# Making a slitting saw arbor



## chucketn (May 21, 2011)

I recently acquired a few HSS slitting saws with 1 keyed bore, in thicknesses from .040 to .125 (Thanks again AdeV). Now I need to make an arbor for them, for my X2 mill which has an R8 spindle.
I have Googled, and Googled, gathering drawings, articles, and tips. 
Heres what I think I know: 
Arbors for slitting saws are available commercially, of varying quality, shank type, clamping method (internal or external cap, multi sized bore), and of course varying price.
Slitting saws, as opposed to wood working saws are hollow ground for clearance, like a parting tool, so they are thinner at the bore.
For the hobby machinist, it is not necessary to include the key, so if the saw jams, it will spin on the arbor, rather than shatter. (I also have the X2 belt drive Mod, so not an issue)
Though I have found some I consider affordable, I would rather make one.
What I would like to do is start a discussion on the general attributes of a good, serviceable, shop made saw arbor. Would you use an internal cap, or external cap, and why? Would you make it on a R8 blank stub, or straight shank to be used in a collet, and why? The biggest R8 blank stub I can find is 1 1/8. Is that big enough? Does the arbor need to be hardened/tempered or not, and why?
How much bigger than the 1 bore, does the clamping part need to be? 1 1/8? 1 ¼? 1 ½ (diameters) ?
I hope Im making sense. I have enough confidence in my abilities to make the arbor, but have been confused by the many design variations. Plus, Im not an engineer.
Thanks in advance to all who contribute to my education.

Chuck in E. TN


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## Tin Falcon (May 21, 2011)

Well the arbor size is one inch how big is the blade ? How deep do yo need to cut. I would think the bigger the arbor the better grip and stiffer the set up. I would think for general set up find the happy medium in between the max depth of cut and and max grip. When in doubt for something like that search the catalogs a commercial version is usually a good starting point. If you find something you like copy it . if you find something that has shortcomings tweak to your liking. 
You can always make an arbor beefier than you think you need if it is to clumsy turn it down until yo like it. It is easier to remove metal than put it back on.
Tin


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## peatoluser (May 21, 2011)

I don't think you would need to harden the arbor. when the saw jams, back off the feed and it'll start spinning quick enough. In other words it just wont spin long enough to damage the spindle. Plus , if it did, a green arbor is always easier to true up than a hardend one.
 I have no experience of large(r) saws, (mine are 2" dia 1/2" bore) but they run O.K. on a land of 3/32 i.e. the O.D. of the arbor is 11/16 , and my thinest saw is .007 (well, was. I inadvertently moved the carriage when the saw was still engaged in the slot I had just cut and broke it)
but Tins right. make the register as large as practical. If you need a deeper cut, it's an easy matter to skim the arbor.
I made mine with an endcap that was bolted to the arbor with an Allen bolt, but found that the bolt would sometimes foul the vice, or
 stop me cutting to full depth, especially if the part is small and you can't have much sticking out of the vice.
I solved it by countersinking the endcap and using a countersunk screw, but for a larger bore saw, you could try this rather neat solution
http://mikesworkshop.weebly.com/slitting-saw-arbor.html


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## chucketn (May 21, 2011)

Tin, the saws are 2 1/2", 3", and 4". I really want to make 1 arbor for all.
Peatoluser, I have that link in my notes. I'm leaning toward a male cap with the screw counterbored or countersunk. That way the depth will adjust to the thickness of the blade in use.

Chuck in E. TN


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## DLM (May 21, 2011)

I think i would use a piece of stock 1 3/8 or 1 1/2 in dia. and turn it in your lathe to fit what ever Collete you want to use in your mill then mount that in your mill and machine the end for a nice fit for the saw blades, that way you will have 0 run out. I think i would go for the female cap and a counter sunk cap screw. Don't think it would be necessary for a harden arbor. I have some factory arbors that i have modified and they were not harden.

Don in Pueblo


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## MachineTom (May 22, 2011)

I'l share my experience with slitting saws on a Bridgeport. Being cheap I first bought a simple saw arbor without a key, as some slotters did not have a key slot. A cap held on with a center bolt clamprd the saw, looked good. It worked okay slotting AL, slotting steel, okay, these were .050 deep or so .060 wide. Then a slitting saw was installed, about halfway cut the saw jammed for a couple seconds, being on a 2hp BP in backgear, the arbor kept turning continued the cut. That center bolt was sucked into the arbor because the blade and cap stopped but the arbor kept turning destorting the cap. That took a 3' cheater bar on a 18' wrench to unscrew. I then bought a keyed arbor and haven't used that cheapo piece since. Last month I bought another arbor this on a 3/4 straight shaft, rather than the R8 drive.

Does your mill have geared low speeds, as a 3" cutter in steel needs 80rpm cutting speed and power, that you can't get by variable speed alone. Without a positive key to drive the blade you will not have satisfactory results with sawing.

Here's a shot of the keyed arbors, the chips are bronze from the 4" installed slitter.







The work was .875 thick depth of cut 1.150


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