Setting a lathe tailstock

[DAPPH]

By angle do mean to the centre axis or just meandering? As you quiet rightly say theorectially it shouldn't happen. Drilling oversize is possible with a good size drill, unless your using a small drill and it's flexing a bit like Dynarod. They drill for oil that way. Saddam was stealing it from Kuwait (one place I haven't worked in) by drilling horizontally. That's possible. Cheap drill and not centred from the off. My cheapo Chinese drills are very much a mixed bag. Had some centre drills where the chamfer had been ground in reverse. Trying to explain to the seller was like Basil and Manuel. But not sure which one of us was Manuel in the end.
Some hadn't been hardened.....etc.

Poorly unevenly sharpened /angled cutting edges will also lend to holes wandering that's why a good centre point drill in a locked up tailstock ram is used to advance a hole for the first few mm.


Out of a nice grey & blue windowed presentation box of 0.5 to 15 mm in 0.5mm's HSS twist drills made in Turkey & sold in the likes of B&Q big box stores four of the smaller drills had been sharpened with the web of the drills justified to one side ... to almost 1/4 of the drill diameter
As soon as I discovered the 1.5 mm drill was off I checked the rest & reground all of the badly ground drills

 

[DAPPH]

Seems not but there's no other way to drill an out of straight hole in a part turning on axis. Not one I can think of anyway.

Hold the drill in the chuck and the part in a misaligned tailstock or badly set up tool post .

Especially if the tool post is sitting on a raised metal mole hill due to PO's not using the correct tool post clamping bolt .
Like my lathe was like when I got it . . almost every time I put pressure on the carriage or compound slide ... the work piece & the tool post clamp slowly but surely started to rotate the tool post out of square as the pressure was applied via the carriage rack . or compound slide .
A couple of hours with home made warlocks engineering blue a 22 inch mechanical hacksaw blade scraper and a couple of chalked up fine files and the mole hill was removed giving am an all over checkable flatness when I reassembled things with a completely new right sized T nut and a self made high tensile steel centre bolt .

Warlocks engineering blue ? It's a home made emergency substitute for proper engineering marking blue dye

A little ink out of a BIC biro type pen mixed in with a little zinc & castor oil baby's bum cream . Penatent ( sp? ) nappy cream can also be use with the ink ...you only need a little .. it stores well in a tiny scent tube bottle
E45 cream's too runny for most purposes .

 

[prepman]

Poorly unevenly sharpened /angled cutting edges will also lend to holes wandering that's why a good centre point drill in a locked up tailstock ram is used to advance a hole for the first few mm.


Out of a nice grey & blue windowed presentation box of 0.5 to 15 mm in 0.5mm's HSS twist drills made in Turkey & sold in the likes of B&Q big box stores four of the smaller drills had been sharpened with the web of the drills justified to one side ... to almost 1/4 of the drill diameter
As soon as I discovered the 1.5 mm drill was off I checked the rest & reground all of the badly ground drills

Might be of interest or not? But I was watching mrpete222 on Youtube and he was producing centre drill abors. During it he showed a snazzy holder where the centre drill just pushes in and locks. He admired it but made a different style himself. I liked it and decided to work out how to make it and made 2 different size ones. Turning the morse taper for them is a bit of ball ache using the topslide. But... Makes an easy time of centre drilling. Also made a wobble broach by mutilating an old lathe live centre as they're £400 or were.

 

[DAPPH]

Pharm ,
It sounds like you have multiple things that need checking /sorting .
Clean the tailstock chuck ensuring there are no tiny burrs or bits of metal that are going to make the chuck jaws advance ever so slightly out of alignment . Wind up the chuck to close it and insert it in the lathe chuck to hold it square & true . You might need to use a bit of good round stock in the chuck such as the biggest twist drill you have if the lathe chuck is too small to hold the tail stock ..... jaws in first .

Now run the lathe and see if you can detect any off true running activity using the rod & roller bearing in the tool post exercise . This is to prove that your tail stock chuck is not bent &that the jaws are working evenly as they should .

Check that the tail stock is centrally clamped and pressure gib screw adjusted so it can only just move along the bed when oiled using a few pounds of effort . It should not freely skid along like a block of red hot steel on an ice rink & it shouldn't waggle about across the bed when you have a long stout bar in the tail stock chuck .

Put the tail stock to the right hand end of the lathe.
Lock the tail stock to the bed , lock the tail stock ram , wipe the join between the bed & the tailstock body clean of any oil or stuff .
Now add tailstock chuck , insert the thickest longest rod you have to fit in the tail stock chuck and give the left end of the bar a couple of strong wiggles Notice any thing like movement? do this at numerous positions along the bed ...use a big Allen key in the tailstock chuck and a bit of tube for a lever as you get closer to the lathe chuck end .

Now give it a spray of WD40 & a squirt of oil , mix it up with your finger , wiping the excess of off with your finger . repeat the exercise all over again , w wiggle it hard & watch the joint covered by that think film of oil to see if you notice the thin skin /film of oil at the join moving . If you see movement things might need adjusting correctly to get as much movement out as possible whilst still retaining a working lathe.

Do the same oil check with the locked tail stock tube , the compound slide , the cross slide and the carriage . . For the latter get something as heavy /strong & long as you can hold in the tool post clamp and give it a wiggle measuring the deflections if you can ...again any oil film movement will show you were wear or damage is .

If there is no pressure gib adjusting screw on the left end or the right end face of the tailstock body you may have to make up your own packing strips to get the movement reduced or even turn up a true square stepped plate so that the tailstock has on rotatable movement . it must be the same fit all along the ways Any differences might not only indicate wear you don't want but IIRC also indicate a twisted lathe bed .

My pressure gib screw on the tailstock block to prevent front of lathe to rear of lathe movement is at the left hand rear face on the tailstock ..it made a tremendous difference when finally set up correctly , it took me months of very methodical checking to discover it & it's function .


One last thing :-
I learnt a few years ago is :-
Once you get really used to your lathe and yours & the lathes foibles , you can turn fair quality things with a worn , slightly out of adjustment lathe so long as the cutting tool is sharp and reasonably sharpened at the correct angles.

 

[prepman]

Found the correct video for the centre drill...

I made one that extended the centre otherwise it was to short and didn't need the grubscrew, but not split just a tight fit with pins that engage in the flutes.

 

[Pete.]

Hold the drill in the chuck and the part in a misaligned tailstock or badly set up tool post .

That could drill a crooked hole but the part would not be turning on axis.

 

[Brad93]

May be of use

 

[prepman]

Poorly unevenly sharpened /angled cutting edges will also lend to holes wandering that's why a good centre point drill in a locked up tailstock ram is used to advance a hole for the first few mm.


Out of a nice grey & blue windowed presentation box of 0.5 to 15 mm in 0.5mm's HSS twist drills made in Turkey & sold in the likes of B&Q big box stores four of the smaller drills had been sharpened with the web of the drills justified to one side ... to almost 1/4 of the drill diameter
As soon as I discovered the 1.5 mm drill was off I checked the rest & reground all of the badly ground drills

Just going through my Chinese twist drills and bad news none will cut (even after attempted hardening) Slow speed steel?. The good news ......I've got lots of them.