Colchester Master 2500 Taper Attachment

[RobinHood]

My lathe had the taper attachment but the retaining clamp bracket, bracket extension, eccentric pin, and the push rod all were missing. You can see the components in the bottom left of the manual page below. So i made the parts.



I started with a piece of 1018 cold rolled and turned the taper part using my other lathe. The cone shape has no function other than to mimic the original cast one


Then i bored the hole to receive the eccentric pin to 5/8"


A bit of sawing with the band saw in the vertical position to rough out the remaining features of the main body

And finish milling


I needed to cut a short piece of steel to make the clamp shoe for the bracket. Here is how i used wood and a same size metal piece to do that


The eccentric pin was next. It was made from a junk of 1.5" mystery metal round bar (i think it is 12L14, just by the way it turns). The OD and concentric 5/8" pin were turned first so that i could flip the part and hold it in a square collet holder in the 4J to turn the other, offset, 5/8" pin, like so


I previously made the rectangular connecting rod clamp block (bracket extension). The connecting rod is a piece of 3/4" drill rod. The knurling is not the best on the eccentric pin as i was trying to make it better (it was really nice, but not full peaks) and pushed the tool in too far and started rolling over the peaks and made a mess of things... You can see all the parts here


Here are some images of the parts on the lathe.


Now i have a fully functioning taper attachment on my Colchester Master.

Next are tool holders for the OEM Colchester/Dickson tool post...

 

[YYCHM]

What does the knurled eccentric piece do?

 

[RobinHood]

As far as i can tell, it is there to compensate for any height difference between the connecting rod and the retaining clamp bracket. It is basically a fine adjustment. I could have done without it if i made my clamp bracket drop the required amount.
I think this set-up is used on Colchester Student, Triumph and other models - they possibly have different connecting rod heights. The eccentric pin allows for that.

 

[Dabbler]

Nice work! I have to make a similar clamp/bar for my new lathe - I'll post pics when I get around to it...
I love the eccentric pin - very elegant!

 

[John Conroy]

Very nice work! It looks like the taper attachment on my new lathe must be a copy of the Colchester design. Its nice to have pics of the original design as I think some improvements are in order for mine.

 

[Swissmat]

Hey RobinHood, fello Canuck here hailing from Victoria .. just stumbled across your post while searching for info on taper attachments for my Colchester Student Dominion lathe .. thanks for the pics! I'm trying to match our lathes up but it seems yours is more modern than mine .. your taper attachment looks very much like the one Clausing-Colchester sold with their Northamerican versions of the Student .. do you happen to have one of them?

 

[RobinHood]

Sorry, the lathe is a Colchester Master 2500. I just updated the title of the thread.

The taper attachments of the Student, Master and Triumph are either the same or at least very similar.

Are you just missing parts? Or the whole unit?

 

[RobinHood]

Another note. Is there a connection between your handle and the country?

 

[Swissmat]

hey, yep, Swiss by blood, Canadian by choice

I don't have a taper attachment but they pop up on ebay .. currently one there but I'm thinking it's more like yours than what my manual depicts .. so, no go for me .. I'll keep looking!

 

[RobinHood]

hey, yep, Swiss by blood, Canadian by choice

That makes two of us.

Some lathes require extensive cross slide modifications as well when installing a taper attachment. Don’t know your Dominion well enough to be sure, but the Master and Triumph have telescopic lead screws in the cross slide so switching to taper turning only involves tightening a SHCS and setting up the taper itself. No disconnecting of lead screws nuts, etc.

 

[Swissmat]

jo gruezi i dem Fall

I'm just doing the research to see which parts are needed .. often people show off the taper attachment only .. with brackets and bolts and what not but fail to elaborate on the cross-slide parts like a telescoping lead screw etc. .. I'm just trying to wrap my head around what's involved .. ThisOldTony built his own for a Colchester Student with some considerable restrictions (he has to uninstall the leadscrew nut and has a limited range everytime he installs it) .. your solution sounds like the right thing to have so that when you need it once in a blue moon, it's there and ready to go

 

[RobinHood]

Gruesseuch!

I am familiar with TOT‘s taper attachment build. That seems to be quite often the case when one installs a TA ”aftermarket”. Don’t get me wrong, nothing bad about the idea, just a lot harder to do because, as you point out, the restrictions / ease of use of a aftermarket TA.

I was lucky in that the Master had all the “vitals” (telescoping lead screw, the actual TA with all the major components) and was only missing the connecting rod and clamp block. These parts were “easy“ to reverse engineer as I have quite a few pictures of what they needed to look like. Plus I knew exactly what their function was and had made a mock-up out of wood to get within ballpark dimensions.

Let me know if you need me to measure / or send specific pictures of details on the TA in case you decide to build one from scratch.