3" slitting saw, 1/4" thick, with 3/4" dia flush arbor?

[laggeddag]

I need to make a circular slot that has a 1.5" radius. Tough part is that I can't reach deep enough into the cut if the shaft is bigger than 3/4".

So I think that means I need a blade with a 1/2" diameter hole. Unobtanium?? I dont want to pay $300 for a custom blade from harvey as this is a continuing production operation and I expect alot of wear.

There are plenty of relatively inexpensive cutters that otherwise fit the bill except they have a 1" hole, so that means an even bigger shaft outside that hole..not going to work. Cant grind them down because that shaft diameter is the material clamping the saw.

Seems like making an arbor adapter would also be tricky as it would have to be welded to the blade and then ground down below the surface of the teeth.

 

[dian]

slitting saw 1/4" thick?

Keyseat cutters. Other uses? -

The Home Shop Machinist & Machinist's Workshop Magazine's BBS

 

[laggeddag]

slitting saw 1/4" thick?

Keyseat cutters. Other uses? -

The Home Shop Machinist & Machinist's Workshop Magazine's BBS

sure keyseat/slitting but I am having trouble finding one that has a diameter big enough to cut 1.25" deep with a shaft that is less than 3/4" dia

 

[ratbldr427]

If it were me I would tig a 1" shaft whatever length you need in the cutter flush one side.Then turn the other 3/4". A cup mandrel to hold the cutter is easy to make.

I have used carbide tipped circular saw blades to make unusual cuts in steel but none are 1/4" thick.They have 5/8" holes but you don't get any control trying to make repeted cuts to increase width since they are so thin and flexable.

 

[laggeddag]

If it were me I would tig a 1" shaft whatever length you need in the cutter flush one side.Then turn the other 3/4". A cup mandrel to hold the cutter is easy to make.

I have used carbide tipped circular saw blades to make unusual cuts in steel but none are 1/4" thick.They have 5/8" holes but you don't get any control trying to make repeted cuts to increase width since they are so thin and flexable.

Okay so I get a normal slitting saw of my reqd dia (3") with a normal hole (1")

I get an arbor for 1"

Install it in the saw so its flush with the bottom.

Tig weld in place.

Concentricity is maintained by the bore? Doesnt the top and bottom surfaces of the saw provide some alignment and prevent tilt when its clamped in the arbor? I worry it wouldn't get aligned right during my weld and since I am welding the flat side I wouldnt be able to use a surface plate to make them flush.


Also I'd have to make the tig welds flush since I literally need them to go inside the cut.

I guess I could make them deep welds then grind them flat

 

[Limy Sami]

I've silver soldered / brazed arbors in before now and they've worked a treat.

 

[Bill in PA]

If you want to go through the trouble, you could build a cutter that takes 1/4" square positive inserts (SPMT). Would be economical to use with four cutting edges per insert. Would not be difficult to make up a couple disks while you are at it. Make it out of 4140 prehard.

Off the shelf indexable slot mills won't have the cutting depth you need.

Won't work if you need a dead-sharp corner though. I don't know if you can get the square milling insert with a .004" corner radius or not.

Bill

 

[gbent]

I've silver soldered / brazed arbors in before now and they've worked a treat.

Good solution.

You can also finish the shank after welding to insure concentricity.

 

[Limy Sami]

Good solution.

You can also finish the shank after welding to insure concentricity.

Which was how I did it .......clamped the thin cutter to a faceplate and worked from there.

 

[ratbldr427]

That was what I tried to convey,turning the 1" arbor after welding to 3/4" will take care of any concentricity or RO errors.
You might as well make an accurate cup mandrel out of scrap a 1/4" deep and the id on size.You could use some small strap clamps around the od to bridge the teeth or else pop a few holes in the cutter body to serve as screw holes for clamping and driving .

 

[henrya]

Good solutions have been presented. I think the biggest problem is going to be breakage of the tool as much or more than wear. For the cut you’re making this is gonna be flexy and flexy breaks things.

I don’t know the requirements of the slot you are cutting, but if it is dimensionally critical, you may not be able to resharpen the cutter because of the diameter size change of the saw blade.

 

[TGTool]

[I dont want to pay $300 for a custom blade from harvey as this is a continuing production operation and I expect alot of wear.]

I don't quite understand the reasoning here. If if were a one off part I'd be reluctant to pay that much for the tool. If it's a continuing operation the cost is amortized over all the parts you make.

 

[mnl]

My guess is he expects to need several of they and is hoping that an off the shelf solution will win out over $300 x several. Of course there could easily be price breaks from Harvey for more than one so the math is not clear.

 

[laggeddag]

My guess is he expects to need several of they and is hoping that an off the shelf solution will win out over $300 x several. Of course there could easily be price breaks from Harvey for more than one so the math is not clear.

The thing about the math is that I am not sure how many parts I'd get out of a $300 harvey tool. I have no experience machining this sort of operation with a tool like that. I suppose it has lots of teeth so I would hazard a guess that I'd get alot more cuts out of it than a typical 4 flute end mill in 7075.

So in that respect, yes maybe it would amortize and make perfect sense.

I did buy a random 3" dia 3/16" thick staggered tooth slitting saw / keyseat cutter off ebay. I'd like to get a few of these cuts under my belt and see how things go before actually buying an expensive production tool.

All the ideas are great thanks!

So for making an arbor for my cheap saw thats enroute...

I have a TIG welder and experience using it

I have a propane torch, maybe a MAPP torch too, but they are both consumer grade so not much output

I do not have oxy acetylene

Would TIG make the most sense here given what I have? Or should I get a different torch and go the brazing/soldering route?

 

[gbent]

Run what you bring. I'd tig it with Inconel 625 .

 

[laggeddag]

okay its here!

The ground ring in the middle is about 0.002" thicker than the teeth.

In a dream world, I would like to do something easy and controllable...like how about this:

-make an arbor that is just undersize (whatever is appropriate) the 1" hole in the saw, with a keyseat so it can lock into the notch

-make the exposed part of the arbor shaft 3/4" (thats my req'd diameter)

-preheat saw and arbor using oven to some high temperature so that I can use my wimpy propane torch

-take the saw and arbor and use some simple method to precisely align them to be concentric and normal (not sure how I'd do this yet but lets say I figure out a way)

-using propane torch, feed in a solder/brazing material to fill the gap and bond them together

-Then once its all bonded together, use a grinder to hand grind that ground ring down below the teeth.

Is this realistic?

If this wont work I can go the TIG route. Maybe the TIG route would be easier.

I have never brazed, and have never brazed or soldered steel. Hopefully it would occur at a temperature I can reach with propane and preheating that does not change the temper.

 

[laggeddag]

So I guess my question here is, can I braze this without softening the HSS teeth or will the teeth heat up and lose temper before I've bonded the arbor to the central hole?

 

[BSCustoms]

You could also try ABtools as you tell them what you need then they make a tool and test it to make sure it works. More money but saves your guessing.