Slotting/slitting saws and the lack of concentrically

[starr256]

I have a couple of slotting saw blades (6 x 0.312 and 5x0.125) that are not concentric with the arbor hole. One is almost 0.010" variation. What bothers me is the noise made in the head of the milling machine each time the high side of the contacts the work piece. Worse than a normal interrupted cuts. A real clanging of gears. Is this OK? Note that these were acquired as "Used" blades.

 

[GeneT45]

Doesn't sound OK. I've used some eccentric slitting saws (normally thinner than those you describe) and all I usually hear is the interrupted cut. Aside from the eccentricity, maybe too much for your machine (cutter thickness, speed, feed)?

GsT

 

[WobblyHand]

Remember you do have to run these HSS saws pretty slow. 100-150 SFM for steel. Using SFM=100, RPM = 100(SFM) x 3.82 / 6(diameter) = 382/6 = about 64 RPM

To make the math easier use RPM = SFM x 4 / diameter(inches)

 

[Huub Buis]

I have an arbor for each slitting saw. None of them is concentric. When they get dull, I regrind them using the arbor. Every regrind, the concentricity gets better but never as good as an end mill.
I run them a 50% faster than normal HSS speeds. Seems that the teeth don't get to hot because they are only engaged a short time every revolution. They last about a year before they get a regrind.
I always add cutting oil to the part where the saw enters the part, not on the slitting saw it self.

 

[markba633csi]

Well made saw blades should be very concentric- I'd say within 0.003" or less
I have some 3" Polish made 0.025" blades from ToolMex that are about that- 1/2" arbor

 

[Jim F]

Could be the chinesium arbor ......

 

[David2011]

The Joe Pie video is a good way to make a slitting saw arbor. I used it as a guide for making an arbor for saw blades that have a 1" bore. I overshot the ID by a few thou so making another body is on the list of things to do.

 

[WobblyHand]

Could be the chinesium arbor ......

Pretty easy to indicate. Recommend the OP measures the total indicated runout TIR to see if that's the major source of error. Also use a micrometer to measure the diameter of the arbor. If the diameter is small, (too loose of a fit), the saw will runout.

The cure for arbor runout is to get a good one, make your own, or live with the runout if it's not horrible. When I was just learning to use a lathe, I tried making a saw arbor and had difficulty. In my case, it was taper, and due to my inexperience I didn't know how to fix it. Going to give it a try again, roughly following Joe Pie's method.

 

[Dabbler]

A high precision arbour and quality slitting saw will always have a tiny runout. In over 40 years and seeing almost a hundred shops, I've never encountered a guy who could claim no runout on his slitting saw. The regrind idea is SUPER promising, and is attractive to me!!! Great idea @Huub Buis !!

 

[Huub Buis]

A high precision arbour and quality slitting saw will always have a tiny runout. In over 40 years and seeing almost a hundred shops, I've never encountered a guy who could claim no runout on his slitting saw. The regrind idea is SUPER promising, and is attractive to me!!! Great idea @Huub Buis !!

I use a cheap "diamond" Chinese disks (1"), a Dremel and my CNC mini lathe to grind these. The most difficult is counting the teeth.
I grind once a year drills, mills (tip only) taps and roughing mills (some times), rotary broaches and slitting saws. All equipment is covered with cloth and after grinding all equipment is cleaned and the mini lathe gets his yearly maintenance.

A rotary table and a manual mil can also do the job (slitting saws, end mills).

I don not regrind center drills any more because the factory grind is better than my regrind.