mandrel wobble......need help

[wizical]

So I have a couple of questions and need honest opinions.

1) Out of all the companies, who makes the best mandrels? I bought PSI Mandrels and I am not too thrilled with them. I need a suitable replacements and needs everyone's opinion.

2) Ive noticed that the PSI mandrels that the dimple doesnt seem deep enough, does anyone else run into this problem??

thanks

 

[Randy_]

Are you using a 60° live center??

 

[redfishsc]

Randy is right, 60* live center is a must.


The best mandrel I've used, and it's a good one--- is the silver-colored mandrel from WoodCraft, and it's also one of the cheapest (under $4) for just the rod. It does not flex nearly so much as other rods I've used.



As a side note, be sure to search the site for "mandrel whip" or "out of round pens" and look over the topics-- this has been discussed many, many times here and there's some fantastic info to help you.

 

[TBone]

If the problem is that you have runout, then check out Russ Fairfield's web page on how to straighten them. This is after making sure you're using a 60* live center.

 

[randyrls]

Originally posted by wizical

So I have a couple of questions and need honest opinions.

1) Out of all the companies, who makes the best mandrels? I bought PSI Mandrels and I am not too thrilled with them. I need a suitable replacements and needs everyone's opinion.

2) Ive noticed that the PSI mandrels that the dimple doesnt seem deep enough, does anyone else run into this problem??

thanks

Kevin; I have found that the PSI mandrels tend to be one or two thousandths smaller than the mandrels from Woodcraft and Berea. Sometimes I have to "relieve" the PSI bushings to make them fit on Woodcraft mandrels.

You can check the mandrel by mounting a bare mandrel on the lathe. Just snug up the tail stock. Turn on the lathe at minimum speed and lay a lathe tool across the mandrel. Runout in the mandrel will produce vibration in the tool.

Hope this helps.

 

[wizical]

sorry, let me clarify the problem.

I bought PSI Mandrels cause people have told me they are really good, but I have run into nothing but problems with them. I use a 60 degree live center(which i bought from little machine shop), But what I have noticed is when i bring the Live center up to the mandrel, it seems like it barely fits. has anyone else run into this problem. Im probably going to get mandrels from AS, I hear they are pretty good

Thanks for all the advice, i truly appreciate it

 

[Randy_]

Sometimes the clearance hole at the bottom of the center dimple is not quite right. You could try filing about 1mm (no more) off the tip of your 60° live center and see if that helps. (Carbide tipped live centers excepted) I have not done this myself; but several guys here have and said it helped.

 

[Randy_]

Originally posted by redfishsc

.....The best mandrel I've used, and it's a good one--- is the silver-colored mandrel from WoodCraft, and it's also one of the cheapest (under $4) for just the rod.....

Be careful with this solution. Last I knew, the Woodcraft mandrel had a different thread on the HS end than most other manufacturers (8x32?) and the WC mandrels would "ONLY" fit into WC arbors. I have never used CSUSA or PSI mandrels so I don't know if their mandrels thread into the MT arbors or what size thread they might use; but the Berea mandrels have the same thread on both ends.....10x28.....which seems to make a lot of sense from a manufacturing point of view.

 

[TBone]

Also check your bearings on the live center. I had to get a replacement from LMS because they were bad on my first one.

 

[randyrls]

Originally posted by Randy_



Be careful with this solution. Last I knew, the Woodcraft mandrel had a different thread on the HS end than most other manufacturers (8x32?) and the WC mandrels would "ONLY" fit into WC arbors. I have never used CSUSA or PSI mandrels so I don't know if their mandrels thread into the MT arbors or what size thread they might use; but the Berea mandrels have the same thread on both ends.....10x28.....which seems to make a lot of sense from a manufacturing point of view.

Randy; Yes, You are correct. I like both the Berea and the Woodcraft mandrels and have no problem with either one. I use the MT2 taper in my lathe spindle nose and it works well.

 

[MobilMan]

wizical- I have a 60 deg live center & the problem didn't get better. I use the standard live center that came with the Jet, but like you said "the dimple isn't deep enough. Just drill it a little-1/8 to 1/4 inch--deeper. Put the MT-2 in the headstock, but not tight, stick the tailstock in the end of the shaft & use it to push the shaft into the taper. Just snug it up.

 

[Randy_]

Originally posted by MobilMan

wizical- I have a 60 deg live center & the problem didn't get better. I use the standard live center that came with the Jet, but like you said "the dimple isn't deep enough. Just drill it a little-1/8 to 1/4 inch--deeper. Put the MT-2 in the headstock, but not tight, stick the tailstock in the end of the shaft & use it to push the shaft into the taper. Just snug it up.

If the method you propose works for you, that's just great.

Unfortunately, what you propose is mechanically unsound and has caused a lot of people some grief. The tip that comes with the JET live center is a 30° point and is intended to be inserted into wood blanks. (unless JET has changed their tips recently) It "IS NOT" designed to be used with a center dimple in metallic stock. For a center dimple in metal, you need to use a 60° live center for best results!!

Below is a rough sketch that shows the fit of 30° and 60° tips in a center dimple and why a 60° is the preferred choice.

The upper drawing is the 30° tip and you can see that the bearing surface between the tip and the mandrel is very tiny. Because the bearing surface is so small the wear is concentrated and causes the tips to wear out prematurely. It is also possible that extra pressure will be needed to create enough friction to make the LC spin and this could lead to a bowed or bent mandrel.

In the lower drawing, you will notice that the angle of the 60° tip exactly matches the angle of the sides of the center dimple thus creating a much larger contact area. Less wear and more friction....that is the way the system was designed to function.

Sometimes, the center dimples are drilled with clearance holes that are too shallow. I have drawn a purple line to simulate where the bottom of the hole might be if it is to short. With a little imagination it is easy to envision that the extreme tip of the LC point would rest on the bottom of the clearance hole and there would be no contact between the dimple wall and the tip. This situation would totally defeat the purpose of the centering dimple as the tip would dance around on the bottom of the clearance hole and the wall of the dimple would provide no centering effect at all. Additionally, this would cause severe wear on the tip of the LC. As you might imagine, this possibility is more likely to occur with a 30° tip. If the clearance hole is too shallow, the easier solution for most folks is to file a bit off the end of the tip.

 

[Randy_]

Originally posted by randyrls

Originally posted by Randy_



Be careful with this solution. Last I knew, the Woodcraft mandrel had a different thread on the HS end than most other manufacturers (8x32?) and the WC mandrels would "ONLY" fit into WC arbors. I have never used CSUSA or PSI mandrels so I don't know if their mandrels thread into the MT arbors or what size thread they might use; but the Berea mandrels have the same thread on both ends.....10x28.....which seems to make a lot of sense from a manufacturing point of view.

Brain fart on my part. That should read 1/4" x 28tpi.

Randy; Yes, You are correct. I like both the Berea and the Woodcraft mandrels and have no problem with either one. I use the MT2 taper in my lathe spindle nose and it works well.