Unused Xmas Gift

I was given a face mill with four gold coloured inserts and have not used it as I'm not sure if it will be any use to me.

I have used the one blade type with HSS tool on aluminium and have found it quite satisfactory with good results.

With this face mill if I face steel which is under the dia of the tool would the inserts chip, as I found on the lathe that when turning steel round with a flat the insert chipped.

With aluminium this did not happen as its soft, what minimum size steel can this face mill do with out the inserts chipping.

I would have a go but I don't want to damage the inserts, hope this makes sense.

Thanks Bob

Milling inserts are always going to have to withstand impact as they come round into contact. I'd try starting with light cuts on alli, then brass, then mild steel progressively. If they do chip, they're not going to be very useful anyway.

More of a problem can be the hammering that the milling machine spindle splines get with the intermittent load. Not so much of a problem on new machines, but I'm slowly getting through making a new drive shaft for my early '60s Beaver machine because the 9° of slack in the splines really makes the machine shake when any cutters are partly engaged, shell/face mills especially.

I think the only way to find out is to try it!

Multi-insert face-mills have been available for many years and I don't recall any general complaints about them being more likely to chip inserts than any other type of tool-holder.

The nervousness about chipping carbide is partly folk memory and partly real. Carbide inserts usually consist of many small particles of a very hard material like Tungsten Carbide bonded together in a matrix. Not solid - more like the grit in a grinding wheel than HSS. The matrix is usually a metal. Early inserts were brittle, but they've been gradually improved over the last 80 years or so. Modern formulations are much less brittle. Unfortunately, one way of reducing the cost of inserts is to cheapen the matrix material and to cut down on the amount of carbide in the mix. This might be done by a reputable maker selling tips for work not requiring high shock resistance, or it might be done less honestly because low-cost matters more to the customer than high-performance. Another issue is manufacturing rejects - a batch of inserts might fail shock-testing and be sold-off as 'unbranded'.

My experience with cheap inserts has been generally acceptable - most are happy to take interrupted cuts. But about 20% of my inexpensive stock have failed prematurely - especially sharp ones and threading tips. The very worst were bought cheap at an exhibition: opening the box a few months later I discovered them to be obvious rejects, they work - but not reliably. Inserts bought from the usual suspects on the forum are OK rather than brilliant, but for my lightweight hobby needs top-quality inserts aren't economic.

We don't know if the inserts that came with your tool are good or rubbish! I've had new tools come with inferior inserts and new tools arrive fitted with good ones. Can't tell by looking but cutting steel will soon give the answer.

Another point is whether or not a 4-point tool is useful in your particular workshop. The advantage is they can remove metal at high-speed but that may not suit your equipment. A mill driving four cutting points needs a good deal more power and rigidity than one spinning a single-point tool, and a hobby mill might not have the ommph necessary to get the best out of a 4-point cutter. Again, I think you can only find out by trying it. Depending on the mill you might find it's great for Brass, Aluminium and Cast-iron but steel is too much.

Dave

If it's one of these 

I've got one fitted with a 2MT shank on my Centec, and it works a treat. I'm gentle with it, 0.03 depth of cut, 800 rpm and 8" per minute feed rate. Gives a very good finish on steel. The tips that came with it are absolute rubbish, not even flat on the back where they bolt up, but they work, I haven't chipped one yet. When I've used up the stock that came with it I'll buy some decent ones. Even with the small depth of cut it is shifting metal as quickly as a smaller cutter going more slowly. You do need cotton overalls and safety glasses, the chips are hot and fly everywhere

Edited By JasonB on 04/02/2019 14:57:08

Thanks for the replies, its the same as last post Duncans, so will give it a try.

As for the inserts are they standard APMT 1604, how can you tell good from rubbish quality, or is it down to cost, but as stated by Dave, try them first.

Bob

Any insert will chip if you stall or stop the machine in a cut.

It's not down to cost unless you run a machining center, your hobby machine hasn't the power to make the difference noticeable.

I tried a very cheap set of 12mm CCMT tools, came with 10 inserts and tried a destruction test with the boring bar on a 9 3/4" wheel rim running on a 10" lathe. I got chips coming off as sparks which the coating stood up to for 10 minutes before the varidrive belt slipped and chipped the tool.

Edited By Dave Halford on 04/02/2019 19:02:29

Have a look at my posts in this thread to see what a difference some decent inserts made to one of these cheap facemills.