Thread: How to machine a ball screw
I've just received some Chinese 1204 ballscrews that I ordered a couple of weeks back for the CNC conversion project on my Chester 16V mill. I bought them with no machining because I thought I could just machine the ends myself to fit the mill. I knew the screws would be hardened but I didn't appreciate just how hard ! My regular HSS lathe tools just bounce. Is it possible to machine these ballscrews with carbide inserts or should I find a machine shop to grind them for me (though that would probably cost more than the screws themselves).
Any suggestions would be appreciated
Have a look at this thread.
I did a 1604 ballscrew for a chap on here the other week
Just used a carbide tip it did bounce around a bit but once you get under the crust its ok
it depends on your lathe's power. I have machined ends on my little chester using carbide tipped tool
You do need to take a deep cut starting at the face of the screw. It will glow red and so keep a fire extinguisher handy.
I have not tried to machine ballskrew ends yet but on other hardened stuff I just put it in the lathe and grind the first bit off with a handheld angle grinder while its spinning so you don't get it out of round too far and then machine from there. Depending on how tough the steel on the inside is, you might get away with HSS tooling once you grinded away the chrome and thin case hardened layer.
This could be the perfect opportunity to build a toolpost grinder for your lathe ;-)
On reading the previous thread on this subject (http://www.mycncuk.com/threads/2057-...ne-ball-screws), it seems to me that I have two viable alternatives.
1. get them ground down with a cylindrical grinder (but that still leaves me with having to get a m8 thread onto the end), and would probably cost a fair bit.
2. drill into the softer core (which I have found that I can do) and shrink fit or loctite an extension which I can them machine to suit
I'm not too keen on trying the annealing route without knowing what type of steel I'm dealing with, though I may try it on a sacrificial end. One ballscrew I got is about 80 mm longer than I need so if I mess up just the tip I can cut it off and try again
I'll have a go this evening and see what happens
I have the same little lathe but have uprated the motor drive electronics. The lathe is good enough for hobby precision ballscrew machining if you use carbide tooling. I have done this.
The other option is to anneal the portion of the screw you wish to machine. Wrap a wet rag around the portion of the screw you do not want to heat. build a little brazing enclosure out of 4-5 bricks, use a brazing torch or a plumbers torch to heat the end. You need to get it cherry red and let it cool at it's own pace. If you do not keep the screw cool, there is a chance it will warp but this can be rectified later too.
Again, I have done this with satisfactory results and the screw machines like mild steel.
As to the ballscrew, I will try the annealing trick. I have about 3 inches to play with so even if it goes wrong I can just cut off the bad bit and start again..
As a matter of interest, after annealing, did you cut with carbide or would HSS do ? Reason I ask is that I don't have any carbide tools, but have lots of HSS available.
I used carbide tooling. When it is properly annealed however you can file the section you heated, so I imagine HSS should be fine.
IT is a good investment to buy some indexable insert tools and a good toolpost for the DB7.
I swapped the motor drive out for a Parker SSD DC drive after the original motor controller blew up literally. It give very good torque at low RPM and is fully adjustable.
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