Aligning the tailstock?

mark wrote: ...how do you go about shimming the tailstock.

The tailstock is already split horizontally, surely?

That's an ambitious first project. Drilling accurately through 120mm won't be easy. Might be advisable to drill halfway from both ends.

First make sure the bed is straight and the lathe turns parallel with a bar mounted in the chuck alone. Adjust the lathe feet until it does. Then turn a test piece between centres measuring the diameter near to each end. Adjust tailstock until the diameters are the same. If you cannot get the two test diameters the same then it is possible the tailstock centre height is not the same as the headstock centre height (either due to an improper re-grind or you don't have the original tailstock. Shim either the tailstock or headstock until the heights are identical.

hth

Bob

out of interest ...how do you go about shimming the tailstock.

mines a little too low on the s&b 1024 (bought an upgraded 3 morse tailstock)

all i can think of is to cut the thing in half and join it back together with a shim in it .

or do you mill out patches in the bottom ....screw bits of steel into them in with counter sunk headed bolts /.....and surface grind.

all the best.mark

In the absence of a gun drill, start with 15mm bar. Clamp one end in the chuck and the other in a properly aligned fixed steady. Face the end off and use a spotting drill, or centre drill if that's what you've got, to start the hole. Drill the hole with a new, long, split point drill

part No HSS-66087C, for instance.

use plenty of cutting oil in the hole and withdraw the drill often to clear the flutes and lubricate the hole.

Once you've done that, mount the "tube" between centres and turn it to the final diameter. This will ensure that the hole is central. Then counter bore for the bearings.

With a gun drill, the operation becomes a lot easier.

Mark Rand RTFM

Austenitic stainless can be an absolute bugger to machine. It work hardens, which means that it can be difficult to take successive fine finishing cuts and it drills horribly. Also austenitic stainless is quite ductile so it is not very suitable for your spindle, for which you would ideally use something a bit harder to get a higher yield stress. You might want to use a free-cutting mild steel for the sleeve. For material for jobs like this spindle I often use a high-tensile bolt.

Thanks for that Mark. I need to start with the 12mm dia ground ba because...it is ground! This bar will have a seal running along it, s I can't have a machined finish.

By the way, the material I ended up with was 12mm dia ground bar - 30 grade (.04% C, 1.5% Mn .025% S). My friendly supplier told me thi stuff would be fairly easy to machine because of the Sulphur content).

Could I use a 10mm slot drill mounted in a tailstock chuck to do th counterbore for the bearings?

Cheers,

Garth

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Bob,

Regarding the test diameter method: I tried this with a 10" long 1 dia bar last week, And got a 10 thou difference initially. I adjuste the tailstock and got it down to 2.5 thou. I could get it spot on, bu looking at the brass scale riveted tothe tailstock, it is nowhere nea the centre line on there (perhaps 1mm off. Why is this? Non-origina tailstock? Is the above method valid using a 3 jaw chuck? I assume th clamping force of the chuck will put a lot of force on the tailstoc and make the results invalid?

I read somewhere where you could turn another similar test piece t check for bed alignment (obviously not using the tailstock), althoug the bar needs to be about 4" long presumably to avoid chatter at th free end. Is this a valid way of testing bead alignment?

Cheers,

Garth

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Mark's point is that the likelihood of ending up with your 8mm drilled hole concentric with your nicely ground 12mm OD is very small, especially over that length. Be aware that drills do have a tendency to wander, and even if the starting hole is spot on (which it should be, drilling from the tailstock) the exit hole may well be significantly off-centre depending on the type/accuracy of the drill you use. So turning between centres after you bore the hole will allow you to achieve concentricity. If that is not an issue for you, that's fine.

Bear in mind that if you do machine the outer surface, it is possible to get any level of final finish you want by using a combination of techniques - fine feed on the final cut, followed by successive grades of wet&dry, followed by metal polish, for example. Perfectly possible to get a mirror finish for not very much effort.

Regards, Tony

Tony,

Understood regarding the concentricity issues, but so long as th bearing pockets in each end of the bar are concentric that is all tha matters. If I can get away with that then the surface finish issue wil solve itself.

Regards,

Garth

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In article , Tony Jeffree writes

George Thomas included some very useful notes on deep hole drilling in the Model Engineer's Workshop. Apart from obvious things (use a sharp drill, withdraw frequently to clear cuttings etc.) the key thing is to ensure you have an absolutely spot-on start to the hole by drilling the first section undersized and then using a boring tool to open up to near size.

On short lengths I often use a fine file soaked in oil (a No 6 cut Swiss flat file) as it is less prone to round over the edges, though I have also used Tony's method on long bars with excellent results.

David

You could also consider EN24T, which is a lot harder than EN1A even in its annealed state, and can be hardened a lot more. It is reasonably easy to machine to an excellent finish with a new TC insert. Mallard Metals have a decent range, has a good finish too, much better than MS bar.

David

The edge rounding issue can be overcome by sticking strips of wet&dry paper to a wooden stick - in fact, you can buy sticks with paper pre-attached from some suppliers.

Regards, Tony

On or around Fri, 02 Nov 2007 11:30:49 +0000, Tony Jeffree enlightened us thusly:

AIUI, the 8mm hole is a clearance hole for a 6mm shaft, so a few thou off centre won't be an issue. AIUI2, the 12mm outer bit is not intended to rotate, or not at any notable speed, so balance won't be an issue either.

Personally, were it me, I'd bung the 12mm in the chuck and drill it about

60-and-a-bit deep from either end... although it could be that you'd want to get it ground at the end of the process - but if it's hard enough, and you don't grip it *too* hard, it should be OK.

the only thing I do similar to this is drilling through a piece of 20mm BMS

124mm long to make a hollow axle. I used to drill it in 1mm increments, to various depths, but recently decided this took too long, so now it gets drilled 8, 10, 12, 14, 16mm. This is 'cos actually making a tapered hole is far too much hassle.

The initial stage is to drill 8mm 65mm deep from one end, then I drill the other sizes, then turn it round in the chuck and repeat. The steps are different depths on each end.

having done the drilling I clean the outside up with a bit of fine-ish emery while spinning it in the lathe.

I daresay I could make it lighter by using a higher quality steel...

Hi Garth,

Your second paragraph describes the method I referred to in my original reply. If you have the myford manual then this is described in detail. You need to do this first to make sure the bed is not twisted

No sure why you seem to be 1mm off at the tailstock and yet are turning near parallel. You can do a crude comparison with a center in both the headstock and tailstock and slide the tailstock upto the headstock and compare the two tips.

Bob

Correct.

!AIUI2, the 12mm outer bit is not intended to rotate, or not at any notable speed, so balance won't be an issu either. ! Correct. ! Personally, were it me, I'd bung the 12mm in the chuck and drill it about

60-and-a-bit deep from either end... although it could be that you'd want to get it ground at the end of the process - but if it's hard enough, and you don't grip it *too* hard, it should be OK.!

O.K. ! The initial stage is to drill 8mm 65mm deep from one end, then I drill the other sizes, then turn it round in the chuck and repeat. The steps are different depths on each end. ! O.K. ! having done the drilling I clean the outside up with a bit of fine-ish emery while spinning it in the lathe. ! O.K. ! I daresay I could make it lighter by using a higher quality steel... ! Lighter. Interesting. How did you guess weight might be an issue? I even considered Carbo fibre for both shafts, or even getting it manufactured for me (wouldn't cost me anythin after all), but then I would not be able to practice using my lathe ;-).

So...I am using bought in 10mm dia ball races in each end. What is the best method o machining their housing 'counterbores'? I was thinking trying a 10mm dia slot drill in som scrap and see if they fit. Or just trying a drill, but this wouldnt leave a square bottom If these don't work I suppose I could try getting my tint carbide insert tool in there Failing that I'm running out of options guys!

Cheers,

Garth.

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drill in some

square bottom.

Bore it with a boring bar. A slot drill will produce a relatively flat bottomed hole and might do the job ok, but there is a chance that it will produce the wrong sized hole. Chronos do some nice Glanze boring bars in the 5 and 6mm range that are the right size for this job. Go in axially, but a bit under depth, taking about .25mm per cut until you have the diameter you need. Then clean up the bottom of the hole radially. Alternatively, shove a 9mm drill down the hole to within a mm of the depth you need and then finish off with the boring bar, but it's hardly worth the extra operation, since you already have the 8mm hole.

Mark Rand RTFM

Bob,

Yep, did that, and it looked about right...still the marks on th tailstock were misaligned.

Regards,

Garth

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