Turning radius on hardinge hc chucker

[ronnrwb]

I have a project coming up turning some titanium baffles for a form1 suppressor build. I have never messed with titanium before. I also have new to me a Hardinge hc chucker that I was thinking about using being multiple parts and machining steps are needed. My idea is to machine an emergency collet to hold the part. The cones on the baffles are going to have a 3/8" radius. I was thinking of using a corner radius endmill to machine the inside of the cone and a carbide radius tool bit for the outside of the cone. Having never cut titanium will this work? If so will c2 carbide like used for aluminum work? Is there a radius cutting attachment for the chucker that would work better if I could find one? Any advice would be appreciated. Thanks

 

[L Vanice]

Hardinge made a "BA" bed adapter that fits the HC bed between the headstock and carriage. The top of the BA has a small dovetail (same size as the DV/DSM lathes) that allows the radius attachment or the slide rest for a DV-59 or the lever cross slide for the DSM-59 to fit and sit at the correct height. BA's are not very expensive, but the Hardinge radius attachments bring pretty high prices. Hardinge made three different radius attachments for the three different dovetail bed widths found on their post-1946 lathes.

If you can make form tools held on the turret do the job, it will cost you a lot less.

Larry

 

[ronnrwb]

Thank You for the response. Ya my idea was to use the 3/8" radius carbide tool bit as a form tool, having not machined titanium before I was not sure if the wide cutting edge would work.

 

[FredC]

Do not get locked into the idea that you have to use carbide. I have roughed in high speed tools then finished them with a brass bar with lapping compound. I do not have a lot of experience with titanium, but I worked for a fellow than ran quite a bit of titanium in multiple spindle screw machines before I worked for him.. We only used high speed tools flooded with cutting oil on those screw machines. Just attached a photo of a muzzle break crowning tool made this way. There is a bunch of glare in the photo but the lapping lines can be seen.

 

[FredC]

Another way to make a radius is to plot out the coordinates and bring a tool to each point. If done correctly you will file it smooth and polish it and get a very good radius. If you are doing just a hand full it is quite effective. More than just a few or a repeat job then a form tool would be best. The attached photo was done on a 9 inch Southbend with the CAD generated table under the part. I made an extra and the customer buffed it to a mirror finish for me. Idea for this came from Guy Lautard's book Tables and Instructions for Ball and Radius Generation I just checked and it was out of print in September. Maybe back now.

 

[eKretz]

I think a form tool on Ti with a thin wall will be very difficult to get to work well. Tool pressure is pretty high on Ti in my experience. I'd aim for setting up some sort of swing cutter for the radius. Plotting does work well but as Fred also noted, is very time consuming if doing multiples.

 

[kenton]

You can also adapt almost any radius turning tool to fit your lathe.
Here is a lantern style radius turning tool I modified to fit my tool post:

 

[L Vanice]

You can also adapt almost any radius turning tool to fit your lathe.
Here is a lantern style radius turning tool I modified to fit my tool post:

The original name for those tools was Shaplane and they are still made. Old ones can be found on eBay, but they are not cheap.

Eagle Rock Shaplane Radius Tools

A precision machining tool designed for creating accurate and smooth radius profiles on workpieces. Available for both concave (inside) and convex (outside) radii, these tools are ideal for metalworking tasks that require detailed shaping.

www.penntoolco.com

Larry

 

[eKretz]

I know of a Hardinge radius cutting attachment for sale but I believe asking price is $650.

 

[jims]

I think you should check out Micro 100 radius tools.

 

[kenton]

The original name for those tools was Shaplane and they are still made. Old ones can be found on eBay, but they are not cheap.

Eagle Rock Shaplane Radius Tools

A precision machining tool designed for creating accurate and smooth radius profiles on workpieces. Available for both concave (inside) and convex (outside) radii, these tools are ideal for metalworking tasks that require detailed shaping.

www.penntoolco.com

Larry

I didn't realize I had anything valuable there. It was given to me with a bunch of other "machining junk" and it sat in a drawer for along time until I had a project come up where I could use it.

 

[ronnrwb]

I think I'll try the form tool first. My thought is to turn the outside profile first to help with rigidity. I can then machine the profile into the emergency collet to help support the part when I bore out the inside profile with the corner radius endmill. If that doesn't work, then I'll buy a radius attachment. I don't mind buying tooling, it's like buying myself Christmas presents.

 

[CarbideBob]

Point swing vs form tool.?
One of these is faster. One of these has a LOT more tool pressure.
With the form tool one can come in front, then out, then side so that all is not cutting until the last bit.
Work your way in.
Gotten napkin sketches and requests for internal rads of 1 inch to be used on a huge lathe. (they are always neutral on top).
Yes, I can make it. I doubt very much that it will work well.
Full contact is a nasty chip and milling it very different than turning it. Think about where the metal has to flow and deform.

"will c2 carbide like used for aluminum work" is confusing to me.
I would never use C2 in aluminum unless I had absolutely no other choice for blanks... C3 good.. C2 bad.
In this yep, high cobalt micro C2 and maybe a coat if you like speed.
Just to make more it confusing some C6 grades like chewing on Titanium which one would not think given there Titanium Carbide content.
Anything above a C3 is a mix, and a mix of all sorts of things in various percentages.

The trend is micrograin C2 base and a coating to do the work. Why? Please do not ask or question the things behind the curtain.
Rabbit hole and go ask Alice. Better yet follow the yellow brick road.
Bob

(PS, I am still trying to understand this stuff so less than 2 cents from the not knowing side and respect for any other views)

 

[eKretz]

It's possible that the form tool might work with extra support baked in. The tool pressure will probably be very high, and Bob's very good suggestion of walking the cutter around the radius while roughing absolutely will help with that.

And Bob, I've used those very large form cutters on big lathes. Once you get to a certain size workpiece you can almost use whatever size form cutter you want, because the work is so heavy and the machine so rigid that they can take all the heavy cutting forces without batting an eye. At times though, still have trouble with chatter. I have often used the exact method you described to walk the cutter around a large radius, it works well, and I didn't think to mention it. Another trick is turning the tool upside down and running the spindle in reverse. One more is to either jog or turn the spindle completely off and bar the work around by hand. In all cases, it's critical to have a razor sharp edge. Also that neutral top rake can sometimes be absolutely imperative - otherwise the tool can get pulled in by the rake and cause an uneven bounce in the finish. (That's not to mention that any change in that top rake will alter the form of the radius - although this is normally not that critical for most applications).