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Thread: Rotary table grinder
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8th May 2020, 06:11 PM #1Most Valued Member
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Rotary table grinder
Here is a little grinder that was made by my dad just after world war 2, he was maybe 25.
This was a prototype and was the smallest of a few grinders that he built, money and machinery was in short supply back then so if he needed a machine he made it.
It looks like it was a bit of a rush job, pretty rough in places but must have done a lot of work as it is well worn.
I believe this machine was used for grinding the smaller range of oil pump and hydraulic motor castings, it is very badly
worn so I don't know what it was used for towards the end of its work life, but it must have still been grinding something.
I started to work on this machine a year ago and then got side tracked elsewhere, anyhow i am attacking it again.
Here are some pics, sorry i could only find one pic of the assembled machine from before i pulled it apart, the other pics show
the bolt holes for the rotary table mounting broken, the table is about 65mm thick so i machined out a recess and bolted in a 4140 plug and replaced the 5/16" shaft bolts with 10mm, i redrilled the bolt holes as the old holes were not accurate and were probably drilled with a Black and Decker.
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8th May 2020, 06:40 PM #2Most Valued Member
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Spindle slide
The top casting has a brg at each end and a shaft through the centre that is driven by the motor on the top, the shaft is the spindle for the grinding wheel. This casting slides forwards and backwards (by a hydraulic cylinder) traversing the grinding wheel across the part being ground on the spinning rotary table, this is the flogged out part of the machine.
Most of the wear is at the back end, likely the weight of the motor so i might/maybe fit a lighter motor.
I made a couple of brackets to hold the casting on a mag table and got myBIL to give it a skim.
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8th May 2020, 07:32 PM #3Most Valued Member
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Top of machine
Maybe i am ready for the nursing home......
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8th May 2020, 10:05 PM #4
Hi John,
Maybe i am ready for the nursing home......
On the news the other day they were saying that mental health problems have increased 200% since the lock down started and that physical abuse issues have also increased.
Me I'm fine, don't know about the other guyBest Regards:
Baron J.
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8th May 2020, 10:20 PM #5Most Valued Member
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That's an interesting piece of machinery, thanks for the details of how you went about repairing it.
KrynTo grow old is mandatory, growing up is optional.
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8th May 2020, 11:09 PM #6Senior Member
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- jilliby nsw
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Lots of hours of work there but its coming along nicely. Looking forward to a video of the rejuvenated machine doing a demonstration grind.
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8th May 2020, 11:34 PM #7Most Valued Member
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9th May 2020, 12:00 PM #8Most Valued Member
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Great work John, does it have a hydraulic drive for the rotary axis too. Arter were the big boys in this style of rotary grinder back in the day. Very impressive machine your dad made though.
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10th May 2020, 12:16 AM #9Most Valued Member
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G/day Ralph, yes the rotary table sits on the drive shaft on the hydraulic motor, it is slightly modified though.
The bottom end of the shaft sits on a ball brg and it has tapered bronze bush at the top, the ball sits on an adjustment bolt
to adjust freeplay.
I had never heard of Arter so I looked them up https://www.artergrinder.com/ thanks for that m8 you are a machinery encyclopedia.
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10th May 2020, 05:05 PM #10Most Valued Member
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A little progress
I knew this was going to be a challenge when I first contemplated using the mill to grind, an old mill at that.
Then there was the problem of the grinding wheel being so far away from the column, other than the Z axis measurement
on the DRO being next to useless I have perfected my technique for adjusting for the depth of cut using a 1/10ths indicator.
It took a little while and a few oopsies to work out the best cut depth, 0005" cut width, 11mm, feed rate, 375mm/min, it is happy with that combo. Heavier/deeper grinds caused the shaft support bush to get hot and also the top plate started getting warm and
was moving around causing high and low spots, 0005" it barely warms at all.
Another problem is the plate is arc welded on all the way along, as I grind the outer edges it seems to be relieving stress in the plate and it is dipping down in the centre.
Yesterday it pizzed rain and the mill started moving so i knocked off. Today i checked and found that i had been grinding out of parallel to the rotary table so something/s moved and i now know to keep a closer eye on things.
Started grinding this morning and things were not going great, i noticed the sun had come out so i stopped and put the indicator on the job and went and had a cuppa, it moved 8 tenths in that time.
I think i will wait for some nice overcast days to continue with this.
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10th May 2020, 06:05 PM #11Most Valued Member
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That's a pretty good surface finish for low rpm grinding like that, it must be the high feed rate keeping surface speed high,,? I have tried some grinding on my little mill at hone and even at 4000 rpm I was still getting poor finish.
Sent from my SM-G973F using Tapatalk
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10th May 2020, 06:12 PM #12
Hi John,
If you are trying for precision, as soon as things start to get warm it goes out of the window !
I had a read at that "Arter" link, surprising that they say they still have spares for the original first machines that they made.Best Regards:
Baron J.
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10th May 2020, 06:39 PM #13Most Valued Member
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Pics can be deceiving, at the mo it is passable tho as i am only roughing it down with a soft 47 grit wheel, i reckon the wheel looses maybe 2 tenths of cut depth from one side of the job to the other, it is doing 3700 rpm. I have a fair bit of mass there, that angle plate would 15kgs and the arms it is attached to are solid, not hollow, i have counterbalance weights half hanging off the back of the mill table. The support bush also is adjusted with a bit of finger pressure to stop/reduce the chance of the wheel bouncing and causing chatter.
When i get it close to where it needs to be i will put a harder 120 grit over it. Plan B is to mount the grinding spindle on the front face of the angle plate and use a cup wheel to finish. I have to do this anyway as the sides and the underneath of the sides also need to be ground.
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10th May 2020, 06:42 PM #14Most Valued Member
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10th May 2020, 08:44 PM #15Diamond Member
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Great work on the repairs. That would be a very handy machine. Thanks for sharing.
All The Best steran50 Stewart
The shortest way to do many things is to do only one thing at once.
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