gear cutters?

[blighty]

thought I would post this before I give them a phone.....

Need to cut some gears, not done this before so it may be something I'm doing,

the cutters are 48dp N06. N03.

The material I'm using is EN16. The second the cutter touched the metal all the teeth striped. I thought it may be the material being to hard?? so I used the other cutter on some Ali. this went well. I then machined up some blanks in mild steel. this time it managed to cut a few teeth before the sparks began to fly. Another cutter gone.

As this cutter was half a mil out of true there was 3 teeth left on it. I ground off what was left of the others. slowed the feed down and tried again. same thing.

cutter.... 400rpm. feed 20-30mm/min, I'm now thinking my cutter speed is to high. But I'm up to 50 quid in cutters at the mo and I have another cutter on its way to replace the first one. don't really want to spend more on cutters..... and I need to replace the cutter that died today.

 

[BaronJ]

EN16 is a high tensile steel which has excellent ductility and good shock resistance, but is more resistant to shear loading and frictional wearing. It is an alternative alloy steel grade to other chromium and nickel high tensile steel specifications and is readily machinable in the supplied condition. EN16 is a popular 'all-rounder' and is used in a wide variety of general engineering applications.

If you are sure that this is the steel you have then yes I would agree that the speed and or feed was wrong. Though Chinese cutters are not always good ones.

 

[blighty]

thanks for the reply.

The first steel was EN16. then ali and last mild steel. They cut the Ali fine at 100mm/min and 1000rpm. the Mild steel was about 400rpm 20mm/min.

The cutters have HBM written on them. don't know where they are made and I'm not going to name the place I got them from on the forum......yet

 

[BaronJ]

HBM is a fairly well known name for machine tools, sold by RGD and I think a German company. Other than that they could have cutters made anywhere.
Gear cutters do seem to be quite expensive, though I'm surprised that they broke like you describe.

 

[Asm109]

What diameter is the cutter?

 

[blighty]

one cutter is 57.5mm. the other one should be the same, but as I said the teeth are about .5mm of centre. Both have 12 teeth. the arbour has no run out.

 

[xpylonracer]

Slow both your cutter speed and feedrate, you may find it cuts OK.

Xpylonracer

 

[Rod Cole]

What about death of cut, I always took a few passes, a little deeper each time, and as said above, I run both the speed and feed slower~

 

[Charles Lamont]

On the EN16 you are using cutting speeds that would be fast, probably too fast, even for carbide tooling. For cutting a tough steel with a HSS cutter, a peripheral speed of 50 ft/min (15 m/min) is quite enough. At 57.5 mm diameter, that works out to 83 rpm. So for mild steel you could go up to about 160 rpm, and about 500 for the ally. Going even slower would help to preserve expensive cutters.

 

[blighty]

not going to use the EN16. both gears should be mild steel, with one being case hardened. ill order the gear i killed today and have another go Thursday.

DOC is 1.22mm.

ironic thing is that i opted to get the cutters and have a go my self as the gears i need are £130.

 

[Hopper]

....
cutter.... 400rpm.

That is the rpm you would use for a 1" diameter cutter on plain mild steel.
Using a 2+" cutter on EN16 you need to be down around 100rpm as Charles says.
No wonder you had sparks flying!

 

[blighty]

Its looking like I've been a bit of a pleb. I wouldn't run a 2 inch end mill that speed so why would i run this cutter that fast.

new one turned up. will have another go Thursday.

over the weekend was looking up how to make your own involute gear cutter... just in case...
interesting read, how to get the profile for any cutter using a button tool bit.
http://mikesworkshop.weebly.com/designing-gear-cutters.html

 

[Tim1974]

En16 is tuff stuff slow speeds and plenty of coolant or just straight cutting oil is the way to go .

 

[john_k]

EN 16 is also supplied in different "conditions" - i.e. heat treatment. Condition T is quite hard - you would probably struggle to machine with HSS at all.
Maybe you should check the hardness before proceeding.

 

[chrsbrbnk]

look this isn't production and the cutters are spendy think like 30 fpm max and good cutting oil on the cutters you already dulled up the resharpening is pretty straight forward grinding only the face of the tooth

 

[blighty]

we have success...

got in the shed this morning and gave the new cutter ago. mounted a mild steel blank. NOT EN16, slowed the cutter down to 280rpm or 10hz not keen on going lower as cooling for the motor may be a problem. redid the code to 30mm/min. 8 minutes later i had a cut gear

the front of the gear looks fine. but the back looks like the teeth are a bit thinner. maybe a trick of the light or my ageing eyes or a burr or.........

ill do the rest in the morning and post some pics.

 

[blighty]

finished off the gears, still need to put them on the grinder to get them down to size.