Quick change toolpost

Hi,

just a quick question.

as per the earlier post, I’ve struggled a bit to get certain tool bits on centre, if I buy a qctp which I’m interested in, does it mean I can basically use any size tool and can move the tool bits up and down in the holder with the adjustable screw.

thanks

chris m….

Hi Chris,

Yes, you can as long as the cutting edge can be set at the lathe centre line. There will be a limit to the size of the tool.

Thor

For any given tool-holder, there's always a maximum sized tool it will accommodate. The maximum depends on the lathe and the QCTP that's been fitted to it. Buying a QCTP won't solve all tool height problems at a stoke.

The safest solution is to find out the maximum sized tool that the lathe will take and buy the next size down. In theory my lathe will take 12mm tools, but I generally use 10mm or smaller because they can always be shimmed to fit. Once the size has been identified, it's easy thereafter.

Dave

Just because a QC Tool Holder will take a 12mm(for example) tool doesn't mean that there will be enough movement on the post to get the tool to centre height on the lathe.

There's no real reason to use such large tools on most of our lathes - I use mostly 8mm on my WM250, which I bought for the mini-lathe that preceded it but 6mm would be entirely adequate. A homemade tangential tool with a 1/8" square bit does a lot of useful work....

My cheaper, no makers name QCTP works OK with the toolholders purchased to go with it but the supplier has discontinued the system and now I'm stuck as other makes don't fit or only with difficulty. False Economy! Reason seems to be like what was described by a contributor in a recent copy of MEs Workshop. Another darned roundtoit! I did find that fairly small tools fitted, allowing height adjustment as detailed above by Nicholas. Hefty tools are only suitable for very large lathes tearing off great depths of cut or shapers where there are considerable stresses involved with the tool bashing the work at the start of each stroke.

QCTP drawings usually show the distance from the centre of the spindle to the mount face f the post.

When I enquired about it, the swing was mentioned(330 in my case) this guides you to a maybe suitable toolpost setup. Then the centerline of the spindle was important and eventually the toolpost you get will allow you to get certain sizes of toolholder with insert tips actually on centre. I can get 6mm, 10mm, 12mm, 16mm on centre, I think i must shim the 6mm, but however if you have enought QCTP toolholders its not an issue anymore. My QCTP Toolholders has a gap of 20mm, I have not tried a 20mm toolholder, it will probably not work, cannot shim down.

I assume various makes will not have the same variances possible even though they qwote from a swing number, was confusining initially.

Many have given good advice here - stick with the smaller size cutting tools - 6x6mm is great for most jobs, up to 10x10 if you are into heavy stuff, or work requiring longer stick-out of the tool.

If you are using mostly HSS cutters you will inevitably get into grinding your own cutting edges, and making a single point tip from a virgin 12x12mm HSS blank is a lot of work on the average shop grinder.. I was given some ( 30 off..) 25mm x 12mm x 150mm blanks many years ago - they were Swiss made, and a very nice steel indeed - mostly they are used as spacers in the mill and shaper. They do fit my bigger lathe but grinding is not worth the effort.

A lot of beginners seem to want a QCTP. system. I did too and somewhat regret having done so. They are not as rigid as say a 4 way holder and to get the full benefit you will need a lot of holders. This finishes up as being one very expensive exercise.

I do use my expensive QCTP, but revert to a 4 way holder or even mount the tool on the topslide (a la Myford holder if I have any serious metal removal to do.

I also use HSS tooling and indexable tooling. Maybe it is just me, but I can always get a better finish with HSS,

My advice is to use the sizeable wad of money that a decent QCTP will cost and spend it on other real essentials that you will find the need for as you progress. If money is no object then treat yourself to a QCTP system.

Andrew.