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Taper sleeve adapter

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Me.05/11/2020 15:50:19
136 forum posts
30 photos

I'm in need to make an adapter sleeve for an odd size taper for my milling machine.

The sleeve has the same taper as the BT30.

I need to know the best way to cut and internal and external taper on the same piece of material - the wall thickness will end up approx 3mm thick.

Can anyone suggest the best way to tackle this - would you cut the internal taper first or the external and also, what would be the best material to make it from.

Ian Parkin05/11/2020 16:03:08
995 forum posts
235 photos

I would start by making a dummy male internal taper that can be mounted in your lathe? Concentrically

then cut your internal taper to fit that. Mount the adapter on the dummy taper and cut the external taper

Adrian R205/11/2020 16:38:46
137 forum posts
5 photos

I think I'd cheat if possible and buy something that has the correct internal taper, mount it on an existing taper tool that I could hold in the 4 jaw chuck and clock to be sure it is concentric and then see whether I could machine the odd size taper on the outside. The bought in something might be case hardened so may need a bit of a preparatory grinding to soften it up before lathe work starts.

Logic is that this saves a bit of work and gets you a professionally hardened taper where you most need it.

IanT05/11/2020 16:54:35
1945 forum posts
194 photos

I have essentially the same problem but I've not tackled it as yet. I should add that it's a Horizontal Mill and that I have the original arbour (and so can measure/copy it's taper off-mill quite easily).

My thinking is that I'll machine the adaptor's external taper between centres, so that I can remove it (as required) to test the fit as I get near to final size. Once I have a blank tapered part that fits the mill taper, I can then through drill, tap it and fit a temporary drawbar. Then I'll rig up a boring bar on the mill table (using the top-slide off my lathe to feed it in). I can then machine the second (internal) taper in-situ. Once the internal taper is done, I can enlarge the through hole at the rear, to pass the draw bar that will normally be used with the tools in the adaptor.

That's generally my plan

I just need the motivation now - e.g. It has to fight its way to the top of my to-do list (and it's getting colder down the Shed)



Brian Wood05/11/2020 17:25:58
2498 forum posts
39 photos

One design detail I would incorporate would be to make an external extraction feature of a thread and matching castellated ring upon which that a hook wrench can be used to jack it out.

It will save hours of frustration and small words later on

Regards Brian

Edited By Brian Wood on 05/11/2020 17:26:57

IanT05/11/2020 18:11:58
1945 forum posts
194 photos

Not so much of a problem I suspect on this sort of 'steep' taper Brian - but very useful on MT ones I'd agree.

So a screwed nose on the adaptor itself (to get the tooling out of it) might be a very good idea. I guess a good use for my fledgling 3D drawing skills when I get around-to-it.



Pete White05/11/2020 18:40:56
153 forum posts
16 photos

Double post, internet works like a rubber band. 

 I hopefully have a new reliable connection coming next week, much cheaper and according to quite a few mates does actually work.......Fingers crossed.

Edited By Pete White on 05/11/2020 18:48:51

Pete White05/11/2020 18:43:20
153 forum posts
16 photos

Both are your tapers with be non stick or release with a tap, don't over think it.

I can't think of a better way than how I achieved the required sleeve.

I had in stock a 30 int taper with a 1 inch spigot used for mounting a boring head

I chucked up a piece of bar and machined an internal taper to a blued fit to the 30 int taper.

Rough turned the outside to the approx size of a 1 3/8 taper.

chuck another billet and turn a spigot on the end to suit the hole in the 30 int tool.

without removing from the lathe, drill and tap the four mounting holes and a center tapped hole for securing the 30 tool.

secure the half made sleeve by the center taped bolt, and machine the outside to fit your mill, with the ability to remove it and replace it to check for a blued fit, without loosing concentricity.


Ady105/11/2020 19:51:01
4907 forum posts
726 photos

The internal one is the difficult one to finish off if you don't have a reamer

Emgee05/11/2020 20:39:41
2312 forum posts
277 photos

I believe the dimension shown on your caliper was 34.4mm for the large end of the tool taper so the sleeve you want will have a wall thickness of 1.325mm (34.4 - 31.75) /2


Me.06/11/2020 10:41:12
136 forum posts
30 photos

Wow - Thanks all for your input - I will read through and work out the best route - as Pete has already done this operation I will pick his brains a bit more.

What material do I need to use - does it need to be relatively hard or would a mild still be the preferred choice.

Me.13/11/2020 21:27:33
136 forum posts
30 photos

Ive just had a thought - I note there's a BT40 to BT30 Adaptor. Arc Euro Trade part number 120-010-44030

If I use one of these it already has the internal taper already cut - then all I need to do is recut the outer taper to suit my Herbert taper... Job done.

Your thoughts please.

old mart13/11/2020 22:08:53
3510 forum posts
216 photos

You are likely to find the steel of one of these adaptors hardened, so HSS will not do. I would turn a male BT30 part for the adaptor to be attached to first. Getting the angle correct will be a nightmare, even if your lathe has a taper turning attachment. The fit needs to be within one minute of angle to work properly.

Me.13/11/2020 22:21:05
136 forum posts
30 photos

I'd not be using HSS to cut the adapter - the fact that the taper angle on the 40 is the same as the taper I need shouldn't be that hard to set it up to cut - I could even set up a tool post grinder to help.

Edited By Me. on 13/11/2020 22:22:01

old mart13/11/2020 22:31:11
3510 forum posts
216 photos

If the angle is the same as the BT type, and all the BT are the same, I wonder how the BT40 would look just offered up to your spindle? If you order one of the BT40 to BT30, try out the fit before doing anything else. An alternative solution might jump out at you.

Me.13/11/2020 22:40:18
136 forum posts
30 photos

Th 40 is too big and the 30 too small - I have had already had loads of advice as to what would be the best route - The original idea is to make a taper sleeve adapter from scratch but if the BT40 to 30 would already have half the work done then turning the outer taper to suit my spindle would be the easiest route for me.

DC31k14/11/2020 07:51:06
586 forum posts
1 photos
Posted by Me. on 13/11/2020 22:40:18:

The 40 is too big and the 30 too small

Are you aware that there is a 35 taper in between 30 and 40? See:

Me.14/11/2020 08:46:24
136 forum posts
30 photos

Hi - yes I am aware of the 35 but that is still too big for my needs - For information - the early built Herbert machines used a specific to Herbert, it is the same taper angle as the NT/BT range but was in between. 1 3/8 (34.4mm)

This is why I need an adapter sleeve - just trying to work out the best route - If the 40-30 adapter sleeve is half way done then it shouldn't be to difficult to modify the outside of it to fit my spindle.

I just need a method and material choice for come up with the best result.

Brian H14/11/2020 10:20:50
2292 forum posts
112 photos

The 1 3/8" NS taper was not specific to Herbert machines but was given in a British Standard for machine tool manufacturers.

My 1943 Machinerys Handbook gives the taper details and mentions that it is to a BS but without giving to number. There were four of these NS tapers, 1 3/8, 1 3/4, 2 3/4 and 3 3/4.


IanT14/11/2020 11:14:37
1945 forum posts
194 photos
Posted by Brian H on 14/11/2020 10:20:50:

The 1 3/8" NS taper was not specific to Herbert machines but was given in a British Standard for machine tool manufacturers.

My 1943 Machinerys Handbook gives the taper details and mentions that it is to a BS but without giving to number. There were four of these NS tapers, 1 3/8, 1 3/4, 2 3/4 and 3 3/4.


Yes, agreed Brian - The 1 3/8" NS taper is the one used on my Victoria HO.

Have a look at the bottom of this page...

NS & Int Tapers



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