Author Topic: Toolpost removal  (Read 4292 times)

Offline AdeV

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Toolpost removal
« on: November 13, 2009, 04:22:37 PM »
This should be dead simple, right? Unbolt & remove. Replace with freshly (yet to be) made quick-change device.

My world, as ever, is not so simple.  :bang:

The toolpost on my lathe has some fancy mechanism inside it which, when the lever is moved anti-clock, unlatches & swings the whole unit by 90 degrees. At 90 degrees, the toolpost latches down again, the lever is pulled smartly clockwise to re-clamp it down. These actions are repeated as required. It's a "sort of" QCTP, so long as you only want four tools. It's probably been on since the lathe was new, as I am about to demonstrate...

Anyway, I managed to disassemble the main parts quite easily. Top cap off, handle off, un-named drive bit off, screw-in thingy bit off, miniature roller bearing off, main toolpost off, latch mechanism off:
 
From left-to right: cap, handle, drive thingy, screw-in thingy, roller bearing, toolpost, latch widget. It's not easy to see, but there's a couple of sticky-out bits with springs to force them out when the toolpost allows it.

BTW, if you click the image, it'll take you to a page where you can see the full-sized (1600x1200) image, if there's a detail you're interested in

And here's the rest of the toolpost, that's bolted to the topslide (or is it compound slide? - which is the British version?):
 

That fancy looking shaft rotates through 180 degrees only. The lowest spline engages with the latching mechanism (the "fixed" portion of which is in this picture; the ring with the notches rotates about 90 degrees, before a spring winds up too tight to let it go any further. It springs back to the "home" position as soon as you let it go). The threaded portion of the shaft accepts the screw-in plate (4th piece from the left in the top picture). The top spline is engaged by both the driver plate thingy, and the handle.

Now, you'll probably have noticed that the compound slide appears to not be on the lathe at this point... that's because I had to remove it to try to figure out how to remove the tool post. And boy, is it a toughie. Here's the underside of the compound slide:
 

The hole to the far left centre is one of the two allen bolts holding the toolpost on (or was, I've removed it). The brass bit just to the right of the centre is, I think, the nut that travels up & down the leadscrew. I presume it withdraws through that hole once you've removed the screw. A portion of the screw itself is just visble in the U-shaped hole just to the left of the centre.

Just barely visible in this picture is the second toolpost allen bolt, behind the leadscrew:
 

OK, so I have to remove the leadscrew to access the allen bolt, to finally remove the toolpost?? Who designed this thing???

So, next job, I suppose, is to remove the handle. Only there doesn't appear to be any way to unbolt the pin(s) that are holding it on. Maybe they've been ground smooth, maybe they're just a hammer fit (shurely not? Everything else has been bolted or screwed on). Any bright ideas? I don't want to drill them, but I can't see any other way just now:

 

I'm hoping that once the handle is off its spline, and the dial removed, it'll be a simple 2-bolt job to remove the retaining whatever, so the leadscrew can be withdrawn. But it's too late & I'm too tired to continue now.

Another issue is the cross slide, which is very stiff to move. I thought, once I'd removed the cross slide, it ought to be a doddle to turn the wheel; but no, the stiffness is all in the leadscrew. Maybe the taper turning unit is doing it. Ho hum. I guess that's the breaks when you buy old knackered kit....
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...

Offline sbwhart

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Re: Toolpost removal
« Reply #1 on: November 13, 2009, 04:38:06 PM »
Adev

The handle will be held in with a taper pin:- try and fine the end with the smallest diameter, file urself up a brass punch and tap it out  :hammer: from the smallest end.

Without having a good look around and handling the rest of the tool post I can't help you much, those sort use to be very common in industry, before the QCTP came along.

Hope this helps

Stew
A little bit of clearance never got in the road
 :wave:

Location:- Crewe Cheshire

Offline AdeV

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Re: Toolpost removal
« Reply #2 on: November 13, 2009, 05:35:46 PM »
Adev

The handle will be held in with a taper pin:- try and fine the end with the smallest diameter, file urself up a brass punch and tap it out  :hammer: from the smallest end.

Without having a good look around and handling the rest of the tool post I can't help you much, those sort use to be very common in industry, before the QCTP came along.

Hope this helps

Stew

Thanks Stew - I did try tapping the narrow end with a screwdriver & my trusty plastic hammer, but I barely tickled it really, as I wasn't sure if I was doing the right thing. I think I've got a tiny piece of brass knocking around from an old floppy disk drive which will make an ideal base for a punch  :thumbup:

It's quite a clever assembly really; as the "normal" QCTP seems to be both much easier to use AND much simpler to design & make, I have to wonder why this sort of device ever made it past the drawing board...
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...