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Correct use of slitting saw for deep cut.

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IRT29/12/2019 23:11:37
69 forum posts
17 photos

I am trying to cut a deep (0.875" slot in 5/8" steel. The slot needs to hold a hacksaw blade.

My first attempt with a slitting saw ended with the slot wandering off. Not a great surprise as the saw had a pronounced dish to it before I started.

I have just ordered a new saw and arbor from ARC (not the supplier of the original).

There seems to be a lot of conflicting information on how to use a slitting saw.

What approach should I take to have the best chance of achieving an accurate slot? Plunge from the end, plunge from the side a full depth or multiple small depth cuts from the side?

I suppose there is a 4th approach: the hack saw. This is the last resort.

Andrew Johnston29/12/2019 23:29:59
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5188 forum posts
599 photos

Use a coarse tooth saw and I'd do the cut in two passes from the side. Rather less encouraging is that the only way I've found to stop a saw going walkies on a deep cut is to use the horizontal mill, as it is much more rigid and the arbor provides better support for the saw than the Bridgeport.

Andrew

not done it yet30/12/2019 08:19:39
4163 forum posts
15 photos

What material? There is the possibility that cold rolled may make things more difficult.

What diameter saw? Leaving the minimum unsupported would be good for a narrow saw.

I’m as AJ - I have only used slitting saws with the horizontal mill.

Clive Hartland30/12/2019 08:39:10
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2516 forum posts
40 photos

For deep slots I alwayys cut a guide slot about 1mm deep, this seems to stop the saw from wandering out of line when going deeper. Use coolant and not too fast.

Ian P30/12/2019 10:21:02
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2321 forum posts
94 photos

I think a clue to the problem was the 'pronounced dish' in the blade.

It sounds as if the arbor is not clamping the blade properly. I have seen slitting saw blades that were eccentric but never come across one that is not flat.

Ian P

mark costello 130/12/2019 15:54:04
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577 forum posts
12 photos

I slot 3/8" (Imperial ) deep 303 stainless steel. I do it in 3 passes. Black cutting oil run through a drip oiler into a Noga Mister is the heavy dutiest setup I've found.

John Baron30/12/2019 17:19:28
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168 forum posts
62 photos

Hi Guys,

I recently cut a tapered slit in a 82 mm long length of gauge plate using a 0.8 mm slitting saw with a 6.35 mm bore for an adjustable parallel I was making.

07-12-2019-02.jpg

I used a length of 1/2" steel rod to make the mandrel. The thread is M6 with a tiny shoulder that fits into the bore of the blade.

07-12-2019-04.jpg

The mandrel was held between the lathe three jaw chuck and the tailstock live centre in order to rotate it.

10-12-2019-016.jpg

I used a simple wooden jig to secure the piece that I was slitting. I used the other tapered parts as a wedge to hold the parallel whilst I slit it. The lathe was run at its slowest speed without using back gear.

10-12-2019-017.jpg

10-12-2019-018.jpg

The cutting lubrication was Trefolex applied using a brush. The hole you can see through the middle is threaded M6, and is used to pull the two sides together in use.

Part of the problem with cutting a slit like this is that as the cut progresses the blade pushes the workpiece backwards and then down. As you get to the end of the cut the blade is trying to lift the work.

10-12-2019-003.jpg

10-12-2019-004.jpg

As can be seen it worked quite nicely, even though the blade did start to deflect as it got to the deepest part of the cut.

18-12-2019-002.jpg

The two half's of one parallel showing the brass guide and the slit bottom half.

18-12-2019-004.jpg

One thing that did take me by surprise was that the thin end twisted ever so slightly ! I didn't expect it to stress relief as it did, A little tweak with a mover whilst in a vise helped sort that problem. Both pieces now slide all the way from end to end.

old mart30/12/2019 19:28:36
1237 forum posts
115 photos

One thing to be aware of when sawing deep cuts is that the blades have no set, so if the metal moves due to stresses being relieved, it could pinch the saw.

I'm never sure if it is best to cut in stages, or the full depth in one pass.

Edited By old mart on 30/12/2019 19:31:42

not done it yet30/12/2019 19:46:55
4163 forum posts
15 photos

One also needs to consider conventional or climb milling when using a milling machine. . Most hobby machines are insufficiently rigid to cope with heavy climb cuts.

Likely need to make the same consideration if using a lathe - the above was the ‘climb milling’ equivalent.

Martin Connelly01/01/2020 20:34:27
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1014 forum posts
118 photos

Do not let the blade get hot. The blade will warp or dish if the tooth area gets hot and the centre remains cool (the arbor is a good heat sink). A spray bottle of water based cutting oil is useful for this if there is no flood coolant.

Martin C

Bandersnatch01/01/2020 21:52:07
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1483 forum posts
42 photos

(dumb post deleted)

Edited By Bandersnatch on 01/01/2020 21:56:44

IRT05/01/2020 19:04:48
69 forum posts
17 photos

A new saw and arbor arrived from Arc this week.

I used the vertical mill, and made the cuts in one pass.

Two 1/32" slots, 0.875" deep cut without any issue.#

Thanks.

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