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Colchester Taper Attachment

RobinHood

Active Member
Premium Member
#1
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.

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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
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Then i bored the hole to receive the eccentric pin to 5/8"
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A bit of sawing with the band saw in the vertical position to rough out the remaining features of the main body
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And finish milling
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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
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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
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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
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Here are some images of the parts on the lathe.
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Now i have a fully functioning taper attachment on my Colchester Master.

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

Active Member
Premium Member
#3
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

Well-Known Member
#4
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

Well-Known Member
Premium Member
#5
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.