Slitting saw question

This topic has 19 replies, 10 voices, and was last updated 9 March 2018 at 19:26 by Roy M.

Viewing 20 posts - 1 through 20 (of 20 total)

Author

Posts
2 March 2018 at 09:21 #343946
Eric Cox
Participant
@ericcox50497
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
Advert

2 March 2018 at 09:21 #25851
Eric Cox
Participant
@ericcox50497
2 March 2018 at 09:47 #343950
JasonB
Moderator
@jasonb
Coarse

Should be able to do it in one pass

Slow speed
2 March 2018 at 09:52 #343952
Brian Wood
Participant
@brianwood45127
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
2 March 2018 at 11:01 #343965
not done it yet
Participant
@notdoneityet
Check out some of the many videos on utoob?
2 March 2018 at 20:59 #344088
JasonB
Moderator
@jasonb
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.

A few thoughts and I would welcome others comments

I should have been able to cut this at 100rpm on my X3 with it's smaller 600W motor as it has two geared speed ranges, SX2.7 is direct and that is probably why it stalled as although the motor is a higher wattage it was running slower. (will do it in the morning to confirm)

I would usually agree with Brian's advice to reduce speed if saw struggles but in this case that would just have made the stalling worse.

What depth of cut can be used varies from one machine to another and should not be treated as the only thing when advising of what cut to take. Rate of feed should also be taken into account as a lower powered machine can be stalled by too fast a feed, type of drive train is also a very important factor as a fully belt or geared head machine will have more torque than a 2 speed range or direct drive vari speed machine of similar wattage.

J
3 March 2018 at 11:25 #344156
Ian S C
Participant
@iansc
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
4 March 2018 at 09:34 #344315
Zan
Participant
@zan
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
4 March 2018 at 10:01 #344320
Anonymous
Posted by Zan on 04/03/2018 09:34:59:

Speed and depth of cut is usually limited by stopping the saw slipping in the holder…………..

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

Andrew
4 March 2018 at 10:21 #344324
JasonB
Moderator
@jasonb
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.
6 March 2018 at 14:25 #344688
Zan
Participant
@zan
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
6 March 2018 at 16:14 #344695
not done it yet
Participant
@notdoneityet
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.
6 March 2018 at 20:59 #344763
Anonymous
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
8 March 2018 at 00:01 #344932
Zan
Participant
@zan
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!
9 March 2018 at 10:02 #345136
doubletop
Participant
@doubletop
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
9 March 2018 at 10:15 #345137
Anonymous
Posted by Doubletop on 09/03/2018 10:02:58:

……………… to making ny own arbours in an attempt to deal with eccentricity.

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
9 March 2018 at 17:18 #345228
Roy M
Participant
@roym
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.
9 March 2018 at 17:36 #345230
Michael Gilligan
Participant
@michaelgilligan61133
Posted by Roy M on 09/03/2018 17:18:08:

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.
9 March 2018 at 18:43 #345249
Zan
Participant
@zan
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
9 March 2018 at 19:26 #345259
Roy M
Participant
@roym
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
Author

Posts