Blanks stop spinning when carbide cutter comes into contact with it??

[UCLAJediKnight]

Hey everyone,

I have run into a problem I am not quite sure about. When I push my carbide cutter into the spinning blank, the blanks often stop spinning and "catch" on the cutter. I can see the mandrel spinning beneath.

Some more information:
- I am using a lathe that is only around 3 years old. My father-in-law has turned 100s of pens on it but recently upgraded and got the old one.
- I use the carbide cutters from Eddie Castelin. I haven't been "thrilled" with them compared to my father-in-laws EWT carbides, but they have been serviceable. I used the EWT to turn some great handles for Eddie's carbides.
- I use a mandrel saver
- I have had this problem at a variety of RPMs.

My initial thoughts were that I was not tightening the tailstock enough. When I really crank it down the blanks cut better, however I notice a burning smell.

Thoughts? Need more info?

 

[walshjp17]

I used to have this problem with the EWT bits and switched from the square cutter to a R2 cutter and have had little to no problem since. I have also switched to turning between centers (TBC) using only the bushings and that is a tremendous help.

 

[UCLAJediKnight]

I used to have this problem with the EWT bits and switched from the square cutter to a R2 cutter and have had little to no problem since. I have also switched to turning between centers (TBC) using only the bushings and that is a tremendous help.

hmm, I definitely get the problem more with Eddie's R2 than with the square cutter. I don't think I'm quite ready to TBC. Could my cutter be dull? I have the problem even with new cutters.....

 

[Edgar]

I mostly use Eddie's R2 cutters, but I haven't run any tests to compare them with EWT cutters, so I can't say if I think one is more likely to have this issue or not.

My own observations though -- I only have this problem when I'm initially turning the blanks round & usually a little tightening of the tail stock is adequate to stop, or nearly stop the problem. I have also found that a slight upward tilt of the carbide tip rather than going straight in helps somewhat and taking smaller bites (about 1/8" to 1/4" at a time) rather than a whole cutter width.

Turning the corners down on a sander before starting on the lathe should also help & make the cutters last longer - I'm just too lazy to do that on a consistent basis.

I have also found that it works better to do one tube at a time, even with a mandrel saver.

Edgar

 

[Marc]

I think you have not quite tightened the mandrel saver enough. In my opinion, there is a balance between too tight and not tight enough. I also use the R2 cutter. On wood blanks, I do a plunge cut to round using about 1/3 of the carbide cutter. Occasionally, I will stop the blank on the cutter just as you have described. Sometimes the tail stock has slid back a bit and sometimes the quill lock has loosened a bit. I will re-tighten the tail stock, then loosen the quill lock and crank the quill handle down a bit more and proceed down the blank with the plunge cut until round.

Once round, the blank rarely gets stopped with the cutter. If it does, I repeat the above steps.

Of course, one of the dangers with over-tightening the blank of the lathe, even with the mandrel saver in place, is that you can bend the mandrel and cause all sorts of fit problems. Once I have turned close enough to be between 1/16 and 1/32 from the bushing, I loosen up the blank and spin the wood 90 degrees while not spinning the bushing. That can help with some of the fit problems that come from the blank being too tight.

 

[seamus7227]

I don't think I'm quite ready to TBC.

Oh but i think you should try to! it is much easier than using a pen mandrel, and your blanks will always be true!

 

[kovalcik]

Tighten the mandrel saver more. Within reason, you will not bend the mandrel with the mandrel saver because the force is not on the end of the mandrel but is instead against the bushings and blank. Tighten the tail stock a sixteenth to an eighth of a turn at a time until the stalling stops. Not sure what the burning smell would be since everything should be turning the same speed.

 

[UCLAJediKnight]

Thank you everyone for the replies!

Another quick question, when you say "tighten the mandrel saver," do you mean for me to tighten the tailstock (turning wheel on end)? Or do you mean for me to tighten the mandrel saver INTO the tailstock, as in tightening the clamp lever???

Sorry if I am using the terms incorrectly. I am better using lathes than I am with the vocabulary.

 

[Edgar]

You should retract the mandrel saver into the tailstock before moving the tailstock up to where the mandrel saver makes contact with the end bushing. Then lock down the tailstock & turn the wheel to tighten the mandrel up against the bushing.

Watch your tailstock as you tighten the mandrel. If the tailstock is moving back as you tighten, then you might need to make some adjustments to the tailstock. If you really crank down hard, the tailstock might move a little, but not very much.

 

[UCLAJediKnight]

You should retract the mandrel saver into the tailstock before moving the tailstock up to where the mandrel saver makes contact with the end bushing. Then lock down the tailstock & turn the wheel to tighten the mandrel up against the bushing.

Watch your tailstock as you tighten the mandrel. If the tailstock is moving back as you tighten, then you might need to make some adjustments to the tailstock. If you really crank down hard, the tailstock might move a little, but not very much.

thank you. that is a clear explanation. Is it normal for there to be some "play" in the barrel of a tailstock?

 

[kovalcik]

Ed got it. Use the tailstock wheel to push the mandrel saver into the bushings/blank. Use small increments and only enough to do the job. It is never good to use gorilla strength to tighten things. If needed, that is a sure sign that something else is wrong.

There should be no play in the barrel of the tailstock, but sometimes if I do not put enough force on the locking lever, my tailstock does not lock down hard enough and as I turn the wheel, the tail stock assembly is pushed back away from the head stock instead of exerting more pressure.

 

[Tim'sTurnings]

I would suggest tightening the tailstock so there is more pressure on the mandrel saver and your blank and especially take smaller cuts. I found that when the blank stops when I am turning it is usually because I take too big of a cut with the turning tool. Taking smaller cuts should take care of most of your problem. I also do not use carbide on a regular basis because it is easier for me to use the HSS tools. Carbide catches a lot more than my HSS turning tools.
Tim.

 

[plano_harry]

You have plenty of suggestions on proper use of the mandrel saver. (mine's on the shelf )

If you are holding your cutter flat and hitting the corners of the blanks, that is a rough way to do it. Try rotating the handle of your cutter, so your cutting edge is rotated up about 40 degrees rather than flat (zero degrees) creating a shearing cut with less of the tool in contact with the blank corners, less pounding as each corner hits the tool. 3,000 rpm will also help reduce the impact loads as well, reducing "catching/stopping" the blank.

 

[randyrls]

If this lathe is a mini lathe like the Jet 1014 or one of it's clones, look under the tail stock. If you see a round washer, the tail stock may be slipping under pressure. This is a common problem with this type of lathe. I remember that someone here on IAP made a replacement washer with a larger contact area for more grip.

 

[maxwell_smart007]

If the play is in the barrel of the tailstock, try extending it a bit (mine slops when it's in the fully retracted mode), and then tighten it down securely...

A blank that stops spinning is either too dull a tool, or too loose a knurled nut - if it's a ne wcarbide cutter, then the nut is too loose...

 

[ironman123]

All has been said about blank spinning and what to do about it but if you are not pleased with your cutter tips, another suggestion is KN400 radiused Byrd Shelix cutters. They are 15mm X 15mm X 2.5mm. From Oella Saw and Tool.com and they are a good price.

Ray