View Full Version : Stupid Question from Newbie

11-15-2004, 10:17 PM
I know what a Morse taper is....but what is an R8 taper...how does it differ from a Morse taper and which is better on a mini mill?

Thanks for your help! This is a GREAT GROUP!

11-15-2004, 10:39 PM
The R8 spindle has a steep angle at the nose and a straight shank over the rest of its length. R8 collets, drill chuck shanks and other tooling are pulled into the spindle by a threaded draw bar which has a nut which protrudes at the top end of the spindle. The R8 spindle has tons of tooling available for it and is pretty substantial.

The morse taper spindles offer a limited choice (compared to the R8) of tooling. Also, the morse taper can be difficult to remove once it has been drawn in tightly.

11-15-2004, 10:39 PM
R8 is a taper that is standard on Bridgeports. It is the most common spindle taper for home size machines, so tooling is more available and cheaper for R8 spindles.

As for capacity, I don't know which one can handle more. I'll leave that to the more knowledgeable folks around here. There are a lot of them.


11-15-2004, 10:51 PM
That explains it....thanks for the help. So if I were to eventually by a mini mill, looks like I want to go for an R8 taper.

I appreciate your help!

Kelly in southcentral Idaho

11-15-2004, 10:54 PM
I had the choice between R8 and MT3 when I bought my RF31 mill/drill - I went for MT3 as everything I had for the lathe would fit it, plus I had never (and have still never) seen an R8 tool whilst browsing in a shop, have seen plenty of MT though. However, in the US things are probably a lot different to here!

11-16-2004, 02:42 AM
Chuck on Morse Taper size 2 on the left, a stub arbour Morse taper 3 in the center and a chuck on an R-8 taper on the right.


11-16-2004, 02:51 PM
kelamigo: you may want to consider MT3, if that's what your lathe uses. It's very useful to be able to share tooling between lathe and mill.

11-16-2004, 03:53 PM
If you have MT3 accessories already then you may want to stay with the MT3 mini-mill.

The MT3 stuff I use is plentiful through Enco, Little Machine Shop, and Grizzly (and I assume others).

MT3 items may need a couple of taps to release from the spindle but if you have to really hit it you're tightening your drawbar too tight.

My mini-lathe and mini-mill both have MT3 spindles.

11-16-2004, 05:20 PM
Evan, what would keep the stub morse from slipping? There's no driving tang. R-8's have a keyway that engages a pin or key in the spindle on my import mill.

11-16-2004, 05:39 PM
Both types of taper drive through friction between the taper and the spindle. The MT3 stub taper is a drawbar MT3 usable for making something like a slitting saw. The slot in the R-8 is just for orienting the tool the same way in the spindle for repeatability and so it doesn't spin when tightening the drawbar. It doesn't drive the tool. The drawbar sucks the taper into the spindle and the taper friction does the driving. The main claim to fame for the R-8 taper is that a steep taper like that is not self locking like the MT. When you loosen the drawbar it falls out. The tang on a MT like on the left is also not supposed to do the driving. It is for removing the taper using a knockout wedge tool.

[This message has been edited by Evan (edited 11-16-2004).]

11-16-2004, 05:40 PM
<font face="Verdana, Arial" size="2">Originally posted by JeffG:
Evan, what would keep the stub morse from slipping? There's no driving tang. R-8's have a keyway that engages a pin or key in the spindle on my import mill.</font>

JeffG the tang on a morse & the pin on a R8 are not there to do the driving. If they are then either or both parts of the taper are dirty or dammaged.


11-16-2004, 05:44 PM

that is not a driving tang, the tang is for removing the arbor using a drift pin.
the arbor is secured with locking action of the slight angle of the arbor.

Ivy McNeil

[This message has been edited by Ivy_McNeil (edited 11-16-2004).]

11-16-2004, 05:53 PM
I have to tap the drawbar to release my R-8's from the mill spindle. Am I overtightening the drawbar nut? Both spindle and tools are in "near-new" condition, and kept lightly oiled.

11-16-2004, 07:23 PM
If it comes loose with a good tap, you are properly tightening your drawbar Jeff.
If your shank just falls out when loosened, something is damaged and/or dirty, or you are not tightening it enough. If you have to beat the heck out of it, back off some next time.

11-17-2004, 09:50 PM
Hey cnc machine tools dont use r8 right? they use MT or something else?

11-17-2004, 10:31 PM
MT3 works just fine in a mini-mill.

11-17-2004, 10:40 PM
Hey Elnio,
MT3 works, R8 works. If you want to share some tooling with a lathe, you might want MT3. If you want to take your expensive investment in tooling for the mill (endmills, boring heads, drill chucks, facing cutters, etc. etc.) and move it to a larger machine (mill, mill/drill) later, go R8.

11-20-2004, 04:59 PM
My preference would be R8. If you have exiting MT3 tooling that you want to use, get an R8 to MT3 adapter. The downside is that you lose and inch or two of operating space because of length of the adapter.