mt 3 vs r8

[stuart websterParticipant @stuartwebster87240]

looking for advice before i buy a new mill on 3mt or r8

[stuart websterParticipant @stuartwebster87240]

[Simon Williams 3Participant @simonwilliams3]

R8 is much the nicer taper as it is not self-holding so it lets go when you undo the drawbar. It used to be true that you could find a better range of tooling on R8, that's probably no longer true. But things like collets work better if they are not self holding.

BUT

If you have no other method to turn an MT3 drill then a mill with a MT3 socket up the spindle is the better option by far. It is true that you can get a R8 to MT3 socket adaptor but it will take up too much headroom as the R8 isn't big enough for the MT3 to sit inside it, it has to be below it so the overall length of the adaptor is problematical.

Seasons greetings all

[OldironParticipant @oldiron]

R8 is usually considered superior to 3Mt. If you have a lathe it may pay to go with the same taper you have on it so items like collett holder etc are interchangable. I am sure there are several posts in the forum somewhere on the subject.

regards

[John HaineParticipant @johnhaine32865]

Indeed there are many!! For example this thread:

**LINK**

And I'm sure there are others.

[Howard LewisParticipant @howardlewis46836]

being a steeper taper, R8 releases easily, no need to belabour the bearings in the Mill. to release a tight M3.

My lathe and Mill both use 3 MT so work can be changed from one machine to the other

The Mill Drill is over 20 years old, when R8 was less common, and the lathe came with a 5MT / 3MT adapter sleeve.

Both systems have their advantages.

Your Choice!

Howard

[Anonymous]

My Busy-Bee (Canada) WM16 lookalike mill was an early model and came with MT3. Later models had R8 and BB duly came up with an R8 conversion kit for the earlier models. I fitted that and wouldn't want to go back.

That said, it's almost permanently fitted with an ER-32 collet chuck so perhaps it's academic in my case. (Although it's nice to know that I can unload the collet chuck easily when I need to).

[HOWARDTParticipant @howardt]

If you are using it primarily for milling then R8. Morse taper is better suited to drilling, MT3 as standard is used on drills upto 31.5mm, bigger sizes are available as reduced shanks in MT3. R8 I think would have a problem driving a large drill, R8 equipped mills recommend a smaller maximum drill capacity. Aside from that R8 is easier to work with when changing holders as it is not a locking taper to the extent of a MT and will release with very little persuasion. I had a MT mill but now have a R8 and prefer this.

[Mike PooleParticipant @mikepoole82104]

R8 was developed by Bridgeport as a taper for a milling machine, the popular Bridgeport and its clones have made the R8 widely used and supported. Morse tapers are a self holding taper for drilling and need to be modified to use a drawbar for milling tasks as the side thrusts exerted by milling will soon loosen a morse taper without a drawbar. If tempted by MT3 then choose a machine with an ejector mechanism to release the taper, having to knock the drawbar with a mallet to release the tooling requires me to turn off my mechanical sympathy sensor. MT3 drills start at around 22mm diameter and a drill that size is getting pretty long and use up a lot of the Z axis height. Although drilling with the mill can be very useful for setting out accurately placed holes and doing drilling operations while the job is set up in the mill. I would not get rid of my pillar drill in favour of using my mill as a drill, both machines have their strengths. I went R8 on my mill and feel I made the right decision. R8 collets give the maximum amount of Z height if things get tight and it is certainly worth acquiring some in my opinion, although you will find my ER collet chuck spends the most time in use. My lathe has a MT2 head and tailstock taper so interchangeable tooling would not be an issue for me.

Mike

[Thor 🇳🇴Participant @thor]

Hi Stuart,

Both my small lathe and my milling machine has MT 3 so I can use the same toolholder both in my lathe and in my milling machine. If you use large drills with a Morse Taper shank a milling machine with MT 3 makes sense. I agree with Mike, if you buy a milling machine with MT 3, get one with an ejector mechanism, mine has and it works very well.

Thor

[old martParticipant @oldmart]

If you have a choice at the time, always choose R8, This forum has frequent threads with stuck Morse tapers in mills as they do not often have the extraction slot that drilling machines have. It is easy to get R8 tooling with MT2 sockets, both tanged with an extraction slot and plain which require a drawbar in the appropriate size which is easy using studding and nuts.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Oldiron on 19/12/2021 17:00:01:

… If you have a lathe it may pay to go with the same taper you have on it so items like collett holder etc are interchangable. …

That's my reason for going MT, and once in a blue moon it's useful to share tooling with my lathe. Otherwise MT or R8 wasn't an important requirement.

My feeling is the taper doesn't make a significant difference unless you happen to have access to lots of cheap surplus R8 or MT tooling in good nick,.

Having gone MT I've never ever had the slightest desire to use R8, and I guess R8 owners rarely wish they'd chosen MT! Both work with mild advantages and disadvantages.

Dave

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