table saw rpm

[hackberry jake]

I recently bought an antique $35 table saw and I have been fixing it up to use as a dedicated box-joint machine. I looked up different charts online having to do with circular saw blade speed. This was the main one http://vermontamerican.com/article/circular-saw-blade-speed-chart/ .  It has a 3/4" arbor, which is very uncommon now-a-days. So I ordered the Freud 8" box joint blade set from the rain forrest company and took it to Larry to enlarge the hole in both saw blades from 5/8" to 3/4" on his bridgeport mill. While I was talking with him, I told him that I had ordered pulleys to make the blades spin at about 7,800 rpm (blades rated max speed is 9,000). He said that seemed awefully fast, so that got me to thinking. I looked up averge speed of normal 10" table saws and they ranged from around 3,000 rpm to around 5,000. But this saw wont be used normally either. It will always be cutting 1/4" wide notch out of the end grain of boards using a set of 8" blades. Without ordering any more pulleys, I could still get 6,200 rpm by using one of the pulleys that came on the saw and one of the ones I ordered. I figure I will try the slower speed first and go from there. Have any of you guys played around with blade speed before?

[sawguy21]

The motor likely turns 3450 so you are proposing to more than double that. Over driving the blade will result in loss of torque and I am not sure the arbor will withstand the speed for very long.

[beenthere]

May depend as much on the number of teeth in the blade. Tooth-cuts-per-inch.
Also, the wood you are cutting may affect the quality of the cut, as well as the cuts per inch.

A lot of variables, one of which is rpm.

[hackberry jake]

The motor is actually a 1750 rpm repulsion start motor. That puts the pulley size at 13.75" diameter for the motor pulley and 3.15 on the arbor. This is for the 7,800 rpm. The original arbor pulley is 4". If i use the 4" pulley I will get the 6,200. The bearings in the arbor are my main concern.

Edit: I just did the math again and I came up with 7,639 rpm with the 3.15" pulley and 6,015 rpm with the 4" pulley. Wouldn't faster rpm equate to less tear out? I believe they are 20 teeth per blade and using both blades is going to be similar to a 40 tooth blade.

[Ljohnsaw]

That's a pretty slow motor for a table saw.  Normal motors (I've seen) are the 3450 (or so) rpm.  Mine is that and the pulleys are about equal in size (slightly larger on the motor) so my blade rpms is probably around 4k.  My old saw has a giant 1/2 hp Craftsman motor turning an 8" blade.

[hackberry jake]

  My old saw has a giant 1/2 hp Craftsman motor turning an 8" blade.

I know what you mean. The one on this saw is a 3/4 hp. It's bigger and heavier than a modern 5hp.


 

[Just Me]

 I was curious one day when I got hit in the gut with a kickback how fast the piece was going when it hit me. So I figured out tip speed on that saw, and being a curious sort I figured out saws from 16 inch down to 4 1/2"

Without exception the saws I figured out were between 100 and 110 mph tip speed. Not sure if that means anything........

Cool old saw......

[VTwoodworker]

I think that 6200 would be on the high end of the desirable arbor speed.  You did not mention what HP the motor is.  The 6200 rpms would be a better match with the 8" blade.  But since you will be cutting out box joints at that speed it will take some HP and if it is under powered the blade maybe prone to bogging down and stalling.  At that speed the saw may also be prone to vibration but you won't know until you give it a try.

The paint job looks really good on that saw.

Wayne

[POSTON WIDEHEAD]

  Hack, has that saw got a blade guard to go with it.....under the table?

[hackberry jake]

Hack, has that saw got a blade guard to go with it.....under the table?

Nope, never came with one originally. I am going to make one for it so that I can hook it up to the dust collection as well.

[BmoreReclaimed]

Hackberry, you are the man!  I also have the urge to buy up the good old stuff, so I can relate to you man, you always have some new project going on.  To my knowledge almost all of our tools in the woodshop are run around 3450rpm, the motors are all rated that and the pulleys are usually at a glance the same size.  I had a vintage 12" jointer running at 1750rpm(compressor motor speed) and was able to use it.  Cut fine, but noticeably slow.  Went to grainger later in the week for the right pulley, 60-120 bucks is still pennies on the dollar when it comes to the quality of these machines

[Magicman]

The best cutting table saw that I ever owned was an old Craftsman turning 5500.  Wish I still had it.   :-\