My suggestion is to accurately determine the existing taper. Using 2 precision balls and a depth mic. A smaller ball should locate near the small end of the taper. Measure the depth from the nose of the spindle to the top of the ball. Select a larger ball that fits near the large end of taper and measure depth to top of it. Now you have 3 known dimensions, diameter of each ball and the distance between ball centers. Make a cad layout of the 2 balls and spacing. Develop a common tangent line which well define the half angle. The ball contact diameter (at tangent point) will define the diameter of the taper relative to the spindle nose. Twenty/thirty years ago I probably could have explained more elegently. Currently 82+.

It came to my mind just now. You can use silicone rubber for making molds to create the shape of the spindle. Tape or somehow cap the top part of the spindle to make it watertight. Spray some oil into the spindle and wipe the excess. Mix both components of the silicone rubber (arts & crafts store, Bezos’s online store and I think I’ve seen them in Walmart). It releases easier than caulking silicone, pours better, a.s.f. Pour into the spindle and wait for it to cure (usually 24h). These types of silicone rubber is extremely flexible and elastic enough to release very complex forms or figures made from resin. I remembered my audiologist getting the form of my ear canal to make my hearing aids. You’ll be able to imprint all the minute details inside, even the pin or key for the 3C collet. With this silicone plug you will have a better idea of what to do. I’d buy machinable MT4 to MT3 adapter and turn to the same dimensions of the plug, (length, angle and diameters). I hope it gives you more ideas.

Chuck, Definitely a dilemma. MY opinion is: NO MATTER what, 1st order of business is disassemble and remove the spindle in order to properly measure the taper to see what you actually have. DO the job properly and dont make short cuts; ie don't make a shim to make it fit. Measure the existing taper to see what you actually have and from there figure out whether to re grind it or ream it to proper dimensions.....I am surmising that the option of reaming it to a proper dimension would be the best way to go... as grinding it wouldnt be as precise. It would be like cutting and reaming a guns chamber. With your connections I'm sure you can find a proper reamer somewhere, that would cut the size you need .....again just MY opinion and what I would do. Will prob try to call you today a bit later and also discuss something w you !!!!! Don

Hello from Spain... throughout my professional life I came across some cases similar to yours on machines that used non-standard cones or that had a seizure of the cone and re-machined them at will... in all cases I solved it in 2 ways...the first is to make a new shaft complete with a standard cone that adapts to the tools that are intended to be used...in the other case what I did was machine the existing cone itself, transferring it to an industry standard cone. ..I think either of those two solutions would solve your problem all the best michael

That is a real problem, Chuck. I don't have a clue but maybe you can induce Tom Lipton to drop by for a visit. Thanks for the video keep on keeping on.

Before doing anything too involved, I'd make an accurate blueprint of the existing spindle taper, and see if it's possibly some common( at some point in history ) taper such as B&S. If it cross references to nothing common, make a custom collet, and permanently chuck a straight shanked ER collet of whatever size is appropriate.

Honestly, it sounds like somebody had a new taper drive made (or the original piece modified, possibly in place?) to accept 3C collets instead of Morse 3. Either for headroom reasons (as you've alluded to), because they had an abundance of 3C collets, or because the original Morse taper was damaged. The poor contact is either due to poor machining or a tradeoff to make a 3C collet fit at all (or because that's what was needed to clean out a damaged area). If this is the case, a plug of sufficient precision could help. If nothing else to restore the Morse 3 taper if you're going for originality. One possible trick to nail the concentrically (and possibly improve it beyond the 0.001") is to machine outer taper first, but leave the inner taper undersized and clean it up with the machine itself by installing the partial plug into the machine. You'd need to rig a single point cutter to the table, get it cutting on-center, and nail the universal head angle to match the inner taper. But, that's a lot of stuff to get right, and if my above hunch is right, the previous person got it wrong, which led to the current situation.

With a .651 ID for the 3C, you won't have much material left at the upper end of the bushing, but your plan sounds feasible. I suppose you would need to ID grind the spindle first to eliminate most of the concentricity issue, then that may give you a little more material to play with for the bushing. This might be a real test of your grinding skills and provide us some interesting content! Thanks for sharing Chuck.

Hi Chuck, I have a feeling that it really is a MT3 but it needs to have a groove in the side of it like the 3C collets have. A MT3 diameter at the big end is .938 which would make the nose of the MT3 stick out a little as expected. And, after looking at your reassembly video, the taper looks close to the 2.87° included angle of a standard MT3.I really recommend revisiting the MT3 again for a closer look. Most MT3 collets don't have the groove in the side so maybe that's the issue? Can you take a good photo of the inside of the spindle so we can have a better look?

(Large Diameter = .928 Small Diameter = .730 Length = .400 ) = Compound Angle of 13.9014 degrees. To cut a matching taper, I'd set the lathe compound at 14 degrees, cut a piece of test material and then adjust as necessary.

The spindle shaft looks pretty straightforward. I'd make a new one with your preferred tooling choice. Long term I wouldn't be happy with shims or cobbled together options. It may not be the popular choice, but you can solve the issues or cover them up until they bite you. Good luck with it.

You could turn the head vertical. plug back of hole with paper towel, and pour Cerrosafe into hole then remove the slug. get a good representation of actual taper. Better than clay,

I just went trough the comments and there atre some good ideas in there. Pick one and go for it. And most of all, take all the time you need.

Chuck, before you do anything, make a proper detailed measurement of the existing spindle taper (end to end) using depth micrometer and ball bearings as suggested by others. Search machine spindle tapers and see what comes up. This is too odd, it has to have logic and only a full measurement will help you solve it. If it turns out someone has ground it to a completely non standard taper then bushing it will sort of work but will never be good, so I would then be tempted to pull the whole spindle out and see how involved making a new one would be. You have enough creator friends with heat treatment and grinding capability so it would make a great collaboration series. I still can't believe any engineer would have a taper ground to a non-standard size, it makes no sense as you would be forced to also make everything you wanted to put in the spindle. Cheers, Jon. Edit, would your contact be willing to post you one of his MT3 collets to try, I think this would be worthwhile also.

I have a thought not too sure if it could be done but in other trades they use the wax to make a mold per say like the dentist does or jewelers do so you could use a bolt to simulate the draw bar to plug the hole then pour the casting wax in and let it set up then maybe push the cast out with the draw bar then you would have something you might to be able to measure not sure just a thought in passing Thank you for your time and efforts to share with the community. I enjoy watching and learning from you 🙂🙂🙂

Hey Chuck, that's the same setup as my lathe. It has a MT3 spindle and uses 3c collets with an adapter. I'd be happy to send you photos and dimensions of the adapter if you want.

Ideas is all here. Definitely a tough one. I am feeling like a sleve isnt the correct way to go. It would have to be bery hard. Maybe pull the spindle out and see how it is made and tons of measurements before you do anything. Then you have a starting point. Dont let the 3c collets you paid for be a finialish decision maker. You dont have enough material for a regrind. A build up could be more effective than a sleve. i imagine 2 bearing races, a thread, a gear race and keyway. Maybe machine a new spindle. 4340 ht would suffice. Before removal mark any nuts or fasteners and depths you can to be close on preload.

3C collets have a male thread on the end. MT3 collets have a female thread on the end of the collet. In this video you're showing the nut, take that collet chuck out of the vertical head, first thing. There might be an MT3 in the spindle. EDIT: I would yank that draw bar and get the tool out of the vertical head. If you have any MT3 collets you could test the taper, there isn't a tang on them like a lathe tailstock, they have a female thread that accepts the draw bar.

My Atlas lathe uses the 3C collets and has a Morse 3 taper. There is an adapter for the 3C collets that is much like what you propose making. The adaptor extends out from the spindle a short way providing enough material to accommodate the collet, Don't see why it wouldn't work. If you think that it will be useful I will send a picture of the adapter to you.

I think your idea is sound. I would make sure the bore of the spindle has min. runout, if not grind the spindle bore, make min runout and give you more room for your 3c bushing. Regrind bore to make it easy to make the bushing. Probably a good idea to make the bushing and heat threat then grind bushing ID when in the spindle for min. runout. Just my thoughts. Many others I think have the same idea. Take care Chuck.

I think a spindle regrind is in order. Regrind the taper so that the 3C collets have better spindle taper engagement.

I just finished making a center for my rotary table. I found it to be a MT3 bore. The major diameter ended up being 0.940”. That allowed it to sit flush in my table. To get that measurement, I used a threaded MT3 to JT 2 shaft. If the manual says it’s a MT3, then most likely it is. The ER 32 holders come in two shanks. MTA and MTB. A being the tang end for a tail stock. B the threaded end. If you have any MTB 3 shafts laying around, try it to see how it sits.

The first thing would be to remove the spindle from the machine and put it in the lathe for precise measurements and repair. If the taper is close but, as you said, the collet is going in too far, you could remove a bit of the spindle nose.

Chuck, I wouldn’t make a shim first thus. Firstly, it will be too thin. A shim isn’t an adapter. That’s not its purpose. I wish I was there. It’s hard to determine what a problem is from a distance. It’s very odd that someone else has the same mill with a Morse 3, but that yours isn’t really that or the 3C it came with. I’m wondering if someone had already ground that taper for some specific use, a use that is now lost to history. Regrinding that internal taper with the head seems like the best idea. But what to grind it to? The taper you show is close to, but not a 3C. Since you want to take as little metal off as possible, you don’t want to grind to something that will do that. If the 3C collets fit, but the taper is off, and you don’t mind those collets, then I suggest grinding the taper to fit them. That seems to be the least work. No matter what anyone says, unless your friend already took the head apart, don’t do that. Precision bearings only go in one way. That is, they’re aligned with the casting and each other. Taking it apart will damage the accuracy. If your grinder has excellent bearings (otherwise it shouldn’t be used for precision grinding at all) then regrinding the short internal taper is easy, by just going in 0.001” steps. As long as you can match the correct angle.

It is not proper to shim tapers. I have seen sold by the Hardinge Company, Morse Taper collets in both Imperial and Metric sizes. They weren't inexpensive thirty years ago when I needed a set for a Lars Gorton tool grinding machine I had purchased then.

This may be totally impractical but I don't see it listed below. How complicated is that spindle to recreate from scratch? Probably not an option if the drive gear is integral to the spindle but if it is keyed and pressed on it might be do-able. I guess heat treating and grinding may be required so not a small job. Mr. Lipton might be able to help or ABOM79 has a shiny new CNC lathe that he is practicing on.

Put a R-8 in just to look at fit. 4-C and R are similar enough. Dang Chuck wish you was north of Detroit

Have you asked Dean if he has any SB old school collets to compare the aftermarket ones too? I would blue up with dyecom both and compare mating surfaces. Could be my best guess!

Hi, Chuck Can you purchase a properly sized spindle on the used market??? If not, just make a new spindle to match your 3C collets, or maybe an R-32 or smaller style spindle. Maybe Tom Lipton could regrind the spindle to match your collets. I'm just not clear , if you have enough material left in the spindle bore to grind it straight to match your 3C collets. If not maybe you could over bore/grind the back part of the spindle, where the straight section should be, and use a sleeve on your draw tube, to create a sufficiently tight clearance to hold the rear of the collet concentric with the bore. I would love to see, and hear about your solution. Tim

Chuck, I have a dividing head with a B & S taper it has a sleeve in it to accept a No 2 Mores taper , I wouldn't see why your idea wouldn't work...providing you have enough materiel left to "git er done"..!

Seems like perhaps the original spindle was modified or replaced. Can you make a whole new spindle? The plug could work, but it sounds like it might end up be very thin walled. Since the collet sits so far back, maybe pull the spindle, set it up in a lathe, machine off the front face, then use a tool post grinder to fix the taper?

You might have a 3AT collet which is similar to but different from 3C. The 3AT collets are shorter but the thread is very similar and the body is bigger at 0.687" instead of the 3C 0.650". 3AT has a 0.935" nose while 3C is 0.854". So they are close and somewhat interoperable but the taper of 3AT is 30 deg. while the 3C is 24 deg and your numbers might match 30 deg. closer (I got ~28 deg. from the number you gave in the video, which is in between). Maybe you could borrow a 3AT collet and try it? My lathe takes 3C collets but I have seen 3AT's pop up in used tool settings before. As people are saying below, you can measure the taper very accurately with two ball bearing balls and a depth mike--I have done this when making 3C fixture blocks (hex and square) for my collets.

Man that’s an interesting taper. Makes me think of something similar to a Flex Jacob, but smaller. I looked through the B&S tapers, couldn’t find a close enough match. I’ll keep looking because I like a challenge sometimes. Maybe it’s something obscure like a NMTB 20.

How about regrinding the spindle to take an ER 25 or 32 collet? Thread the outside of the spindle to take the nut. The taper for a 3C is 12deg and an ER 16deg. The ER25 is a bit bigger than the 3C and the 32 more so, which would probably fit nicely after flaring the taper to 16deg. I don't like the idea of a shim too much but what do I know. I'm just thinking out loud.

I think you have a good plan. Keep Charlie out of the shop and take your time. Kimber

chuck what about the possibility of making an adapter to fit over the spindle nose you could grind a couple of flats on the spindle and secure it with set screws. your adapter could be made for 3c or 2mt or er. you could finish grind the adapter on the spindle for max concentricity just a thought

whats the runout on the other end of the spindle could the bearings on that end have runout?

Chuck I don't know what you have there but look at a table for the Jarno Tapers , its in the Machinery's Handbook , Hope you find something that works .

Could the collets be a Brown and Sharpe tapper? Just a guess. I have a rotary table that uses Brown and Sharpe collets, and there are close to Morse tapper 1. Good luck.

Can you make a new spindle to suit your requirements. Kit from down under

The best fix is to make a new spindle shaft cut to something you can use

you wil need this little machine shop sells them Collet Adapter, 3MT to 3C you can see thr totaly different taper of 3c and mt3 in the picture

I gonna say it’s a 4c like my Rockwell 10” lathe. Those collets can be found. Three c is to small

Possibly a B&S #9 taper? A B&S #7 is very close to a #2 mt.

could someone hahe changed it to a r8 housing

Chuck. I have a similar problem with my Bridgeport clone. But I am only looking at.0015. I thought you said you only had .0005 TIR. Maybe I need to go back and watch the video again. What is the TIR when you use a gage pin or dowel pin inside one of the 2C collets. (Is it the same as the Wobble Mill?) If it is not the same, then record the difference and rethink the problem and solution. Boss Kettering said the problem will always tell you the solution. (FYI Boss Kettering invented the electric starter for Delco Remy) . If you are just interested in the taper there is a low temp metal similar to lead that gunsmiths use to measure the taper within the chamber of a barrel. It is a very stable material. I have some but right now my 72 year old brain will wait till I lay down to sleep and I will remember it. If you follow Dee Dee (Don Dyar) he corrected a similar problem on his Brown and sharp mill by doing an internal scraping of the taper. It will be interesting to follow your research and repair of the problem. My Hobby is rebuilding (not just cleaning and repainting) vintage and antique. Machine tools. I will be back to read other's comments and your future videos on the Sweet little Mill. I watched the series with you and Dean working on the head. kzfaq.info/get/bejne/a6uTe9ZoyNCdZ6s.html

Hoi it looks like an R8 taper except the pin , and an M3 taper has to be smooth without the pin.. it seems the bore itself is to big to guide the end of the collet this has to be max 0.0005 play. and I am not shure the taper of the collet wil match an M3 taper at all.

Sorry about situation. Kiss off existing work envelope. Make permanent er collet adapter to fit existing spindle bore. Your just gonna have to loose a little work Z work envelope. I see why the guy unloaded this mill.

What ho Chuck, differing tapers will still run true even if only meeting on a ring not the full taper, what is important is the parallel section at the threaded end, if that is sloppy you have no chance of concentricity. Morse and the likes of ER tapers rely only on a taper and that has to be a good match, the C ranges have a taper and parallel As to the fix, you have many options, from a regrind to a sleeve job to a whole new part, as to which is best it depends on cost, abilities or even what is possible depending on measurements. You didn't want a simple life did you?😂😂😂

Some good ideas in here. Sounds like you have to do something. I don't think I qualify for an opinion. Good luck, Chuck.⚒️🔩🔧