Spring Tool Holder

[Hawkeye]

Recently, there has been a fair bit of mention of spring tool holders. The purpose is to allow the holder to flex when the cutter tries to dig in. The flexing is done in such a way that the cutter will bend down and away from the work. Normally, any flex in a lathe toolpost will allow it to flex down and into the work, causing chatter.

The first video I saw on the topic mentioned that they are often used for holding form cutters, such as could be used to make the shaped handles for lathe feed screws. With this in mind, I made mine to take either a standard 3/8" HSS tool or a wider form tool.

I saved a lot of machining by using the portable bandsaw to slab out large sections. This also leaves a few pieces that can be used for other projects.


In looking at examples of factory-made spring tool holder, I saw that some had an insert in the bottom, bridging the spring gap to provide some sideways rigidity. Easy to do, so why not? Note that the spring slot is cut last, since its purpose is to take out some of the natural rigidity of the holder.


The finished tool holder. You can see the side tool slot, which could be used for a threading bit or a small form tool. The third setscrew at the far corner is used with the corner one to hold a wide form tool across the front of the holder.


I haven't cut anything with it yet, so I can't give you a report on how (or whether) it works.

 

[chuckorlando]

Looks good. Let us now how she works

 

[Philco]

Nice job Hawkeye, I too am anxious to see how well it works. I would be curious to know how well it works with a parting tool.
Phil

 

[Bill Gruby]

You sure do nice work Mike. Mine isn't home grown . I modified the QCTP holder for it. Mine cuts threads only.

"Billy G"

 

[Hawkeye]

After I got home from work today, I figured I'd better take the holder for a test run. I poked through the big box of shaped 3/8" cutters that came with the lathe and picked one to try.

It has quite a bit of top rake. A simple round-nose 1/4" wide. I set the speed at 195 RPM, to suit the 1 1/4" HRS stock.


I got pretty aggressive cranking the crossfeed in. It's kind of scary to see your toolholder suddenly bend down and back up again when the tool digs in. I went in about 3/16".

It doesn't eliminate chatter as promised in some writeups and videos, but maybe a neutral top rake would change that. I did manage to clean up some of the chatter by feeding it in to make contact, then let it spin for a while. The flex allows it to feed the edge in gently until it's nearly clean.


While it doesn't eliminate chatter, I think it will be useful when I need to do some deep or heavy form cutting. I may not use it as much as the tangential toolholder, but it will be a welcome addition to the setup.

 

[xalky]

Did you try it without the sideways rigidity insert? I'm just curious to know if the chatter would be reduced without it. :thinking:

 

[Hawkeye]

Interesting suggestion, Marcel. It would be easy to try.