Author Topic: How true/straight slitting saws run?  (Read 734 times)

Offline PekkaNF

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How true/straight slitting saws run?
« on: November 29, 2018, 02:52:53 PM »
Cheap or bit more pricey slitting saws seems to wobble a bit. How much is normal?

I have one 80x1 mm that wobbles about 0,15 mm, not normal 8-figure, but more like on big one and two minor ones on other way, no way of using slanted washers to correct it.

Made one slitting saw holder that runs true to 0,01 mm....pretty damn good. I never got two piece affairs very concentric. Desided to make one-piece design with one time chucking.

Pekka

Offline chipenter

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Re: How true/straight slitting saws run?
« Reply #1 on: November 30, 2018, 04:19:19 AM »
Is that a left hand thread for self tightening ?
Jeff

Offline awemawson

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Re: How true/straight slitting saws run?
« Reply #2 on: November 30, 2018, 04:39:59 AM »
If not, no problem putting the saw on the other way and running in reverse.
Andrew Mawson
East Sussex

Offline PekkaNF

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Re: How true/straight slitting saws run?
« Reply #3 on: November 30, 2018, 05:36:09 AM »
This is still work in progress....Andrew is right. I was playing with it when assembled it....saw could be put either way, my mill/drill rotates both ways (big mill does not).

It still has two issues that are not implemented.

1: Better way to prevent nut from rotating...I was thinking of making a keyway to bushing and to arbor. Two issues here: a) Should have milled the keyway to arbor after roughing - it's made out of 42CrMo4 and sometimes that has stress. b) Collar/bushing is made out of 42CrMo4, bit tough for my standard keyway broaches. Setscrew would be a possibility, but not pretty.

2: No keyway in arbor, thinking of making two holes on face and matching pin key. Without any flat or other than chucking into collet tightening method is not that elegant.


I have three slitting saw arbors and none of them had 22 mm hole, Needed to make one more. And I failed once in 22 mm fit (wanted easy, but not sloppy fit) and then on assembly. Made it in two parts  (classical model) and fit was too tight 16 mm arbor needed 5 tons to press trough, it was straight for a day, finished it and first time I used it went banana for 0,2 mm.

Instead of repeating the failure I wanted completely different arrangement....I considered Spirit Tool type arbor for MT3, but with standard M12 draw bar most of the parts would have had 2-3 mm wall thickness and some other dimensional issues (when drawn on paper on kitchen table) and I came with this solution.

Thick saws are pretty true, but one millimeter thick slitting saws seems to be wonky....do I just have a bad luck or are they all bit uneven?

How about carbide saws?

Pekka
« Last Edit: November 30, 2018, 08:43:41 AM by PekkaNF »

Offline picclock

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Re: How true/straight slitting saws run?
« Reply #4 on: December 11, 2018, 02:14:41 AM »
I don't use slitting saws much, and have broken/destroyed a few due to cutting too fast and and too deep  :palm:.

I have had good results by using large thick washers to support the edge, say 4mm for aluminium or 3mm steel. So if your cutting a 15mm deep slot then make up a washers which allows a cut depth of up to 4-5mm for the first cuts. Remove the washers for subsequent cuts as the first cut tends to guide the saw to the correct position. If you are cutting very thin slots go for smaller diameter saws. I've found that the fixing bolt tightens with the mill running in the normal direction.

I have yet to find a slitting saw that cut evenly around the circumference. I think its the nature of the beast that some teeth protrude slightly more than others. Cutting speeds are slow because of the larger diameters.   

I used to use an MT2 adapter, but now use a lathe made 20mm adapter in an ER32 collet, quicker to change. This gives a wide enough shoulder for the support washers.

Best Regards

picclock
 
Engaged in the art of turning large pieces of useful material into ever smaller pieces of (s)crap. (Ferndown, Dorset)

Offline chipenter

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Re: How true/straight slitting saws run?
« Reply #5 on: December 11, 2018, 04:21:24 AM »
Trim saw blades work well but are noisy , they can be 1mm thick , work them to hard and the teeth break off .
Jeff

Offline PekkaNF

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Re: How true/straight slitting saws run?
« Reply #6 on: December 11, 2018, 05:54:08 AM »
Trim saw blades work well but are noisy , they can be 1mm thick , work them to hard and the teeth break off .

That looks pretty good....what sort of metal thicknesses you have cut with it? Any prescription of steel?

Pekka

Offline PekkaNF

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Re: How true/straight slitting saws run?
« Reply #7 on: December 13, 2018, 08:27:31 AM »
Bit related vid...
=1324

Tried to make it start at 22 mins ...right at the interesting stuff, but parser seems to vomit timeline....worth watching at the beginning. :D

Offline chipenter

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Re: How true/straight slitting saws run?
« Reply #8 on: December 13, 2018, 10:17:46 AM »
I have cut steel en8 cutting a 300 x 16mm length of cast iron broke two teeth . that photo was taken in 2012 and was my go to saw and is still sharp , just doesn't sound right .
Jeff