Reaming the tailstock taper

[JimM]

I'm still having problems drilling centrally on my lathe, as per a previous post the bit always seems to jump up and away from the operator. I've doubled checked and the tailstock is as aligned with the headstock as I can get it so my next thoughts are towards the tailstock ram. It looks a bit gouged and chucks do sometimes slip so was thinking of giving it a quick go over with a reamer.

Is it simply a question of putting the reamer in the headstock spindle (I'll have to use a MT2-MT3 sleeve) sticking the lathe into lowest backgear and advancing the tailstock ram onto the reamer or is there a more scientific approach ?

Cheers

Jim

 

[bearcar1]

Hello Jim, could you possibly have a chuck of questionable quality or perhaps out of alignment causing your problem? What happens when you mount a ground test mandrel of known quality between centers? Or have you tried that approach. If this setup proves to clock true that would point towards the chuck as being the culprit of the fault. Have you tried seating the chuck 180* in the ram? If it is the chuck it should throw the misalignment off by that amount at the headstock. If the gouges you speak of are inside the bore of the ram then yes, this could be the root of your problem and a clean up ream is in order. Use some Pussian Blue on the chuck taper and seat if home in the tailstock, then remove and inspect the taper for high points. If there aren't any then the tapers are OK and again I would suspect that the chuck is defective and in need of corrective measures or replaced. To perform the procedure you speak of mount the reamer in the headstock and clock it at the shank for accuracy and then turn the spindle by hand while gently advancing the tailstock ram onto the reamer using copious amounts of oil and only removing enough material to clean up the inside bore of the ram.

BC1
Jim

 

[JimM]

Hi BC1

Thanks for the input, I've ruled the chuck out as the problem happens with all 3 of the chucks I've tried. I will give the Prussian Blue a go though, it will be a good test to see if the reamer makes any difference

Cheers

Jim

 

[Blogwitch]

How old is your lathe?

The tailstock on my old Atlas was doing exactly as yours is doing. It turned out to be the ram had worn the tailstock casting and the casting had to have an insert put into it to get it back into trim. The first sketch on here shows what I am on about.

http://www.homemodelenginemachinist.com/index.php?topic=2114.0

The way to check is to wind out the tailstock ram nearly all the way out, and with the tailstock locked down, see if there is any up and down movement on the ram.

If there is, you will have to repair the main casting as I did. If not, you first need to see that the ram is parallel to the bed, both along the side and the top, and if it isn't, you are in trouble, as that will mean the tailstock and headstock castings will require bring into true alignment with each other. The headstock isn't usually a problem, as that can usually be done with shims, but the tailstock is a totally different matter.

Always search for the source of the problem, only then start to look for a cure. Otherwise it can be like giving a laxative to cure someone who has the craps. It can only get worse.

Bogs

 

[Stan]

I would not attempt to hold a reamer in a chuck and ream the tailstock. I would put a dead center into the spindle to hold the reamer in line and turn it with a wrench or tap handle. This method lets the reamer self center in the tailstock and removes the risk of reaming at an angle.

Remove the absolute minimum amount of material, which will be just the high spots. You can tell by feel on the tap handle when the reamer seats into the taper.

 

[JimM]

Thanks for the further comments

Bogs - I was a bit tight for time tonight but gave the ram a very quick go over with a DI (mounted on the cross slide) and thankfully it looks pretty parallel. I'll do a proper check later in the week but hopefully that will confirm my initial test as I don't think my abilities will run to doing your fix. If you were nervous doing it, it would really be pants filling time for a newbie

Stan - thanks for the input, I'd already ordered the reamer this morning but hopefully it will have a centre spot for use as suggested

Cheers

Jim

 

[Groomengineering]

Hi Jim. Had the same problem on my 9" SB, after chasing my tail on the tailstock (so to speak) it turned out the spindle bushings were worn. Tightening them up helped immensely.

Just a thought.

Jeff

 

[Richard1]

I know you say it happens with 3 different chucks so it can't be the chuck but it would still be worth double checking this. I have had the same problem on a Myford lots of broken centre drills which I just put down to me being useless with a lathe. Got frustrated one day with this so mounted the chuck in the headstock taper put a bit of 3/8 silver steel in the jaws and checked with a dial indicator to find it running out by 0.01. Thought I had a bent arbor so knocked the chuck off to find that there had been a bit bit of swarf damage to the Jacobs taper. This had apparently been there ever since new as I had never before had the chuck off. It is unlikely you have 3 defective chucks but it is quick to test and worth confirming.

Richard