slitting saw tooth grind patterns question

Are there any reasons they would be anything but flat top?

dee
;-D

Could be wrong but I can't believe they are flat! Don't they need at least a few degrees of negative rake..clearance, to allow the tooth to actually cut material. Are you talking side rake, not back rake?

Stuart

atomarc said:

Could be wrong but I can't believe they are flat! Don't they need at least a few degrees of negative rake..clearance, to allow the tooth to actually cut material. Are you talking side rake, not back rake?

Stuart

Click to expand...

side rake, wood cutting saws usually have different saw tooth patterns for rip, cross cut, laminate and other uses. I assume that since metal does not really have a grain orientation the various side rake angles are not used.



I am trying to figure out if i want to sharpen them what will i need.

dee
;-D

Most slotting and slitting saws are hollow (taper) ground to achieve clearance while some have straight side and no clearance. They don't have set like woodworking saws. A normal sharpening procedure would be carried out on the face only unless the periphery was badly damaged, then some back grinding could be done.

Stuart

The only reason there is a question about the slitting saw relief angles or lack thereof is because the teeth are "small" compared to, say, a typical 10" woodworking blade. Careful examination of a slitting saw blade with a ten power magnifier can reveal much. First it will show the general sharpness of the blade and indicate how much it has dulled. And it will reveal the grind angles on the teeth. I do not know how a person could get by without owning and using often a magnifier like this: Amazon.com: BelOMO 1x Triplet Loupe Magnifier. 21mm (.85") Folding Magnifier, High-Quality Optical Glass with Anti-Reflection Coating for a Bright, Clear and Color Correct View: Arts, Crafts & Sewing

I have had good luck using a clicker finger and on my surface grinder to touch up the top clearance of the teeth on various slitting saws. I have only occasionally needed to also grind the face. With an indexer a 32 tooth blade can be sharpened in a couple of minutes. Here is a vid of one I made a while back:
Denis

dcsipo said:

Are there any reasons they would be anything but flat top?

dee
;-D

Click to expand...

Special profile to fit a feature on a part?

IIRC saws for copper used to be ground with the corners taken off as in the triple chip design, (all teeth not alternating) it was supposed ??? to reduce binding.

Thanks everybody that clears it up for me

dee
;-D

I was taught that sharpening slitting saws was done on the top like you would approach a normal cutting edge. Primary clearance and secondary clearance if needed. The only exception was profile cutters like gear tooth, etc, where they were sharpened on the front face to preserve the profile. I think it was considered the second choice because you couldn't control the precise height of each tooth as you would be able to grinding the periphery.

Agree with Denis....having a loop for cutters and just for measuring over a gauge block or what ever...should have a loop in your tool box..


For steel the flat top is very common with all teeth the same. Larger cutters may have a slight angle to the top face so giving some sheer angle..perhaps 5*

Yes flat to the OD ..with a face rake for the material ... and clearance often a primary and secondary.. and third heal angle to give chip space.
Triple chip grind...
For cast iron and steel the dull saw can be examined and for wear land to the OD and to the corners and wear can be shifted with using a modified triple chip grind with having the chamfer blades OD perhaps .015 taller then adjusting the size or the bevels to give more or less cutting length to the fat tops. Yes this increases the chip load for all the blades double or so. Often the best grind is by spinning a circle grind OD then with the clearance angle grind up to the sharp edge.. surprising many cutters and saw are a little off for face grind so fingering each tooth can have error.

Good to have a portion of the tooth rest finger to ride the cutter side so giving more solid support. The finger would have a double top with one to be the tooth rest and the other to ride on a constant perhaps the side. The same concept of double top finger is for reamers with one top to support the depth the finger can go and the other (lower) the finger in the flute face.

Any hook or top rake can tend to draw a finger when grinding and the double finger helps to avoid this

It is not uncommon with larger saws to tickle the face to take perhaps .005 (face) then the rest from the OD..Taking all the crater from the OD would use up a lot of the cutter's life. Yes depends on the wear. *But yes taking from the face can mess up the spacing so it is not uncommon to bump a little locator spot on the back end to make all the same then hit the cutting face locating from that bump spot.

dcsipo said:

Are there any reasons they would be anything but flat top?

dee
;-D

Click to expand...

The Slitting Saw and the Woodruff Cutter
Slitting Saws and Woodruff Cutters work in much the same way, so we can just call them saws for now. Saws have one big difficulty. After we understand that difficulty we will solve it and increase their performance. First a little background.
After you dig a hole in the ground to fix a water pipe you need to put the dirt back. However all the dirt won’t go back because it doesn't fit any more. The dirt has been "upset". That is, all the little grains of soil and pebbles are no longer nestled together in a compact form. This upset condition also happens in metal during the cutting process.
Upsetting the metal increases its volume. So the metal in a chip that is cut from a bar takes up more space after it has been cut. Parting off steel in a lathe using a slender flat top “part off" tool creates a long slender upset chip. This chips volume is greater than when it was compact material in the parent metal. And greater also are its dimensions. The chip is longer, thicker, and wider. The wider condition is what causes the problem. The “Kerf” or groove being cut has a width as wide as the part off tool. During the cut, the emerging chip is actually wider than the groove being formed. So the chip is in the groove under a "press fit" condition. As the bar is rotated the press fit chip is being forced down against the cutting tool. The tool has to support the pressure of the downward cut in addition to the downward force created by the emerging chip. The deeper into the bar the tool cuts, the greater these forces multiply; because the chip grows longer before exiting the groove. The tool will break during this process unless the cut is shallow or the feed rate is very light. A light feed rate will create a very thin "ribbon" like chip with light forces; but this takes a much longer time to do the work.
The difference between a part off tool and a slitting saw is a slitting saw has many "part off tools" or teeth around its axis. Manufactures of these saws make them with tooth forms which have flat ends on the teeth like a part off tool. These teeth then cut a chip which is as wide as the slot just like the lathe tool and with the same problems of high destructive forces caused by the "press fit" chip being formed. Unlike the lathe tool the saw has many teeth. So if one tooth misses cutting something the tooth following right behind it can scoop up the remainder. Now for the "Fix".
A double cut saw blade has chamfers on alternate teeth. These chamfers on one corner of the tooth are made by grinding away one third of the tooth on the right side of the first tooth and then on the left side of the next tooth and so on. This grinding is done on each tooth at about a 45 degree angle. Now when the saw cuts, it cuts a chip on the left and then a chip on the right. These chips are only two thirds as wide as the slot. The following tooth has its chamfer on the other side and so it picks up the remainder of what the first tooth left. The forming chip isn't wide enough to rub both sides of the slot so the slitting saw can cut very freely and take a heavier chip load. Higher production can then be the result.
Stanley Dornfeld
San Diego

Stan Dornfeld

Stan

Have you got any performance data on those "stagger tooth tigers" ;-)?

It seems like a good idea, but i have never seen a slitting saw ground that way.
Better in ductile materials like Alu and steel than CI or brass I bet.

The main reason you don't see them, is the manufacture don't have to use them. WE DO!

The extra grinding is expensive.

CIron is probably ok sense it breaks up in granules so the kerf doesn't have to handle it.

Besides that, you can snuggle up to the grinder and grind what you need.

The BEST ONE of all is the triple cut. Tooth (1) |-\ (2) /-| (3) /-\ Cutting width a few Thou overlap.. What a what a GOOD ride it is, and it makes a 16 finish. I'm talking copper.

Ok, some more, The Old Farts always say NO MORE THAN 2 TEETH IN THE CUT. I've done well with that. However, it really inhibits the depth of cut. You can cut deep, but you have to step in many times. Hence the chamfering.

That's about All.

Regards,

Stanley Dornfeld