L1 spindle taper regrind, what grinding wheel?

This sad tale begins about 10 years ago when I had 2 employees. One of whom was an "expert" lathe hand. The expert was running some parts on my Leblond Servo Shift Regal. Picture this, 900 rpm he engaged the threading lead lever instead of the turning feed. Why was the threading lead screw engaged? who knows. Anyway the carriage / toolpost hit the 10" chuck with a crash I heard though I was outside at the time. Major carnage as you can imagine. Broken gears and a bent spindle. I bought the headstock contents of a machine that had been in a fire. This gave me all the gears I needed but the spindle was a L0 instead of an L1 as my lathe was equipped with. I needed it running so I removed the chuck from the set true mount and took a light cut off the the mount to true it up, replaced the chuck and that is how it is today. It is .007 out of true. I want to true it ID and OD so I can use my Rubberflex collet chuck on it. that gets to the question what grade of stone do I need to get a proper finish? I would rather not remove the spindle to remove the nut so I will have to reach inside it when I do the OD. Where can one buy mounted stones of a known type and grit? What type do I need?

No one has any idea?

Personally I have no experience regrinding a spindle but I'd look on msc they have small stones for pretty cheap. One of the 46 grit in I hardness or maybe 60 grit if you need a finer finish will get you there. These stones usually need an arbor though and I'm not really sure why you need a pre mounted stone? Typically your toolpost grinder will have an attachment or some of the dumores will even have another spindle for mounting these internal stones.

Here is a guy making an arbor
Tool Post Grinder: Making and Extension Arbor for Inside Diameter Grinding - YouTube

moonlight machine said:

No one has any idea?

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I have a pretty good idea but it might not relate to your case. You want to grind ID and OD. How ? Rpm ? How's the grinder looking like ? 7 thou is quite a bit to remove with a small grinding stone - I'd use a soft one to speed things up. Best finish would be a harder stone but then both grinder and lathe bearings need to be mint or it'll rattle.
There just isn't enough detail to be of help. Only keep in mind that absolute best you can do is to copy the inaccuracies of your lathe's bearings.

I would recommend that you remove the spindle and have ground in a cylindrical grinder. Lathe bearings do not make good grinder bearings.

JH

James H Clark said:

I would recommend that you remove the spindle and have ground in a cylindrical grinder. Lathe bearings do not make good grinder bearings.

JH

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OK if I go that route who can do it and get it right?

moonlight machine said:

OK if I go that route who can do it and get it right?

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There are a lot of services that come to you to regrind spindles on vmcs and lathes so unless you need ultra precision I think it could be done installed. Sure the bearings aren't to the quality of a cylindrical grinder but you could hold .0004" and that's beyond the accuracy of my rubberflex chuck. That's my opinion though. If you don't have a proper grinder I'd say call one of those companies that come to you. I also think sending it off wouldn't result in that great of an end product because the spindle is bent so they won't be able to really line it up how it is once it's in the head. Also this sounds like a salvaged machine so do you need better than .0005"? Will the cost be worth it? It blew me away getting quotes for some rebuild work. If it costs $2000 to regrind it is it not better to go pick up another lathe for $2500?

Personally I'd take a shot at regrinding it with a toolpost grinder. Take this all with a grain of salt though and do what you want

Ianagos said:

There are a lot of services that come to you to regrind spindles on vmcs and lathes so unless you need ultra precision I think it could be done installed. Sure the bearings aren't to the quality of a cylindrical grinder but you could hold .0004" and that's beyond the accuracy of my rubberflex chuck. That's my opinion though. If you don't have a proper grinder I'd say call one of those companies that come to you. I also think sending it off wouldn't result in that great of an end product because the spindle is bent so they won't be able to really line it up how it is once it's in the head. Also this sounds like a salvaged machine so do you need better than .0005"? Will the cost be worth it? It blew me away getting quotes for some rebuild work. If it costs $2000 to regrind it is it not better to go pick up another lathe for $2500?

Personally I'd take a shot at regrinding it with a toolpost grinder. Take this all with a grain of salt though and do what you want

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Tool post grinder is what I was going to use, I guess I'll start with the stone I used when I reground the taper on my Bridgeport. When I was done with that one a .0001 indicator showed no movement.

moonlight machine said:

Tool post grinder is what I was going to use, I guess I'll start with the stone I used when I reground the taper on my Bridgeport. When I was done with that one a .0001 indicator showed no movement.

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I have had similar results using only a mounted Metabo using ordinary mounted points. I am sure the Metabo bearings aren't perfect (they are pretty good though), but they don't have to be perfect. It is the average of all the movements made by the Metabo that results in the final grind. The first time or two that I ground ID's in this way I was skeptical that I'd get a good result. Now that I have ground 9 tapers this way with superb results, I am convinced it is a very good way to get a taper that is as good as the bearings that support it and that matches any runout in those bearings. Also costs practically nothing in time or materials. If you do it and don't like the results, you can always send it out with only your time lost. I am betting you won't have to send it out.

Denis

moonlight machine said:

Tool post grinder is what I was going to use, I guess I'll start with the stone I used when I reground the taper on my Bridgeport. When I was done with that one a .0001 indicator showed no movement.

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If you were able to get your bridgeport cleaned up that well I think you'll be fine here. Good luck

These are the guys I used to send my spindle rebuild grinding to if you decide to pull the spindle. Very reasonable and super accurate. Can drop my name and say from Midwestern Machinery . I used contract for them and was a partner in it too.

http://dongotool.com/ They may even tell you the stone to use on your tool post grinder.

Hard turn it

moonlight machine said:

This sad tale begins about 10 years ago when I had 2 employees. One of whom was an "expert" lathe hand. The expert was running some parts on my Leblond Servo Shift Regal. Picture this, 900 rpm he engaged the threading lead lever instead of the turning feed. Why was the threading lead screw engaged? who knows. Anyway the carriage / toolpost hit the 10" chuck with a crash I heard though I was outside at the time. Major carnage as you can imagine. Broken gears and a bent spindle. I bought the headstock contents of a machine that had been in a fire. This gave me all the gears I needed but the spindle was a L0 instead of an L1 as my lathe was equipped with. I needed it running so I removed the chuck from the set true mount and took a light cut off the the mount to true it up, replaced the chuck and that is how it is today. It is .007 out of true. I want to true it ID and OD so I can use my Rubberflex collet chuck on it. that gets to the question what grade of stone do I need to get a proper finish? I would rather not remove the spindle to remove the nut so I will have to reach inside it when I do the OD. Where can one buy mounted stones of a known type and grit? What type do I need?

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I have been working in tool and die job shops since 1958. All of them had toolpost grinders in the drawer somewhere. They were never used.Every thing was HARD TURNED WITH CARBIDE. The first thing that I would do is make make a quick removable 6 or 8 inch handwheel for your compound. EVERY lathe should have one anyway. Now choose the sharpest pointiest most ridged carbide insert or tool bit that you have.Try to make a setup that you can remove and reinstall quickly for multiple resharpening. 80 degree would be best.The L1 mount has a keyway slot .Use a pencil grinder to chamfer the outer edge.This will help stop carbide edge chipping.Have plenty of dykem to coat and recoat your work.Now start cutting at about 1000 rpm maybe .001 per pass.YOUR CARBIDE WILL CHIP, YOUR WOKPEICE WILL LOOK UGLY. Just tuch up your insert and recut and recut.Eventually it will clean up and you will get a nice smooth surface. Your handwheel will help smooth the tedious hand cranking.I have done this on a d-6 mount.It might take a few hours or more ,but you can do it.I did a lot of repair taper turning on engine lathes reworking welded injection mold parts .On the other forum, there is a post(how to measure an internal taper).I replied a fast and easy way to set lathe compound. Good luck Edwin Dirnbeck.

edwin - may I ask which other forum?

richard newman said:

edwin - may I ask which other forum?

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Home shop machinist


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Setting your compound is very important. Once you have done it the way that I illustrate and see how easy and accurate it is ,you will be more confident in your procedures. Also even though your L1 taper is not running true.if you put a plunger dial indicater on it with plunger horizontal and on vertical center line AND ROTATE the spindle half way between plus and minus ,your indicater should read pretty much zero zero as you move your compound. I hope this helps. Like I said I have spent years doing this sort of thing and it can be done. Good luck Edwin Dirnbeck

edwin dirnbeck said:

Setting your compound is very important. Once you have done it the way that I illustrate and see how easy and accurate it is ,you will be more confident in your procedures. Also even though your L1 taper is not running true.if you put a plunger dial indicater on it with plunger horizontal and on vertical center line AND ROTATE the spindle half way between plus and minus ,your indicater should read pretty much zero zero as you move your compound. I hope this helps. Like I said I have spent years doing this sort of thing and it can be done. Good luck Edwin Dirnbeck

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I was thinking about turning it. Thought about making a insert for the key slot, that should help with the interrupted cut. But how hard should it be? I don't think the spindle is all that hard given the damage caused by knuckleheads not cleaning the taper before installing the chuck. I have a servo power feed for my compound so that will make it easy. the big handwheel is a good idea though. I must say how much I appreciate your posts, so much of what goes on here is political crap. I love it when I can learn from someone who has been there and done that. Ray Behner and Motion Guru are two others I am impressed by.

Never to old to learn

moonlight machine said:

I was thinking about turning it. Thought about making a insert for the key slot, that should help with the interrupted cut. But how hard should it be? I don't think the spindle is all that hard given the damage caused by knuckleheads not cleaning the taper before installing the chuck. I have a servo power feed for my compound so that will make it easy. the big handwheel is a good idea though. I must say how much I appreciate your posts, so much of what goes on here is political crap. I love it when I can learn from someone who has been there and done that. Ray Behner and Motion Guru are two others I am impressed by.

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Thanks for your kind words. I have never actually seen a lathe with a power compound,it would be nice for cutting long tapers.I woulnt worry about the interrupted cut at the keyway. I have remachined some 6 inch dia. by 7 inch long 50 ROCKWELL H-13 TOOLSTEEL mold parts that had 15 or 20 full length slots amd many holes,plus all welded up real ugly.Keep us updated on your progress. Edwin Dirnbeck

Can you hard turn it? Bevel the keyseat in the spindle to remove the sharp corner, not much just te depth of the cut plus 0.005"

If you remove 0.007" from the taper diameter you move the gageline 0.024" towards the retaining nut collar. is there sufficient draw allowance to do this?

I suggest an A40H vitreous bond white grinding wheel commonly used for tool grinding. it's quite soft and self-dressing to a degree. But you'll have to dress it often if you wish a good finish and a geometrically accurate taper is to be attained. You can grind it with a DuMore or Themac tool post grinder but it will be a time consuming job. Much depends on the accuracy and consistency of the slide used to provide the tool path, usually the compound.if a there is no taper attachment..

Another point is The retaining nut is sure to interfere with wheel access to the gageline. you'll have to gin up a way to hold the retaining nut back against the headstock. Duck tape, probably.

This is precision grinding. Depths of finish cuts will be less than 0.001" - more like 0.0003". Get a couple of 0.0001" indicators on biscuit magnets or mag bases of some kind. to track movements. .

Dumb to suggest in this knowledgeable crowd but it doesn't hurt to bring it up: drape the whole lathe in heavy poly to prevent grinding dust from getting everywhere. Overlay the poly with wet shop towels to protect the plastic and smother the dust to some degree. A shop vac nozzle right under the point of grinding is a hell of a good idea. Anything sensitive to abrasive dust nearby?

I hope you ran the perp through a self-feeding brush hog feet first.

Forrest Addy said:

This is precision grinding. Depths of finish cuts will be less than 0.001" - more like 0.0003". Get a couple of 0.0001" indicators on biscuit magnets or mag bases of some kind. to track movements.

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I'm a grinder fan also. On a Heald you'd be taking two tenths at a pass. That's on diameter with a rigid high-qualty spindle turning the stone on the biggest-diameter arbor you could fit in the hole with flood coolant. Toolpost grinders are flimsier

Norton used to have a whole bunch of catalogs of all their small stones. They had pretty good suggestions for which grade to use on what. On the bigger wheels I'd call them up and ask what was best for what I did, they made informed suggestions that usually worked good.

Maybe michiganbuck will chime in, he's got his grinding shit down. About hard turning, the Haas tools that were hard-turned would stick in the spindle, the ground ones did not. That was enough for me and hard turning.

Someone asked me off line what Metabo die grinder I used. It was this one:

Buy Electric Hand and Die Grinders | Zoro.com

Obviously the side-arm was set aside.

This variable-speed grinder with its long nose easily lends itself to ginning up a solid mounting system. I have two mounts. One is for the surface grinder and one for the compound on my lathe. The stones I used were 46 grit AlOx like these:

34265 w225, grit 46 - medium, aluminum oxide vitrified mounted point with 1/4" | eBay

I was surprised how much grinding you could get out of such a stone. Having the grinder securely mounted eliminates the bouncing around common in hand-held die grinding and greatly extends stone life. My guess is that the pounding on the stone due to bouncing breaks the stone down far more than controlled cutting. Truing the stone and freshening the surface for the final cut and sparkout were done with a conveniently mounted single diamond.

Denis

I also have a Foredom which I can mount on the lathe and grinder. It is handy for small work, but I think it would be a bit lightweight for this size work