Chinese 200 Series QCTP

A fellow group member and I are both experiencing a little issue with
the 200 series QCTPs fitted to our BH600 lathes. With the post central
bolt tightened to a "normal" level the post sometimes rotates when the
tool holder is unlocked/locked. Being a practical sort my solution has
been to really tighten up the post but I wonder if anyone else has
experienced this and found a more elegant solution. We have checked
the usual things to ensure that the post is flat on the bottom, the
bolt thread is clear, the T nut is below the top slide surface etc but
haven't found anything obvious. Has anyone else had a similar problem
and cured it? Otherwise, just how hard should we expect to tighten the
central bolt holding the post?
Thanks
Keith
Reply to
jontom_1uk
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Keith
I solved a similar problem by inserting a small piece of 'non-slip' matting - shelf liner type material, looks like an old Aertex vest - between the underside of the toolpost and the topslide. I also tried fine emery cloth, which also worked. --
Chris Edwards (in deepest Dorset) "....there *must* be an easier way!"
Reply to
Chris Edwards
I have one of these on my Harrison L5, but as it doesnt have a t slotted cross slide Ive had to use a long M12 bolt and make some spacers to fit the bore. I havent had it shift on me, but I do tighten it up quite a lot. I use about 12" long ring spanner on the bolt.
Dave
Reply to
dave sanderson
Never had my one move either and I'm not brutal on tightening. Must be a BH600 issue rather than the toolpost
Charles
Reply to
Charles Ping
Keith, The answer must lie in two flat- flat surfaces being together. Frankly, if that was the case, the whole gubbins would not have moved. The logical deduction must be that one or the other surface is concave- or becomes distorted upon tightening.
Is there any practical experience of a top becoming concave? My Myford long top slide on the saddle had been pulled out of shape with incorrect bolting down by the previous owner. Now George Thomas also refers to the problem in Model Engineers Workshop Manual. Again, 'Martin Cleeve' made a fabricated block for milling and this kit is or was sold by Blackgates. When I had a Axminster 9180- near a 918, I built a steel subtable following the afore mentioned concepts. Coming back to your own problem requires a possible solution. assuming that the top is or becomes buckled, it is pretty difficult to surface grind or scrape it flat- flat and it would thin the lot if done. So, I would hollow the bottom of the tool holder around the bolt hole to leave a ring. Again, has this been done? The answer is that Cleeve did it on one of his fabricated tool holders with great success. I had one for years.
If you follow Cleeve through on a ML7 top slide which he made, his single bolt at the side- mark you- held despite being only finger tight.
I may be wrong- but it is worth a try Cheers
Norm
Reply to
ravensworth2674
Thanks for all the ideas Guys with help I hope that I have finally found the problem with mine.
Chris, thanks, I had forgotten about the lesson we were all shown that a piece of paper wrapped round a MT in a worn socket could stop it moving. My only excuse is that it was a long time ago!
Dave, my post is fitted with a locking lever (just welded to the nut) but it is only 4 1/2" long so will not produce anything like the torque your ring spanner will; when I've fixed what I believe the problem to be I'll think again about if the handle is long enough. I have an aversion to bashing handles with my hand as I've seen a few hands damaged that way.
Charles, I can't really blame the BH600 (do I sense a tinge of "yuck" in your comment :-) Vbg) However, the mounting system supplied by the importer is I now believe part of the problem.
Norm, thanks for your pointer and I have previously used the principle of relieving the centre to allow a firmer "ring" contact with total success. The BH600 however has a very wide T slot (1 1/4" wide) and so contact between the tool post and the top slide is actually two strips 5/8" wide by 3" long. Your other comments about possible distortion was also very useful as checking for it led me to find what I believe is wrong.
The T nut supplied is some 5/8" thick and as I said very wide so one of my first checks was to ensure that there was a gap between the bottom of the post and the top of the T nut so that proper clamping force was exerted. This checked out fine at the front with a .005" feeler having no trouble entering the gap. However, on further checking the back of the post, it doesn't; in fact a .002" feeler is grabbed by the post as soon as you start to tighten it. Obviously either the T slot is not parallel with the top surface of the Top slide or the T nut is tapered. Either way I'll mill the T nut thinner and that should (fingers crossed) cure the problem. No time today so it will have to wait until the domestic authority is satisfied with the progress on the bathroom.
One other question on this toolpost, it has a 3/8" UNC tapped hole in one of the side faces, any idea what this is for?
Thanks again to all, enjoy Harrogate if you are lucky enough to be going.
Best regards
Keith
Reply to
jontom_1uk
Hi Keith,
I did try to avoid the apparent teaching you how to suck eggs( which I can't) and a cry from the heart but it did happen to me.
Somehow, it does suggest that we go off at a tangent and think of blueing in and scraping everything in that imaginary circle to mate. Don't fire rude remarks as it ain't according to proper workshop practice- you experts!
I did mention a sub table which can be bolted down so as not to slip but you can bugger about with it- and not lose precious metal.in the lathe itself. Has it been done? Well, 'Cleeve' did it and so did Prof Chaddock.
Meanwhile, Keith, I am also up to the curly bits in work and I am trying to get to Harrogate- with John's bottle.
Have domestic bliss
Norm
Reply to
ravensworth2674
Norm, guilty as charged :-). Missing the obvious is a major tendency with me, despite being told about it many times. I'm much more interested in "that" obtuse and complex piece of emerging engineering that "really" causes all the problems. I expect you have seen this but I think it is typical of me (and not only me?):
"The Lone Ranger and Tonto are camping in the desert, set up their tent, and are asleep. Some hours later, The Lone Ranger wakes his faithful friend. "Tonto, look up and tell me what you see." Tonto replies, "Me see millions of stars." "What does that tell you?" asks The Lone Ranger. Tonto ponders for a minute. "Astronomically speaking, it tells me that there are millions of galaxies and potentially billions of planets. Astrologically, it tells me that Saturn is in Leo. Time wise, it appears to be approximately a quarter past three. Theologically, it's evident the Lord is all powerful and we are small and insignificant. Meteorologically, it seems we will have a beautiful day tomorrow. What it tell you, Kemo Sabi?" The Lone Ranger is silent for a moment, then speaks. "Tonto, you Dumb Hoss, someone has stolen our tent."
The BH600 has a relatively high topslide and even though it is a 6" lathe, with the 200 series post you can only use tools less than about 15mm high. There is just no room for a sub table. As you will know from your 9180 Norm, the mounting on those is in effect a sub table, one of my most successful improvements was changing mine to a four bolt sub table.
Norm, hope you enjoy a good ride over to Harrogate in that new mini. Take care with that bottle you know how "cranky" John can get when he is thirsty! I'm sure that a long day serving all those "nice" customers and explaining the CNC at least a thousand times will make his throat very dry. He'll be "right pleased" to see you.
Thanks again Norm, take care.
Keith
Reply to
jontom_1uk
Eh? You have a bar welded to the nut? Doesnt that get in the way? (QCTP not 4 way TP?) or are you using the 4wtp locking lever? I have a locking lever in the top conical piece(silver on mine) and then a nut on the bolt that goes through. I had to make some end spacers for the tube which sits in the hole to reduce that to 12mm(ish). I did notice that if this tube jams slightly then locking/ unlocking the slides becomes quite hard, which might be part of your problem? With no toolholders on the post the tool locking lever is spinnably free when its all clamped up correctly. Mine is the set from arc euro if a picture helps to see if its different.
Dave
Reply to
dave sanderson
Dave
I have what looks the same QCTP but mine came from Warco and is about 5 years old, it is marked "250-200" China. The "bar" is welded at a 30 deg (upwards) angle to the nut on the through bolt, it's all black and obviously done at manufacture. At that angle it clears the toolholder slide locking lever. I therefore have two levers and don't require a spanner at all. I find it a nusance as I'm always unlocking the wrong lever and may well revert to a normal nut and spanner to avoid my lack of attention. My central tube is about .040" higher than the silver conical piece and does not seem to have any interaction between the silver conical piece and the central tube, I can see however that this could well happen if the tube was a little too short or rather a tight fit going through the conical piece or even if the two pieces were not concentric. Dave, hope that explains a little more clearly what I have.
Best regards
Keith
Reply to
jontom_1uk
Apologies Charles, no slight intended. It's just my sense of humour or what's left of it after battling with a few feet of copper pipe all morning. Lunch didn't taste much of other than cardboard either so must be just a bad day.
Best regards
Keith
Reply to
jontom_1uk
Yes I follow that. Mine is marked the same, but came with a nut, a post and iirc a large square theaded bit to make your own t nut from. Would you like a new post etc? I cant ever see me using mine, so its surplus if its of use. drop me a mail off list to small dot planes at ntlworld dot com The spacers I had to make were because the tube in the post is much bigger than m12, which is all that would fit through the harrison topslide (metric bolts free issue where I used to work, imperial didnt) and without them the post wouldnt sit nice and turn/tighten up square etc.
Dave
Reply to
dave sanderson

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