Slitting saw question

I'll be cutting a piece of mild steel (EN1A) with a slitting saw on a WM14 mill.I'll be cutting to a depth of about 1/2". Two questions,

1) course or fine saw

2) depth of cut

Coarse

Should be able to do it in one pass

Slow speed

Hello Eric,

Run a shallow guide cut across the component first then cut to full depth in one pass. Modest speed, say 100 rpm or less with coarse teeth and coolant.

If the saw struggles reduce the speed. The important thing to prevent is loading the tooth gullets with swarf which is why the coarser tooth recommendation was made. Fine teeth clog, the saw ripples and breaks in a trice.

Regards

Brian

Check out some of the many videos on utoob?

Well I have just added yet another video to youtube. with some interesting findings that do go against the old advice based on geared/belt head machines and seem to agree with what I have said before about needing a bit of speed on variable speed machines to get into teh motors sweet spot.

SX2.7 Sieg mill with 750W brushless DC motor belt drive straight to spindle

80mm dia, 1.0mm thick 32T slitting saw brand new, bit of an eccentric runner like a lot of slitting saws

1/2" square bit of bright mild steel

I started at 100rpm but as you can see for the first 15 seconds or so the machine just stalled, changed to 210rpm and it was able to cut though I did start to feed a bit faster and managed to stall it again about 3/4 of the way through the cut.

Handfeed was a bit jerky as I could only use one hand and I did try at one point to look behind the guard but actually video through it was quite good. Also having only the one hand I had to cut dry.

Slow, it all depends on the size of the saw, mine range from 50 mm, to 6", but the cutting speed is the same for both in metres per sec/ feet per min.

Ian S C

Speed and depth of cut is usually limited by stopping the saw slipping in the holder but a singke pass at 1-200 should work

That's why manufacturers provide a cutout for a key.

Andrew

Well I did try it on my X3.

Low range 100rpm and it cut without stalling but felt like it was close to doing so.

High Range 100rpm and it stalled

At 200rpm in the low range it was a lot happier cutting than at 100rpm

Taking 33m/min for mild steel without coolant then speed should be 132rpm for an 80mm cutter.

Conclusion - the variable speed machines with direct or two speed ranges do lack power at the lower speeds to be able to remove metal at the same rate as geared/belt head machines and benifit from being run a bit faster with a lighter feed so the motor is at a more usable speed.

agreed Andrew, but most arbours now don't have the keyway. I cut a 3/32 slot today 3/4 deep at 100 rpm single cut without any problems or slippage

Edited By Zan on 06/03/2018 14:27:18

I am no expert with slitting saws but I am tending to agree with Zan - a slipping cutter is better than a shattered one, should the blade grab. There never was a keyway on the Centec 1” arbors, as far as I know. Most hobby mills don’t have to dissipate serial kilowatts before approaching a stalling situation!

Remember, here, the cross section of a 1 1/4” arbor is more than 50% greater than that of the 1”. The1 1/4” usually have a keyway.

All my arbors, for both horizontal and vertical mills, have keyways. Even the horizontal attachment for the Bridgeport which is not exactly noted for rigidity.

I have a vague recollection of using one of the slitting saw arbors with a series of short diameters, no keyway, and a hollow washer and countersunk screw to hold everything in place. A chocolate teapot was more useful. The arbor didn't run true radially or axially and had little gripping power. I haven't seen it for ages, so I suspect I might have binned it.

Andrew

My arbour for the Bridgeport is substantial but no key. Yes the telescopic saw holders were poor, but useful for small diameter stuff. Mine is lurking somewhere, but not been seen for decades!

I'm glad to see that my limited experience with slitting saws reflects those of the experts. I've tended to avoid using them as much as I could becuase I wasn't sure I was using them correctly. Jasons video, with sound effects, was spot on with my efforts. I've resoured to making ny own arbours in an attempt to deal with eccentricity.

Maybe I'll give them another go armed with the info in this thread, at least I was using the right speed...

Pete

Whatever you do the slitting saw will cut slightly eccentric. Even if the arbor is perfect the saws are ground to a tolerance. A higher tooth load helps so that the eccentricity becomes a smaller part of the load per tooth.

Andrew

I posted some pictures and a 'how to make' explanation for an excellent arbour that I designed. The thread was- 'Slitting Saw Arbour, A useful workshop project'. Posted on 16/01/2017. I used this design professionally both on Bridgeport and CNC machines. You may find it interesting. Roy M.

.

**LINK**

http://www.model-engineer.co.uk/forums/postings.asp?th=124017

MichaelG.

Looks v good Michael I like the robust shank, although I would make it to 3/4" for the R8 collet. I particularly like the standard cap head for locking, better than the M8 cks cap screw in my commercial arbour (which I don't like it's getting worn due to its smaller AF dimension). I would also make the shank longer, the short ones mentioned above often gave problems with finding adequate vice clearance.  Regarding a possible key, it would have to be locked into the cap to allow for different saw widths. Question, would a carefully positioned round key work? Fitted into a hole drilled through the cap into the body so it was half in each

Edited By Zan on 09/03/2018 18:48:36

Zan, some valid points. I have made a few of these for production use and non has failed. I did add a pin to locate in the keyway as a belt and braces add-on for cnc work but there was no signs of were on the pin. I have used this design successfully with a 150mm dia X 8mm staggered tooth side and face cutter without using a key,(on a Bridgeport), I think that an important factor to consider is the clamping force that can be applied using an M10 thread with a full size hex key, as opposed to the normal wimpy arrangement! And the low profile clamp makes working closer to the vice-jaw possible, giving better support of the workpiece, thus reducing as much vibration as possible.Roy M