Spindle thread problem

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dickhob

Member
Joined
Nov 30, 2005
Messages
27
Location
New Milford, CT, USA.
I hope one of you guys can give me some advice. After reading Randy's instructions of changing the bearings in his Jet, I thought it was a great idea and would perhaps quiet down my Jet 1236- of which I think I am the third owner.

I don't consider myself mechaniclly challanged, but I have to say I had a hell of a time getting the pulley off (eBay has some cheap pullers ). It also REALLY helps if you get out the inside C-clip BEFORE you try to tap the sindle towards the headstock!!

Anyway, its all back together- not much difference that I can see BUT I tried to put on my Vicmarc 4jaw chuck. It has a 1x8 adapter. I got about 1/2 turn and it stops. I checked the threads on the spindle and the adapter and they appear to be fine. I have a Penn State mini with the same 1x8 spindle. The Vicmarc goes on just fine. I've got an old Nova chuck and several factplates. Everything goes onto the Jet spindle with no problem.

Just to be sure, I wire brushed the spindle threads. I marked the spindle with a red Sharpie hoping to see where/how the threads were misaligned- can't see anything. I turned on the Jet and lightly filed the front and first thread of the spindle- just in case I'm missing a buggered thread. My Nova goes on better, but the Vicmarc still gets hung up.

I ran the adapter thru a 1x8 tap that I have (I don't have a die).

I'm stuck. Hopefully one of you machinest types can give me some idea as to what is wrong and how to fix it.

This is really driving me nuts.

Thanks
Dick
 
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Dick: I've read through your post several times and must admit to being totally bumfuzzled.[?][?][?][?] I just don't know what to suggest. One question I do have is whether the Vicmarc chuck was ever installed on the Jet before you replaced the bearings or if it previously was used on a different lathe?

Guess the thing I would try next is to remove the adapter from the Vicmarc chuck and see if it will thread on the 1236 and the PSI mini or not and then go from there.

Another thing that puzzles me is your comment, ".....I ran the adapter thru a 1x8 tap that I have (I don't have a die)....." Given the nature of a tap, I think most people would say they ran the tap through the adapter. This may not mean anything at all; but right now, I an grasping at straws.

BTW, just out of interest exactly which model PSI lathe do you have. They sell several mini lathes.

On the surface of it, what you have told us just doesn't seem possible?? Maybe someone else will come along and pick up on something I am missing? I really don't have a clue!!
 
Randy,
Yes, the chuck screwed onto the Jet spindle before I changed the bearings. I admit I more than "gently tapped" to get the spindle back in, but not so much as to bugger the thread. If it is, I sure can't see it (Under magnification).

I took the adapter out of the chuck first thing and have been using only the adapter. Sorry for the wording about the tap, but I did what you said.

The PSI is their Turncrafter Pro belt drive http://www.pennstateind.com/store/tclpro.html

The only thing I can think of is to find a die and run it over the threads and free whatever is the problem.

Thanks
Dick
 
Originally posted by dickhob

......... I admit I more than "gently tapped" to get the spindle back in, but not so much as to bugger the thread........

Thanks
Dick
Click to expand...


I'm wondering if you might have caused the threads to "flare" at the end. If you have a caliper you can measure the outside diameter of the thread close to the headstock and then at the outside end and see what the difference is. I can look at the specs in the federal screwthread standards book if you would like but I think the tolerance on a 1" x 8 thread is pretty loose.

It could be that the threads on the lathe were originally at the high end of the tolerance and the chuck was at the low end of the tolerance, your "gentle tapping" might have upset the threads just enough to make it not fit together again.



Originally posted by dickhob

.........The only thing I can think of is to find a die and run it over the threads and free whatever is the problem.

Thanks
Dick
Click to expand...


This sounds like a good idea. You can get one from MSC for $25 and change.


http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=1724819&PMT4NO=42676931


See you at the wood turners meeting on Monday.

Scott
 
I've tried the file for a few threads. If there is/was a burr I sure can't see it.

I haven't measured the threads as yet, but I did take a flat file and flattened the tops of the first few threads. I'm sure I didn't hit the spindle so hard as to flare the end.

I was hoping I could find a solution other than buying a die that I will probably never use again, but my options seem to be narrowing rapidly towards that end.

Thanks for the suggestions.
Dick
 
Originally posted by dickhob

Randy,
Yes, the chuck screwed onto the Jet spindle before I changed the bearings. I admit I more than "gently tapped" to get the spindle back in, but not so much as to bugger the thread. If it is, I sure can't see it (Under magnification).

I took the adapter out of the chuck first thing and have been using only the adapter. Sorry for the wording about the tap, but I did what you said.

The PSI is their Turncrafter Pro belt drive http://www.pennstateind.com/store/tclpro.html

The only thing I can think of is to find a die and run it over the threads and free whatever is the problem.

Thanks
Dick
Click to expand...

Before you do that....there may be one or two other things to try that are less expensive.

First though, let me ask you if the Vicmarc screwed into the Jet spindle nose fairly freely or was it a snug fit even before you replaced the bushings?

Secondly, did you in fact use a soft hammer...lead, brass, wood or plastic when driving the spindle back into the headstock or were you a bad boy and used a steel headed hammer?? Those spindles are pretty stout and it is hard to understand how you could have deformed the threads enough to cause them to bind using a soft hammer. If, in fact, that did happen, there is a good chance that the new bearings are damaged and that the Morse taper has been deformed as well and may give you a problem as well.

Let me repeat just one more time to be doubly sure we all are on the same page as I see Scott and Paul have gotten on board so we now have some real brain power to exercise. All of the 1" x 8tpi accessories that you have screw on to the PSI spindle and the Jet spindle without any difficulty with the single exception of the Vtcmarc adapter which will not go on the Jet spindle more than about a half a turn or so......right??

You made a comment that after filing the threads "...the Nova chuck went on better..." Are you saying the Nova chuck was a little tight after your bearing replacement.....tighter than before the bearing replacement??

OK, here is what I am thinking and I hope Scott and Paul will chime in on this idea as well. Since it appears that all of the other 1 x 8 accessories fit on both spindles, it would seem fair to say the thread on the Jet can't be too far off. And since the Vicmarc adapter has had its 1x8 thread chased with a proper tap, its thread should be correctly formed as well. Scott's suggestion of measuring the threads is a good one; but you can't do what you ain't got. Were it me, I would lubricate the spindle nose and the threads of the Vicmarc adapter with a good grease and screw the adapter on the JET spindle until it stops. Then with a tommy bar or knockout bar securing the spindle, I would take about a 10" Crescent wrench and try to screw the adapter onto the spindle by no more than another 1/8 turn. (This assuming the adapter has some sort of hex fitting on it that can be grabbed by a wrench.) If you can get that 1/8 turn without too much effort, stop, back the adapter off and re-distribute the grease on the spindle. Repeat the process and see if you can get another 1/8 turn without an excessive amount of force. If you can keep getting those 1/8 turn increments, keep up the process. Chances are that after several iterations, the adapter will get past the problem thread area and spin on the rest of the way without much resistance. WARNING: USE A LITTLE RESTRAINT WHEN TRYING THE ABOVE!!! IF YOU CRANK DOWN TOO HARD WITH THE CRESCENT WRENCH, THE TOMMY BAR/KNOCKOUT BAR MAY SLIP OUT OF THE HOLE IN THE SPINDLE AND BUGGER IT UP.....MORE BAD NEWS!!

One last thing you could try if there is not too much of a taper on the end of your 1 x 8 tap would to be to lay it up next to the threads on the spindle nose and see how well the two mesh. If you detect an area where they don't match well, that may be the problem area. Although dealing with it is another problem, altogether.

Guess I am tapped out again unless someone else says something that lights a bulb.

Good luck!!

Randy
 
Wow, that’s quite a list- I do appreciate it.

I put some calipers on the spindle. I get 24.94mm at the back and 24.57mm on the first full front thread. I’m not very good with these things so I’m not sure just how much you can trust these numbers.

I don’t really remember if the Vicmarc adapter was a snug fit before the bearing change. It did fit the spindle though. The Nova was a little tight before filing and it freed up so it screws on smoothly now.

I did use a 20oz steel hammer on the spindle, but there was a ¾ in piece of oak flooring between the hammer and the spindle. I did carefully "tap" the spindle/bearing in.

The morse seems to be fine. I put in a few tapers and there is not any play or wobble. They turn as well as they did before the change. The tip of a dead center is not perfectly concentric. I don’t have anything to measure how much it is out, but I can live with it. I don’t think I have much choice.

I tried to lube and put a little extra force with a tommy bar. No good. It locks down tight enough that I don’t think more force will straighten out the bad spot.

Your idea of match the spindle thread has pretty well convinced me I need to rethread the spindle. As I laid the tap into the spindle thread and turned it by hand, there is a section that has a noticeable gap in the meshing. I guess I need to spring for the die.

Any more thought are certainly welcome.

Thanks again for all the help and suggestions.
Dick
 
OK, Dick. No new earth-shaking thoughts; but having numbers we can compare is always a good thing.

BTW, a wooden bumper between the spindle nose and the hammer qualifies as a "soft" hammer....you done good!!:D I don't know what the heck is going on; but it is hard to see how you could have damaged the spindle???

Anyway, I measured the nose of my lathe just for the sake of comparison. The results add to the mystery and don't seem to shed any light on the problem. On my spindle,at the very back of the nose(closest to the HS body), there is a short (maybe 1/4" unthreaded section. I measured that first assuming it was the diameter the thread was cut on. It measured 1.006" (25.58mm). Next, I measured the first full thread closest to the unthreaded section and found it to be 0.990" (25.14mm). Next, I measured the thread at the midpoint of the threaded section and found it to be 0.987" (25.08mm). Finally I measured the second full thread from the front and found it to be 0.986" (25.05mm). My numbers agree well with yours, Dick, and the fact that yours are a bit smaller are presumably due to the thread filing that you did. I looked at a web site that shows thread geometry and measurements and the major diameter is supposed to be exactly 1.0" so the threads on both of our spindles are a hair undersized.

Well, I am still puzzled, frustrated like you and feel like I'm banging my head against a brick wall. I'm still having a hard time accepting that the spindle threads are the problem; but everything seems to be pointing that way and I don't know what else it could be???

There is a little tool that is specifically designed to true up threads that are not properly configured or have been damaged. I don't know what it is called or what it costs or whether it would be a better/more economical alternative than buying a 1x8 die. I'll look around a little and see what I can find out. I'm sure Paul and Scott are familiar with this tool and will have some thoughts on whether this would be a reasonable alternative.
 
I've seen the thread files you referred to, but I have a feeling that finding one to fit the 1x8 thread is going to be a problem.

I think Mudder's link is probably the easiest solution. They have some imported dies for a $15. I also checked ENCO- they have imports for $10. I don't think I can do much better that that.

If anyone is interested here are the links I found.

http://www.use-enco.com/CGI/INSRIT?PARTPG=INSRAR2&PMAKA=314-5036&PMPXNO=945250 $10.95

http://www1.mscdirect.com/CGI/GSDRVSM?PACACHE=000000054887473 $15.47-$25.23

It seems we've beat this thing to death. Thanks for all your help. I'll post the final results when I get the dies.
 
Boy, I'm glad when I used Randy's instructions to change the bearings in my Jet Mini everything worked perfectly... because I AM mechanically challenged sometimes.. my Jet 1014 hums like a new machine after changing the bearings... and all of my chucks still fit fine.. thanks Randy.
 
Can you try an experiment just to narrow down the culprit.
You said the the chuck had a 1-8 adapter? Can you remove the adapter from the chuck and then turn it around and try threading it on?
I am guessing that the adapter had a flange on one end. In this case you want to thread the non-flanged end onto the spindle.
Now check carefully to see if the adapter stops at the same point on the spindle...
If it goes on a different amount than the normal way then it would point to the thread inside the adapter being buggered up (even after the tap).
If it goes on the the same spot then it points to the spindle.
 
Thanks Kirk, I tried that already. I can't say it stops in exactly the same place, but its close enough to call it the same.

I've ordered the 1x8 die and it should be here by week's end. I'll let you know how the saga plays out.
Dick
 
SUCCESS:D:D:D

My die came today and after a few minutes of gingerly getting the alignment right, the die did the job. I have to admint the first few threads look quite different from before.

I now have a spindle that will take ALL my 1x8 attachments!

Thanks again for all the help and suggestions.
Dick
 
Congratulations, Dick!!!

Glad the die resolved your problem.

Maybe you can work a deal to trade it to Aderhammer for something so he can get the spindle on his rose engine lathe working??
 
I found the source of my buggered spindle threads. Apparently some of my attachments (I haven't checked the all as yet) have short threads for the length of the spindle thread. When they are tightened on the spindle, they distort the first thread. The die of course fixed the problem.

I found a post last night (I can't find it now- is it me or does the forum have a lousy search function). Anyway it said the back of the accesssory has to solidly seat against the back of the spindle flange. If not you will get wobble, etc.

I cut a nylon washer from a Walmart cutting board and drilled a i-inch hole in it. That spaced the accessory to force a tight fit on the threads. Mayhbe that's obvious to some of you old timers, but for me that is an ha-haaa moment.

All is right with the world again.

What does Aderhammer need? Sorry, but I'm not familiar with his specific problem and my search didn't provide me any meaningful results.

Thanks
Dick
 
You might want to mention exactly which accessories are causing the problem so that others can watch for a similar problem.

As to Aderhammer, check out this thread

http://www.penturners.org/forum/topic.asp?TOPIC_ID=37106&SearchTerms=rose,lathe
 
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