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View Full Version : Looking for slotting saw arbor design using 1" and .25 keyway



curls
11-02-2007, 10:07 AM
Hi all, new to the HSM forum, I'm in the process of coming up with a "keytype" slotting saw arbor that is held in a 3/4" R8 Collet. All of my slotting saws have the typical 1.0" hole and the .25 key way slot to lock the blade in place when used with an overarm bridgport attachment. I have made preliminary drawings using a "floating" .25 drill rod pin that at least makes some contact with the saw key slot, (this would allow retainment and the luxury of using various thickeness of saws) I know that there is a depth of expertise out there and searching the forum, I thought I would see if someone has gone down this road before and found a "better way".:

dp
11-02-2007, 12:43 PM
If I used the keyway on my saws I'd break a lot more saws than I already do.

Evan
11-02-2007, 01:56 PM
No key, just screw it down tight. Slip is your friend.

SGW
11-02-2007, 05:44 PM
Likewise...I've never used a slitting saw with a key. Tighten it up, and the cutting action will tighten it more. I think the main benefit of a key might be to keep the cutting action from tightening it up so much it's nigh-impossible to unscrew.

curls
11-02-2007, 06:28 PM
The majority and experience rules. I will take your advice and not key the slot to the arbor, Appreciate all your inputs, it's nice to have advice at your fingertips.
Steve.

oldtiffie
11-03-2007, 12:00 AM
The key is there for a very good reason - to drive the cutter and stop it rotating on the arbor.

The spacers are likewise there to lightly clamp and position the cutter along the arbor.

The "no key and rely on clamps" method had probably resulted in more smashed slitting cutters and scored arbors than just about anything else.

Another thing that breaks slitting cutters and saws is having the cutter go off on a course of its own that is not in line with the intended course - ie it diverges from the intended cutting path and in so doing is compelled to flex and then ultimately breaks. So - take a light "guiding" cut first.

Another cause is having the cutting teeth cutting circle eccentric to the milling machine spindle bore. Everything between the spindle bore and the bore of the cutter (adapters, collets etc.) can but does not necessarily add to the "eccentricity of cutter circle" problem.

Having too many teeth on a cutter can cause chips to jamb/foul the cutter and cause it to break. The fewer the teeth and the wider the gaps between them the better.

It might be useful to read the following pic
http://i200.photobucket.com/albums/aa294/oldtiffie/Slit_saw1-1.jpg

I use a stub arbor that is direct mounted to my spindle and held in with a draw bar - it is a precision made item for the purpose.
http://i200.photobucket.com/albums/aa294/oldtiffie/Stub_arbor1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Stub_arbor2.jpg


I hope this helps.

DR
11-03-2007, 08:33 AM
FWIW, Hardinge didn't put keyways in 1" arbors for their horizontal mills. On the other hand, a motorized slotting attachment for a B&S screw machine uses smallish, thin cutters, about 2" diameter with a 5/8" hole, that has a keyway in arbor.

Peter N
11-03-2007, 10:28 AM
Evan is dead right, slip is your friend when it comes to slitting saws.

Slitting saws are thin and brittle, and can easily jam in a cut, especially if it's a through slot where it may well 'nip up' up on the cutter.
The positive drive of a key can cause these to shatter when they jam, whereas a friction fit should allow some slip and give you a chance to hit the stop button.

They don't need to be anything fancy either, as this picture of a couple of mine show.

http://www.btinternet.com/~p.neill/Slitting_Saws.jpeg


Peter

Virgil Johnson
11-03-2007, 10:49 AM
To make the arbor run dead true finish the mounting surface (shoulder and the dia. that locates the saw) with a tool bit mounted in the mill vice while spinning the arbor under power in the collet.

curls
11-03-2007, 11:00 AM
Maybe the answer lies in specifically what size and thickness of slotting saw one needs to use, bigger and thicker saws may need the keyway to drive them true, Smaller slitting saws if fed carefully can use friction between the two washers. My 2 cents
Steve

Timleech
11-03-2007, 11:08 AM
I've had a thin slitting saw cut right through the key when it snagged in the work. It was a pig to get the cutter & spacers off the arbor after that, I don't use a key with thin cutters now.

Tim

Evan
11-03-2007, 11:42 AM
This saw is used in my lathe. I can tighten it enough it won't slip, but I don't.

http://vts.bc.ca/pics/saw1.jpg

J Tiers
11-03-2007, 12:24 PM
1/8" saw, 1" arbor.

I still key them, though, most arbors are threaded a way that loosens in my preferred (for other reasons) direction of use.

That's the only one that has done that ever. And the mill has a 1/4 HP motor, so it isn't about power. I may not key very thin ones though, like 20 thou to 60 thou.

http://img.photobucket.com/albums/0803/jstanley/cutkey.jpg

DeereGuy
11-03-2007, 07:37 PM
Heres the arbor I built. No keyway but I do have a close slip fit for everything. No slipping yet but I have only used it maybe 5 times now.

http://i2.photobucket.com/albums/y39/Deere_X475guy/Machine%20Shop/1030061849.jpg

with the bushing it has a dual purpose for holding the gear cutters

mochinist
11-03-2007, 08:19 PM
I think the key comes in handy when you have multiple slitting saws on the arbor, I wouldn't want one to slip while the others are cutting.

Personally I tighten up mine enough so that they can't slip and I have keyed and unkeyed arbors and have yet to have a problem(knock on wood). Learn to use the correct speeds and feeds and use plenty of cutting oil and you shouldnt have a problem.
Maybe the answer lies in specifically what size and thickness of slotting saw one needs to use, bigger and thicker saws may need the keyway to drive them true, Smaller slitting saws if fed carefully can use friction between the two washers. My 2 cents
Steve

lane
11-03-2007, 08:47 PM
UP to 1/8 inch use NO key over are reg milling cutters use a key . Slip is your friend on small cutters . Big cutters you don`t want to slip.

TECHSHOP
11-03-2007, 09:15 PM
I also "factor" in the "cost" if the part is lost or the saw is lost in the crash.
Sometimes the the part is more important than the saw, sometimes it the other way around.

No, I don't always quess right...

Your Old Dog
11-04-2007, 03:30 PM
just turned this up on ebay.

http://cgi.ebay.com/NEW-R-8-MILLING-ARBOR-WITH-SLITTING-SAW-LOT_W0QQitemZ260178556374QQihZ016QQcategoryZ104242 QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

DR
11-04-2007, 03:40 PM
Some here seem to be suggesting that a slipping cutter will not break in a crash whereas a keyed cutter will break. In a "crash" the cutter will break either keyed or not.

A problem with slipping cutters is they can ruin or at least damage an arbor by spinning on it. A slipping cutter can also self tighten the nut so badly you may play hell getting it off.

Given a choice, I'll take keyed every time, but you aren't always given a choice.

curls
11-05-2007, 11:26 PM
<a href="http://photobucket.com" target="_blank"><img src="http://i213.photobucket.com/albums/cc85/sadams1_bucket/arbor2.jpg" border="0" alt="Photo Sharing and Video Hosting at Photobucket"></a>

curls
11-06-2007, 09:21 AM
tried to post a picture, guess I did'nt get it right. What's the drill? ( nonpun intended)
Steve

lazlo
11-06-2007, 10:01 AM
Curls, you almost have it.

You want:

image URL

Like so:

http://i213.photobucket.com/albums/cc85/sadams1_bucket/arbor2.jpg

Rudd
11-09-2007, 09:28 PM
Lazlo, your pic didn't make sense till I turned my head 90 degrees.. (g) Still, the cutter and the vise weren't oriented right.
I have an older horizontal. B&S taper #9. I'll waste a hundred cutters and a thousand parts before I risk messing up that arbor, as far as I know a replacement is unobtanium without paying cubic dollars.

As far as saws hanging up, my problems have always been rigidity of the set up. I've recently had to slit a bunch of essentially bayonet plugs, .310 OD brass about 1.25" long, two cuts 90 degrees off. I discovered why there were hammer marks on the handle of the used, but in good shape/by mill manuf. vise. I had made a little fixture to hold said plugs, and had "armstronged" it tight, used the "make a light guiding cut" advice, and kept wrecking parts when the saw jammed, usually on the second cut when I was essentially cutting through an unsupported semi-circle that was .155 at it's thickest. Taking a manly sized frammer to the vise handle, squaring up, and just plunging from the end of the bayonet with a REAL SLOW hand feed has yielded joy. Brass may work harden, but not as hard as the saw. I really think the whole problem is rigidity of the set-up. Some one over at PM said something to the effect of make sure your set up can't move, and if it does move, it can't. If the part moves something that might equal doubling the chip per tooth, a hang up is likely, and we're talking what, 3 thousandths or less?

BTW, is the "Fork in the Road" cafe still in existance? Was just up the road from my house. Used to have good times at Liberty Lunch, but that's prob. before your time.

Rudd
11-09-2007, 09:35 PM
Lazlo, your pic didn't make sense till I turned my head 90 degrees.. (g) Still, the cutter and the vise weren't oriented right.
I have an older horizontal. B&S taper #9. I'll waste a hundred cutters and a thousand parts before I risk messing up that arbor, as far as I know a replacement is unobtanium without paying cubic dollars.

As far as saws hanging up, my problems have always been rigidity of the set up. I've recently had to slit a bunch of essentially bayonet plugs, .310 OD brass about 1.25" long, two cuts 90 degrees off. I discovered why there were hammer marks on the handle of the used, but in good shape/by mill manuf. vise. I had made a little fixture to hold said plugs, and had "armstronged" it tight, used the "make a light guiding cut" advice, and kept wrecking parts when the saw jammed, usually on the second cut when I was essentially cutting through an unsupported semi-circle that was .155 at it's thickest. Taking a manly sized frammer to the vise handle, squaring up, and just plunging from the end of the bayonet with a REAL SLOW hand feed has yielded joy. Brass may work harden, but not as hard as the saw. I really think the whole problem is rigidity of the set-up. Some one over at PM said something to the effect of make sure your set up can't move, and if it does move, it can't. If the part moves something that might equal doubling the chip per tooth, a hang up is likely, and we're talking what, 3 thousandths or less?

BTW, is the "Fork in the Road" cafe still in existance? Was just up the road from my house. Used to have good times at Liberty Lunch, but that's prob. before your time.