Reply with QuoteVery cool. I need to get into thread milling this looks like it would be a cheap way to get some practice. Real thread mills are quite expensive up here.
How did you generate the code for the toolpaths?
Tom
Threamilling on the cheap. . .
I had this urge to try to convert a Renishaw MP3 to use on the Pulsar. Inspired by this thread here: http://www.cnczone.com/forums/vertic...robe-head.html
But it needs an adapter plate to connect to the TTS system.
Here's my mockup of the probe and adapter (electronics to be done later):
My idea was to use a cheap ER20 collet chuck and thread it onto the adapter plate that the renishaw screws onto.
So I needed a way to create the ER20 thread (M25 x 1.5).
Since I don't have a true threadmill, I decided to try using a lathe boring bar type chucked into an ER32 collet.
Internal Lathe Threading Boring Turning Tool with Blade for CNC Machine Sale - Banggood.com
It seems to work out pretty well, never having threadmilled before. . .
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Re: Threamilling on the cheap. . .
Very cool. I need to get into thread milling this looks like it would be a cheap way to get some practice. Real thread mills are quite expensive up here.
How did you generate the code for the toolpaths?
Tom
Re: Threamilling on the cheap. . .
Tom I just let fusion do it. The tool is 0.450 in diameter - I had it do 3 passes at 125ipm
Re: Threamilling on the cheap. . .
I have a couple of car bide thread mills purchaed from carbide depot on eBay. Two are single tooth and support a range of sizes and pitches. The other is a multi-tooth for specific NPT threads.
The basic code is straightforward to do by hand if your CAM program doesn't handle them. Basically a spiral with each turn varying by the thread pitch. Depending on internal/external threading you may need to program leadin/leadout moves. And as Brian's video shows, you may also need multiple passes at different DOC plus potentially a spring pass at final depth to clean up the thread. One thing I learned is that even the commercial threadmills may not be totally precise as to cutting diameter, so I found it necessary to calibrate each one. Basically started with a conservative DOC and advanced it a couple of thou until I got the fit I wanted.
A threadmill will do any diameter external, but obviously for an internal thread the tool has to fit the hole. For climb milling external threads would be cut top to bottom and internal threads bottom up.
Feeds and speeds would be based on SFM and chipload, but then you want to compensate for the fact that the center of tool is moving at a different feed rate than the cutting tip. So you's got faster than calculated for an external thread and slower for an internal.
Single point thread milling is slower than tapping, but if you have odd size holes to tap you don't need to buy as many taps. If you have a lot of hole, multi-tooth threadmills that do only one pitch are clearly faster (fewer rotations).
An advantage I've found with external thread milling over dies is that there is no burr at the last thread. I use this a lot in making studs.
Re: Threamilling on the cheap. . .
I suppose this occurs for any arcing cut, yet I've never heard of anyone compensating for it. It would be nice if our CAM would automatically adjust IPM based on whether the cutter was making contact on the inside or outside of its arc, no? So HSM profiling would go faster when doing curving profiles and slower when doing curving pockets.Originally Posted by kvom
And to OP, great post! I am in need of a larger threadmill than I currently have, but I'll see if I can hold any of my boring bars first.
Re: Threamilling on the cheap. . .
Here's a discussion of threadmill feeds and speeds. http://www.harveytool.com/secure/Con...s/SF_71000.pdf
In the example (4-40 thread in stainless) the compensated speed for an external thread is 5.4ipm vs 3.15 linear. For internal it's .9 I suspect that for small threadmills the internal compensation is likely necessary to protect a fairly fragile tool. For external it's a question of efficiency in a production environment. For a boring bar in aluminum it's unlikely to matter as much.
