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Milling machine taper choice ?

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fizzy21/10/2017 17:55:58
1482 forum posts
102 photos

Ive got two milling machines - one R8 and one MT3. The R8 wins every time. Hate the MT so much that ive bought a cheap chinese er32 collet set and thats permanently in the MT mill.

Chris Evans 621/10/2017 18:15:15
1175 forum posts

R8 every time, tooling is cheap and plentiful my collets go up to 3/4" and 20mm for the metric set. Take no notice about the alignment key, I've used R8 equipped Bridgeport mills for over 50 years and most had the alignment key removed as does my present machine.

Andrew Johnston21/10/2017 18:41:58
3780 forum posts
454 photos
Posted by Nige on 21/10/2017 16:37:47:

I looked up R8 and in the reading on Wikipedia it says that R8 tapers are keyed, would that be in addition to the small set screw that is not driving the taper. The image on Wikipedia appears to show a keyway on what appears to be the parallel portion of the collet but no sign of a set screw

The keying is not in addition, the setscrew is all you get. As you saw the collet has a keyway on the parallel portion. The setscrew is in the spindle and protrudes into the bore to mate with the keyway in the collet. The setscrew has a plain cylinder on the end that actually mates with the collet keyway. It allows the collet to be aligned in a specific orientation every time, but I've no idea why the original designers thought it necessary.


Andrew Johnston21/10/2017 18:58:37
3780 forum posts
454 photos
Posted by John Haine on 21/10/2017 16:43:54:

R8 every time, even over Int type (except maybe on CNC)

I've got an INT40 taper on the horizontal mill, and would like it on the vertical mill. It's probably overkill for the CNC mill though. No way I'm going to be swinging this Dedlock cutter on an R8 spindle:


As far as I can see INT40 and INT50 tooling is quite common, but INT30 rather less so.


Howard Lewis21/10/2017 19:00:53
1167 forum posts

Like others, I bought my Mill/Drill before R8 became popular in the hobby world. Being a faster taper, it unsticks more easily. If you don't want, or need, machine to machine compatability, go for R8.

Disliking pounding the bearings, I made an ejector for my 3 MT drawbar tooling. Turned a short plain diameter on the underside of the nut retaining the pulley on the spindle, and trapped a thin plate with two equally spaced tappings (1/4 BSF) under it.

Made up another plate with a central tapping (1/4 BSF again) and two clearance holes to match the centres of the captive plate Two bolts through the clearance holes, one setscrew in the central tapping. Screw the lot together, tighten the central setscrew and Tooling is ejected. For tooling with tangs, a drift through the slot in the spindle and a tap with a mallet suffices. In this day and age the threads would be M6.

Yes, if buying again, would choose R8, but am living with what was easily available at the time.


Nige21/10/2017 19:23:41
280 forum posts
120 photos

Thank you everybody, a comprehensive lot of answers and it seems like an easy decision to go for R8

John Haine21/10/2017 22:36:25
1919 forum posts
110 photos
Posted by Emgee on 21/10/2017 17:30:25:
Posted by John Haine on 21/10/2017 16:43:54:

I've got an Int.30 spindle on my little CNC and it's OK, but you either have to have the right shank on a collet chuck (I have ER16 for this machine) or use individual holders. They both give a lot of overhang and you lose headroom under the mill.

John, with an INT30 taper it is possible to enclose the ER16 taper into the tool shank, just the depth of the closing nut would be below the spindle end.
Emco used BT30 tooling which is the same dimensions arbor as INT30, a large part of the ER25 collet seat is within the shank and has minimum protrusion from the end of the spindle.


Indeed, but you don't seem to be able to buy them like that! All the ones I've seen have ~40mm between the BT30 part and the end of the ER16 collet closer thread. One day I'm going to make one.

Muzzer21/10/2017 22:54:16
2725 forum posts
439 photos

Something like this?

My machine needs all the Z axis room it can get but I manage with the "standard" gauge lengths which are typically 50-70mm or so (measured from the large end of the taper to the end of the collet face.


Mark Rand22/10/2017 01:31:20
362 forum posts

In that size, NMTB30 is much preferrable to R8, even though the dimensions of the end are identical. MT3 is not sensible for milling machines given the choice of either of the others. R8 is much cheaper for tooling, INT30 gives better capability.

Disclaimer:- My 2hp Beaver VBRP Mk1 is NMTB30 and I wish it had the '40 spindle.

If someone offers you an NMTB40 machine then forget all the otherssmiley.

John McNamara22/10/2017 05:55:41
1149 forum posts
101 photos

Yep a 40 taper spindle is the way to go, the tooling is cheap enough from Asia new, there is also a steady supply available second hand, there are several variations see this link **LINK**

Or this thread

Older tooling will probably have a 5/8" imperial thread newer tooling may be metric, so you will need two draw bars I am trying to focus on metric tooling In case I ever find a cheap CNC mill that I can refurbish..

My current mill is a Shizuoka VHRG **LINK** When I got it it was black with grime it had been neglected. The is a fair amount of wear so I have to coax it to get reasonable accuracy from it. Where it shines is in the amount of metal I can remove without it complaining or vibrating, this is where heavy old machines win easily against lighter imports. both the vertical and horizontal spindles are 40 taper.


Edited By John McNamara on 22/10/2017 06:00:10

John Haine22/10/2017 08:47:25
1919 forum posts
110 photos
Posted by Muzzer on 21/10/2017 22:54:16:

Something like this?

My machine needs all the Z axis room it can get but I manage with the "standard" gauge lengths which are typically 50-70mm or so (measured from the large end of the taper to the end of the collet face.


Something like that would indeed be ideal Murray, if it only was available with an int30 taper and ER16!

Nick Hughes22/10/2017 11:26:40
145 forum posts
1 photos

The key in R8 taper spindles is there only to prevent the collet rotating, as the drawbar is tightened or undone.

For the ISO/NT 30 thaper spindle, I have a set of these collets :- **LINK**

that I use on my Syil X5 and manual mill, when I need that little bit extra height capcity.


Edited By Nick Hughes on 22/10/2017 11:28:08

Muzzer22/10/2017 14:18:29
2725 forum posts
439 photos

There's a lot of confusion over the various flavours of 30 and 40 taper tooling.

The difference between NMTB and ISO (aka INT or NT, technically DIN 2080) is that NMTB has an imperial drawbar thread (1/2" for 30 taper, 5/8" for 40 taper) and the other has metric (M12 for 30 taper, M16 for 40 taper). As far as I know, the Mercans use UNC (eg 1/2" 13tpi etc), whereas UK imperial tooling probably uses BSW (1/2" 12tpi).

The other flavours like BT, SK, CAT etc are intended for use with a pullstud, so have no parallel shank. However, if you have a manual drawbar, you could make a longer drawbar and use them instead of the ISO/NMTB style, potentially giving you more choice of toolholders. However, if you have a captive or power drawbar like me, you need to standardise on tooling style (including the thread).

You can buy new, good quality 40 taper tooling for £25 inc vat (or less) due to its popularity but 30 taper is more expensive and less easy to come by. But generally, metric is the norm over here, so I'd look out for ISO / INT / NT (DIN2080) rather than NMTB.


Edit - you'll notice that ISO40 tooling here is almost half the price of the (smaller) ISO30 equivalent and there is a larger choice of types and sizes.

Edited By Muzzer on 22/10/2017 14:23:19

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