should I convert these?

A 6" vise is overkill for a RF45 style mill. A 4" is more appropiate for that size mill & IMO 5" max. I have a 5" GMT vise on my PM45 & it's slightly too big. Not enough Y axis travel to make use of the 5" full capacity. Better to save your money rather than getting something too big & most importantly the weight. I take my vise of the table quite often, a 6" is still light enough for me to be carried by hand but I'm glad I have a 5". I also have a 4" vise as well. I prefer the 5" though.

But those GMT 6" Premium vises are pretty nice. I'd love to have one but don't need one on my current mill. But if you plan on upgrading to a full size knee mill in the future than the 6" will be perfect.


Here's what the 5" looks like on my mill.
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I couldn't even complete this cut without my bellows & DRO scale getting in the way. Not enough Y travel & the 5" vise is not even maxed out.
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Here's what a 6" vise looks like on another PM45 (gt40's)
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The company Tork Craft at http://www.torkcraft.com sells similar devices. They are specified for sheet metal up to 5 mm thickness. The ones they supply have three flats and are typically used in sheet metal panel work. I have used my 35mm saw to make a hole in a 0.8mm thick 316 stainless steel sink without lubrication and through 3mm mild steel sheet using tapping fluid. Low speed and a steady hand are vital. I recommend the three flat option though I have used mine also on the milling machine using a drill chuck. I have changed my 1/2 " Reduced Shank Drills to have three flats on the shank for getting rid of slip.
 
I just used a deep cutter to drill a 3/4" hole at least 1" I used a ER32 COLLET and cut like butter. No slip
 
What you have are good tooling, but they are not hole saws and should never be used in a collet holder. Hole saws were originally designed with a thin walled barrel and hacksaw like teeth with a set on them which could be used in anything from a portable drill on up. What you have is a metal cutting tool for cutting holes using a machine tool and which has many times the torque stress while in use, that a hole saw has. It must be run geared down to fit the load those wider teeth will be imposing on the machine. Properly used, it will be cutting a continuous chip with each of it's teeth. The tooth loading and torque arm of these tools require a much more Skookum tool holder than a collet holder. Chip removal and heat will be more problematic also so try to use large amounts of coolant. (Preferably through the tool holder you use) Some of these have a rotating water joint incorporated into the tool holder which is great for chip removal if the tool has a water passage in it.
 
I think the cutter you have is designed for much thinner material. The design allows for cutting material about half the thickness of the tooth depth. There's no place for the chips being removed to go except the gullet. The tooth geometry is such that a lot of material is being removed, plus the surface area contacted by each tooth is 3-4 time that of an end mill or annular cutter. I suspect this tool has or had a special application. It's possible it wasn't designed for steel. Have you talked to the machinist you bought them from?
Russ
 
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