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Old 05-08-2009, 07:07 PM   #1
mnewsholme
 
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Default dovetail cutter speeds

Im cutting some dovetails on a hemingway kits ball turning tool. Whats a typical speed to run the cutter at? at widest diameter cutter is about 1" diameter. do I calculate cutter speed for tip diameter or for average diameter? I'm cutting en1a steel on an x3 mill. Also what sort of depth of cut should I be using. I've already done first two dovetails using 400-600rpm and depths of cut between 0.2 and 0.3mm. Went ok and gave a decent finish but there was a lot of vibration. not sure whether I need to change cutter speed or depth of cut or both. Any suggestions please

matt



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Old 05-08-2009, 08:10 PM   #2
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Default Re: dovetail cutter speeds

Matt, were you using any form of lubrication ? - If you use a lubricant, you should be able to run at a higher spindle speed - also, your cutter will last longer. It also depends on the rate you feed at.

I know this is not much help - I'm sure one of our more experienced members will be able to provide a better answer

Regards, Arnold



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Old 05-09-2009, 09:16 AM   #3
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Default Re: dovetail cutter speeds

As dovetail cutters are normally straight toothed they cut with a very harsh intermittent action and hence calculating a speed/feed combination based on normal helical type milling cutters can give unsuitable results.For this reason I always use my eyes and ears to determine the speeds and feeds for cutters.As you have already mentioned a lot of vibration It would seem that although the finish is good the cutter speed/feed is probably too high for your setup.Calculating a cutting speed for any form of tool is only a guide for people who require a fast removal of metal as if in a production shop,which normally means that large rigid machines with good fixturing are being used.The life of the tooling is also expected to be much reduced from its maximum.Therefore I always try to make any machining I do to be a be a steady,pleasant,easy on the nerves operation that does not over stress either the parts being cut or the machine tool doing the cutting.So to sum up,if in doubt start with a slow spindle speed and just take a small cut and see what happens.If it all goes well then just up it a little,your machine will tell you when to ease up by complaining(a bit like wives really).Most cutting operations will not suffer by being done at a slower rate than is possible and the tool will still be good to use again after you are done.
I also find that on some dovetail cutters that they have too many teeth on them which can cause chatter and vibration.This I cure by grinding off alternate teeth on the cutter to let the tool cut more smoothly.A bit drastic I know but it does work,but only do it as a last resort.
The above lecture is only the procedure that I use and is by no means to be thought of as the correct method as I am sure that other people have better methods,if it is of any use to you then good luck.

best regards Steve C.

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Old 05-11-2009, 03:20 AM   #4
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Default Re: dovetail cutter speeds

I've cut a few dovetail slides in cast iron and in steel. I know this might not be best practice in machining, but I've found that the slower the spindle speed the better. I usually run my dovetail cutter on the slowest spindle speed. Just means you have to feed the work slower.

Chuck

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