Can’t get close to the Headstock. Making a Backplate. Help!

This topic has 10 replies, 6 voices, and was last updated 27 July 2018 at 21:14 by SillyOldDuffer.

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27 July 2018 at 16:20 #364167
SillyOldDuffer
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@sillyoldduffer
I'm making a chuck back-plate to take an ER32 collet chuck and have encountered a problem at the last stage where accuracy matters.

I have the blank fitted correctly to the lathe spindle and now want to true the outer face and then make a 115mm diameter register by removing 9mm of metal around the rim to leave a boss. The blank is a coarse grained cast-iron that cuts fairly easily.

The problem is, as the photo shows, I can't get the tool-post full-left closer than 40mm of the working surface.

With the tool protruding the normal distance from the 4-way, there's still a gap of about 25mm.

The saddle can't get closer because it is jammed by the telescopic spring swarf guard on the leadscrew. I could remove the guard but it's a fair bit of work. (The lathe is a WM280)

I'm tempted to overhang the toolshank as far as it will go to finish the face and then use a boring bar to make the register. Not tried anything like this before and am worried about chatter or the long reach flexing and trashing the accuracy. It's these last cuts that will determine the run-out of the collet chuck. I don't want to mess up making the register.

How would the team suggest I tackle this please?

Thanks,

Dave
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27 July 2018 at 16:20 #9274
SillyOldDuffer
Moderator
@sillyoldduffer
27 July 2018 at 16:30 #364168
KWIL
Participant
@kwil
You must have some topslide movement available, you are maybe too cautious about overhang?

Since you still have someway to go, you can check your accurancy, a long way before you trash it!
27 July 2018 at 16:30 #364169
HOWARDT
Participant
@howardt
Usual is to stick a boring bar in the tool post.

Is the compound slide full extended ?
27 July 2018 at 16:31 #364170
JasonB
Moderator
@jasonb
Good diameter boring bar to counter the extra overhand and stick it in reverse.
27 July 2018 at 16:40 #364173
John Rudd
Participant
@johnrudd16576
Dave,

My WM clone has the same issue…..for the sake of cleaning the leadscrew periodically, I'd be inclined to remove the covers, it gains you the precious 40 mm or more…..better than having overhanging tools ( oooh err missus…. 😛 &nbsp
27 July 2018 at 17:40 #364184
SillyOldDuffer
Moderator
@sillyoldduffer
Following Jason's advice, cut with my biggest boring bar in reverse and the backplate faced off OK. It was necessary to adjust speed to reduce chatter, and there was a sweet spot where the lathe trundled round cutting OK without shrieking like a banshee!

I need to cool down before having another go. Cup of tea, walk in the fresh air and then I'll cut the register.

So far so good.

Thanks,

Dave
27 July 2018 at 17:46 #364185
Gary Wooding
Participant
@garywooding25363
I gave up constant messing around and removed the lead-screw cover. I never regretted it.
27 July 2018 at 18:39 #364192
JasonB
Moderator
@jasonb
Mine being and early 280 did not come with a cover. That flywheel was hitting the carrage legs so had to use the boring bar to get close enough.
27 July 2018 at 18:47 #364193
SillyOldDuffer
Moderator
@sillyoldduffer
Posted by Gary Wooding on 27/07/2018 17:46:55:

I gave up constant messing around and removed the lead-screw cover. I never regretted it.

I can see why. Mostly I work with a 3-jaw, less often with a 4-jaw. They both come out far enough that the leadscrew cover isn't a problem. I've not used the faceplate on this machine yet so this is the first time I've felt the pain.

Fingers crossed that the collet chuck is in range; it's quite a lot shorter than the big chucks. If not, the obvious cure is to remove the cover. Bit of a shame as it's nice not to have to fret about swarf getting into the half-nuts. Removing it gives an extra 40mm of saddle movement each way, which is a real benefit

Dave.
27 July 2018 at 21:14 #364223
SillyOldDuffer
Moderator
@sillyoldduffer
Success!

As I feared a fair amount of chatter but I got an accurate result. Final step is to drill three plain holes to take the mounting bolts. I was going to push on and do it tonight, fortunately common-sense stepped in. The humidity here is rising unpleasantly, bit thundery, and I'm hot and tired. Exactly the conditions required for making really stupid mistakes. I'll wait until tomorrow and cock it up then!

Many thanks for all the suggestions.

Cheers,

Dave
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