How do you tell how fast a lathe is turning?

[Nick Fisher]

I just picked up a Delta 46-612. Great find actually, when I went to look at it, everything was there, but it would only turn at one speed. Bought it for $150. Got it home and I came to find out that the wire the moves the reeves drive wasn't connected. One trip to the store for a washer and screw and 45 cents later I had a fully working lathe(now worth around $1000). Not a bad deal(feel kind of bad for the guy though). Well, I decide to upgrade some of the belts to get rid of the vibration(they were worn). I installed some link belts and now its amazingly smooth, I can pace a nickel on edge on the bed while running, and it won't move or fall over(SWEET!). But because of the difference in belt lengths, The range of speed changed. Depending on which belt I lengthen or shorten with the reeves drive, I can change the range from slow/fast, to med-slow/really fast. But I'd like to find out what the actually revolutions are. Does anyone know how to tell how fast it's spinning? I'd like to get somewhere near the factory settings, though I may go with a slower bottom end(for large pieces).
Thanks,
Nick

As I was typing this, I thought of an idea, I could turn a large diameter circle, then trace a pencil along the face while it is spinning towards the center. If I traced it slowly for, lets say 5 seconds) and count the lines it makes on the face, I should be able to tell how many revolutions it makes during those 5 seconds, then I can just multiply it out. Does anyone else have any ideas?

[Alan Zenreich]

Many places (including this one (http://www.harborfreight.com/digital-photo-sensor-tachometer-66632.html)at harbor freight) sell an inexpensive tachometer. You put a piece of reflective tape on the moving piece and point the tach at it.

[Nick Fisher]

Excellent, that is a much better way to do it, thanks,
Nick

[Jon McElwain]

Strap a stick to the spindle, perpendicular to the lathe axis. Put your head close to the spindle and turn on the lathe. Count how many times it whacks you in a minute and you have your RPM's!:D

Ha! You could set up a bicycle computer (http://www.rei.com/product/751833/cateye-velo-5-cc-vl510-bike-computer?cm_mmc=cse_froogle-_-datafeed-_-product-_-751833&mr:trackingCode=BD824FFE-FB85-DE11-B7F3-0019B9C043EB&mr:referralID=NA) and have a permanent digital tachometer for the lathe. Bike computers can be bought for $20 or less.

[Russell Neyman]

About a month ago I checked among the Creekers looking for an accurate recommended speed chart and ended up with a pretty good one. (I have it in a PDF file, but need to send it to a personal email if you want a copy.) One turner noted that many of the high end lathes don't have any speed indicator at all, and the instruction manuals were pretty much saying let it fly as fast as you can (or dare) loosely following the idea that the smaller diameter, the higher the speed. Pretty scary.

[Nick Fisher]

PM sent, thanks,
Nick

[Sid Matheny]

HF also has a cheaper one that is a digital contact tach.
http://www.harborfreight.com/digital-contact-tachometer-66400.html

Sid

[Harry Robinette]

I use the one from HF that Sid was talking about just put a piece of tape over the hole in the spindle. Then just hold the end of the tack to it. I made a sheet up that shows my speed at each mark on the dial. It's only there because I sometimes have guys in to turn and they want to know their speed. I turn the speed to were I fill comfortable and away I go.

[Jim Burr]

No pic's no lathe

[Allen stagg]

Can do a search for pulley sizes and get rpms based on pully sizes and motor speed to get speed. Search for gear or pulley speed calculator.

[Roy Turbett]

I had the same issue when I changed belts on my Powermatic 90. Multiply the speed of the motor by the diameter of the pulley on the motor and divide by the diameter of the fixed pulley on the lower reeves drive. This will tell you how fast the lower reeves spindle is turning. Multiply the speed of the lower reeves spindle by the diameter of the lower reeves variable pulley and divide this number by the diameter of the upper reeves variable pulley and you will arrive at your spindle speed. If your lathe is adjusted correctly, the minimum and maximum size of the upper and lower reeves drive should be the same. On my PM 90 this is accomplished by adjusting the lower reeves pulley up or down.

[Nick Fisher]

210122210123
So here is my lathe(first time posting pics, hope they work), So the cheap way I figured it out was to turn a piece of wood round, then drag a pencil across it for 15 seconds, then multiply it by 4. Ended up I was spinning at 340RPMs, dead on. Cool stuff, but it only works for the slower speeds(though that's all I really care about). Thanks for all your help, I may go purchase a tachometer later on, but this gave me what I needed. Thanks again,
Nick

[Michelle Rich]

I wonder why one would really need to know the speed..one turns at a speed that is appropriate for the piece being turned, not some imaginary speed on a chart. So knowing is irrelevant. ( yes, I know, I'm a cold bucket of water :-) ) But have fun finding out!

[Roy Turbett]

Michelle -

I agree with you and turn at a speed that is appropriate for the piece being turned. However, when I put risers on one of my PM 90's to convert a spindle lathe to a bowl and hollow form lathe I needed a new low end speed which is why I took the time to make the calculations I did. There is a significant difference in the speeds you get with different motor pulleys and how you adjust the lower reeves pulley. And with a stock pulley the slowest lathe speed is too fast for all but the smallest bowl blanks. This won't be a problem if I ever get around to adding a VFD.

Roy