Rotary table and back plate.

[Honest John]

Let me say from the start that m a little bit out of my comfort zone talking or even enquiring about what I understand are called rotary tables. I have a desire to mount my Woodturning scroll chuck onto a rotary table which in turn can be mounted onto the ways of my Woodturning lathe. I intend to attempt some forms of "ornamental" turning to decorate some of my turnings, much along the lines outlined in recent articles in Woodturning magazine. The problems I am finding is that backplanes that bolt to the table and have a threaded nose to screw chucks onto do not seem to be available in the 1 1/4 inch by 8 that I require. I found a rot table on the Warco site that looks very suitable (but is out of stock) and the same manufacturer supplies a backing plate that is designed to fit this table but has a Boxford thread on it, which I understand is 1 1/2 by 8. Presumably some skilled and tooled up artisan could turn this down to the correct size for me ? Now the bit that is really confusing. The back plate sold by Warco has a short morse 2 taper on the back which is supposed to ensure concentricity when fitting to the RT, and it is then bolted with 2 T nuts. The manufacturer says that the fitting is very secure and stable as the whole of the backplate is in contact with the surface of the table. Now to my simple mind it seems likely that if the whole of the backplate is contacting the table, then the taper must be loose enough to allow this to happen. If that's the case then how can it be guaranteed to run true?
Sorry for the long rambling post but like I said the metalworking business is out of my comfort zone. I would be interested if anyone with experience of these devices could aid my understanding.

 

[Inspector]

Most rotary tables have a through hole in the middle, often a morse taper but not always. Lee Valley sells a straight shank adaptor that would fit the chuck thread.
http://www.leevalley.com/en/Wood/page.a ... 69091&ap=1
With it you could, depending on the size of the RT, have it turned to the taper size matching the RT, or hold it in the RT with a morse taper collet. An appropriate bolt at the back of the RT acting as a draw bar holding them in place. There should be sellers in the UK that have the LV tool.
http://www.arceurotrade.co.uk/Catalogue ... er-Collets

Instead of a RT you could use a 5C Spin Index with a collet that fits the LV adaptor. It will give you 360 positions to play with but if the number doesn't divide into 360 you can't do it. Seven facets for example.
http://www.amadeal.co.uk/acatalog/5C-Sp ... 011TD.html

Here is on with an ER collet adaptor. Easier to find in your neck of the woods I think.
http://www.arceurotrade.co.uk/Catalogue ... -Adaptor-2

Pete

 

[Honest John]

Thanks for the reply Pete. I imported a chuck adapter from Lee Valley earlier in the year as I couldn't find one in the uk with the right thread size. I use this for mounting a chuck in a live centre in my tailstock which provides some solutions for my segmented turning build ups. In theory this item would probably allow me to do what I want when mounted in the M2 taper in the centre of a rotary table, especially if it was locked in with a drawer bar. It just struck me as a more stable fixing if it was bolted to the surface of the rotary table. I can see that a simple parallel sided hole in the centre of the table could be useful to centre a backplate that had a spigot. Locking down with t nuts would then just draw the spigot in the hole. With a M2 taper however, tightening the t nuts will also tighten into the taper. It just seems strange (to me) that the effect would seem to be referencing onto 2 surfaces, the face of the RT and the M2 taper ? I guess I'll may just buy the RT and Boxford backplate when they are back in stock and make sure that I am happy with the way that the surfaces mate together, and then either return them to Warco if I'm not happy, or find someone to re turn the Boxford thread down to 1 1/4 X 8.

 

[woodpig]

I agree, it doesn't sound ideal does it. It only needs the machining to be very slightly out for the morse taper to be loose or the adaptor standing proud of the table. Several companies supply these adaptors though so maybe they know something we don't!

 

[Inspector]

You guys are trying to two things at the same that aren't intended. The taper is used by itself, possibly a dead centre with a lathe drive dog in one of the slots and a tail stock. Or an object clamped to the table. If the object is to be centered then it would be dialed in with an indicator. If you want to centre a chuck with a backplate you would have at most a small stub that just fit the RT hole.

Pete

 

[woodpig]

I think you've misread what John wants to do. He simply wants to bolt a wood turning chuck onto a rotary table. His chuck is threaded 1 1/4" X 8. He has found an adaptor plate with a stubby MT2 taper on the back ( for centralising it on the RT) but it's threaded 1 1/2" X 8 on the front. He's hoping to have the adaptor rethreaded to fit his chuck. This is the adaptor:

http://www.warco.co.uk/rotary-tables-en ... chuck.html

His concern is how well the adaptor will fit the RT and the only way to know that is to buy one and try it out.

John, I have also seen similar adaptor plates with a short cone for centralising it on a RT. I suspect users are expected to turn it down slightly if it's a tight fit as they do say it can be turned off completely if it's not needed :wink: RDG tools have them.

http://www.rdgtools.co.uk/cgi-bin/sh000 ... ml#SID=413

 

[Honest John]

Thanks for the replies guys. I'm glad you've grasped the problem, I was beginning to doubt myself in my understanding of how this could centre properly. I hadnt noticed that RDG Tools also had theses parts, so I think a trip to their counter is in order when I get back from the Highlands next week. I've used RDG before for online purchases but I understand they have a counter where you can discuss requirements and actually get a grip on items.

 

[woodpig]

Have you seen this John. It's in two parts.

https://youtu.be/z2PjSGLwO2E

 

[Honest John]

Wow. Thanks Woodpig. I had missed that one on YouTube. I work with wood purely for the fun and challenge of doing it and generally being creative. Prior to starting out on this road of indexing on and off lathe I was was thinking through using a small router on turned work, and it looks like this could all come together into something interesting. This particular path looks like one that is likely to involve me in some significant expense, but hey ho you only live once! Those two videos on YouTube are already starting to ferment some new ideas!

 

[woodpig]

I'm glad it was of interest John. It was quite interesting that the guy in the video had a wood chuck on a Morse taper but wasn't using it. I'm looking forward to seeing what you come up with.