Offset centre

[JOHN ROBERTSParticipant @johnroberts]

Hi. In the new year I am going to need to tun some tapered parts. I have a Chester DB10 Super B and would like to make an adjustable offset centre for my MT2 tailstock. Does anyone have a drawing for a simple one. I have a milling machine and enjoying a bit of fitting.

Thank you

[peak4Participant @peak4]

John, do you have a boring head?
I made a solid carbide centre out of a broken centre drill, and fit that in the boring head in lieu of a tool-bit.
Mount the head in the tailstock horizontally, and you can dial in the offset directly.
I guess you could also mount a suitable sized ball bearing in a bit of bar, and use that instead.

Bill

[HuubParticipant @huub]

Great idea using a boring head.

[DalboyParticipant @dalboy]

Have you seen the Hemingway kit 

[Dave SParticipant @daves59043]

Why not just offset the tailstock?

Thats why they have the ability to do that

 

Dave

[Thor 🇳🇴Participant @thor]

Hi John,

I assume you are looking for something like this:

Link

or this.

 

Thor

[JasonBModerator @jasonb]

I use the boring head all the time these days rather than upset the tailstock alingnment. I have a small rotating ctr that fits mine but turning your own dead one would work.

The main advantage over the designs that I have seen or just moving the tailstock is that the screw on the boring head allows for easy adjustment of the taper. Boring head also tends to be smaller than the sliding offset tools I have seen so less likely to get in the way of the toolpost. Though the second link above gets over these issues

[DC31kParticipant @dc31k]

I think someone in the past posted calculations (in relation to general vertical and horizontal tailstock alignment) that showed the horizontalness of the boring head is not super critical, so just ordinary care is needed to put it into the tailstock for an acceptable result.

Something to assist this might be a block that goes between the top slide and the flat on the head.

If length were an issue, the Morse arbor on the boring head could be removed and an adaptor that clamps it to the OD of the tailstock barrel be made. That might incorporate a key, to interface with the keyway on the barrel.

[Clive FosterParticipant @clivefoster55965]

I have a vague memory of someone posting picture of a boring head lightly modified for this use by cutting a proper flat on one side so a spacer could be used between boring head and cross slide to easily set it absolutely horizontal. Maybe a marginal increase in rigidity and confidence that you’d not twist it slightly when adjusting too. On reflection probably both sides were modified to preserve balance. But very little material would need to be removed from the common style boring head shown in Jasons picture so out of balance from only doing one side would probably be negligible.

Much to be said for fixed spacers et al for setting things up. In retrospect this antediluvian penguin regrets not spending time making such devices rather than doing things from scratch thinking “I’ll only need to do this once or twice”.  All too often when the setting gauge was produce after the fifth (or tenth) time of setting up the making took barely longer than setting from scratch. Unearthing a material from the “useful bits” box usually being the longest part for the job.

Clive

[John MCParticipant @johnmc39344]

I made (in 1986) this adjustable  offset revolving centre when I needed to turn a number of tapered shafts.  Since then it only gets occasional use.  Recently used by a friend to machine a Brown and Sharpe taper.

For the occasional job a boring head is entirely adequate, I would not bother doing as I did, unless turning tapers became a regular job, as it was for me back then.

 

[JOHN ROBERTSParticipant @johnroberts]

I don’t really want to offset the tailstock. I like the boring head plan so I’ll give that a go. The taper isn’t critical as it’s just a column on an engine.

I have seen the Maxwell H kit and the design sent by “Thor” so maybe a hybrid of the 2 might be an interesting project.

The fun will come when I set it up to cut the flutes on the milling machine!

Thanks for all the replies. It’s always good to have other people’s suggestions

[JasonBModerator @jasonb]

If anyone want the boring head dead level then all you need do is stuff a bit of 1/2″ or 12mm round bar in the cross hole and stick a digital angle block or your engineers level against that.

Editor Neil has an article in the current ME&W about fluting simple columns. If you have any questions just ask, as I have done some larger ones.

 

[JOHN ROBERTSParticipant @johnroberts]

<p style=”text-align: left;”>JasonB</p>
Yes the bar in the boring head looks like the easiest option.

I have spotted the article in the ME&W but not read it yet. I was planning on making a spare column and setting it up on the mill table at about half the taper. I want the flats between the flutes to be roughly parallel so the flutes will taper slightly reducing in width towards the narrow end.

I’m sure I will waste several happy hours in the workshop tryin to get just the right look. The joys of model engineering, time spent tinkering is ever wasted.
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