Correcting drill press runout

[Mark Davison 1Participant @markdavison1]

I have recently bought a Medding MF4 drill press that has noticeable run out in the chuck (~0.5mm). I have tried a different chuck/arbor and it is still the same. I’m assuming it is minor damage to the inside of the MT2 taper in the spindle (i can feel some with my finger).
How do I correct it without risking making it worse. I don’t have a lathe so am anticipating carry out the action in situ.

I bought an MT2 reamer but it appears to bottom out on the tang drive slot before making contact properly with the taper. I could sort this by grinding some material off the end I suppose (of the reamer that is).

My main question is how should I hold the reamer? With a normal tap wrench? Or try to hold it loosely in a drill vise. Do i run a risk of making things worse?

Edited By Mark Davison 1 on 17/01/2018 07:11:09

Edited By Mark Davison 1 on 17/01/2018 07:12:00

[Mark Davison 1Participant @markdavison1]

[Brian WoodParticipant @brianwood45127]

Hello Mark,

On the assumption that the bore damage is localised and it generally is with a ding of some sort, use the reamer hand held.

It will be more comfortable fitted into the next size up drill sleeve to give you something to grip and work it by hand.The rest of the 2MT bore will guide it and ensure that the reamer doesn't get pushed off by the raised piece; you should be able to feel it cut as contact is made.

Keep the reamer moving to avoid taper grab and always is a clockwise direction, even when backing out. I would do the work dry. I hope that fixes it for you

Brian

[HopperParticipant @hopper]

Posted by Mark Davison 1 on 17/01/2018 07:09:53:

My main question is how should I hold the reamer? With a normal tap wrench? Or try to hold it loosely in a drill vise. Do i run a risk of making things worse?

Edited By Mark Davison 1 on 17/01/2018 07:11:09

Edited By Mark Davison 1 on 17/01/2018 07:12:00

Whatever you do, don't start the drill press and try to ream under power. Do it by hand, turning the reamer with a tap wrench or similar while holding the drill press spindle stationery. If you have a burr you can feel, as you say, it might just take a half turn of the reamer or so to knock it down. Softly softly.

[Martin ConnellyParticipant @martinconnelly55370]

Mark, morse tapers in drills work beautifully as a simple tool holding and driving method – until someone starts putting damaged male tapers into the female. Once this happens it doesn't take long to have something slip under power and damage the female taper. It's always maddened me at work to find people have been using the male tapers of drills and sleeves as hammers and still expect them to work properly. Anyway if someone has put a damaged or dirty tool into the drill it only takes one slip under power to cause the problem you are reporting so hopefully cleaning it up with the reamer will fix it.

Martin C

[Mark Davison 1Participant @markdavison1]

Sobm6 main problem is the reamer appears to be too long and bottoms out of the shoulders of the slot that holds the tang. I’ll try grinding it a bit shorter.

[not done it yetParticipant @notdoneityet]

If it is only a superficial ding, I would start with trying something a little less aggressive than the reamer. Some strips of abrasive, glued to a good morse taper, may be sufficient to remove the offending marks. Revert to reamer plan, only if required.

[Clive FosterParticipant @clivefoster55965]

If the reamer is too long and arguing with the tang slot its possible that its already been reamed out in the past and taken a touch too deep so the tang or tang base to taper curve just contacts the bottom of the tang slot causing the taper to rock over fraction when inserted. If the depth error is very small the MT taper will still hold but not quite true. Seen this before when trying to figure out why some drills and some tapers were pretty much OK in my well used Pollard 15AY whilst others wouldn't stay put or go straight. A bit of measuring showed that the tang to taper interface shape and position on the taper varies a bit. All fairly similar but not that closely controlled.

Agree with "not done it yet" that something less aggressive than the reamer should be tried first if its only a small, localised ding or two.

My Pollard spindle was, frankly a right mess. Half an hour of reaming by hand was getting nowhere fast so I fixed the reamer dead upright with a nice strong bolted down mount and had at it under power at bottom speed. Using plenty of lubricant and being careful on the feed handles. Went in maybe 3/16" before the taper was clean. Barely enough room left in the slot for the extractor wedge to enter. One day I'll pull the spindle and mill it up a touch further. Which will be a major PIA with a gear head drill and no manuals or parts book for guidance tho'. Holds like a bolshie badger or pissed off pit-bull now. First time I've ever had an unabashed MT spindle about the place and still amazed how much easier it all is.

Yes Mr Hopper I was indeed a very naughty boy to power ream. One for the "Don't do as I did, do as he says." book.

Clive.

 

Edited By Clive Foster on 17/01/2018 15:04:13

Edited By Clive Foster on 17/01/2018 15:05:15

[HOWARDTParticipant @howardt]

Miniumum diameter of the reamer should be around 0.5696/0.5700". The plug depth is 2 9/16" with a total taper depth of 2 5/8". If the reamer is to this diameter and goes in further then you have a worn taper. I would blue up a tangless taper and see were it fits, this will give a better idea of what the error is that you need to correct.

[Mark Davison 1Participant @markdavison1]

Comparing the reamer with the arbors I have the reamer is best part of 1/2″ longer using a fixed diameter (smallest end of the chuck’s arbour) as a reference, hence bottoming out.

I bought a soft ended arbor from Warco during the week just to see if the runout was in the spindle or the chuck. It looks as if it could be the chuck as there is very little run out at the end of the arbor (although this could just be related to it only being 1″ long of course).

I have previously seen some plastic MT honing things online that looked a lot shorter than the reamer and I wonder if they may be a better solution. Problem is I can no longer find them

[Mark Davison 1Participant @markdavison1]

Ignore that last bit, they were felt strips not an abrasive stone/diamond strip

[Martin ConnellyParticipant @martinconnelly55370]

Sounds like the problem may be the arbor that the chuck is mounted on is bent. As you say these arbors are soft and I have seen bent ones at work. Replacement arbors are cheap and there should be some indication on the chuck of its socket size or the model of chuck that you can look up to find this out.

Martin C

[Mark Davison 1Participant @markdavison1]

I cleaned out the spindle with fine wet and dry placed against the arbor as suggested.
Turns out it was the arbor/chuck After all, not the spindle. A new arbor and chuck runs as true as the soft ended blank arbor that I tested previously
In hindsight this should have been the most obvious culprit from the start. A previous owner had tack welded the (Jacobs) chuck to the arbor with two small MIG welds. I can old assume one is pulling it off centre slightly. Tried grinding them off but I think the penetration is a fraction too deep so it is junk.

Edited By Mark Davison 1 on 31/01/2018 19:28:50

[Clive FosterParticipant @clivefoster55965]

Mark

Glad you are sorted but don't give up on the 'junk" welded up chuck and arbor just yet.

I'd set up a true running, turned in situ if need be, stub a bit longer than the chuck is deep and close to its maximum acceptance size in the lathe. Grab it with the chuck and have at the weld with a HSS tool ground to a shape similar to D or E carbide inserts. Basically a diamond. Blunter, larger tip angle, within reason is better. That way you can get at the weld area with minimal cutting of the chuck and arbor. Weld will almost certainly be softer. Be a bit generous with your cut depth so as to be sure that chuck and arbor will separate once removed from the lathe.

Although the weld suggests that either the female taper in the chuck or the male on the arbor is damaged in some serious way I think it more likely that previous operator was inexperience, stupid or both. Frankly if you just loose a 1/16 inch or so of mating taper length it matters not al all.

If they are actually damaged cleaning either or both up is a nice exercise in precision setting up and careful machining. I've done 5 or 6, maybe more, over the years with every success so how hard can it be? Bit of thought, patience and not getting rush-headed about things gets the job done.

If the male taper really is seriously affected just lay on a decent layer of weld with an ordinary stick welder and start over. She'll be fine. That sort of approach is almost essential if you need to fit a chuck to a Fobco 7/8 which are notorious for having a longer than usual taper in the spindle so common chuck – MT arbor pairs don't reach in far enough to fit. It is within specified gauge lengths but normal practice is to make things shorter! easy show off job.

Clive.

Edited By Clive Foster on 31/01/2018 19:54:04

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