slit saw jams

[Iain DownsParticipant @iaindowns78295]

Hi, respected experts.

And the rest of you!

I have a 100mm dia slitting saw in my CMD10 micro mill.

I'm trying to cut off a piece of 1"x1" mild steel at 45 degrees. I have the bar clamped on an angle plate at 45 degrees with the bar rising up from front to back.

The I'm running the slit saw from front to back (the table moves towards me). For the main part, this is fine until the saw gets to the end of the bar at which point it start to struggle, regardless of the feed speed, and jams. saw speed seems to make little difference, though it's a bit better at high speed due to more power and inertia.

I'm cutting off about 1mm.

I've tried slitting the back for a bit and that works OK until the cut gets too deep (there's not much scope for getting to the front and back with 150mm travel). when it jams.

I had very similar problems last time I tried to cut with this and gave up. However, In the past I've succeeded in cutting decent chunks with a slitting saw (the last time it worked I was cutting a one inch square 12 inch long cast Iron bar all the way along at an angle of 55 degrees).

I've put an indicator on the saw. There's a wobble of around 4 thou as I rotate it – which is consistent with a 1 thou spindle wobble at about 150mm down.

There's a few thou rise as the table moves left to right and there appears to be a ridge – that is as you move towards the centre of the saw the indicator rises by a thou or so over perhaps 10mm and then settles down. I suppose I should put the blade on my surface plate and check it.

None of these factors explains to me why it's jamming (and blowing fuses at an alarming rate).

Could this be happening because the blade is blunt? It's not done a lot of work, but perhaps my ham-fistedness has scored another own goal.

Am I expecting too much?

I wanted to use the saw to get a great surface finish (this is for a sliding clamp), and of course I don't fancy the hacksaw approach. I could revert to hacksaw, mill and lap, but I'd like to know what I'm getting wrong this time!

Iain

[Iain DownsParticipant @iaindowns78295]

What am I doing wrong THIS TIME!

[HOWARDTParticipant @howardt]

Slitting saws have no relief on the sides. They are primarily meant to cut no more than the depth of the tooth. Having said that I also use them in 3 and 4 inch for cutting off material of all sizes and I have them stall frequently. The problem is caused by swarf not clearing, it doesn't take much to fill the gap between the saw and the metal slot already cut. What you need is a flood coolant to clear swarf, not very practical on a small machine without extensive splash guarding.

[EmgeeParticipant @emgee]

plus 1 for flood coolant.
If no flood available try an air jet to clear the swarf from the blade, also add a cutting fluid of some kind.

Emgee

[colin hawesParticipant @colinhawes85982]

Quite often there is stress in the bar which tends to close the slit when the cut is deep and pinch the saw. this is much less likely on cast iron than on steel. If it is possible to clamp the end being cut off this may help. Colin

[JasonBModerator @jasonb]

How many teeth does the saw have for cutting 1" x 1" you don't want more than a 40tooth one at 100mm dia

Also is the saw wandering in the cut, if it is getting deflected up or down it will get tighter the more you cut.

Which side of the bar are you cutting as you might be climb cutting

Alternative would be to rough saw it with a hacksaw and then mill the cut to the required angle.

Edited By JasonB on 03/11/2017 19:01:29

[Neil WyattModerator @neilwyatt]

Take multiple shallow cuts.

[Anonymous]

Darn it, that's twice my carefully reasoned post has gone AWOL when trying to post. So I'll just give the abbreviated version.

Basically the mill isn't up to the job, for some or all of the reasons given above. Although my mills have no trouble running slitting saws on deep cuts, it's not a technique I'd use for this job. It'd be a hacksaw followed by a cleanup with a normal cutter.

Coarse tooth slitting saws are often hollow ground to give clearance on deep cuts, far deeper than just the tooth depth.

Andrew

[not done it yetParticipant @notdoneityet]

Pretty much too much, I would guess. You have a slitting saw with a likely 1" arbor? That would leave less than 1 1/2" of clear blade and you are trying to cut 1.414 inches deep (possiblybmore if the bar is oversized)? Doesn't leave much clearance anywhere, if any at all. In fact, at 100mm, that is less than 4" diameter. Likely heat from expansion is enough to cause problems.

[Rik ShawParticipant @rikshaw]

My problems with slitting saws are nearly always caused at the end of the cut where the stresses are released and the job closes /pinches onto the saw blade and jams it. Best way to avoid trouble is to assume it WILL happen and take steps to prevent it happening beforehand. There are various ways depending on what you are slitting.

Rik

[Martin CargillParticipant @martincargill50290]

What RPM is the saw running at ?

[Speedy Builder5Participant @speedybuilder5]

An EVOSAW would eat that job in less than a minute. Have any of your friends got one ?
BobH

[John ReeseParticipant @johnreese12848]

What Niel said.

If you have too many teeth engaged in the work on a low horsepower machine it is likely to stall the motor. Take shallow cuts as Niel said. Slotting saws have no side clearance so lubrication on both sides of the saw is essential.

[JasonBModerator @jasonb]

Posted by Iain Downs on 03/11/2017 18:34:15:

I'm cutting off about 1mm.

That sounds like a shallow cut to me!

[Ian Skeldon 2Participant @ianskeldon2]

I would try stopping the cut just before reaching the end and try to wedge something (feeler guage maybe) into the cut to prevent it from closing up and pinching the saw, then continue to cut to the end.

[Enough!Participant @enough]

Why do you feel it's necessary to do this with a slitting saw? It just doesn't seem an obvious method of choice to me.

I'd cut it off with a hacksaw (if I didn't have a 4 x 6 bandsaw, which I do) in, what, 5 minutes? Then clean up with a milling cutter. It would never occur to me to use a slitting saw.

It would also never occur to me to use a 100mm dia saw in a "micro" mill …. I imagine it would take nothing to stall it. Jamming and blowing fuses suggests that the machine is overloaded – not unexpectedly imo.

[Jeff DaymanParticipant @jeffdayman43397]

If you want to make a 1 mm thick part with a nice surface finish, why not start with a piece of sheetmetal or 1 mm gauge plate?

If I wanted a toothpick I wouldn't start with a log and a slitting saw….

Just food for thought.

[HopperParticipant @hopper]

100mm slit saw is a big ask for that little 150W motor in the micro mill. A very big ask. As Neil says, take very light cuts.

A pic of your setup might help clarify exactly what you are doing and some possible solutions.

[John ReeseParticipant @johnreese12848]

Posted by JasonB on 03/11/2017 20:57:50:

Posted by Iain Downs on 03/11/2017 18:34:15:

I'm cutting off about 1mm.

That sounds like a shallow cut to me!

I read that as saying he was making a cut about 1mm from the end of the part. Do I understand the setup correctly?

[I.M. OUTAHEREParticipant @i-m-outahere]

1. Might be worthwhile to check the thickness of the saw for uniform thickness , ideally it would be hollow ground so a few thou thinner in the centre .

[Iain DownsParticipant @iaindowns78295]

Thanks for all the advice.

I am using cutting fluid.

I should have said 'depth of cut 1mm'

If anything the saw is thicker in the middle than at the edge, though I will need to measure it. Either that or it is dished with the dish pointing downwards.

I am able to cut quite deeply at the front and back of the job (perhaps 10-15 mm in) until the load gets too much. There's a limit to how much of this I can do without moving the angle plate. And if a picture paints a thousand words, this one must be worth at least 100…

In answer to 'why on earth would you do it that way …'. Firstly, hacking through a few inches of mild steel with a hacksaw is not my idea of fun. My wine drinking arm would be sore for days. Secondly, my vertical accuracy with a hacksaw remains erratic over long distances. Sometimes it's spot on, sometimes it wanders. Thirdly, I have managed deep cuts with slitting saws on this mill. It gives a lovely almost mirror finish much better than the mill.and as I wanted a sliding surface I thought that would save a lot of tidying up (I'd need to lap after the mill after the hacksaw).

I think what I will do is to check the shape of the saw I'm using and see if it is convex. I've also got another 100mm slitting saw which is still in it's plastic and has fewer teeth. I might try that.

Or I might just give up the attempt and drink with my left arm for a day or two!

Ironically, I'm attempting to build a clamp for the angle grinder chop saw I'm making, so that I can produce nice clean deep cuts at any angle in steel bars.

Iain

[JasonBModerator @jasonb]

Quite likely that as the saw is starting the cut on an angled face it will be deflected upwards which starts it off on a sloping cut which continues to slope upwards the more you cut until it gets too tight.

At the rate you are blowing fuses and risking stripping gears you won't be able to afford any wine, get the saw out it will be good practice, if you can't saw near the line then saw about 3mm away just means a bit more clean up. IF you have a large lump to saw through don't do it all in one go, leave in the vice and cut a bit between doing other jobs in the workshop – 3mm of cut every 10mins won't strain you and job will be done in 1hr.

[john carruthersParticipant @johncarruthers46255]

For slicing up MS stock I use a 1mm disc in an angle grinder, then clean it up after if required, usually it's quite a clean cut. I clamp a sacrificial guide to the work initially then let the tool do the work.

[Neil WyattModerator @neilwyatt]

Why not just mill the end off the bar?

[Clive HartlandParticipant @clivehartland94829]

Perhaps the answer is to use a thicker cutter which will not deviate so much.

Clive

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