Boring Opinions (heh)

[tom_d]

Could just use a vee block with an indicator stuck to it, to set the cutter heights off the surface of the bar. I've seen multiple holes bored simultaneously this way, many times before. It's not that hard to do. (provided somebody wasn't out drinking the night before)

If the cutter is mounted in a through hole, and is not too long, it will not protrude on the side opposite of the cutting edge. This feature can be exploited by simple measurement with a depth mic from the boring bar down to the back end of the cutter. Note the reading and adjust the cutter as needed. (Remember that a 0.010" change in cutter position will change the hole dia. by 0.020")

[BCRider]

TMB, in response to your reply #11 to my rather long post....

It may not have been clear that I switched horses in the middle of the stream. The first part was to use your lathe with the line boring bar as suggested by others but to try to get away from the area with the most wear.

But at the point I was suggesting adding weld bumps and machining them the idea had shifted to using your Lagun mill. But as mentioned you can't really use a boring bar in a boring head that is long enough to do all four holes at one go. WAY too much flex.

At that point I wandered off on the idea of how to create reference features on the two weldments. From your reply I think that seems to be where I lost you. And I can't say I blame you. Even reading it myself it's a bit of a messy explanation.

The TLDR version is that if you can make consistent reference features on the two pieces you can use those to flip the part around and line it up vertically after drilling and boring down through the first two bearing plates and re-align the part to allow you to drill and bore the other two end plates and have the whole thing come out true within only a few thousandths. And it can all be done right in the mill that way.

The problem which you already know is that due to welding distortion you can't really trust the welded assemblies to be true and square. The idea behind skimming at least one of the open faces is that it would give you a that one needed flat reference. And you'd want that anyway because that would become the face which is bolted to whatever it gets bolted onto since that would be the reference you use for setting the bore heights.

And the reference spots cut onto the sides of the tubes on one or both sides would be the spots you would use to square the unit the other way while the reference face is clamped to an angle plate.

Is that any more clear?

Of course this does assume that you have a nice big angle plate you can use to hold the part.

[dian]

Just going to throw something out. Your material WAS t6 temper aluminum BEFORE you welded it. Now you have T0 temper material. Rerun your stress calcs or re heat treat and age it back to T6 temper.
I learned this the hard way on welded suspension arms for a SAE Mini Baja project in school

not really. it will mostly be in w-condition and harden somewhat with time (several days). not much more than 50% ys of t6 though (t4). for annealing you need several hours at temp.

[The Metal Butcher]

I'm going to go with a single cutter.

[nickel-city-fab]

Seems like the bar between centers with 4 holes to mount the cutter in would be about the easiest. A jig could be easily made to allow setting the cutter to the same height for each position. The problem changes from how do I ensure all bores are inline, to how do I make the minute adjustments required to get the bore sizes just right.

Could just use a vee block with an indicator stuck to it, to set the cutter heights off the surface of the bar. I've seen multiple holes bored simultaneously this way, many times before. It's not that hard to do. (provided somebody wasn't out drinking the night before)

[SVS]

I think four cutters would be a way to screw up four times as fast. I can see it for heavy equipment with portable rigs and travel limitations but I don’t see it as best practice on an HBM or substitute there of.

[darryl]

Seems like the bar between centers with 4 holes to mount the cutter in would be about the easiest. A jig could be easily made to allow setting the cutter to the same height for each position. The problem changes from how do I ensure all bores are inline, to how do I make the minute adjustments required to get the bore sizes just right.

[nickel-city-fab]

Plan looks good, Sure theres stuff I would do differently, but its nothing that matters, just preferences. Get some sleep before you make somebody else sick.

[tom_d]

My plan ATM is this:

1. Find appx center on each end and center drill.
2. Mount a big angle plate loosely to the compound ring on the Lagun.
3. Using a headstock center and a tailstock center, put the part between centers.
4. Now that the alignment is fixed, clamp very securely to the angle plate. Tighten angle plate bolts. If possible, run a big C-clamp from the part down onto the cross-slide and clamp it to the bottom of the saddle bridge. This would add a lot of rigidty and keep the cross slide from moving much if accidentally bumped.
5. Remove centers and place a MT6 to MT4 bushing in the headstock. With a long drill or drill with extension (or actually maybe just an annular cutter on a long ass extension ) drill clear though it using the carriage for feed.
6. Replace drill with line boring bar. Preferably mt4 ended, but eh. Other in held with a 60 degree center. Only one hole, and round. Use broken endmils or round HSS.
7. Line bore, checking progress with small hole gauges.
8. Clean up shoulders with flat sided tool.
9. Remove and repeat on the second.

Sound good? Probably gonna take about 8 hours for the two, not counting making the tooling.

Plan of operations looks great. I might be tempted to leave the live center in the tailstock to help push the part into the drill, coordinating carriage and spindle feed motion. The center will help keep things in alignment. After the first wall the drill will help itself to stay aligned. Once the holes are drilled you may not need to clamp the cross slide with anything too big. Maybe a dial indicator in there somewhere just to monitor position, or take a measurement from the end of the cross slide to the apron so you have a "home" reference position.

[The Metal Butcher]

You're about to do a setup where the lathe becomes the functional equivalent of a horizontal boring mill. I'm not sure how many people who participate here have ever done such a thing, so I would like to ask if you could post some pictures of the setup once you're up and running. I think it would be an excellent viewing/learning/teaching experience for many. The ability to share this type of knowledge is what helps make this site so great.

Correct. It's a very classic method, dating back well into the 1800s. In fact, that is what to me makes the name in "engine" lathe. I've heard a lot of definitions, but the one that makes sense to me is that is a traditional style turning lathe with Tee-slots, so that one could line-bore an engine.

In fact Doozer has one of the most modern lathes I know of tee slots on the saddle, a 17" Clausing (Cholchester?). Here is a thread about doing such with a link to a youtube series on doing just that with that exact lathe: https://www.practicalmachinist.com/v...-lathe-263274/

Here is another from a slavic YTer: https://www.youtube.com/watch?v=3vCJV95ZsdY

If you search up some lit, I'm sure you can find folks doing it. Probably more of po'boys without a proper HBM, but there was plenty of po'boys in the early 1900s.

But yes, if you know me I like to post of my adventures. I'll definitely start a new thread.... assuming it turns out well.

Just going to throw something out. Your material WAS t6 temper aluminum BEFORE you welded it. Now you have T0 temper material. Rerun your stress calcs or re heat treat and age it back to T6 temper.
I learned this the hard way on welded suspension arms for a SAE Mini Baja project in school

Some of it has lost its temper, but I think the majority is fine. The inner welding was done with a spool gun very quickly, it didn't get hardly even to 250 degrees. So I think all of it will bore well. I read up on the process of heat treating. It's more than I want to get into.

But you are correct on the stress calcs. That stuff is weak after welding. Hopefully it will be more than strong enough.

---

My plan ATM is this:

1. Find appx center on each end and center drill.
2. Mount a big angle plate loosely to the compound ring on the Lagun.
3. Using a headstock center and a tailstock center, put the part between centers.
4. Now that the alignment is fixed, clamp very securely to the angle plate. Tighten angle plate bolts. If possible, run a big C-clamp from the part down onto the cross-slide and clamp it to the bottom of the saddle bridge. This would add a lot of rigidty and keep the cross slide from moving much if accidentally bumped.
5. Remove centers and place a MT6 to MT4 bushing in the headstock. With a long drill or drill with extension (or actually maybe just an annular cutter on a long ass extension ) drill clear though it using the carriage for feed.
6. Replace drill with line boring bar. Preferably mt4 ended, but eh. Other in held with a 60 degree center. Only one hole, and round. Use broken endmils or round HSS.
7. Line bore, checking progress with small hole gauges.
8. Clean up shoulders with flat sided tool.
9. Remove and repeat on the second.

Sound good? Probably gonna take about 8 hours for the two, not counting making the tooling.

[Erich]

Just going to throw something out. Your material WAS t6 temper aluminum BEFORE you welded it. Now you have T0 temper material. Rerun your stress calcs or re heat treat and age it back to T6 temper.
I learned this the hard way on welded suspension arms for a SAE Mini Baja project in school

[tom_d]

I'm not sure I need more than one cutter. Since setup is so much longer than the cutting, cutting one bore and then moving the cutter from one hole, to another, to another, is really no slower than setting 2 or 4 cutters and cutting 4 bores at once. That and there is less cutting pressure, though I could cut on opposite sides to mitigate that. However, I think that twice the length of bar and only setting the cutter once for each cut would be easiest.



Bamm!! That's why I love this site. Okay, question 3 solved. I have small hole gauges. That will work. Thanks!

You're about to do a setup where the lathe becomes the functional equivalent of a horizontal boring mill. I'm not sure how many people who participate here have ever done such a thing, so I would like to ask if you could post some pictures of the setup once you're up and running. I think it would be an excellent viewing/learning/teaching experience for many. The ability to share this type of knowledge is what helps make this site so great.

[legendboy]

Line bore lol, find somebody with a nice 5 axis mill

[Peter S]

And for a third question: How would you measure the bore while line-boring it? I have tele-scoping gauges, but they won't fit with anything but a tiny bar.

If you run your boring bar between centres (I would), you can remove the bar to measure the bore.

No need to remove the chuck, just machine a centre on a piece of round bar held in the chuck. The chuck jaws give your driving dog something to catch on.

----------------------------

FYI, you can measure the bore with the boring bar in place, not suggesting you need to do this.

Starts at 16:54

https://youtu.be/fMeHiT4yECk?t=1002

Note, the boring bar has holes down its length, you don't have to remove the tool to take a measurement.

It also shows how to face the boss, though it looks like a recipe for chatter.

[nickel-city-fab]

I actually don't use square holes on my boring bars. Too much work. I use round holes that are 1.414x the size of a square bit
Could easily make a between-centers bar like that before lunch