Tool post build

[nickel-city-fab]

Paul, ???? WTF? When I was using an Enco 4-way tool post, it was perfectly on-center for 1/2" tool bits in the SB. So I loaded it with 1/2" tool bits and that was it. No shims required whatsoever.

[Doozer]

If you grind the top of the toolbit for whatever grind you are shaping,
then the cutting edge is below center, yes? I think this is what Paul means.

-D

[nickel-city-fab]

If you grind the top of the toolbit for whatever grind you are shaping,
then the cutting edge is below center, yes? I think this is what Paul means.

-D

Probably.
But I don't grind the top at all,
preferring a neutral rake most of the time.
Even in mild steel.
Its that whole thing about keeping it simple.

[Doozer]

I am a positive rake kind of guy.
I like positive back rake and side rake.
Lower cutting forces and more accurate finish cuts.
But that is why there are so many different kinds of beer.
I love being able to adjust the height of my QC toolpost.
Aloris or the like. Especially if you run a boring bar.
Always want to run them a smidge above center.

-D

[J Tiers]

You must not be taking any material off the top of the blanks then. ......................

And there you have it. That, and insert holders that keep the height the same as the top. Of course that is the deal.... I may be a fool, but I am not a damn fool. Of course you have to do some things to keep the height correct.

I have a few hundred toolbits of all sorts, collected from sales over the years. Usually some goofy thing is just what I need to do some odd thing, and I pull it out, modify and use ..... Some of them, that do not get used as-is, have the edge halfway down through the thickness. That's not what I do.

BTW, you CAN put in a chipbreaker, but if you grind back enough to get into it, you have to grind through it and start again.

Is it limiting? to some extent, sure. But it is not so limiting that I have to change what I do.

Am I refusing to buy a QCTP? Nope.... I'll do that when the price/benefit ratio gets to where I like it. The Bostar is getting close, and folks are not saying it is trash......

The other issue is center height. That drawing is modified to cover the guy who was asking, whose center height was 1.5". mine is 0.875", and there is much less material under the slots.

Is every one of the slots perfect? Nope.

I didn't make the post, it came with the machine. So, since I had to take a little off the compound top, due to dings and damage, I had some wiggle room. I use a spacer under the post, which puts two of the slots virtually exact, while the others are split around the ideal. But none of them are bad enough to be a problem even when working on features that may only be 0.080 or so in diameter.

It's a good approach, and for cases where you just have to get into the last thou (which is hardly ever) nobody will stop you from using a shim. Just because I don't need to has nothing to do with you.

[Paul Alciatore]

Well, I am glad it works for you.

I do retain my observation from years of working with the simple, one position tool post that came with my Unimat. Perhaps with a four position tool post there is less need to change tools and therefore things work better.

Sorry to burst your absolutism, but it works.

It's a really odd thing but the toolpost does not realize that it actually does not work.....so it just keeps working as always. And it really does not care about your opinion, when you have not ever used it.

Have never used a shim with it, and for some reason it puts things on center no matter what any armchair critics think.

[Paul Alciatore]

Neutral rake! Well, there you go. But if you use a tool with either positive or negative rake, then the height WILL change when you sharpen it.

Perhaps that should have been stated so the poor newbie does not go chasing after ghosts.

Or do you just toss them out when they become dull? I guess that would work.

And thank you, Doozer.

Probably.
But I don't grind the top at all,
preferring a neutral rake most of the time.
Even in mild steel.
Its that whole thing about keeping it simple.

[J Tiers]

............................

Or do you just toss them out when they become dull? I guess that would work.
......................

No need. The beauty of a neutral rake is that you need only sharpen by grinding the "front" face of the tool, for standard HSS or brazed tooling. Insert tools are consistent in presentation of the edge as inserts are changed, regardless of rake, so it is possible to make the post to accept whatever tool you happen to have.

While there is an argument to be made for the positive rake as a lower power-demand cutter (perfectly correct), you may recall that I am an advocate of the "slicing" cutter, a cutter which has the edge straight, and presented to the end of the part (edge at the left of the cutter blank). That makes a cutter with the edge right at the top of the blank (as required) and also can have considerable rake across the tool blank (as desired). If sharpened regularly, a surprisingly small amount is taken off, and the change of edge height with sharpening is a non-issue for many many touch-ups. Tools which are noticeably lower are still perfectly usable for larger work, so nothing is lost. So far I have not needed to "downgrade" more than one or two cutters.

Another point is that the necessity for absolute location on center is not a given for every workpiece. The larger the work, the less a given absolute error changes the cutting action. Conversely, the smaller the part diameter, the more important the height. So there is considerable scope for small errors to be tolerable on the bulk of lathe work.

Given the ability to slap a tool into the post without concern for height in most work, contrasted with piles of shims that must be adjusted for each tool change, I will (and do) happily accept the convenience in most work as more than adequate compensation for needing to use a special tool for small accurate work. That is especially true since one usually changes to a special tool for small delicate work anyway.

Incidentally, if one is not provided with a special toolpost such as that illustrated, it is easy enough to make a single block to raise any size of tool to the correct height using an ordinary 4 way, or single position post. While semantically one can call that a "shim", it is certainly not a wobbly pile of various thickness shims. So, much of the same result can be obtained using a traditional 4 way by making a block for each size of tool in common use.

In fact, for one lathe I sold a while back, I made a single position (English style) block post. I equipped it with 3 or 4 of those blocks, stamping each with the size it was made for. It was no issue to use, and the buyer appreciated it.

[nickel-city-fab]

Yes, you are right that the height will change when using a full grind. Nope, I just hone them when they get dull, preserving the existing shape. Usually just the front and side is all it needs. Most of the time I use carbide nowadays, and that does definiteltly need to have the height changed depending on the tool. Which is why I switched to a QCTP. They're just much more convenient, and smaller.

Neutral rake! Well, there you go. But if you use a tool with either positive or negative rake, then the height WILL change when you sharpen it.

Perhaps that should have been stated so the poor newbie does not go chasing after ghosts.

Or do you just toss them out when they become dull? I guess that would work.

And thank you, Doozer.

[J Tiers]

Yes, you are right that the height will change when using a full grind. Nope, I just hone them when they get dull, preserving the existing shape. Usually just the front and side is all it needs.

Yep. That does keep it simple, doesn't it?

Inserts of course cost more but have the same result.... no change.

[nickel-city-fab]

Yep. That does keep it simple, doesn't it?

Inserts of course cost more but have the same result.... no change.

To be completely fair, the inserts that I use have a very high positive rake, and only cost about $1.50 ea. They are much more convenient from the standpoint of repeatability and standardization. The drawback is that every insert tool that I have requires a different height, and stocking a different insert ($$)