Mills and Lathes

link1896

link1896

Mr Greenfield
My leadscrew/half nut/drive gears all add up to significant backlash, I only cut threads in one direction, I allow for a dead zone after the threaded area of the work piece to stop in, wind the cross slide out, come back past the starting point, and wind cross slide back in the next cut.

What's the difference between your metric and imperial gear set that has an influence on backlash and won't allow the above to work for you?
 
Dales Cannon

Dales Cannon

lightbrain about 4pm
Staff member
To cut metric threads you cannot disengage the lead screw. No idea why, that is what is says in the manual. So run it in, stop the lathe, back the tool out, reverse the lathe and so on. Tried using the thread dial as you would an imperial thread and it was no where. I did line up by eye once and it was good but next time no.

My cross slide looks the same as yours but I have another set of gears to drive the lead screw and a gearbox on the lead screw as well.

Edit:

"Metric Thread Cutting – The only difference in metric thread cutting is, the half nut must remain engaged during the entire threading process. The thread dial cannot be utilized.
Set the machine up for the desired thread pitch . Start the machine and engage the half nut. When the tool reaches the workpiece, it will cut the initial threading pass. When the tool reaches the end of the cut, stop the machine by turning the motor off and at the same time back the tool out off the workpiece so that it clears the thread. Do not disengage the half nut lever. Reverse the motor direction toallow the cutting tool to traverse back to the starting point."
 
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link1896

link1896

Mr Greenfield
SummitFever said:
This means your lead screw has an imperial pitch. That's why you can't disengage because the dial wheel will not correspond to an even thread position so you have no idea when to re-engage.
Click to expand...
Ahhhh pre colour/metric era, maybe even from back when the world was flat. I was scratching my head on that one, thanks summit.
 
Dales Cannon

Dales Cannon

lightbrain about 4pm
Staff member
SummitFever said:
This means your lead screw has an imperial pitch. That's why you can't disengage because the dial wheel will not correspond to an even thread position so you have no idea when to re-engage.
Click to expand...
That was my guess. Explains why the M8 cross slide screw didnt love the new nut.
 
link1896

link1896

Mr Greenfield
Getting ready to grind the jaws of my three jaw chuck using this method

My tube for preload is an old 1 1/8th headset cup that appears to be nice and round
 
S

SummitFever

Eats Squid
How flogged out is your 3 jaw? Jaw grinding is good if you've actually worn the jaws down in the front compared to the back. If its runout you're fixing then it may well be the scroll. You can "fix" the runout for one bit of the scroll but then may have problems in other areas. His method is OK if the jaw slots/chuck slots are not worn. If they are, then clamping on the end will result in grinding your jaws tapered.

For high accuracy, its either the 4 jaw (at the expense of time spent clocking the workpiece up) or a collet chuck (at the expense of money and flexibility). There are occasionally silly deals on collet chucks to be had...
 
link1896

link1896

Mr Greenfield
SummitFever said:
How flogged out is your 3 jaw? Jaw grinding is good if you've actually worn the jaws down in the front compared to the back. If its runout you're fixing then it may well be the scroll. You can "fix" the runout for one bit of the scroll but then may have problems in other areas. His method is OK if the jaw slots/chuck slots are not worn. If they are, then clamping on the end will result in grinding your jaws tapered.

For high accuracy, its either the 4 jaw (at the expense of time spent clocking the workpiece up) or a collet chuck (at the expense of money and flexibility). There are occasionally silly deals on collet chucks to be had...
Click to expand...
Thanks Summit. A bit of everything, it's rare I need to hold pieces internally, I'm mainly clamping things externally. I've just ground the jaws, happy at 0.015mm runout around 25mm clamping diameter.

Next to shim the head stock square and parallel to the ways.

Sometime in the not too distant future I'll replace this old girl with something of quality.

Today's work buys me some time.

 
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link1896

link1896

Mr Greenfield
Had another few passes at grinding. Now I'm
Happy. Can almost not resolve the runout at the chuck jaws, let's call it 0.005mm. At 250mm out from jaws runout is 0.08mm. Chuck clamps up entirely differently now, as all three jaws clamp simultaneously and evenly.

Now to get the head square and parallel to the bed, and get the chuck jaws engraved so jaws go back to their correct homes when I rebuild next.
 
Dales Cannon

Dales Cannon

lightbrain about 4pm
Staff member
My very old and well abused Pedestal (pedophile?) drill was definitely on its last legs. When I used the 2" hole saw it vibrated so badly you ended up in a different suburb by the time the hole was finished. And it had a tendency to drill oval holes, but only when you were drilling something important like a brake rotor. Pretty sure it is a 1463 model year with serial number 001.

Anyway #1 owed me for rego and insurance on his ute and toy and finally paid me back so I grabbed this.



Very tempting to go bigger and bigger but tooling is expensive. I did a deal on some old floor stock and they threw in a few extra bits as well as knocking off some $. It came with a 125mm fly cutter. Never seen a fly anywhere near that big.

Next on the list will be a lathe upgrade. Not until next year. Again biggest issue is all my tooling will be pretty much unusable thus the lathe will need another $1,000 or so thrown at it.
 
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