Rotary Table Problem

I have one of Warco's HV4 Rotary Tables which has not been greatly used in the 7+ years I have owned it. However, I want to use the table on an item about 2.5" diameter, held in a mandrel in an ER32 collect chuck. The collet chuck is screwed onto a fitting with a M2 Morse taper into the rotary table. The fitting was turned true in the lathe having been secured to a M2 blank end arbor fitted in a M2 to parallel adaptor and set up to run true, so I was sure this item was good.

Out of interest, having set up the part on the mandrel in the collet chuck on the table I clocked the part which I had just turned true with a DTI. It showed about 0.010" run out of true over the 360 degrees. Checking why, I put a brand new M2 blank end arbor from Arc with a 1.5" diameter end - this I reasoned should - must - run true, it didn't.

Then I found that although I had put the new arbor in the RT M2 taper securely (I thought!) there was slight movement on the top. 'Bluing' the new taper and trying it in the 'hole' showed that it fitted well at the bottom but was not touching at the top. I then tried it in a M2 to 1" parallel adaptor - perfect fit.

So the conclusion is that the M2 hole in the RT is not true and required remedial action.

My thought was to run a M2 reamer down the hole, but wondered if this would work, would the hole be too hard for the reamer, would the reamer ream true or at an angle?

I thought that if I centred the RT under the quill I could hold the reamer in the quill and gentle do it, which would hopefully make it ream true, but would the material being reamed be too hard?

Anyone been down this route? Any advice or thoughts other than using a reamer?

Chris

Try a needle file on the hole and see if it's hardened. .

If not, centre it on bore and use MT reamer.

If it is hardened, you will probably need to tilt RT at an angle and use a carbide tip boring bar in mill spindle to open up bottom of hole. Going to be some math and trigonometry involved if you need to bore it

You could always use a milling MT socket designed for a draw-bar which will probably pull things into a rigid setup?

All you would need is a 'top hat' washer underneath and correct bolt

Edited By Peter Jones 20 on 11/12/2020 19:30:47

Hi I fitted the rotary table on to a faceplate on the lathe and clocked, with a dial indicator, the outside of the rotary table then I wound the rotary table and it ran true. Next I checked the center bush and it ran out and after setting the angle on compound slide found angle was also out. Using a dremmel mounted on toolpost and a grinding wheel I then trued up the center bush. Problem solved.

David

Edited By David George 1 on 11/12/2020 19:33:00

Don't you need a pretty large lathe to do a set up like that?

I could have done it when I had Colchester (10" dia over cross slide no problem) but with the machines I have today it wouldn't be possible

Chris

Might be worth touching the edge oif the hole at the top with a file to see how hard it is. It has to be reworked anyway so the very minor damage will be of no account.

I've seen it said that generally the centre holes are no harder than the table itself but have no links to authority to back up that statement. I have seen rotary tables with parallel bores showing minor abrasion marks suggesting that they were not hardened.

If done carefully power driving an MT reamer works well to clean up an internal taper. Take it steady, use plenty of lubrication and enough pressure to keep the reamer cutting. I did similar, albeit the other way up, to refurbish the MT 3 taper on my Pollard 15AY pillar drill which was in very bad order.

Even with limited depth of material to remove the taper shifts up the hole by a considerable amount. Nearly 1/4" on my Pollard. Worth the effort as it now takes almost no effort to make a good taper stick.

I'd go for it. Think I got my reamer from Chronos, mid-range value for money price. Not super cheap but not high end super quality as I only ever expected to do the one serious job.

Clive

If it was fitting at the bottom but not at the top it would indicate the wrong taper, something protruding at the bottom (not allowing the 2MT arbor to seat fully) or something impacted in the 2MT cone.

I have a chinese 2MT ER collet chuck that was definitely not 2MT taper. Luckily at the price I could afford to throw it away (although I still have it as an example of typical cheap chinese tat). Not much chance of redress from Warco after all this time, but they might just rectify it for you, if asked nicely.🙂

Always worth checking carefully on arrival, if bought second hand on epay, or within the warranty period if purchased new.

Chris, I would forget about the taper & put the mandrel in a 3 jaw chuck if you have one & indicate the part true to the rotary table rotation.

Tony

Peter - David, thanks for the prompt replies. I see Arc's M2 reamers are to HRC 60-62 which is encouraging! Might just tackle a hardish bore, but I will try a needle file test first as suggested. Needless to say I do not have a M2 reamer!!

I did clock the top of the RT, thinking it might have a slight list relative to the mill table, but it was spot-on. I didn't clock the bore but will do tomorrow - I do hope that it runs true, I don't fancy having to grind it true, for a start I haven't seen a grinding wheel on a long enough shaft to put in the Dremmel to get all the way down the bore. Don't fancy having to machine it with a carbide boring bar either for that matter.

Peter - are you suggesting one solution might be to replace the M2 socket in the RT ? - I hadn't thought of that one.

Chris

Is the RT centre hole other than a Morse Taper would be my first question? I have in the past found RT's with B&S tapers - close to MT but not close enough! A lot of American equipment uses B&S tapers and I think older Chinese / Taiwanese stuff was aimed directly at the US market.

If you have a range of ball bearings you can measure the taper and check whether it is MT or not by differing size of balls dropped down the hole and measuring the depth they give.

Edited By Oily Rag on 11/12/2020 20:05:35

Reams tend to follow the original bore on this type of item, you would have to bore the hole true before reaming you could remove the bush from rotary table and check for concentricity or replace the bush with a new one or make a parrallel bush of any size you like.

David

If it were mine, I would put the shorter test bar in a four jaw chuck and get it running true with the MT2 end sticking out. Then I would remove the top of the rotary table and fit it on the end of the MT2 bar. A Morse taper extending socket often has a parallel large end and would also chuck up nicely, just zero the runout on the male taper. The bearing inside the RT top could be carefully turned true to the internal MT. Then a bush could be made to run the halves of the table.

The Soba 6" RT that I bought privately had a large ammount of radial play, and I chuckad the needle roller bearing in the bin and turned up an aluminium bush with 0.0005" clearance and greased it and it has been ok for years now.

Edited By old mart on 11/12/2020 20:12:29

Huh, by the time I had posted my second post there were another three posts I've only just spotted - better read them now!!!

Chris

The taper in the RT is supposed to be M2 according to the spec but as NDIY deduces the taper is wrong, hence it only fitting at the bottom. As far as I can see, there is nothing protruding at the bottom and nothing impacted in the bore, it's clear as a mountain stream. I will test the bore is running true, test if the bore is hard, and if all is good then buy a reamer and give it a burst.

Chris

Chris,

If this is a short taper (i.e truncated) it is quite possible that it is a B&S taper and a #2 MT will go into a #7 B&S taper but the tapers are 0.050" per inch for a MT and 0.0418" per inch for a B&S. Is your RT taper mouth size 0.700" and how deep is it? Big end dimensions are 0.700" for #2MT and #7 B&S is 0.720"

I'd agree with that. Personally I'd dispense with the Morse taper and have a parallel bore. Much easier to make fixtures to align parts.

Andrew

Fixing the Morse taper will get your fit, but as already mentioned, the reamer will follow the hole. If the parallel hole appeals to you, then boring at least part of the depth of the hole would be the answer, but check the wall thickness first. The bored hole will have to be in line with the od of the axel that the top runs on. If you hold the axel in a three jawed chuck, it will only run as well as the chuck jaws.

.

+1

My little BCA has a parallel bore in its 8” rotary table

the fancy pin which registers the tilting head in its ‘trammed’ position also fits that bore ... and its tip has a very slight ‘lead-in’ taper, which locks it in place quite securely. [*]
The knurled head of the pin has a female centre drilling, which is convenient for preliminary location of the table.

MichaelG.

.

[*] The bottom section of each hole must presumably therefore, be similarly tapered.

My little 4" table has a short parallel 1/2" diameter centre hole at the bottom of which is a tapped hole. This is really useful for holding things down like rod ends for rounding off.

Thanks for that Oily Rag - will measure the taper mouth tomorrow as well.

Andrew, Old Mart - a parallel bore, now that has given me something else to think about. Quite like that idea, especially in the long term. Options, options, Guess what I will be thinking about as I go to sleep shortly!

Michael - I am not following your last paragraph, but it is late at night.

Chris

Just a final thought for today - does anyone know how the MT bore is held in a HV4 rotary table, like is it a press fit, secured by adhesive, have a locking screw, whatever else comes to mind?

Chris