Unconventional way of making a rack

[Ian ParkinParticipant @ianparkin39383]

I had the need for a longer rack (2ft) for a large fobco drilling machine

I couldnt envisage what/how to do it with my workshop equipment

a local gear cutter wanted £300 or so to make it assuring me that it was absolutely critical that the tooth form was perfect and any inaccuracys would lead it it jamming wearing quickly

I think It was mr J.S who suggested cutting the teeth with my vertical mill and then setting the head over and then doing the angle

4 end mills later (3mm ones) i had cut straight down (100 teeth)

1st question what depth of cut and speed and feed should a 3mm endmill be able to cut in MS?

I tried setting over the head but it was giving a dreadfull finish as the bit was moving rather than cutting

So i bought a gear cutter suitable for a rack

Thinking of ways to use it maybe mount a motor and gearbox on the mill spindle or a right angle drive

Made an arbour out of 1" ms and mounted that in the lathe mounted my precut blank in the toolpost and gingerley fed into the cut….perfect 2 different heights on the toolpost and job done in 2 hours doing 5 teeth at a time before moving the blank in the toolpost

Cutter was spinning at 210 revs…

2nd Q is that about right for a gear cutter 3" diameter hss cutting MS?

This was as I progressed so I had the moving steady supporting the arbour

turned the blank around and changed set up for the ends

this the finished rack and the original which is only 10 "long and a sealey one I bought which worked fine but didnt look too good

And this is it installed in the machine

I've motorised the bed…absolute luxury

switch gear mounted in a moveable box if it gets in the way it can move

Edited By Ian Parkin on 06/04/2016 17:35:01

[Ian ParkinParticipant @ianparkin39383]

[pgk pgkParticipant @pgkpgk17461]

As I understand it mild steel cutting speed about 100-150 surface feet/min depending on exact spec steel..so call it 120sf/m. For hss it's (4 x sf/m)/diameter in inches.

So 3mm (1/8th in) hss endmill = 4x120x8 = 3840rpm

And a 3" cutter = 4 x 120/3 = 160rpm

A good job

[Ian ParkinParticipant @ianparkin39383]

Is that why my end mills were breaking then because I was only running at 1600?

[John PParticipant @johnp77052]

Here was my solution to cut a rack 20 DP 159 teeth 25
inches long, the head on the mill was rotated 180 deg ,a
power take off gears down and provides a 90 deg turn
to drive a shaft . A simple plain bearing shaft has another
90 deg drive and is mounted on the overhanging head
ram and is braced very securely to the mill column.Has
a silver steel cutter made on the Eureka device at
20 DP ,a simple cnc file drives the cutter through the
blank and then indexes along to the next tooth.Cut
depth set by lifting the knee.

Photo's in album cutting racks.

John

[pgk pgkParticipant @pgkpgk17461]

Posted by Ian Parkin on 06/04/2016 19:36:02:

Is that why my end mills were breaking then because I was only running at 1600?

So I've been told but my mill doesn't run faster than 1600 either. It's also feed-rate +/- coolant.

I've been cutting copper with a 3mm endmill recently but I've been taking it slow with multiple shallow cuts 'cos my last milling with a 1.5mm ended up with broken endmills too.

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