Thread: Orden TC grinder

Hi pipeclay,
using centres in the lathe is the same as using Bench Centres.
You spin the actual shaft by hand nothing else.

Phil
Precision-Inspection-Bench-Centres.jpg

Gee Phil - you should know better than to post pictures like that!
First you will have Stuart thinking that he needs one for his indicator collection, then he'll tell us of all the wonderful things he's done on it so a few of the rest of us will decide we have to make one and then...

Michael

Originally Posted by Bryan

The 3 jaw puller did the job with a minimum of force. Which allowed me to mount the spindle between centres and clock the bearing journals for runout - which was the whole point of the exercise. And runout there is - about .035mm at worst. I tried to set the journals on V blocks and clock the tapers, but my setup was too crappy to get meaningful numbers. Will see what I can do about that, but it's probably academic as I'll need to either try to straighten it or make a new one. I've had modest success straightening slender shafts with a cheap press and patience, but this one is short and chunky. Not much to lose by having a crack I suppose.

Bryan - an overnight thought. Have you checked various places along the shaft? The shaft is chunky and I wondered rather than it being bent whether it has been bad from new. To manufacture a shaft like that the method is probably rough it out on a lathe and then grind the ends so if it was not set up properly it may be that you have vibration just from an eccentric mass. The fix for that could be a skim of the centre section. Bent I'd expect to see a point of maximum TIR but if eccentric there should be the same TIR in several places.

Michael

Originally Posted by Bryan

The 3 jaw puller did the job with a minimum of force. Which allowed me to mount the spindle between centres and clock the bearing journals for runout - which was the whole point of the exercise. And runout there is - about .035mm at worst.

I haven't got the time to think about it too closely, but it seems to me that all you've demonstrated is, that there is runout on the bearing area WRT the centres. That does not *necessarily* demonstrate that there is runout WRT any other area. It's indicative but not definitive. The centres could be out.

I think you need to mount up 3 gauges, 4 would be better, one on each of the machined bearing areas and one on each of the tapered areas. See what runout patterns you observe. Or clock each area separately and record the results on the shaft with a fine tipped pentel pen etc.

PITA doing this sort of stuff - I just spent time tweaking my Chipmaster to turn parallel between centres and got it down to 0.0002" over 5" which was as good as I could manage. I did machine the HS centre in position before I did anything else.

PDW

Hi Brian,

I think here are two things, one is runout, the other is balance.

Even if the taper run out relative to the bearing location is zero, there could be runout elsewhere causing vibration.

If it turns out that it is a bent shaft, what next?

Try and straighten it?
Machine a new one from scratch?
Find someone with a cylindrical grinder?

I'm going to suggest that you ignore it... and re-assemble the head, then with the thing running, figure out a way of holding a TPG or similar, or maybe some other existing attachment, and regrind the taper in-situ with the spindle running.

Regards
Ray

Ray, I like your thinking. Actually that was the first thing that occurred to me, some kind of in-situ truing, but I decided I wanted to know what was going on in there.

Michael, Peter, I did clock it at both tapers and both bearing registers and the error was greatest at one of the registers: .035mm. The amount and location (o'clock) of error was consistent at each place after repeated tests. So I'm convinced the shaft is bent. Attempts to straighten it with my little press were completely futile.

In short, I assembled it and it's now showing .05mm TIR at the wheel arbor. That's about half what I got previously. Why I don't know. Maybe I goofed. Maybe there was an assembly problem. Anyway what matters is, how much runout can be tolerated? Given that the wheels are not a tight fit on the arbors, and that they get trued anyway. I don't have a wheel yet but I powered it bare and vibration was negligible. If it vibrates too much with a wheel I will consider ways of truing the taper as Ray suggested.

To put the project in perspective, all I want to do at this stage is single point tools and maybe drill bits. Super finishes are not required. And start to learn a bit about grinding. If I can achieve those things for minimal cost I'll be happy. And just for the record, I knew this machine was a roughie when I bought it, I'm happy with it, and its condition is no reflection whatsoever on Harty.

BTW, where do you guys buy your wheels (online)?

What size wheels are they Bryan?

I get norton Surface Grinder wheels (12" x 1" x 3") from my local place, anywhere that stocks norton should be able to get them.

the only online place i know of is AbTec in the UK Abtec4Abrasives / Sanding / Grinding / Polishing

Cheers,
Ew

Bryan (and Ewan),
you may or may not recall that I have a few 12x3x1 and 12x3x3/4 grinder wheels 'surplus'.
Let me know if you can use them.

Thanks Joe, but I want a cup wheel, 125mm as far as I can tell.
The only online source in Aus I know of is https://www.bolt.com.au/straight-cup...1007_1008.html
Postage I think was about a $13 minimum a year or two back. Guess that's ok.

Hi Bryan,

I've picked up a few CBN wheels on ebay, a bit mixed, but there are bargains if you are patient, if you want to buy on-line then travers have a pretty good range Flaring Cup Grinding Wheels | Travers.com

I've bought wheels from Australian Industrial Abrasives they don't sell much on-line, the hardest part is figuring out what the best solution is for whatever you are grinding, for general use, white alox is a good starting point.

Regards
Ray

Hi Bryan,

Do you have more than one wheel arbor?

Stuart

Originally Posted by Stustoys

Hi Bryan,

Do you have more than one wheel arbor?

Stuart

I have a rouge spare here....now there are plenty of different tapers around but you never know your luck. If not it may fit your grinder Joe-or someone elses. I'll measure it up tomorrow.

Ew

If you're going to be changing wheels on the arbor and not arbors on the shaft. I can't see your runout being an issue.... though I've been wrong before. Though I'd say it will be an issue if you end up with multiple arbors with diamond/CBN wheels.(based a sample of one lol)

Originally Posted by PDW

I did machine the HS centre in position before I did anything else.

Well if arent going to machine it is one setting the that will help, but if you are, it doesnt matter where the HS center is(though it sure will help if you have to remachine it at a later date)

Ray, yes white alox will be my starting point. I forgot I actually have a thin flaring CBN wheel I got from an ebay seller in eastern Europe a while back. Seems very fine and may be good for finishing and touch ups, but alox will be needed for shaping (should have mentioned I don't use carbide tooling). I recall looking for surface speeds for CBN and not really finding any. Is it supposed to run faster than alox? Also I'm thinking since you can't true it AKAIK, your setup would need to be good. That's why I couldn't get it to work on a bench grinder.

Stu, I only have one arbor at this point, but hope to make some more.

Ewan, Harty said he couldn't ID the taper. It's nominally 1" x 3/4" x 1" long.
Finding one or two would sure save me some hassle.