Parting off tools and holders

[Agroshield]

Trying to work out exactly how its attached.

On that one, there are four capscrews. You can see the counterbores for two of them at the back - the other two are in the bottom of the T-slot (see the vertical line going down from the end of the capscrew in the diagram). Look up the quantity of part 22588 in the manual for confirmation.

The Chipmaster/Bantam one has six capscrews all on the top surface of the Tee-base. I have a dimensioned drawing of it somewhere I can send you if it would help. Clearly, the actual numbers are too small for a Student, but the proportions might help.

The best guide to how it bolts down will be the top of your cross-slide - what threaded holes are there from the factory.

The Tee-base is so you can set the distance between the cutting edge of the parting tool and the tool in the main toolpost. Turn down the diameter with the main tool up to a bed stop. Back out the cross-slide with the carriage still on the same stop and part off to a known length.

Notice how on the one you show it has two tool slots at different heights, one for right-way-up tooling (reverse spin) and the other for upside-down tooling (standard rotation).

Could I commend to you a Joe Pi video called 'production parting' - the little stop he makes that bolts to the toolpost is very cool. If you have a Dixon toolopst, you can mount it in the station facing the tailstock and on the Morse taper holder that has sat unused gathering dust for 20 years.

 

[Misterg]

This:

I’ve got one of them and I’m very happy with it. It works a treat. I’ve also got one of those 2mm wide insert parting blades that also works very well, even mounted on the QCTP.
(This is on a Chinese 7x14 mini lathe, albeit secured to a decent lump of metal.)

I would recommend them - a lot less messing about than an inverted, rear tool post.

 

[hooblah]

Good to hear. I've gone with the larger size with 12mm tooling (250-101) and i'll be sacking off the top slide and fitting this directly to the cross slide so it's as rigid as possible. Not too fussed making tapered parts. If I need that then I can always mount the compound back on. The biggest issue when using a lathe that's so old is the wear... I have to lock everything down else it moves around.

 

[prepman]

Yes 4 in parts

 

[prepman]

On that one, there are four capscrews. You can see the counterbores for two of them at the back - the other two are in the bottom of the T-slot (see the vertical line going down from the end of the capscrew in the diagram). Look up the quantity of part 22588 in the manual for confirmation.

The Chipmaster/Bantam one has six capscrews all on the top surface of the Tee-base. I have a dimensioned drawing of it somewhere I can send you if it would help. Clearly, the actual numbers are too small for a Student, but the proportions might help.

The best guide to how it bolts down will be the top of your cross-slide - what threaded holes are there from the factory.

The Tee-base is so you can set the distance between the cutting edge of the parting tool and the tool in the main toolpost. Turn down the diameter with the main tool up to a bed stop. Back out the cross-slide with the carriage still on the same stop and part off to a known length.

Notice how on the one you show it has two tool slots at different heights, one for right-way-up tooling (reverse spin) and the other for upside-down tooling (standard rotation).

Could I commend to you a Joe Pi video called 'production parting' - the little stop he makes that bolts to the toolpost is very cool. If you have a Dixon toolopst, you can mount it in the station facing the tailstock and on the Morse taper holder that has sat unused gathering dust for 20 years.

During normal turning operations, do you remove the post/tool? If it can stay in place then it's a real bonus. Otherwise the front quick change wins out.
This is what I thought would work. Shown with an hss tool for simplicity. Couple of locating dowels in base and one retaining bolt. Shim tool to height and leave in block. First draft and not accurate dimensions. Could all change. Already see the necessity for a base.

 

[Agroshield]

During normal turning operations, do you remove the post/tool?

You would only need to do so for very large diameter stuff that would not fit between front and rear tools otherwise.

Drawing with some dimensions here: https://bbs.homeshopmachinist.net/forum/general/1937394-colchester-student-rear-toolpost-help-needed Attached below as you need to log in there to view it full size. The guy who posted it is Mark Presling who has a YT channel, so you might track him down and beg a more recent copy.

 

[prepman]

You would only need to do so for very large diameter stuff that would not fit between front and rear tools otherwise.

Drawing with some dimensions here: https://bbs.homeshopmachinist.net/forum/general/1937394-colchester-student-rear-toolpost-help-needed Attached below as you need to log in there to view it full size. The guy who posted it is Mark Presling who has a YT channel, so you might track him down and beg a more recent copy.

View attachment 350071

Yes I saw this when I was trawling for answers. But I don't think I'll bother with a T slotbase. I don't have a cutter for one thing and the miller is setup for horizontal. Although saying that......all may change and often does Got some good slabs of MS.

 

[prepman]

Have now ordered this.... all change by the second Slitting saw burnt out....so..

Pardon our interruption...

 

[Gritineye]

Be sure to make your rear tool post so that the cutting tool can cut right up against the chuck jaws without hitting anything nearby.

Easy to overlook this but you'll be surprised how many times it comes in useful.

 

[prepman]

Be sure to make your rear tool post so that the cutting tool can cut right up against the chuck jaws without hitting anything nearby.

Easy to overlook this but you'll be surprised how many times it comes in useful.

Yes I was waying that up....easy to slip up and regret later

 

[prepman]

Your most ‘shallow‘ and ‘deepest’ chucks need to be accomodated.

Very rarely change chucks...tend to brutalise everything into the three jaw Making some square stock adaptors.
Inconsistency is my middle name ......though I may change it.......

 

[prepman]

Well now I have the base plate. Orientation is the next decision. Easy to pick up mount holes with it at 90 to the cross-slide. I suppose that'll be the best way too for alignment?
Anybody?

 

[Agroshield]

The right hand side of the photo. There is no advantage and some disadvantage to the left side. The right side allows you as discussed above to set the parting tool relative to the main tool. It also allows you to set it for parting up tight to the chuck. The left way, the cutting force will be trying to slide the upper block in the tee-slots.

It might be the photo or the perspective, but even the right side, it looks too close to the toolpost. Put a holder with a 25mm boring bar in the station above the file and screwdriver. Guess a bit at your upper rear toolpost block and see what measurement you have between them to accommodate the workpiece. Remember that the parting blade has to stick out half the diameter of the work it is parting off. To me, the further back it is, the better. The back edge of it flush with the end of the cross slide is what I would aim for. Make a T-nut for the coolant block and put it on top of the base plate if necessary.

It is difficult to find any pictures of the factory one in situ. I wonder if there is anything to be seen on the 'Colchester Lathes Company' video on YT.

 

[prepman]

The right hand side of the photo. There is no advantage and some disadvantage to the left side. The right side allows you as discussed above to set the parting tool relative to the main tool. It also allows you to set it for parting up tight to the chuck. The left way, the cutting force will be trying to slide the upper block in the tee-slots.

It might be the photo or the perspective, but even the right side, it looks too close to the toolpost. Put a holder with a 25mm boring bar in the station above the file and screwdriver. Guess a bit at your upper rear toolpost block and see what measurement you have between them to accommodate the workpiece. Remember that the parting blade has to stick out half the diameter of the work it is parting off. To me, the further back it is, the better. The back edge of it flush with the end of the cross slide is what I would aim for. Make a T-nut for the coolant block and put it on top of the base plate if necessary.

It is difficult to find any pictures of the factory one in situ. I wonder if there is anything to be seen on the 'Colchester Lathes Company' video on YT.

Looking at the discolouration pattern it appears have used all 6 holes. The top isn't flat as the base plate rocks maybe 2- 5 thou. Might be easier to use the orbital sander than scrape it.

 

[Agroshield]

The top isn't flat as the base plate rocks maybe 2- 5 thou.

Given the source of the base plate, it might not be the best to assume it is flat. My money would be on the Colchester cross slide being flatter than the Chronos base plate. Sweep the cross slide with an indicator held in the lathe spindle to check it. If the cross-slide holes have been used previously, there is some chance that a burr has been raised around the threaded holes, so a light stoning and touch with a countersink can put that right. If you do need to tweak the base plate, first check the top is flat enough and then make the base flat and parallel to the top.

 

[prepman]

onwards....drilled a couple of holes to mount the base. Machined some long bolts to fit t slots.
Very pleased as the flats are spot on. Pics shown extent of travel of cross-slide (fully retracted).
Shaping the ends of the rec' stock was irritating. Kept making misjudgements. Ordered cs skt
hd screws for base.

 

[prepman]

Well it works! Finally got around to finishing it off (as a prototype). Very impressed with the difference. So not a wasted effort.
Much higher feed rate and not a gut-churning excercise. Loking at feedrate, I make it .007"/rev ? Swarf clears away nicely with inverted blade and no judder. Positioning and refining to follow. (or not?)

 

[Agroshield]

Very good. A shallow mesh basket can be used to catch all the parted off bits or a coat hanger wire in the tailstock chuck poked up the hole.

 

[prepman]

Of course it did! Never any doubt. Well done. Everyone who has anything less than a really rigid lathe should have one, if practical.

Certainly was never going to be a wasted effort.

The cutter on mine is mounted in a holder which, in turn, is mounted to the tool post. The holder was designed (I think) for the slightly bevelled cutter, so the tool,post has a simple rebated slot for the holder. Makes no difference to the operation, but on occasions the extra stiffness of the holder helps if the cutter .needs extending from the post

I bow to you Oh Master. You are my inspiration. In other words... you where spot on, the difference is very noticeable.

 

[prepman]

Very good. A shallow mesh basket can be used to catch all the parted off bits or a coat hanger wire in the tailstock chuck poked up the hole.

Taken out of context it would sound like some sort of fetish....but I get your drift.