WM16 cutting conundrum

Have a problem when milling

Stock i5/8 x 3/4 is in the vice overhanging by 3in

The vice is as near square ( 2xDTI ordered to get it 100£ in future) as makes no difference with what i need to do

First take a cut on thr top side ( the 3/4)

Then i want to get the 5/8 sides down to 0.531.

I mill the back part by taking about 20thous off

Then get the cutter to the front one to get it to width, and here is where the problem sides

Checking that the front is still 'parallel' to the rear i fine that over a cut of 2 inches it tapers .007 over the length from left to right

I am not taking massive cuts 10 thous max going do as i near reqd width

I would have thought the irrrsipective of the angle of the vice jaws the cuts should be parallel. There is no play in either the bed or the quill or the vice bolt

Amy ideas as to why it is doing it? perhaps smaller cuts?

Can I assume that what you are trying to do is similar to this:

The relieved section will be about 2" long and is 3/16" thick. I did it in two steps, each about an inch long. Trying to do the full length in one pass caused too much chatter. I've just measured the thickness variation on the finished part - about 3 tenths of a thou. Some pointers:

The cutter is a 6mm professional quality 3-flute carbide endmill and is razor sharp

I took a couple of spring passes which removed extra slivers of material

The cut shown is conventional milling, but on the reverse side the cutter was climb milling - it's not something I sweat over

Material was hot rolled steel

The DRO helps to move the cutter back to exactly the same position

The rear jaw of the vice is set with a DTI to be less than 0.01mm out over 150mm

Andrew

Andrew

Yep. you have it in one and i have a DRO on both axis!!

The length i need is only 1.9inches!!

Tghe cutter was a four flute end mill brand new from Tracy Tools, and i have been using them for years

The two DTI will be used to square up the vice in future, i did have a system where you place a length of steel in the channel of the bed, turn the vice upside down and tighten it to the bar. then mill out a channel in the base of the vice corresponding to the width of the bed slot Put the bar in that, and by turning the vice over and placing the bar in the slot the vice should always be square. It was a bit off but nothing to worry about but as i will be milling out a radius rod from solid i need everything sdopt on. Hence the DTI

What are you doing wrong? Sticking it out.

The part should be in the centre of the vice and supported by a parallel or two. so that the minimum material necessary to make the cut is above the jaws. If you are not sure how flat and square the workpiece is skim the first surface to be sure. The cut should be on the top surface. When you have done one side turn it over and do the other surface keeping the same flat face in contact with the fixed jaw and tapping the part down onto the parallels.

Martin C

I've bought from them in the past, but no longer do so. Make of that what you will.

Why two DTIs? I only use one and just run it down the back of the fixed jaw tapping the vice until there is no movement as the table moves.

Andrew

The only reason I can think of for the OP's problem is that if the material is cold-formed, eg BMS, cutting the first side relieves surface stresses and causes the material to bend slightly.