Ridged tapping Vs Flex tapping
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    Default Ridged tapping Vs Flex tapping

    How are speeds and feeds different when flex tapping as oppossed to ridged tapping?

    Let's say 1/4-20 tap going into cast stainless steel

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    What do you mean by flex tapping? Using a tension/compression holder?

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    My taps usually break when I flex them.

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    Quote Originally Posted by lastrada View Post
    My taps usually break when I flex them.
    How do you get the pieces out of the part?

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    Quote Originally Posted by 007Rob View Post
    What do you mean by flex tapping? Using a tension/compression holder?
    I guess a compression holder. Guys at the shop call it a flex tap holder.

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    For ridged tapping the feed in IPM is pitch X RPM. For a compression holder I usually increase the feed by 5-10% to allow the holder to compress.

    Tap depths are nicely repeatable with ridged tapping, tension/compression tapping not so much. If you’re tapping close to the bottom of a blind hole using compression holders the machine needs time to decel and reverse so the faster the rpm, the more risk of bottoming out and breaking a tap. The feed rate is not sync’d to the rpm like ridged tapping.

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    Quote Originally Posted by Booze Daily View Post
    For ridged tapping the feed in IPM is pitch X RPM. For a compression holder I usually increase the feed by 5-10% to allow the holder to compress.

    Tap depths are nicely repeatable with ridged tapping, tension/compression tapping not so much. If you’re tapping close to the bottom of a blind hole using compression holders the machine needs time to decel and reverse so the faster the rpm, the more risk of bottoming out and breaking a tap. The feed rate is not sync’d to the rpm like ridged tapping.
    Thank you so much. I will keep what you said in mind.

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    Quote Originally Posted by specgrade View Post
    I guess a compression holder. Guys at the shop call it a flex tap holder.
    You sure that they're not talking about a synchro holder? I could see one of those being called a flex holder.

    If so, you just program those as rigid.

    The exact type of holder is not something you want to guess about, unless you like digging out broken taps.

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    The holder expands and collapses as the tap goes into and out of the hole.

    Guys around the shop call it a flex tap holder, idk?

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    Quote Originally Posted by specgrade View Post
    The holder expands and collapses as the tap goes into and out of the hole.

    Guys around the shop call it a flex tap holder, idk?
    A tension-compression holder springs in and out from a dead point mid travel. You program that with normal feeds in both directions, just like rigid, but you need to be aware that you cannot ever be completely certain about where the tap will bottom out in Z, so increased clearance at the bottom of the hole is wise.

    A tension only holder springs outwards only from a hard stop. You usually program those with a slightly reduced feed so the holder extends as the tap screws in.

    Both cases it's a good idea to leave a little more clearance at the top of the hole to ensure the tap screws all the way out before you retract.

    A synchro holder is semi-rigid. It allows for expansion/collapse and twist, in imperceivably small amounts. You just treat that like a rigid holder.

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    Quote Originally Posted by specgrade View Post
    How do you get the pieces out of the part?
    I think that's another whole thread...

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    Quote Originally Posted by aj View Post
    I think that's another whole thread...
    I couldn't find the thread about how lastrada gets the broken tap out of the part.

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    Quote Originally Posted by specgrade View Post
    How are speeds and feeds different when flex tapping as oppossed to ridged tapping?

    Let's say 1/4-20 tap going into cast stainless steel
    .
    extension compression holder and not all holders do both allows tap to move length wise. if machine spindle has backlash the Z stops moving but the spindle can still turn as it slows down. the tap screws itself in extra depth usually can see it turning extra with no Z movement
    .
    often when its free of tapped hole you can see tap pull back from the spring. since spindle turning extra can vary depending on rpm its hard to predict how much farther or extra tap will go into hole.
    .
    a machine that does synchronize tapping Z moves so far per revolution. spindle stops turning as Z stops moving. to the point often if you reach Z stroke soft limit spindle turning and Z moving stops tap still in hole and tap not broken. at higher rpm some machines have trouble getting into sync and machine stops with alarm before it tries to tap hole usually. some cnc just alarm too often at higher rpm tapping and you use slower rpm to tap, that machine can handle with out alarm stopping. some older cnc cannot handle as fast a rpm as they could when cnc was new. troubleshooting why can be difficult. sometimes easier to limit tapping rpm for reliability.

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    Quote Originally Posted by DMF_TomB View Post
    .
    extension compression holder and not all holders do both allows tap to move length wise. if machine spindle has backlash the Z stops moving but the spindle can still turn as it slows down. the tap screws itself in extra depth usually can see it turning extra with no Z movement
    .
    often when its free of tapped hole you can see tap pull back from the spring. since spindle turning extra can vary depending on rpm its hard to predict how much farther or extra tap will go into hole.
    .
    a machine that does synchronize tapping Z moves so far per revolution. spindle stops turning as Z stops moving. to the point often if you reach Z stroke soft limit spindle turning and Z moving stops tap still in hole and tap not broken. at higher rpm some machines have trouble getting into sync and machine stops with alarm before it tries to tap hole usually. some cnc just alarm too often at higher rpm tapping and you use slower rpm to tap, that machine can handle with out alarm stopping. some older cnc cannot handle as fast a rpm as they could when cnc was new. troubleshooting why can be difficult. sometimes easier to limit tapping rpm for reliability.
    Thank you so much. I understand what you are saying and will keep it in mind.

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    Quote Originally Posted by specgrade View Post
    Thank you so much. I understand what you are saying and will keep it in mind.
    .
    sometimes machine have a 2 speed gearbox and tapping at 600 to 700 rpm or high rpm for low gear gives problems but if you use above 700 rpm it works cause machine switches to high speed gear
    .
    older cnc often have certain rpm range where you can occasionally have problems but if you go faster or slower rpm the problems do not happen.
    .
    had a cnc where at certain rpm the machine vibrated and the back tool magazine door would vibrate tripping the safety switch into think door was open and machine would go faster and slower every second as if it wasnt sure to fully shutdown cause when it slowed it vibrated less and so it read door closed and when read closed it sped back up in rpm. often just changing rpm 10% and it would stop doing that. hard to describe. just saying some machines have problems with certain rpm. used to have to put duct tape on back tool magazine door so it wouldnt vibrate so much tripping the safety switch that shows door is open

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    Quote Originally Posted by specgrade View Post
    I couldn't find the thread about how lastrada gets the broken tap out of the part.
    by throwing it in the scrap bin

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    Not all machines have "rigid" tapping so the spindle is not perfectly synced with the feedrate. Our older Hurco's were like that.

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    Quote Originally Posted by specgrade View Post
    How are speeds and feeds different when flex tapping as oppossed to ridged tapping?

    Let's say 1/4-20 tap going into cast stainless steel
    In materials that can be tapped fast, rigid tapping allows much higher RPM to be used. As mentioned in previous posts, the lack of synchronization in floating tapping will not allow high spindle speeds to be used. At high spindle speeds the the spindle is still turning at the programmed speed when the Z reaches the programmed depth. At that point the spindle turns off and decelerates to a stop. During that deceleration, the tap continues to pull itself into the part. The faster the spindle turns, the more revolutions it takes to stop. Then when the spindle starts up in reverse it has to reach 80% of the commanded speed before the Z axis begins moving up. During this reverse acceleration the tap is backing out of the hole yet the Z is not moving.

    In rigid (synchronized) tapping, the control begins decelerating the spindle as the Z approaches the programmed depth and both the spindle and Z stop at the same time. When reversing, the Z begins moving out as soon as the spindle starts to rotate.

    Depending on machine controller, the feed programmed for rigid tapping may need to programmed in the pitch of the thread rather than a calculated feed based on RPM X pitch.

    I have a machine than can rigid tap up to 6000 RPM. Just for giggles I did program some 6-32 x .375 deep in aluminum at 6K. It worked great, but the machine never made it to the full 6K before having to stop and reverse. Probably hit about 4K though. In any case it was fast.

    For 1/4-20 in cast SS, you are probably only going to run ~400 rpm and likely slower depending on what alloy you are working with. At those speeds most machines are not going to have much difference in cycle time between rigid and floating tapping.

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    Another advantage of rigid tapping is that retraction can be made 20x faster. Peck rigid tapping is also possible, if needed. (Talking about Fanuc)

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    We've got two Fadal mills. One ridged and one "flex" tapping. When a ridged program has to be run in the "flex" machine. We have trouble adjusting for "flex" in the program to get the desired results.

    Would it be difficult and/or expensive to turn the "flex" machine into ridged?

    Thank you so much for all the useful replies!


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