Check Morse Taper in Headstock and Jacobs Drill Chuck

[Winander]

I have a Sherline lathe and when I use a Jacobs drill chuck in the headstock (#1 morse taper) the end of the drill revolves like a paint stirrer.

I've checked the taper in the headstock is clean. I have no other tools that fit into it and consequently don't know if the headstock taper is out or the one on the drill chuck. I have a dial test indicator and could see if the headstock taper is round a various points, but how would I test if it is laterally aligned? Is there anything I could do to test the taper on the jacobs chuck?

[ralphrobertson]

Hi Richard,

Presume you have used the long bolt to tighten up the chuck thereby pulling it into the taper. Link here to the part for the Sherline chuck shows what I mean.

https://www.sherline.com/product/1010-ojt-532-jacobs-drill-chuck/

Ralph

[Winander]

Ralph,

Thanks for the suggestion because I don't have a drawbar and should use one.

For anyone else's reference the drawbar is 1/4" 20 (i.e. UNC) 5" long. If you get one with a cap screw, the allen key you require is 4.75mm / 3/16 inch - you'll have more luck searching for the imperial size.

I had to buy four bolts for the drawbar, so bought 4 keys, so if anyone wants a set, PM me. You'll have to make the centring/thrust washer, the spec for that is here https://sherline.com/wp-content/uploads ... 55inst.pdf

[Stephan.wintner]

Set the dial indicator up so it rides on the inside of the (empty) headstock and revolve the headstock spindle. The runout should be insignificant. If it is not then the spindle bore is not concentric to the headstock bearings. (Revolve by hand of course).

If the spindle bore is running true, install the Jacobs chuck, chuck a piece of reasonably straight round bar in it, then using the dial indicator measure the runout on the bar next to the jaw. Note the value and mark the high spot. Then measure 1 inch from the jaw. The difference between your measurements tells you if you have a parallel offset or an angular one (or a mix of both).

If you can dismount the chuck from it's arbor, you can check the arbor alone. But it might be better to just buy another arbor and test the new one.

You don't have a three or four jaw chuck, dead center, or collets? It'd likely be worth working through them all to ensure they are reasonably good. Note that a 3 jaw or Jacobs chuck is not likely to be as concentric as a collet or dead center.

You should also test whether the tail and headstock are properly aligned. (You asked about lateral alignment.) The only ways i can think of doing that start with a collet and drawbar and some bar stock.

Watch this video, it should give you ideas. https://m.youtube.com/watch?v=kMB_SfDCwEg

I'm sure a more experienced machinist has better ideas than I.

Stephan

[davebradwell]

There's something very wrong here. Your chuck should push into the morse taper and stick there, held solely by the friction in the taper. You should be able to feel the taper gently engaging over its full length without rock. If it's not fitting properly, pulling it in with a drawbar will cause further damage. There may just be a piece of swarf or dried grease in there.

A distinct possibility, especially if it's a second-hand machine, is that previous owner has been ramming bits of steel bar as far as possible through the 3 jaw and bruised the taper. This is very common and both my used lathes are seriously damaged. Try running the lathe slowly and feel the inside of the taper with a piece of plastic rod or dowel - knitting needle, perhaps? Cure here is to get a morse taper reamer but I'm not sure how this will work with the short taper you have - perhaps matching short reamers can be found.

If you are just drilling, you don't need a drawbar to hold the chuck in. This is for milling and you shouldn't be milling with a Jacobs chuck, anyway, especially such a small one. Is the problem with your chuck? If you've had a dig-in while milling then it will be knackered. These chucks can't take a side load so holding parts for turning would be another no no.

Bent drill, perhaps?

DaveB

[Winander]

Thanks both for the good advice.

I've tried about 20 drills and all exhibit the same runout. I haven't used the headstock chuck much and only to drill thin material. It does stick into the taper and stays there when drilling with some pressure without a drawbar. I haven't used it at all for any milling operations, but the lathe and all the accessories are second hand. The taper on the chuck has a polished ring which may indicate a poor fit or damage to the taper in the headstock.

If you look at the specs on the link Ralph posted, Sherline claim 0.003" or less runout and sell the chuck with a drawbar.

I'll try all the measurements suggested. I have been trying to drill through 26mm of flat brass, initially with a 3mm drill in the tailstock chuck and the work in a four jaw scrolling chuck. I have found the tailstock chuck accurate and assumed the chuck held the work laterally aligned but it didn't and the drill wandered. So I bought a vertical slide and tried a new work piece with the headstock chuck with a 1.8mm drill and that wandered - I had checked the work was at 90o to the slide. It's possible the slide isn't vertical and a myriad of other possibilities I need to check. All good learning experiences, but a little frustrating.,

[Jeremy Suter]

If you are just drilling, you don't need a drawbar to hold the chuck in. This is for milling and you shouldn't be milling with a Jacobs chuck, anyway, especially such a small one. Is the problem with your chuck? If you've had a dig-in while milling then it will be knackered. These chucks can't take a side load so holding parts for turning would be another no no.

Bent drill, perhaps?

DaveB

Spot on. I could not say it better myself

[davebradwell]

Did you spot the hole position with a centre drill first? It will almost certainly wander if you didn't.

From the mark on your morse taper, it's almost certain there's a burr down inside the mandrel.

Thanks for the support on the chuck issue, Jeremy, as it's not a universally held opinion. I had plenty of dire warnings about transgressing, though.

DaveB

[Winander]

Did you spot the hole position with a centre drill first? It will almost certainly wander if you didn't.

From the mark on your morse taper, it's almost certain there's a burr down inside the mandrel.

I did spot the hole. I'll see what I can see down the mandrel.

Thanks for your help, much appreciated

[Stephan.wintner]

Can you try the ink on the taper test, like the video? That would help identify any burrs or poor matching in the taper.

Stephan

[davebradwell]

It must be inconceivable that the tapers have been machined wrong. A dig-in might have made it slip, spin and be damaged by "picking-up" or seizing.

If you have the job securely clamped to a vertical slide and you drill down to the cone with centre drill first, then when you change to the real drill and bring the job up again then it should/must go through straight even if slide is slightly off-square. Don't forget some packing behind the job as it's a mortal sin to drill into the machine....or touch the chuck jaws with the tool, bruise the taper, etc, etc.

Not sure about some of your descriptions - a 4jaw scroll chuck sounds like a 4 jaw self-centring chuck. Certainly a luxury item.

Going back to the first problem, the wobbly drill - is the chuck body running true when clocked? This would be a sign of where the problem lies. Does the same chuck fit in the tailstock?

If you like collecting accessories then a small ER collet chuck would be the thing, unless Sherline have a different way of doing collets. These will take the side load.

DaveB

[Winander]

If you like collecting accessories then a small ER collet chuck would be the thing, unless Sherline have a different way of doing collets. These will take the side load.

Sorry but I haven't had any opportunity to examine the lathe today. Lathe terminology is not my forte, I merely wanted to emphasise it's not an adjustable 4-jaw (which I have also).

I was thinking of getting this https://www.rdgtools.co.uk/acatalog/2MT ... 95133.html despite the url, it is 1MT.

The tailstock is 0MT and works fine and there's no provision for a drawbar.

[Winander]

Can you try the ink on the taper test, like the video? That would help identify any burrs or poor matching in the taper.

Seems reasonable although quite a number of minor imperfections, but I know nothing about such things.

1MT Jacobs.png

[ralphrobertson]

Hi Richard,

I was thinking of getting this https://www.rdgtools.co.uk/acatalog/2MT ... 95133.html despite the url, it is 1MT.

I bought a set of ER16 collets from RDG for my Sherline lathe as per your link and I am delighted with it. I had a problem with the M6 tapping in the collet holder and had to get it changed but this to me seems a far better option than buying the individual and expensive Sherline WW collets. Money well spent.

Ralph

[Winander]

I bought a set of ER16 collets from RDG for my Sherline lathe as per your link and I am delighted with it. I had a problem with the M6 tapping in the collet holder and had to get it changed but this to me seems a far better option than buying the individual and expensive Sherline WW collets. Money well spent.

Hi Ralph,

Thanks for the endorsement, I was concerned at the 10mm upper limit of the ER16's capacity for holding work, but wanted the 0.5mm lower limit (ER20 has a 1mm lower limit). If I need to work on anything bigger I can use the tool in the collet.

Did you have to get the tapping changed to 1/4" UNC of the standard Sherline drawbar?

[Terry Bendall]

I posted something on this yesterday but it seems to have got lost somewhere. The problem may be dirt or swarf in the tapered hole. It is good practice to wipe the item to be inserted into a morse tapered hole forst and clean the hole. With a small hole the most pratctical method is a pice of paper towel on a piece of rod or wooden dowel. Rag should be avoided since that may transfer more dirt than it removes. As others have remarked the use of a drawbolt for this purpose should not be necessary.

If testing as Stephen suggested the bar must be straight.

You should also test whether the tail and headstock are properly aligned.

There are various ways of testing this. One method is to put centres in the headstock and tailstock and slide the tailstock up so the centres touch. The points should be in alignment both vertically and horizontally. A variant on this is to trap a 150mm long steel rule beteen the centres. The rule should be at 90 degress to the late centre line and will exaggerate any errors. A futher method is to get a piece of silver steel of the largest size that will fit through the spindle and as long as will fit betwen the centres Ideally hold in a collet to centre drill each end. Support the bar on the centres and hold a dial test indicator in the tool post. Traverse the carriage along the bed - there should be little or no movement of the indicating needle.

Lathe terminology is not my forte,

One of the best books I have ever found on the use of the lathe is the Amateur's Lathe by L.H. Sparey. It was first published in 1948 so to some extent is of its time. It is mainly directed towards the larger sort of machine used by model engineers but the principles of using the machine, terminology and the sharpening of cutting tools are all exactly the same. Last time I looked it was still available new but secondhand copies should be widly available. I still make frequent use of my copy.

Terry Bendall

[ralphrobertson]

Hi Richard,

Think I might have misled you there, my collet holder was faulty, the thread for the M6 bolt wouldn't take so I got the collet holder changed for another the same. I bought an M6x100mm stainless bolt from Accu which fits perfectly. I bought 4 of these as this was a price break and have 3 spare so if you don't have one let me know and I will stick one in the post for you. You will need a collar as you can see in the photo of mine.

Ralph

20220228_092109.jpg

[Winander]

Thanks Ralph that's most helpful.

Terry,
I have the book, bought after your recommendation but not had the time to read it. I think I should make more effort.

[Winander]

I had time this morning to examine the lathe. It has a hole through the mandrel to locate a tommy bar to hold the spindle whilst tightening the chuck. The only things I have to place in the mandrel are a centre and the Jacobs chuck, the latter only ever to drill through thin material that would not be affected by any runout. Thinking about it today, when I last used the centre, things didn't work out as I thought they should.

In my ignorance and unawareness, I never contemplated that he tommy bar could damage the morse taper. It appears to have done so. I haven't done it much, but have done it more lately.

You can see the hole on the left and the ink that came off the taper on the drill chuck that has accumulated as it was rotated, plus some scoring nearby.

IMG_1807.png

This is the taper on the drill chuck, the scoring on the left corresponds to the hole and I can feel it with my fingernail, the ding on the right is, I believe concave. The narrow end of the taper is to the right.

IMG_1812.png

I would like to ask the best way to remove the raised edge on the hole. Would wrapping the taper on the drill chuck with wet and dry and rotating it be a good idea?

[Stephan.wintner]

I don't think that is a good idea - or anyway i think i see a better approach.

I have a small, tapered, cylindrical Swiss file. I'd try to get at the edge from both the inside of the morse taper and the inside of the tommy bar hole, and locally ease the edge. You only should need a few thou.

Then try the ink check again, but only rotate a little bit (maybe 20 degrees clockwise, then back 20, remove & check. ) and see if the pattern is even all around.

I'd also try the ink check on the center, make sure both are seating nicely.

Stephan

[davebradwell]

Your file will likely just throw up more burrs. I see ArcEuro have a morse taper hand reamer for £15-88 which you say should go right through the hole. This is how I sorted out my battered Myford and it worked well enough. At least it guarantees you'll end up with a true morse taper. To sort out the drill chuck mandrel would suggest using an oilstone on just the high spots - don't work right round with paper except very lightly to highlight these. Where there's a ding, you'll find a little wall round the pit so these will need tackling too.

Can't understand how the drawbar wrecks the taper as they go in from opposite ends and the drawbar shouldn't reach the tapered bit.

DaveB

[Winander]

Can't understand how the drawbar wrecks the taper as they go in from opposite ends and the drawbar shouldn't reach the tapered bit.

Dave,

Not quite sure who is confused but the damage was caused by a bar through the spindle used to hold it whilst tightening the chuck. I don't have a drawbar.

Stephan,

Thanks for all your help, but I think I'll go with a morse taper finishing reamer - less chance to make an unholy mess of things. If requiring repair, the headstock would have to be returned to California!

I put a dial indicator on the mandrel and it was about half a thou out.

[davebradwell]

I get it now - when all else fails, read the post properly.

DaveB

[ralphrobertson]

If requiring repair, the headstock would have to be returned to California!

It might be worth you talking to the Sherline agent here in UK, that is Mill Hill Supplies. Talk to Kevin there, he is a very helpful chap and I can only recommend their service after I bought some spares from them to fix a couple of issues on the milling machine I bought along with the lathe.

http://millhillsupplies.co.uk/

Ralph