Slitting Saw , Enlarging The Hole ?

[Subwayrocket]

I have a few blades I want to enlarge the center hole, they are 3-1/2 to 5" steel blades 3/32" thick .
I have a few ideas on how to go about it . Can anyone that has done it with relative success give any thought on doing this ?

I know if the enlarged hole is not dead center then I essentially end up with a fly cutter

I have a coaxial indicator , I have a boring head and bars (indexed and brazed carbide) .
Also have a 10" rotary table . I have alot of aluminum and steel flat bars and square tubing
for clamping , have some copper sheets, etc ...I also thought about sandwiching/clamping the
blade between plywood . Been tossing around a few ideas , thought i'd just pose the question
to anyone who has already done it .

Thanks in advance for any input and comments .

~Steve

 

[JimDawson]

I enlarged one the other day........ inadvertently. The blade jammed, everything else kept moving, and sparks were flying. Elongated the hole about a 1/2 inch before I could hit the E-stop.

Clamping the blade between two pieces of something would be the way I would do it. Aluminum might be the best, it would carry away the heat generated by cutting.

The real problem that I see is cutting the HSS blades, carbide might work, but the blades are HARD. Grinding might be a better option. An air grinder or something like that, attached to the quill or spindle, and your RT might be a good setup.

If you have a lathe, some kind of a tool post grinder setup (air grinder again) would work also.

 

[Subwayrocket]

Grinding might be a better option. An air grinder or something like that, attached to the quill or spindle, and your RT might be a good setup.

it's funny you mention that , I thought about making something that I could mount a grinder to an R8 tool holder ... I read alot of posts saying that grinding on the mill is a bad idea. I think I could adequately cover all the ways and everything , but many people say it's a bad idea . If i use the rotary table , i'd have to really ensure the table is extremely centered to the quill , and then the hole extremely centered to the RT or else the hole would end up off center . Thanks for giving your thoughts. I appreciate it ! Hope u dont mind me trimming your quote ...lol

 

[JimDawson]

I think I could adequately cover all the ways and everything , but many people say it's a bad idea

Some people think getting out of bed in the morning is a bad idea also, after all something bad might happen

With reasonable care you'll be fine.

 

[mikey]

Those blades are hardened and brittle. Might be better to make a slitting saw holder to fit them.

 

[Subwayrocket]

getting out of bed in the morning is a bad idea.

Have you seen any projects showing ways of mounting a grinder to the quill , or to say a modded R8 tool holder ? I also TIG weld to make something.

 

[Subwayrocket]

Those blades are hardened and brittle. Might be better to make a slitting saw holder to fit them.

That would be easier , but I dont have a lathe . Sure wish I did but the mill has my finances in the dumper right now ...lol

 

[Chipper5783]

It is possible to cut HSS using carbide (I have done so one time). I suggest using insert tooling, because it will be hard on the inserts (that way you can get multiple tries for each insert). You also should ensure absolutely as stiff and solid a set up as you can possibly get. I think a lathe and boring bar will be a stiffer set up than RT and boring head in the mill.

Perhaps make up an aluminum disk and cut a recess for the saw (in the lathe) - like a dummy face plate. Make up a clamping cover that screws to the dummy face plate. Do not remove the aluminum plate from the chuck (start with the smallest saw and keep opening the recess for the larger saws). Carbide insert boring bar (largest one that will fit, preferably solid carbide) - new insert edge.

Cover the machine well (very tiny HSS chips will act like grinding debris).

Let us know how it works out. David
Oops, no lathe - scratch that idea.

 

[mikey]

They are usually cheap to buy. Please don't misunderstand me - I'm not trying to discourage you in any way, not even a little, but a slitting saw must run concentrically and the more teeth it has, the more this matters. If the saw is off center even a little then one part of the saw contacts more and will thereby heat more. If that saw heats enough it can warp and then can bind in the cut and the blade will snap.

 

[Subwayrocket]

They are usually cheap to buy. Please don't misunderstand me - I'm not trying to discourage you in any way, not even a little, but a slitting saw must run concentrically and the more teeth it has, the more this matters. If the saw is off center even a little then one part of the saw contacts more and will thereby heat more. If that saw heats enough it can warp and then can bind in the cut and the blade will snap.

Yes , I hear you on all that . And yes they are cheap . I can afford a few ...it's more just part of the hobby for me...see if i can do it. Maybe learn something in the process . I have some slitting saws already so this is not out of necessity. And yeah , no lathe . Wish I had one ...maybe next year , tax time . There's only so many changes that go "un-noticed out here ...dont know how the misses puts up with me...she's an Angel !