View Full Version : Slitting saws

05-01-2007, 10:50 PM
I've needed a slitting saw twice and both times it did the job badly but left me with a usable part. The problem both times is the saw made a curved cut and it got worse as the cut got longer.

In both cases I did the cut full depth which amounted to about 1/2" both times. I did the cut slowly, used coolant. In hindsight I suspect two things: Not as square as I thought, and I may have had better luck by nibbling away it the slit in multiple passes. Never seen any literature on this operation so was flying by the seat of my blind stumbling luck.

Interestingly, the first cut walked off the line along the line of the cut but produced a good vertical cut initially, and the second cut warped over the depth of the cut immediately.

Surely there's a right way to do it - and I fully understand the need for alignment being a critical requirement. In one case I used the chuck of my lathe, and in the second I used my mill. I think in either case, multiple passes may have worked.

How do alla y'all do it?

05-01-2007, 11:15 PM
Sandwich the slitting saw as much as possible to stiffen it up, the thinner the saw the more passes you will have to take.

05-01-2007, 11:21 PM
Run the saw slow and feed slow with light cuts, never had a problem. riceone.

J Tiers
05-01-2007, 11:30 PM
DEpends on the slitting saw..... but some are just not intended to be buried in the work.

If you have one that is an alternate tooth side-cutting type, looks like a thin side mill, you can bury it deeper.

if it has NO side teeth, you can't go much over the gullet depth and expect good results. Yes I know they are hollow ground, but......

05-01-2007, 11:52 PM
how thick a blade? for the thin ones, I remember the first attempts with the same problem. here's my explanation and solution. because of clearance between the bland and holder etc, the blade inevitably only cuts on a few teeth. if you feed as if you think its cutting on all, you over feed and essentially crash the couple of teeth that are cutting. instead of these teeth taking a nice small chip, they are subjected to higher loads than they would like (even if they did cut on all, these fragile little tools can only take s small chip) and the teeth deflect too much, and not in a straight line. after a few revs the blade is now being guided in a curved slot.

you can can go full depth, but you have to keep the feed way, way down especially at the beginning. this is a manual feel feed rate at slow rpm. fortunately its an infrequent enough activity i survive the boredom of slow slitting cuts. if design allows, its easier to power through a large size than baby the 1/32" ones

05-02-2007, 12:33 AM
I think the problem is DOC. I had a similar problem and wrecked my first (sadly, very nice US made) slitting saw. I've had better luck going about twice tooth depth at most and making multiple passes. First pass is even less until I get a groove started.

05-02-2007, 01:01 AM
Make sure the saw is well supported on a sturdy arbor.


05-02-2007, 08:10 AM
There are slitting saws and slotting saws. Slitting saws are hollow ground and intended for deep cutting. Larger sizes may have staggered side cutting teeth as well. Slotting saws are not hollow ground, and are for slotting shallow depths.

Either should be used at low speed and light feeds with coolant.

05-02-2007, 09:15 AM
Also be certain that the mill head is for-sure square to the table travel. Even a little tilt will cause problems.

Another question may be, what is the quality of the sawblade? I've always used the Polish "quality import" blades with reasonable success, but I can imagine that there are some junk ones around that aren't sharpened correctly.

05-02-2007, 10:35 AM
While on the topic of slitting saws, I've had trouble with the arbors. My arbor is one that has spring loaded cylinders that will accept different diameter holes in the saws. I have found that each time I have tried to use the arbor, the saw just spins becasuse the arbor will not hold it tight. I tighten as hard as I can but there just isn't enough friction to keep it held tight.

I have looked for arbors that have a keyway to keep the saw from rotating on the shaft but have not found one. Maybe I have to make a shaft for each diameter hole in the saws. (Similare to the one pictured in a previous post.)


Frank Ford
05-02-2007, 10:50 AM
"I have looked for arbors that have a keyway to keep the saw from rotating on the shaft but have not found one. Maybe I have to make a shaft for each diameter hole in the saws. (Similare to the one pictured in a previous post.) "

I've had the opposite problem. With a big blade, the torque is sufficient to sock the screw down so tight I about bust my hex wrench trying to get it out. I just ordered a stub milling arbor with the hopes of using it with saw blades.

05-02-2007, 11:01 AM
I did the same for my larger blades with 1" holes. Problem is, that nut is invariably too big and gets in the way.

05-02-2007, 01:20 PM
whether you want it keyed or not depends on the saw dimensions, mine are generally three dia on a 1" mandrel. for the thin ones, 1/32 and smaller you don't' want it keyed...have it spin will give you a fighting chance if the blade catches. imo 1/16 and up isn't slitting saw, just a thin plain milling cutter :D

05-02-2007, 09:18 PM
Take an initial light cut and this will help guide the saw during the next pass.

05-02-2007, 11:44 PM
I haven't had a chance to try it yet but I'm now convinced the two problems were machine alignment and DOC. I'll take a whack at it again this weekend as I'm making a couple new tools that require slitting and there's not room for screwups this time.

Here's a picture of one of my thinner saws and a couple arbors I made for them. The brass washers are cupped to clear the hub for better compression. No keys.


Edit: hehe - just noticed when I set the saw in the arbor for the picture I put it in backwards... Better go fix it!