So I am about 3y into my apprenticeship at work and they have been letting me run the CNC mill a bit .I got fairly decent at programming in my last area and now I rotated to a new area( we move every 6ish months to different departments of the plant) We had no trouble tapping on the Hurco mill in the last area but in this area my journeyman likes to tap about 3/8ths deep then finish the threads by hand. so I tried tapping thru the part a few times on Aluminum and it seemed to work fine ( I peck tapped about .250 per peck .750 deep) Today I was using a M12x1.75 on CRS 1018 and the tap broke on me on the 2nd hole ,he said I told you so and showed me the threads and how they were kind of grainie and roughed up on the 1st hole.He says its an Intermittent issue and sometimes it works sometimes it doesn't.We have the spring loaded collet holders .I thought it might be a plunge feed and rpm synchronization issue (possibly with just the metric but I went back and check the TPI in the software Hurco calculates all that for you it was spot on)Can anyone think of any other issues that would cause a problem like this or how to resolve it? He says its been an Issue on this machine since day 1 on this machine Any Insight would be Appreciated ?
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Broken Taps on a Hurco CNC mill
- Thread starter Sjbene123
- Start date
- Replies 14
- Views 1,521
crossthread82
Hot Rolled
- Joined
- Apr 1, 2022
- Location
- Maryland
What kind of Hurco? Are you rigid tapping or using a tension compression head? Why is it not causing problems when he partially taps a hole, if it was out of synch it would booger up even the first couple threads.
VM40 I believe not real sure about the year,I am using the rigid tapping selection in the program. I will have to ask about the holder tomorrow I know its the spring loaded style that compresses not real sure about the exact names. Yeah it tapped .750 deep on aluminum the other day no problems but maybe if it was just slightly out of synch the aluminum might flex just a bit .
Probably just clogged up with chips. If you guys are starting the tap and finishing by hand its obviously very low qtys. If your doing that type of work consider pecking just one turn at a time. Its extremely reliable and still much faster then finishing by hand. Extra min or 2 run time doesnt mean much on some jobs.
crossthread82
Hot Rolled
- Joined
- Apr 1, 2022
- Location
- Maryland
What kind of taps are you using?
Thanks I might give that a try how far above the part do you usally start to let the spindle get up to full speed at 150 rpm do you think .100 is enough
crossthread82
Hot Rolled
- Joined
- Apr 1, 2022
- Location
- Maryland
150 rpm is almost instantaneous. 0.100" is plenty. I usually do 0.050"
Ok so I looked today it's a VMxi30 and I check the thread and it was a spiral fluted tap and it broke in reverse probably .1 off the bottom of the last peck.....I'm starting to think it might be a chip tangling issue .After hand tapping today it seems like if you go to deep there is some resistance when you reverse to pull the tap out
Pattnmaker
Stainless
- Joined
- Nov 2, 2007
- Location
- Hamilton, Ontario
Most of my power tapping over 3/8 has been on a manual mill. But 12 mm 3/4 deep I wouldn't peck especially with a spiral flute. A spiral flute tap brings the chip out the top. Pecking you're breaking off the chips causing them to build up in the flutes.
crossthread82
Hot Rolled
- Joined
- Apr 1, 2022
- Location
- Maryland
Spiral flute taps I would generally never peck tap, since you're kind of defeating the purpose of the tap which is to form spirals of ships that come up and out of the hole. If you are only doing ductile materials like aluminum and 1018 I'd suggest form tapping everything because then there are no chips to worry about.
I've never had any luck going past the initial thread length on spiral flute taps because the chips will tangle up and bust.
This is where I would use a spiral point, tap as deep as you can, then hand tap to depth if necessary.
Not saying this it the issue but you have no torque that low down the rev range. I would up the rev's like mentioned above. One think I've also heard from a coolant rep was is look at the coolant mix, make sure it's towards the upper end of the recommended mix %
