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Slot saw speed

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Roger Benson30/09/2020 16:05:46
24 forum posts

I have just bought a slot saw blade and arbor from ARC and am quite surprised to find that the key way in the blade is to small for the arbor key. When I queried this it appears that this is common. You have to either open out the key way in the blade or machine down the key in the arbor. Surely in this day and age if you sell paired products they should fit.

Anyway onto the question. What is a good starting speed when using a slotting saw. I have managed to dull mine after only 2 light (.2mm) cuts. I have a 50x0.7x13x40T HSS blade cutting into 25mm mild steel tube. I do not think that 0.2mm is too deep or am I to be corrected?

Thanks

JasonB30/09/2020 16:20:05
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0.2mm is tickling the surface and will rub the edge off the cutter, take a decent depth of cut. For steel at say 30m/min you want the blade spinning at 190rpm or there abouts

I don't bother with the key like a lot of others.

Edited By JasonB on 30/09/2020 16:29:21

HOWARDT30/09/2020 16:28:25
595 forum posts
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100mm dia, 30m/min, 100rpm. No key, locking nut diameter and arbor give more than enough friction surface to drive. Any jam that occurs then may spin the cutter rather than break it. Also plenty of lubrication.

SillyOldDuffer30/09/2020 16:39:58
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Posted by Roger Benson on 30/09/2020 16:05:46:

I have just bought a slot saw blade and arbor from ARC and am quite surprised to find that the key way in the blade is to small for the arbor key. When I queried this it appears that this is common. You have to either open out the key way in the blade or machine down the key in the arbor...

Thanks

Never mind that, whether or not a key should be used at all is controversial! One school of thought says they stop saw blades slipping, the other suggests driving them blades hard enough to slip is enough to damage the teeth.

No problem in my workshop - none of my arbours have key-ways! I have 5 or 6 saws and not all of them have notches. The saws work fine...

Don't worry about it. Leave the key out if it doesn't fit. (Tin hat on ready for flak!)

Dave

Tony Pratt 130/09/2020 17:16:59
1237 forum posts
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I do remember back in the day when using a slitting saw with a key the saw jammed the arbor kept turning & the saw just cut through the key.smiley

Tony

Mick B130/09/2020 17:34:46
1737 forum posts
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Posted by SillyOldDuffer on 30/09/2020 16:39:58:
...

...

No problem in my workshop - none of my arbours have key-ways! I have 5 or 6 saws and not all of them have notches. The saws work fine...

Don't worry about it. Leave the key out if it doesn't fit. (Tin hat on ready for flak!)

Dave

No flak here. I only have 1 arbour (don't know why I might want more?) with no key or keyway, and 4 blades, all also with none.

Friction clamping of the blade between end nut and spacer or shoulder has always provided plenty of drive for anything I wanted to do.

Roger Benson30/09/2020 18:04:07
24 forum posts

Thanks all. Need to order some more blades. Is 40T too course or OK for mild steel?

JasonB30/09/2020 18:13:04
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What is the wall thickness of your tube and how are you cutting it ? slices off or along it's length

Emgee30/09/2020 18:18:02
1732 forum posts
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Hi Roger

For cutting steel tube I believe the tooth count (approx 4mm pitch) is about right, if you were cutting solid bar it may be better to go with less TPI to help prevent clogging the kerfs, possibly more TPI on thin sections to keep as many teeth as possible in the work.

As said keep you speed down and apply some lubricant/cutting oil, adjust the feedrate to suit your machine and set-up.
Not having a key fitted could be an advantage or it could induce a jam if the drive to the blade is lost, take your pick but like most I don't use keys with slitting saws.

Emgee

Edited By Emgee on 30/09/2020 18:21:09

Roger Benson01/10/2020 08:24:45
24 forum posts
Posted by JasonB on 30/09/2020 18:13:04:

What is the wall thickness of your tube and how are you cutting it ? slices off or along it's length

It is a tapered hole 2mm to 4mm over a 20mm length.

Paul Lousick01/10/2020 08:38:36
1554 forum posts
584 photos

I run my blades at slow speed (probably 100 rpm or so) with lots of coolant and don't have problems.

Edited By Paul Lousick on 01/10/2020 08:38:52

JasonB01/10/2020 08:56:46
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So assuming you are cutting along the 20mm length then the 40T will be OK as you will have at least 2 teeth in the cut. I would set it up so the blade cuts right through in one go, if the mill bogs down then do it in two passes say 1.5mm and then the rest.

slitting cut.jpg

Have those suggesting 100rpm noted that this is a small 50mm dia cutter so can be run faster than the more commonly use 10mm blades hence my 190rpm suggestion. [ 30 / (0.05 x 3.142)] Also though It may not apply with the 50mm saw but on the variable speed direct drive machines they may not have the torque at 100rpm to drive a 100mm saw so need to be run a bit faster than the optimum for an HSS saw I have found this to be the case on the SX2.7 with a 80mm saw.

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