resistance to toggling. Quite a few bone implants end up failing because your typical buttress screws are only designed to resist axial forces. Loads perpendicular to the screw are resisted only by the shaft, while the threads are basically turned into cutting wedges. They can end up wallowing out the bone around it and loosening the implant. Our implants have shown to be vastly superior in that regard.

@Implmex
The Agathon grinders (models 150 and 175) I just looked up appear very similar to the Makino C-40. Is my inexperienced eye just missing something? Or am I looking at the wrong models?
 
my 8 axis Walter cnc grinder could produce illustrated geometry--but it
is large enough to allow 4 adults to stand in enclosure ---3 spindles

with production limitations you outline I would suggest consideration of preform roughing followed by application of bespoke made form grinding tooling
from company such as ATI

diamond or cbn form tooling will reduce angular swings on manual machines which
are accompanied by high rate of non-uniformity from profile to profile

if you limit axis motion to x and y axes---fewer cumulative errors in dimensioning will appear

ATI makes great tooling and I believe still provide no charge quotes
 

Attachments

  • att.jpg
    att.jpg
    98.6 KB · Views: 79
Some pretty small features and corners there.
By my estimation you are into 1200 grit wheels which rules out plated form wheels such as those from ATI.
Minimum corner break on these is .005 inch which wipes out some of your features so your small flats would just become radii.

Most tool and cutter grinding machines are for making round tools not inserts.
On a wire EDM you'd be into crazy small wire.
I'd use a surface grinder in creep feed but this tool will be tough to make and you will need some way to dress wheels.
Bob
 

Attachments

  • Picture 121sm.JPG
    Picture 121sm.JPG
    89.8 KB · Views: 93








 
Back
Top