Thread: Milling machine taper confusion (ISO40,CAT40,NT40,SK40,NTMB40)

A factory neighbour's Hafco mill uses what I think are NT40 tooling.
Like these:
Main.jpghttps://www.machineryhouse.com.au/M552

Note the little plastic/rubber ring on the top.


1) I have an arbor with a cracked plastic thingy. Does anyone know what they are called? If they can be purchased?



2) Most of the NT40 I have looked at online do not have that plastic ring. Just a straight metal section, like these:
image.jpeghttps://alitools.io/en/showcase/1pcs...-4000258087880



3) I also have an ISO40. I think there are adapters that screw in BT40s to make them compatible. Like these:
0E7D7DDA-09E7-41ED-B5BB-29C604BD9C11.jpghttp://https://au.grandado.com/produ...drawbar-thread

Does that really make it compatible?



If there was an authoritative reference to all the different standards, I could look this up myself.

Sadly, I haven't found one yet.

They are all the same taper, they just require different draw bars to secure them.

Originally Posted by nigelpearson

1) I have an arbor with a cracked plastic thingy. Does anyone know what they are called? If they can be purchased?

No, but I do know that it doesn't matter if it's missing

I think the plastic ring is only to prevent dinging the spindle taper.
The pullstud makes a BT40 sorta compatible; the thread depth is not great and your drawbar may be too long. I heard of a bloke who bottomed a power drawbar in one, and unscrewed it from the toolholder when he tried to release it. Much consternation, not sure how he got it out. Angle grinder maybe.

They are all basically the same thing, it's just as Peter says - the drawbars are different.

SK is the German abbreviation for taper
NMTB (National Machine Tool Board or some such) is sometimes abreviated to NT
There is now an ISO standard, so that sometimes appears

CAT and BT are a version for CNC machines. They can be used with a longer drawbar on a manual machine

On edit - this place is the most extensive reference I've found - Machine Tooling Specifications

Michael

My 1980's TOS mill is officially ISO40, but I think I've got and use almost every variation of 40 taper arbors.
I've tried to standardise on metric drawbar threads as its a pain to be swapping drawbars.

In addition to what others have written I've found:

• NT40 should be UNC drawbar thread, but some of the cheap import ones being sold online are actually metric (which sort of makes them ISO40)
• One of the flavours (SK40 or CAT40) has drive slots that aren't at 180deg to each other. Its been a couple of years since I modified the ones I have so my recollection is a bit sketchy, but I think that the slots may possibly be narrower too.
  Bottom line was I took to them with a carbide endmill and made them fit my ISO40 spindle.
• Those BT40-NT40 adapters are great - I'm using a few of them. Ideally fit them with some loctite as it is a pain if they unscrew from the arbor.
• Good reference here to 3 main differences between CAT40 and BT40 https://www.cncsparetools.com/new/CA...ol-Holder.html

Steve