MT3 Spring Centre

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dazz
CNC Expert
CNC Expert
Posts: 243
Joined: Sat 19 Aug , 2006 11:31 am
Hardware/Software: Viceroy TDS 1/1GB lathe, Imperial, stripped down and rebuilt.
Viceroy Taper/Tracer attachment, Shop made cross slide tracer attachment, VSD.
Location: New Zealand

MT3 Spring Centre

Post by dazz » Mon 23 Jan , 2012 3:12 am

Hi

This is the result of a project to make a precision spring centre. The spring centre is used when tapping threads on the lathe to ensure the tap is properly aligned. The spring centre keeps pressure on the back of the tap as threading advances.

All of the clearances are minimised to ensure that the centre doesn't wobble about in use. The close tolerances also help keep dirt out of the internals.

The MT started out as a cheap $1 MT3 / JT3 arbor. I started by tempering the arbor to blue and ensuring an even hardness through the arbor. I drilled the arbor out and then made a D-reamer to accurately bore and finish the hole. The D-reamer was made from a piece of 12.4mm round HSS.

The end of the arbor was threaded to take a cap piece. The cap retains the stepped pin and guides the pin to keep in on centre. The cap guide hole was bored using a slot drill.

The centre pin is made from silver steel.

I made the spring because I can't buy a suitable size here.

The outcome is a spring centre with virtually no play. This will make tapping and other operations easier to do on the lathe.

As part of this project, I had to make other tools (making tools to make tools).
I made a small boring bar from a piece of key steel. This was used to bore and thread the cap piece.
I made a split clamp, also from key steel, that was used to hold the slot drill in the tool holder.


This design is more complex to make than others I have seen. There are plenty of opportunities to make mistakes. It has achieved the aim of an accurate spring centre.

Dazz
Attachments
IMG_1927.jpg
The D-bit boring out the 3MT arbor.
IMG_1927.jpg (68 KiB) Viewed 4122 times
Spring Centre Exploded (600 x 299).jpg
The parts of the spring centre.
Spring Centre Exploded (600 x 299).jpg (17.68 KiB) Viewed 4122 times
Spring Centre Assembled (600 x 202).jpg
The assembled spring centre
Spring Centre Assembled (600 x 202).jpg (12.25 KiB) Viewed 4122 times
Regards

Dazz

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