Hex bush reducer needed

[Robert Merwiak 1Participant @robertmerwiak1]

Hello Everyone, I hope I’m not over-stepping here but I wonder if anyone with the correct equipment would be able and willing to make me a female…no wait there’s more…a female M16x1.0 to male M18x1.5 reducing bush. I can find for sale female M16x1.5 to male M18x1.5, or female M16x1.0 to male M20x1.5 but not my unicorn…

Can anyone help, please, it’s for a proxxon db250 (wood lathe) so that I can use a ring mandrel that is perfect for what I need?

Rob

[JasonBModerator @jasonb]

Unless you want quite a bit of overhang then trying to tap M16x1 into a M18x1.5 thread will leave a very weak part.

[Trevor Drabble 1Participant @trevordrabble1]

Robert , For your information , carbon steel taps and dies in these sizes are available from Tracy Tools at reasonable costs.

[JasonB]

On JasonB Said:

Unless you want quite a bit of overhang then trying to tap M16x1 into a M18x1.5 thread will leave a very weak part.

I though something like the attached image, the female thread only needs to be about ~8-10mm and then solid thereafter as you go out to the male threaded portion.

[Trevor Drabble 1]

On Trevor Drabble 1 Said:

Robert , For your information , carbon steel taps and dies in these sizes are available from Tracy Tools at reasonable costs.

Thanks, Trevor, do you think it would be possible to use an M16x1.0 tap to change from M16x1.5?

[Robert ButlerParticipant @robertbutler92161]

Robert perhaps best to take on board what Jason advises.

Robert Butler

[bernard towersParticipant @bernardtowers37738]

Not quite sure that I agree with Jason that the part will be weak, yes as a stand alone item but in use will be supported both inside and out after all thats how thread inserts work IMHO.

[JasonBModerator @jasonb]

Threaded inserts do work like that But the ones I have used have a bigger difference between inside and outside threads

If it were just a bush eg fits into a M18 x 1.5 hole and had a M16 x 1. you will only have less than 0.25mm thickness in places.

The longer male/female adaptor shown would be OK as the threads are on different lengths of the part, if the added overhang is OK then all is well.

[duncan webster 1Participant @duncanwebster1]

If by thread inserts mean helicoils they have the same pitch inside and out. This wouldn’t

[JasonBModerator @jasonb]

It looks like the female thread should have an unthreaded section of at least 17mm dia so that it can screw right on and act as a register, just an 8-10mm length of thread is unlikely to get your other brand chuck running true

[DC31kParticipant @dc31k]

It would be useful if the OP provided a proper dimensioned drawing of the male thread (plus any register) on the lathe as well as the female thread (plus any register) on the chuck.

We have ‘engineer’ in the title of this forum, We do not have ‘Mystic Meg’.

A 3D printed prototype could be used as an in-situ test item before commiting oneself to metal.

[JasonBModerator @jasonb]

This is what I would regard as a chuck reducing bush, short as possible to keep overhang down.

Crests of the internal thread would be 16mm , runout groove at the end of the larger thread 16.5mm max. Ok the Proxxon is a small lathe but I would not want to hang some of the bits of wood I have turned on what in effect would be a 0.25mm wall thickness tube

[Michael GilliganParticipant @michaelgilligan61133]

For context … Mystic Meg found this quite quickly for me:

https://www.proxxon.com/en/micromot/27020.php

MichaelG.

.

Edit: __ and she also spotted the statement:

so that I can use a ring mandrel

[Michael GilliganParticipant @michaelgilligan61133]

Fully agree with Jason, but I do  think we need to be designing the appropriate item.

MichaelG.

.

Wild guess: OP wants to use something like this:

https://www.ringsupplies.co.uk/collections/chucks-expanding-ring-mandrels

[JasonBModerator @jasonb]

Looking at some tables of the minor diameter for M18x 1.5 it can be less than 16mm!! This is it at 16.4 so I personally would not want a bush. And that is without the plain section of the internal thread.

[Michael GilliganParticipant @michaelgilligan61133]

Beautifully demonstrated, as usual, Jason.

MichaelG.

[JasonBModerator @jasonb]

Ops, did not have a physical M18 thread on the image above

[Michael GilliganParticipant @michaelgilligan61133]

🙂

[JasonBModerator @jasonb]

As per the OP’s second post an adaptor would be better than a bush and if just for rings or pen turning the extra overhang should not be an issue, different if like my you like to turn 20kg lumps of wet green oak.

[Neil AParticipant @neila]

Perhaps I am missing something here. Would it not be easier to make a ring chuck/mandrel from scratch with the M16 x 1 thread and fit it directly to the lathe without a reducing bush?

From the pictures that are linked to they do not seem very complicated.

Neil

[Neil AParticipant @neila]

Just occurred to me that the OP might already have the ring chuck, so my previous post may not be relevant.

Neil

[Neil A]

On Neil A Said:

Perhaps I am missing something here. Would it not be easier to make a ring chuck/mandrel from scratch with the M16 x 1 thread and fit it directly to the lathe without a reducing bush?

[…]

With resect, Neil … I suspect the thing you are “missing”, is the diminutive capability of that little Proxxon lathe.

MichaelG.

.

https://www.proxxon.com/en/video/27020.mp4

[Trevor Drabble 1Participant @trevordrabble1]

Robert , In answer to your question regarding the thread change , then the short answer is no I’m afraid.  Also ,  for future reference the item you’ve shown is generally referred to as an adapter , whereas a reducing bush is of the form shown in say  a Toolstation catalogue , part number 94885  , and is a frequent and common mistake .  Hope this helps .

[DalboyParticipant @dalboy]

A picture of the ring mandrel you have may help in the design of the adaptor. Can’t you make one that fits the mandrel but have a straight shank to fit the largest collet.

Also does the mandrel allow for support by the tailstock

[Michael GilliganParticipant @michaelgilligan61133]

Just a wild thought … but I think it might make for a better solution.

The headstock spindle is bored to clear 10mm and presumably tapered to accept the collets

So why not put the required thread on the end of a big “blank collet” secured with a draw-bar [or perhaps a nut on the back-end]

?

MichaelG.

[Author]

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