The Shop > Tools
Boley 4LV
RotarySMP:
I have a 0.55 KW (3/4hp), 3phase, 240V 2 pole motor, driven from a 0.55 kw VFD at between 10 and 70 Hz. The reduction is a bit under 3:1 using THD 9mm belt.
The leadscrew is a 5/8 x .200" rolled ball screw, driven from a 1:2 belt reduction from a modern Keling NEMA 23 stepper.
I have not done much threading, and never to a standard in the sense of three wire measurement or gage. I just turn and try.
My lowest spindle speed is 240 rpm (10 hz). At this speed the motor has bugger all torque, so for the 40mm x 1.5 thread you are in an ugly corner between too little depth of cut causing rubbing, and too DOC causing stalling, and too much spindle speed causes excessive tool wear over the multiple passes required.
Basically any smaller diameters work fine, as you up the spindle rpm, providing increased torque.
I use a 3" three jaw, 4" four jaw and a home made ER32 collet chusk. The worst case was turning the collet chucks own thread, as there was bugger all mass. It is a pretty horrible excuse for a thread. I am suprised it fulfills its function at all. Unfortunately, I can't show you this thread right now, as the colet chuck has a job in it which I don't want to disturb.
The second one is on a mill spindle I have been working (on and off) on making. It has a pretty nice thread except for two nasty chips out of the it.
This size thread is really beyond the capacity of this machine. It took a far bit of experimenting to get it done.
Smaller threads like the M8x0.75 for the Proxxon spindle nose work really well.
http://www.cnczone.com/forums/vertical_mill_lathe_project_log/103610-my_homebuilt_spindles.html
philf:
Hi RotarySMP,
Is there a good reason why the taper roller bearing is the way round it is?
It's more usual to be the other way round so that thermal expansion in the spindle reduces the preload on the bearings - I think that with your design the preload may increase thus putting up the temp and increasing the preload etc. etc.
I have struggled to understand how one pulse per rev can work with threading but reading that you need plenty of oomph so that the spindle doesn't slow under cutting conditions helps me to see how it works.
Cheers.
Phil.
RotarySMP:
This spindle is based on a right angle reduction gearbox I picked up from the scrap dealer.
http://www.cnczone.com/forums/attachment.php?attachmentid=105471&d=1271620622
There are cover plates which bolt on both ends came with a bunch of nice shim. Doing the bearings this way seemed like I could use the shims to easily set preload.
philf:
--- Quote from: RotarySMP on November 26, 2012, 04:29:44 PM ---This spindle is based on a right angle reduction gearbox I picked up from the scrap dealer.
http://www.cnczone.com/forums/attachment.php?attachmentid=105471&d=1271620622
There are cover plates which bolt on both ends came with a bunch of nice shim. Doing the bearings this way seemed like I could use the shims to easily set preload.
--- End quote ---
Hi,
I've just had a look at your drawing and I can't see what fixes the spindle axially within the bearings. Or am I missing something obvious.
I'd still be nervous about any increase in temperature increasing the preload.
Phil.
RotarySMP:
Correct, at that point I had not decided. I have since turned a thread onto the other end of the spindle, and made pair of nuts to fix the inner races.
Beacuse the housing block I am using has no shoulders, I can not reverse the bearings, as nothing would then restrain the outer races.
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