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R8 instead of MT3

R8 instead of MT3

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3404618/03/2019 20:33:05
902 forum posts
6 photos

New mill about to be ordered.

Choice of R8 and MT3.

From reading on the forum R8 seems best?

Is this still the current thinking please /



Chris Trice18/03/2019 20:43:10
1362 forum posts
9 photos

R8 is my personal preference. Bridgeports use R8.

SillyOldDuffer18/03/2019 20:50:16
5006 forum posts
1061 photos

I don't think it makes much difference. If you worry hammering the drawbar might damage bearings, R8 is easier to release. Apart from that prices and availability are similar. I would have gone R8 on my mill had it been available, as R8 wasn't I have MT. It's fine.


Michael Gilligan18/03/2019 20:56:09
14603 forum posts
634 photos

If the choice is offered [and assuming that you don't already have loads of MT3 tooling available] I can see no good reason not to use R8 ... It's a properly specified fitting for the job.


lfoggy18/03/2019 21:02:57
97 forum posts
9 photos

I have had difficulty in releasing morse tapers from milling machine spindles in the past which can be quite annoying. Given a choice I would definitely choose R8.

Peter G. Shaw18/03/2019 21:14:31
993 forum posts
39 photos

I had this choice when I bought my milling machine. What swung it for me was that my lathe used MT3 in the headstock, therefore by making the mill MT3 all my direct collets would work in both machines.

In respect of MT3 taper removal, I have an extractor for the mill courtesy of an article in MEW, and a similar extracter for the lathe. I have no deed to batter the end of the collet to get it out.

Peter G. Shaw

Jeff Dayman18/03/2019 21:16:06
1701 forum posts
45 photos

R8 no question.

Vic18/03/2019 21:47:08
2384 forum posts
12 photos

Some of the first jobs I had for my mill required me using fairly large morse taper drill bits so I went with MT3. I have a self extracting drawbar so no release issues. Many mills have them and they’re not difficult to make. I still use MT drill bits in my mill from time to time, they can be had for good prices at the shows. I often have a collet Chuck in the mill as well so changing cutters is not an issue affected by the machines taper anyway. I’d go MT3 again if I had to make the choice. Having said that many don’t seem to know how to use them and over tighten on MT tapers, it’s not needed.

Dave T18/03/2019 22:44:51
36 forum posts
1 photos

R8 definitely

Chris Evans 619/03/2019 07:21:46
1526 forum posts

Another vote for R8 (well it would be from a Bridgeport user)

JasonB19/03/2019 07:27:51
16896 forum posts
1817 photos
1 articles

It's a shame the smaller hobby benchtop mills don't have INT30, the only one I can think of in that size range would be the Boxford but that was not originally a hobby machine. Think you need the initials JS to get one on special order.

Neil Lickfold19/03/2019 07:42:05
579 forum posts
102 photos

Having used both R8 and MT3, if the spindle is good and the register for the R8 is the correct size, then R8 can be often purchased quite cheap for after market parts like boring heads etc.

The MT3 like been said, a lot of people do over tighten them.

An advantage of an R8 over a MT3 , is if the collet or piece is undersize, the back of the R8 keeps it well aligned while the front taper clamps down on the tool and it still runs quite well. That is not the case with the MT3. If you only ever have nominal cutters etc, then the MT3 is fine.

See what else you want in the way of other holders and drill chucks and arbors etc and price them up and availability.

Often availability of accessories that you will use can be a real deciding factor, and not just price alone.


Mike Poole19/03/2019 08:22:38
2256 forum posts
52 photos

I chose R8 as I regard the morse taper as a drilling machine fitting, morse is a self holding taper that was designed for drills, it will not self hold for milling and requires a drawbar which can make it very difficult to release if tightened with enthusiasm. If you choose MT3 try and get or make it self ejecting to avoid the wretched business of beating a stuck taper out. R8 is a self releasing taper designed for milling machines and will always release with no more than a gentle tap. I usually have an ER chuck mounted but if headroom is a problem I have R8 collets which give a bit more Z height. I doubt that any industrial mill will have MT3 and its use is only on hobby machinery as sharing tooling between lathe and mill can be useful for some people.


Julia Stephenson19/03/2019 08:27:31
9 forum posts
4 photos

I like R8 as its much easier to release tooling from the spindle. It's also an industry standard due to the ubiquity of Bridgeport Mills, this means lots of good quality tooling available at a decent price.


3404619/03/2019 08:41:05
902 forum posts
6 photos

Thanks to all

R8 it will be.


John Hinkley19/03/2019 09:33:08
783 forum posts
261 photos

I seem to have arrived at this particular party just as everyone is leaving, but I'll throw my metaphorical hat into the ring, anyway.

When I upgraded my mill from an MT3 spindle one to a much larger VMC, I decided to go with R8. However, having several accessories with MT3 shanks, my first purchase was an R8 to MT3 converter sleeve. That allowed me to at least start using the machine without a massive outlay. As the need arose, or funds allowed, I gradually replaced the ER collet chucks, etc, with R8 ones and similarly replaced the arbor on the boring head. I don't regret the decision I made and neither, I suspect will you, Bill. Enjoy your new machine when it arrives!


Zebethyal19/03/2019 12:00:59
189 forum posts

I don't think I even used the MT3 spindle in my SX2 Mini Mill before swapping it for an R8 one, I intend to use the MT3 spindle on a 4th axis at some point.

I have bought the Tormach R8 collet that allows me to use/fabricate Tormach style holders, that makes swapping tooling a breeze I often just tap the drawbar with my hand after loosening (it will be even faster when I finish my power drawbar).

Tormach also do an MT3 collet, but I am not convinced it releases as well as the R8 one.

Simon Williams 319/03/2019 12:18:54
446 forum posts
75 photos

Do you have the means to turn a drill with an MT3 shank? If yes go R8 on the mill, if no go MT3.

MT3 won't fit in an R8 adaptor, there's not enough meat left so there is no such thing as a compact R8 to MT3 socket.

I bought a Rong Fu mill drill a long time ago, and agonised over this choice as I thought then that the R8 was by far the better choice up the spout of a milling machine, but it made my stock of MT3 shank drills unusable. I swallowed hard and went with MT3 and have never regretted it even if the comments about the taper being a pig to eject sometimes all ring true.

I agree with Jason's comment that ISO30 is a better choice. If only....

Vic19/03/2019 13:54:45
2384 forum posts
12 photos
APosted by JasonB on 19/03/2019 07:27:51:

It's a shame the smaller hobby benchtop mills don't have INT30, the only one I can think of in that size range would be the Boxford but that was not originally a hobby machine. Think you need the initials JS to get one on special order.

I’m not sure if it was a Boxford or a Denford CNC mill where I used to work but that would have been a modest size mill if you took it out of its enclosure and that had I think an INT30 taper?

From what I’ve read it’s interesting that after the war British and European manufacturers largely seem to have gone directly from Morse tapers to “short” self releasing tapers in their milling machines like the INT series. Unlike Morse and R8 tapers the drive is through the flange rather than the taper.


Hollowpoint19/03/2019 14:18:24
259 forum posts
29 photos

I would go for morse taper. There is an abundance of good quality old morse taper tooling around, often much cheaper than more modern R8 stuff. If you have a lathe its likely to be morse taper which makes tooling interchangable between the two. Ive never found morse taper difficult to extract? a short sharp tap on the top of the draw bar and its out?

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