Lathe speed?

[kyaggie]

Hello all,

Lately I've had a few more blank explosions than my "normal" and in trying to come up with a correctable reason I'm wondering what is the best lathe speed (in rpm) to do the best job? For this question assume sharp tools are being used. What speed is too slow and what speed is too fast?

Thanks,
Mike

 

[Dale Allen]

My experience is that it depends on a lot of things.
When I do certain acrylics, I turn up the speed and on some I keep it down to 600-700.
It seems to me that in certain circumstances, a faster spinning stock has less of a chance to grab the tool edge. I keep the speed down when removing the corners and speed it up once round. also, a hard or soft spot will challenge the best turner because of the rapid change in the reaction of the blank.
Best advice is to take your time and add experience with each turning.

 

[jcm71]

Michael,
I don't know what the best lathe speed is, however, generally the faster the better. I turn at about 3500 RPM (R on my Shopsmith dial) with good results. Another reason for frequent blank explosions is a faulty glue job. Is glue visible on the tube after a blank explodes? If not, that is probably the reason. What type of glue are you using and what material are you turning?

 

[kyaggie]

What type of glue are you using and what material are you turning?

I'm turning wood blanks (at ~3000 rpm once rounded) that are both softer/punky burls like buckeye burl and harder blanks like walnut and mesquite. I've had explosions with both types and glue is something that I'm thinking about as a potential culprit also. I am now and have always used Gorilla Glue but perhaps in my quest to make less of a mess I am not using enough to get a good hold. I really don't like using CA to glue the tubes in and I have resisted epoxy just because of the convenience of Gorilla Glue and my past success with it.

Mike

 

[BeSquare]

I also turn at around 3000 on most materials. Though with some softer materials that can cause it to be real aggressive and the tool will really dig in. Most of the blank failures I've had have been because of glue issue. I've gone to epoxy and coating the whole tube in it. I also had one fail because I didn't realize a drill it was slightly vent and I ended up with a slightly oval hole. This caused the tube to not have even support

Hope that helps!

 

[hard hat]

what has your method of applying gorilla glue been? have you been using water to provide the required moisture for the polyurethane glue to cure?

 

[jfoh]

Do not skimp on the glue. If you blow into the blank you will add enough moisture to cure the glue. If the tube is a very tight fit it wipes almost all the glue out as it is seated and makes for a weak glue up. For soft, punky type woods add thin CA to the inside before using Gorilla glue. It makes the wood stronger. You might have to run a drill bit back through to make the hole large enough for easy glue ups. I also scuff the brass tubes to give a better gripping surface.

Some times blow ups will just happen. Sharp tools, light touch and high speeds work best for me on the lathe. If the burl is very prone to blowups you can always use your "sandpaper" skew to finish the turning. A strip of 80 or 120 will shape a blank just as well as a skew. Just takes time.

 

[alphageek]

IMO - for a pen I turn on the top belt of my lathe. There is no such thing as too fast. I personally feel that too slow is a much bigger issue than too fast.

You must be comfortable with whatever speed you choose, but light cuts and sharp tools mean I can spin at fast speeds without issue and the light cuts "feel" better to me at higher speeds.

Now, if you are turning larger diameter objects high speeds can be dangerous so use appropriate caution.

 

[Chasper]

IMHO my lathe goes up to around 3950 RPM and full speed is not too fast, I would turn it higher if it went faster. Anything less that 3000 is too slow.

Also I don't believe that glue is the problem on 99%+ of blowouts. Gorilla, epoxy, CA, any of them work equally well. I use CA because it is faster. Nearly all blow outs are the result of improper tool handling.

 

[1080Wayne]

I suspect a large part of your problem is the nature of the woods you are turning . Burls by nature have very irregular grain . Soft spots are prone to tearing out . You can minimize the problem by putting thin CA on the soft spots before , and maybe a couple times during , turning .

Inspect the grain before turning . If it angles across the blank , it may be best to work from both ends inward rather than straight across in one direction .

 

[ed4copies]

When you turn for several hours, daily, the speed begins to LOOK slower.

So, turn at the highest speed you can, comfortably!!!