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Getting slitting saw to run true

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marcusj	22/03/2011 05:17:22
27 forum posts	I run a Weiss WMD25V mill and I'm having awful bother using a slitting saw. I bought an MT3 arbour that seems to run true - I DTI'ed the 1" arbour once mounted in the MT3 spindle and all seems OK. Then I put a brand new ~70mm x 2mm thick slitting saw on the arbour (nice tight fit) and it cuts on about 2 teeth / rev which makes for v-e-e-ry slow work to avoid stalling the machine. Advice on getting myself up and running to machine nice ~2mm slits at something faster than glacial speed would be welcome!
John Shepherd	22/03/2011 08:40:45
222 forum posts 7 photos	Marcus From your description it would appear that you are mounting a metric slitting saw onto an imperial arbour. Perhaps this is the problem even though you say it is a tight fit? The metric slitting saws I have, all have metric mounting holes and although they are near to imperial sizes, there is a difference.
Ian S C	22/03/2011 10:47:16
7468 forum posts 230 photos	Marcus, put slitting saw in the key word box, and tick beginners questions, and you'll get a previous thread on this subject. Ian S C
marcusj	22/03/2011 13:10:01
27 forum posts	Posted by John Shepherd 1 on 22/03/2011 08:40:45: From your description it would appear that you are mounting a metric slitting saw onto an imperial arbour. Good guess, but I'm not, I bought a 'HSS SLITTING SAW 3" x 2.0MM" x 1" / saw arbour' from a UK dealer on an auction site. Looked at the previous thread but didn't see the specifics of curing run-out??
wheeltapper	22/03/2011 13:18:00
424 forum posts 98 photos	Hi Don't feel too bad, I've tried 6 different saws from 6 different suppliers and they all run off, and that is with a home made arbour as well. some are just worse than others. Roy
chris stephens	22/03/2011 14:12:47
1049 forum posts 1 photos	Hi Marcus, You are not alone in your run-out problem. If you saw(no pun intended) how some people sharpen the things it is not surprising that they are sometimes less than perfect. As you bought it from an auction site it might well be a sharpened one or even worse an oriental cheapie. This might be unfair to the orient, as even quality UK ones can have run-out. This does not help you, but it is nice to know you are not alone. christephnes
marcusj	22/03/2011 15:06:46
27 forum posts	Before posting for help here I did look around other forums on the Interweb and this does seem to be a general problem. For the record, the saw cutter was new but probably is of Eastern origin (inexpensive enough to be, anyway). On the basis that this is a well-known problem, it surely must have a solution (other than buying 20 cutters from various sources in the hope that one has teeth that are actually concentric with the bore)? Surely professional machinists won't put up with slitting saws that only cut on 2 teeth per revolution? I saw one suggestion involving a Toolmex 'SET-TRU' chuck. Seems way OTT to try and mount a chuck under my puny mill spindle, but... ...how about making my own set-tru-like-thingy so that I can run any old cheapo slitting saw straight and true on the mill? How do those set-tru mechanisms work? Hard to make?
mgj	22/03/2011 15:33:58
1017 forum posts 14 photos	I've had self same problem - I don't think I have bought a slitting saw that ran true. The only answer I have is to put them on the Quorn and sharpen them properly - then they do run true and cut a lot quicker. I have heard people say they are supposed to run out, but I don't see the logic in that. The set true mechanisms - they use some screw in wedges that push a plate around centre. I think you could make an adjustable arbour and tap it into place (or 3 radially placed grubscrews) and then use screws to lock it. - rather like setting up an ordinary chuck on its backplate. You'd get about 95% of the result for 50% of the effort - useful perhaps when one doesn't use a slitting saw all that often. Edited By mgj on 22/03/2011 15:34:32
marcusj	22/03/2011 15:49:21
27 forum posts	Posted by mgj on 22/03/2011 15:33:58: I've had self same problem - I don't think I have bought a slitting saw that ran true. The only answer I have is to put them on the Quorn and sharpen them properly - then they do run true and cut a lot quicker. I have heard people say they are supposed to run out, but I don't see the logic in that. The set true mechanisms - they use some screw in wedges that push a plate around centre. I think you could make an adjustable arbour and tap it into place (or 3 radially placed grubscrews) and then use screws to lock it. - rather like setting up an ordinary chuck on its backplate. You'd get about 95% of the result for 50% of the effort - useful perhaps when one doesn't use a slitting saw all that often. Unfortunately I don't have a Quorn nor anything like it (my next Big Project is a Harold Hall grinding rest). Nor do any friends / tame workshops that I know. Like the idea of a chuck backplate-type-thing. Bearing in mind I only need a little bit of adjustment for even the worst offending 'new' slitting saw, perhaps a pair of plates bolted together with slightly larger than normal clearance on the bolt-through plate holes and some beefy washers? Perhaps quite a few screws (at least 4?) to ensure that the plates won't shift under torque from the drive once the screws are tightened? Edited By marcusj on 22/03/2011 15:52:30
David Clark 1	22/03/2011 17:59:52
3357 forum posts 112 photos 10 articles	Hi There I would expect a new slitting saw to run true. If you buy a reputable make from Ebay that should be fine. Foreign ones are not so likely to run true and I doubt they are exactly to size either. regards David
Peter G. Shaw	22/03/2011 19:21:11
1531 forum posts 44 photos	I have a new and unused slitting saw, my first ever, and a new, but now useless mounting arbor and all the comments above rather frighten me. Useless due to my bodged up attempts at trying to skim down the imperial shaft to fit a metric collet. So, I have to make myself a new arbor. So how about this for an idea. Determine the point of maximum offset of the slitting saw and make an arbor with a matching offset in the opposite direction. Now ok it will probably be unbalanced, but would it work? And yes, I understand that I would then need a new arbor for the next slitting saw. Regards, Peter G. Shaw
dcosta	22/03/2011 19:50:17
496 forum posts 207 photos	Hello Peter. Maybe You can do a "normal" arbor but with a smaller diameter than the hole in the saw and a small ring with external diameter equaling the diameter of the saw hole. The internal hole with the same diameter of the arbor should be a little eccentric (in my case less than a millimeter is enough) to compensate the eccentricity of the saw hole as needed. In the same eccentric ring could also be applied the clamping ring. Just an idea... NOTE: Let me say that I have several saws I bought from some of the "majors" and all of them have the "special characteristic" of having an eccentric hole. Best regards, Dias Costa Edited By Dias Costa on 22/03/2011 19:50:58
mgj	22/03/2011 20:42:47
1017 forum posts 14 photos	marcus - the security of the backplate depends on how thick the saw is. - most are 30-60 thou thick, and they are in one parish. However I have one which is 1/8thick for doing rod ends, and at 3" dia or so, there is a fair bit of torque on that on a medium sized mill geared down. So you'll have to make a judgement yourself. however, I think you would be unwise to expect these screws to take all the sidethrust - not without toughening and heat treating. I think you'd use them for adjustemnt, and then have clamping allen bolts to provide the locking power. Then you'd only need three adjusters (NOT 4 - 3 points of contact?) because they are never going to take a cutting load directly. Peter - if you want to get really sexy about it use 2 "concentric" eccentrics -one slides inside the other. Then you can adjust any eccentricity out. Very elegant. Edited By mgj on 22/03/2011 20:43:57
marcusj	23/03/2011 10:04:20
27 forum posts	Posted by mgj on 22/03/2011 20:42:47: So you'll have to make a judgement yourself. however, I think you would be unwise to expect these screws to take all the sidethrust - not without toughening and heat treating. I think you'd use them for adjustemnt, and then have clamping allen bolts to provide the locking power. Then you'd only need three adjusters (NOT 4 - 3 points of contact?) because they are never going to take a cutting load directly. Something like this (frets.com)?
Ian S C	23/03/2011 12:57:29
7468 forum posts 230 photos	I use a home made arbor with a parallel shank, and if the saw cuts eccentricly I use the four jaw chuck and center it, I use the lathe for most of my slitting ops. Ian S C
mgj	23/03/2011 13:08:40
1017 forum posts 14 photos	marcus - that was exactly the idea. the screws are quite handy, but I have a big (for me) 6" Pratt Super Precison chuck, and to get that to run dead true, all one has to do is slacken the 4 locking Allen screws and tap the body round with a soft faced mallet . Any of those arrangements will work perfectly well, and I don't think that something as rarely used as a slitting saw deserves too much complication. Ians use of a 4 jaw is good too if one uses a lathe rather than a mill, but you do have to find a method of measuring run out over the teeth without munching the measurer. Some kind of ring? How much run out will cause you grief?
marcusj	23/03/2011 14:00:29
27 forum posts	Posted by mgj on 23/03/2011 13:08:40: How much run out will cause you grief? Gosh, what a very good question. Maximum runout would be: 'much less than I have now' . (OK, I will measure...)
Peter G. Shaw	23/03/2011 19:05:51
1531 forum posts 44 photos	Dias, Thanks for that. mgj, Don't do "sexy" any more, if indeed I ever did according to SWMBO! And anyway, it sounds a bit too complex for me. Simple stuff for a simple bloke! Regards, Peter G. Shaw
mgj	23/03/2011 21:14:02
1017 forum posts 14 photos	I thought you were looking for a brain teasing workshop project of the GHT type. Not I hasten to add an original thought - we had double eccentric adjusters on the old .50 Browning ranging guns on Chieftain. Works of art, and as good a way of introducing cross bind and jamming the gun as one could find. Gray - I have the problem too, and I promise you my arbors are not bent, and the saws exhibit eccentricity in the nose of the Myford, my DW and the big mill. They must be made like that, - and for a reason? In fact the lathe with the best bearings is the Chinaman and I'll clock an arbor tonight with a spare saw. (And the reason why the Chinaman has the best bearings is because it was retro fitted with some incredibly expensive German machine tool silky smooth bearings with some amazing accuracy designation - quite unnecessarily as it happened, but they are good)
mgj	23/03/2011 22:55:16
1017 forum posts 14 photos	Gray - as you suggest, you have to start at the beginning and work through to the end. Sometimes though its just the order that hurts - hence my smart bearings. Actually the error truned out to be the gib securing nut on the back side of the x slide. There was a manufacturing defect which meant that cuts were not applied consistently. A lot of headscratching later and it was found, fixed (in 5 mins), and now its a superb machine. Dead straight, dead accurate and dead consistent. So I don't know whether to laugh or cry, but its a pleasure to use! I do have to use bearings - my arbors have a thread at one end to take the saw clamping screw , so they aren't double ended. I have to set the arbor true first! Edited By mgj on 23/03/2011 22:57:03

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