Grizzly G0766 trouble knocking out drive center

[casey herring]

Hey guys,

I have a GO766 and have had it for a few months. I am a furniture maker by trade and typically only turn spindles so 90% of the time I have a Robert Sorby stebcenter drive center in. Occasionally though I like to a make bowls for fun and I always have a lot of trouble getting the Sorby center out. I have to put the knock out bar in and bang the crap out of it with a dead blow mallet. Is this normal? Eventually it does come out after 10 or so hits and the the center goes flying across the room. It has actually really taken the desire to make anything other than spindles away because I had the process. I am assuming somewhere in here there is user error so thats why I'm coming to you experts!
Also, I know next to nothing about turning so if I have use a word or term incorrectly please be gentle with me

[Kyle Iwamoto]

I don't have your lathe, but from a mechanical point of view, I'd avoid using a dead blow. They are designed to not hit "solidly". Just use the bar and tap it out. I takes a while, but should eventually work. Unless of course, you got a nasty catch and gouged your spindle and center together. Then I personally would use a regular mallet. Just my $0.02.

[casey herring]

Kyle,

Thanks for your response. I definitely don't feel comfortable using the mallet, dead blow or otherwise, but the bugger is typically stuck in there. Heres a thought, and please remember I know nothing about turning, when I put my spindles on I advance the live center as hard as I can to keep the spindle held well. am I perhaps putting too much pressure into the drive center?

[John Keeton]

I would think the odds are against the taper in the spindle being "off", but the Sorby could easily have a non-visible bend in it or otherwise be defective. Additionally, it is possible your spindle is dirty and seizing on the center. I would clean the spindle, assure it is not marred, and try another drive center.

[Brice Rogers]

I read a similar report about a G0766 on the GGM group. Advice given was to make sure the morse taper and bore were very clean and not to over-press with the tailstock.

If a morse taper has spun in the spindle, it could have put in some grooves. Get a strong light and check that. Also check the center for burrs or galling.

On my Griz G0766, the MT bore in the spindle is not as polished as the tailstock. In fact, I can see machining marks. They could have done a better job, but I haven't had the same degree of problem that Casey has. The various centers that I have all are much more polished than the spindle pocket. I suppose that it might be possible to polish the spindle pocket but I would only attempt that as a last ditch effort.

If the MT spindle pocket and the MT center are not damaged, then you might try some light oil or anti-seize on the center - - as an experiment. Another way to reduce the amount of force required would be to modify the center by removing a portion (preferably in the middle) and then polishing it to remove any burrs.

[Reed Gray]

You do want the tailstock to be snug, but not really tight. Part of the reason for that is that it can add to flexing/whipping of long spindles. Other than that, I would expect that the inside of your morris taper is dirty/rusty. A little steel wool on a dowel could help, but don't use abrasives unless they are very fine, 600 grit or so.

robo hippy

[Brice Rogers]

I have machined some parts including machining a few with a morse taper. Making a good MT requires good attention to detail and is a bit challenging. One of the steps in the process is to check the "fit" by applying some bluing or magic marker and then putting the two mating pieces together and rotating them. This will remove the magic marker at the contact point or points. On a well-machined MT, you normally want a full contact. If the taper is mis-machined, it will make contact at one end or the other and you will see the high spots. This significantly reduces the holding force.

So, my (SWAG) guess is that the MT in the spindle has all of the correct angles and dimensions but the machining is not as polished as it could be and the "micro-grooves" may be causing it to stick. Check for ridges and burrs, polish if necessary, experiment with a lubricant.

[Neal DaMommio]

I sand all of my MT with 1200 grit scotch brite running up and down the length of the center and literately every time I use one I clean the female portion out with my finger. I am not sure if I am actually cleaning the dust out or if the oil on my finger is the cause but this does seem to help. I also pull as hard as possible on the center with one hand as I tap it with the drive rod with the other when I remove. I absolutely hate banging on the center with the rod.

[John Keeton]

All things being as they should, one should not have to do more than one moderate tap with a knockout bar to remove a center from the spindle. So, something "ain't quite right."

[Roger Chandler]

As indicated by some of the above posters, the problem likely exists with the morse taper center. Aftermarket parts are all over the place as far as quality. I have the G0766, and use the Oneway live center most of the time for the tailstock, but do use a cone center from Penn State and a couple of other live centers which all run true and have not had any issues.

When the lathe comes across the seas, it is coated with cosmiline for rust protection in travel and warehouse storage, and that stuff gets sticky over time, so a good cleaning should be done with mineral spirits and a morse taper cleaner. If you have galling inside the taper on the spindle, then get a morse taper reamer from somewhere.......they can be ordered online. [I think I got mine from Enco] Lightly ream it out with a wrench and the reamer, using some light oil for lubrication, then re-clean the inside of the spindle.........you should be good to go. John is correct .....a moderate tap with the knock out bar should be sufficient. You likely have been over tightening the tailstock pressure, so ease up on that going forward.

I have had absolutely zero issues with my G0766, and have put it through some heavy usage with some really large and heavy blanks. The G0766 is a fine lathe!

[Mike Oliver]

So,I had the same issue with my G0766. I was the one who posted in the GGM group to ask for advice. Mine was so stuck, I could not get it out. I called Grizzly a couple of times to ask for advice. The second guy asked me to spray with WD40 and let it set for a couple of hours. When I went back and tapped it twice, the drive center popped right out. When I felt the inside of the spindle, there was quite a bit of cosmoline in there, ans as Roger alluded, that stuff gets sticky. I cleaned it out really well, and have not had any issues since then. Hope that helps.

[Fred Belknap]

I notice that the vacuum chuck leaves a lot of dust in my spindle. I use a plastic thing called a "GreenWeenie" and wrap a piece of paper towel around it and use some WD40 on it.

[Leo Van Der Loo]

Casey, yes first make sure both the lathe and the drive are clean, next I would make a heavier knockout bar, make it as thick as it can be and add weight on the end so you have more driving force to get theDrive center out.

I have a couple of the Robert Sorby drive centers, and those are quality pieces and very well machined, the Grizzly is probably not quite as smooth, anyway a coat of oil or wax would help to remove the drive center and the heavier bar would help.

[Randall Mack]

The same thing has happened to me twice. Both times i was roughing a large green piece. I probably applied too much tailstock pressure. The taper on the spur drive that came with lathe was off and was tossed. Anyway rather than risk this happening again and possibly messing the spindle, I am now using a thread on drive center. Everyone has their opinion on the use of a morse taper for things other than spindle turning. Also consider with mt2 on newer lathes with a 5/8 thru bore, the actual taper surface is quite shortened. So I only use morse taper for real spindle turning.

[John K Jordan]

...when I put my spindles on I advance the live center as hard as I can to keep the spindle held well. am I perhaps putting too much pressure into the drive center?

Casey, Tightening the tailstock that hard bothers me. I do a lot of spindle turning and use several sizes of Steb centers in both a Jet and a Powermatic lathe - they always come out easily with a couple of gentle taps on the rod. I put a little hole at the center of each end of the blank with a gimlet before mounting, both to make mounting quick and precise and to prevent splits in very thin spindles in hard wood. I snug the tailstock but never put excessive pressure on it. You might try a less pressure.

I also regularly clean the Morse tapers in both the headstock and tailstock with a green rubber tool, this one or similar, although I can't remember paying this much:
https://www.woodturnerscatalog.com/p...-Taper-Cleaner
A paper towel on a turned stick should work as well. A very light film of oil is a good idea.

If the spindle MT socket felt rough on the inside I would try polishing it gently with some scotchbrite on a dowel.

I think someone else mentioned how to test the taper - I coat it with machinist's blue (Dykem), let dry, then insert the taper finger tight and twist it a small amount, maybe 1/8th turn. The twist should remove dye evenly from the taper. I used this method to prove to myself that two of the three aluminum tapers I bought from Rubber Chucky were machined improperly. (Mr Rubber Chucky, BTW, denied this was possible and suggested pounding the tapers in with a mallet to seat them. No.)

JKJ