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Question to the forum,, VFD / spindle HP recomendation to ridgid tap

Posted: Wed Oct 11, 2017 11:13 pm
by RandyL
I have no experience, and I need to figure out VFD for my BP series II knee mill. Currently has the huge framed two horse motor that sits upside down under the head. I have allin1 ordered.
I want to be able to ridged tap, I will need to set up 1/1 speed from what I understand.
what do you suggest,, 2hp is enough? 3hp? 5hp?
Thank you for your help!!

Re: Question to the forum,, VFD / spindle HP recomendation to ridgid tap

Posted: Thu Oct 12, 2017 9:46 am
by Centroid_Liviu
For Rigid Tapping, the Rigid Tapping Option would be needed and an encoder belted one to one with the spindle. For the VFD size the "old" rule of thumb was to oversize it according to your spindle motor. Today's VFDs have come a long way and a 2hp VFD should be sufficient for a 2hp motor. If you keep it to 3hp or under you can also get a VFD that would do single to 3 phase and allow you to get rid of the rotary phase converter if you don't already have 3 phase.

Re: Question to the forum,, VFD / spindle HP recomendation to ridgid tap

Posted: Thu Oct 12, 2017 6:03 pm
by RandyL
Thanks for the response, however that does not really answer the question, how much HP from spindle is recommended to say ridgid tap a 5/8" thread into mild steel?
It does not really matter at this point in the road.

I just ordered a HY VFD 5HP rated, so I will start with that and wire it to the 2hp original BP.
I will repulley 1/1 and get a encoder after I get the machine allin1 Centroided up.. :D
Thanks

Re: Question to the forum,, VFD / spindle HP recomendation to ridgid tap

Posted: Tue Oct 17, 2017 5:47 pm
by cnckeith
the 2hp on the boss will tap that hole no problem.
another rigid tap tip.. is....Tap in HIGH range around 700-900 RPM. some guys think it would be better to tap in low range (more torque etc) but its not.
and for really big taps you can the Rigid PECK tapping cycle. the tap backs out of the hole and then re enters chasing threads and then cutting whatever amount you specify and then doing it all over again till the hole is done..very cool..

but, i don't tap much anymore with my Bridgeport especially big holes (anything over 3/8 of an inch) as threadmilling works so well...thats what i use to make threads whenever possible. its a canned cycle in Intercon. and with threadmilling you will never break a tap in a hole and have to spend an afternoon trying to remove it.

Re: Question to the forum,, VFD / spindle HP recomendation to ridgid tap

Posted: Fri Oct 27, 2017 5:45 pm
by RandyL
Thank you CNCKeith that is what I wanted to know. 2hp is what I will stay with. I have a tecoVFD and a BR I will use.

Is a Breakresistor advisable on a mill?
I am not sure if CAM or conversational centroid software places G code for stopping spindal or how that all works.. i assume it applies some sort of gcode as the original BOSS equipment has air applied spindal brake.

As for "threadmilling" can you expand on this topic as i dont know what that is?

Re: Question to the forum,, VFD / spindle HP recomendation to ridgid tap

Posted: Mon Oct 30, 2017 8:50 am
by cnckeith
always use a braking resistor on a vfd running a spindle whenever possible. ask marty about this one!

https://youtu.be/Ibxn6xPRl3I

Re: Question to the forum,, VFD / spindle HP recomendation to ridgid tap

Posted: Tue Oct 31, 2017 9:24 am
by martyscncgarage
RandyL wrote: Fri Oct 27, 2017 5:45 pm Thank you CNCKeith that is what I wanted to know. 2hp is what I will stay with. I have a tecoVFD and a BR I will use.

Is a Breakresistor advisable on a mill?
I am not sure if CAM or conversational centroid software places G code for stopping spindal or how that all works.. i assume it applies some sort of gcode as the original BOSS equipment has air applied spindal brake.

As for "threadmilling" can you expand on this topic as i dont know what that is?
The VFD takes care of the spindle braking. You program the VFD and its decelleration time. When you stop a spindle abruptly there is a lot of energy stored up and it has to go somewhere. It gets dumped to the braking resistor in order to protect the VFD.

Marty