Boring a bearing journal vrs reaming

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liveaboard
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Re: Boring a bearing journal vrs reaming

Post by liveaboard »

As a person with limited skills and a compromised machine, I find boring interference fits a challenge.
I sort of enjoy it actually...
Now I understand that a well skilled experienced machinist on an accurate machine is a different story, but I don't think that's you.

Anyway, you need to make many repeated bores, so if you have a reamer that worked before, I say find the problem and make it work again.

Yesterday I made 4 bores for press fitting small shafts.
3 good, 1 fail.
(grumble, mutter, curse, complain...)
RSG
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Re: Boring a bearing journal vrs reaming

Post by RSG »

liveaboard wrote: Tue Oct 19, 2021 1:42 pm Anyway, you need to make many repeated bores, so if you have a reamer that worked before, I say find the problem and make it work again.
Yes I think that's what I am going to do. I can do .0005" without issue but working down to the tenths with this lathe can be a challenge. Of course if I have one of those fancy $400 carbide boring bars things might be different. I think for now I will go back to the first method of reaming which has worked for years and do the hand ream trick as a follow up.
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pete
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Re: Boring a bearing journal vrs reaming

Post by pete »

You mentioned using a hand reamer RSG but not how you do so. If your tail stock is properly aligned left/right to the head stock C/L, that only leaves a vertical misalignment that almost all lathes will have even right from the factory of a few thou high and/or possibly even larger numbers as low after lots of wear. And any wear would almost certainly show the tail stock quill pointing down hill because the tail stock is heavier at that end. Since your hand reamer if that's what it is will have 4 flats on the drive end there usually driven with something like a tap wrench. When there used on a lathe the best method I know about is using that tap wrench as a anti rotation bar and set the female center that's in the end of the hand reamer onto a dead center held in the tail stocks MT. So in effect you then have pretty much a floating reamer that should follow the hole that's been bored. It's still possible to have a very slight taper to your finished reamed hole due to that vertical misalignment. But unless that's a whole lot, then the reamer length should make any taper almost undetectable and likely not enough to matter on at least shorter reamed holes. Of course this is all worthless if that's already how your doing your reaming with that hand reamer. The same can also be done with a machine reamer without those drive flats just by machining a clamp like the snugs on something like a magnetic dial indicator base and adding a single anti rotation bar to it since I've yet to see a machine reamer without that female center in it's drive end.

I also did a bit of thinking about that floating reamer holder you built. It seems to show as you said a taper reaming result. But that's still not 100% conclusive that the results it's producing are in fact being fully created by the tool itself or how you designed and machined it. Only that a measurable inaccuracy shows up when your using it. So to figure out why you have to eliminate any other causes. If you haven't run a check yet on your tail stocks quill? Extend it almost out to it's full travel, lightly snug the quill lock to remove any clearance and so it centers on the tail stock bore. Then run an indicator set on your cross or top side along both the front and top of the quill using the carriage travel. Your tail stock could also be incorrect enough to be producing at least some of that taper reamed hole your now seeing. But if you don't check you can't eliminate it. I sure know from my own experience having a quill pointing up or down hill or left/right isn't impossible right from the factory. Better of course would be using an actual MT test bar since your then checking just how true the tail stocks female MT alignment is to the lathe ways. Yeah it should be, but who knows for sure. Not many have those test bars though.

I also see lots of threads on other forums saying you absolutely need to have one of those MT test bars to check the head stock alignment. Yeah they help and make it a bit faster and easier as well as narrow down to exactly how the head stock is positioned on the bed ways. But having one isn't really needed if you have a face plate that lathe of yours should have come with. You can still run a general alignment check just by doing the following. Spotlessly clean and check for burrs on your spindle nose and the same for the mounting area on the rear of the face plate. Mount it up on the spindle. Run a full clean up cut across the face of it. I'll use a clock face for direction when looking at the face plate from the tail stock end. So conventionally cutting you'll probably feed the tool from the outside edge of the face plate, or it's 9 o'clock position in to it's center. With that done now run your cross slide almost full out towards the operator, set the tip of a 10ths indicator just past the face plates center hole. Then run the indicator tip from that position out to the back side of the face plate using the cross slide, or in other words it's 3 o'clock position. What this does is show double the error the face plate is being cut at. Checking by using the same path the cutting tool did (9 o'clock to center) will not and can't show what your trying to measuresimply because the indicator tip is duplicating the same path the cutting tool did. All well made lathes are ALWAYS and purposely set up at the factory to face very slightly concave and never convex. For your size of lathe and over the distance your checking I'd expect to see around .001"- maybe as much as .002" convex and still figure it's ok. What this type of test can't determine is if the errors outside of the expected measurements are in the head stock itself or due to a misalignment or extra wear in the head stock side of the cross slide way surface. But if those numbers do check out as ok? Then it does eliminate that as a possible source in the head stock. So if both the tail stock and head stock do pass and your still 100% sure your lathe bed is level and non twisted then you can then be sure the real problem is in the reamer holder. At most it should take less than an hr or so to run those checks and that test cut. Then at least then your certain of what your dealing with.

If I recall correctly you said you had a reamer finish sharpened to a set size by a friend. So I'd assume that's a machine reamer. Even though you built that holder so it's supposed to float and it apparently does, the drive end is still being rigidly held on the part that does float. Misalignment's within the lathe can also cause the reamer to produce that taper your seeing or it could even be a combination of small alignment errors just adding up in the tool and lathe. If that taper is being caused by anything else I'm now right out of ideas. :-)
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Re: Boring a bearing journal vrs reaming

Post by Richard_W »

RSG wrote: Fri Oct 15, 2021 5:02 pm Thanks for the detailed replies Rich and Pete! Always appreciated.

I looked into getting a solid carbide boring bar 12mm dia x 4.5" and the cost blew me away at $400! A bit steep for what it is.....
I have been buying solid carbide boring bars from mmtoolscarbide on Ebay. I have used them quite a lot on a CNC lathe. The one in the listing is 3/8" diameter. You can go through his listings for longer or shorter boring bars. Shorter less expensive and longer for more expensive.

https://www.ebay.com/itm/334180377812?h ... SwwDlg3MDv

I actually just bought another one I liked it so well.

Richard W.
RSG
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Re: Boring a bearing journal vrs reaming

Post by RSG »

Richard_W wrote: Fri Oct 22, 2021 6:27 pm https://www.ebay.com/itm/334180377812?h ... SwwDlg3MDv

Richard W.
Thanks for the link, that's fairly reasonable given the exchange rate and all.
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RSG
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Re: Boring a bearing journal vrs reaming

Post by RSG »

Pete!

Thanks for the detailed post. You certainly take the time to give suggestion to help and that's greatly appreciated.

When I say "hand reamer" I am actually referring to a machine reamer, and since it's only a few tenths over-size I have been able to guide it through the bore by had with a hand-made handle. I'm assuming this is only touching up the bore near the areas the retaining ring pockets have been added to though I think.

As for tailstock alignment I have done extensive testing on it to get it dialled in and have done what I thought to be a pretty good job! I have never checked the tailstock quill after though so I'll do that next. I also have never strapped the faceplate on and checked that either so I'll try that as well.

All I know is when I use the chucking reamer in my "one-piece" integral drill chuck in the tailstock and it cuts fairly accurate, close enough I can live with it. I have just been chasing perfection I guess and was hoping the floating reamer head was the magic bullet so to speak. Guess not, at least not yet. I want to do more tests with the floating reamer holder to see what is going on and will do so when I have a bit more time. I'll be sure to update you when I do.

Thanks a lot!
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pete
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Re: Boring a bearing journal vrs reaming

Post by pete »

Glad some of that might help Ron. It's an interesting problem with a lot of possible causes. But a couple of items to remember and even more so when trying for 10ths. EVERYTHING matters. It's generally accepted on say less than Schaublin, Hardinge, Weiler etc lathes in almost new condition that a tail stock when moved along the ways and then locked in place will show a very slight variance in it's exact position and true alignment at different spots on the lathe bed. Basically it happens and there's little can be done. Part of the reason those changes can be enough to matter is just simple geometry, a 10ths change in the bed gets greatly magnified because of the distance between the bed and the C/L of the tail stock quill. So when running your quill alignment checks try and position it to where it's working position would be when your reaming those holes and do those checks there. Secondly the amount of tension used on the tail stock bed lock is also important. Grizzly as an example I know of has on at least one of there Gun Smithing lathes the usual standard lever and cam lock, but there's also a re-designed outer end on the cam that the lever is attached to. Basically it's a bolt head that allows the use of a proper torque wrench so the same repeatable locking tension is used on work when it's fussy enough to require that.

Comparatively speaking these Asian lathes will generally have thinner wall castings, possibly a bit poorer quality cast iron and certainly not the same high precision fit between the two parts of the tail stock as those much better lathes have. So a change in bolt tension on that locking cam can and does affect where that exact quill C/L position is compared to the head stocks C/L. These issues are one of the reasons why the better gun smiths do use those floating reamer holders and why there a good idea to help compensate for the slight misalignment's as you already know. But I still think it's worth mentioning these cause & effect problems if you don't already know of them. Yeah on work that's got + - .001" tolerance being that careful and fussy would be pointless, at 10ths it isn't.

If I remember correctly someone here posted issues not to long ago about having to remake the plate that pulls up against the bottom of the ways and locks the tail stock down simply because the OEM part on one of those Grizzly gun smithing lathes wasn't large enough to fully lock the tail stock in place when using larger drills. So that might be another area to investigate and a better fitting and longer/thicker plate might help spread the loads better with less deflection? It's another area they seem to cut corners on because it can't be easily seen. Like I said, everything matters.
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Re: Boring a bearing journal vrs reaming

Post by RSG »

Thansk Pete,

To answer some of those questions, yes when I did my tail stock realignment I made sure to do the testing in the exact spot where it resides for reaming figuring that was the most important area to focus on. While my lathe doesn't have a torque cam like some of the gun smithing lathes you mention I am aware of the importance of repeatability and had adopted a rudimentary method of repeatability by marking the cam lever with a marker so every time I do that operation I can get at least close to the same tension. It's not fool proof but as you say, "every little bit helps". I have actually looked at the block under the tail stock and it looks rough, just a raw casting. I think I like your idea about cleaning it up and will add that tot the list, so great idea! As for bed twist I check that every season with my precision level. It doesn't change much but enough that I need to tweak it every once in a while.

I know this lathe isn't a Hardinge or the like but I have learned how to deal with it and as I mentioned to a poster above I can work to the half thou. all day long. Even the spindles which require tenths accuracy I can do no problem, but these journals elude me.


**Edit** - I just thought of a question! Is it possible to leave the tail stock lock open and push the tail stock by hand when reaming a .625" hole? I'm wondering if it would sort of float the same way a floating reamer would?
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GlennW
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Re: Boring a bearing journal vrs reaming

Post by GlennW »

I don't know what method you used to align the tailstock to the spindle, but a .625" reamer is fairly long and rigid. There is no guarantee that the cutting end of the reamer is coaxial with the spindle just because the tailstock quill is. Lots of room for error there.

That reamer is also fairly rigid, so misalignment when cutting aluminum can make it act like a boring tool as it may not centralize.
Glenn

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pete
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Re: Boring a bearing journal vrs reaming

Post by pete »

Depends on the amount of wear on the bottom of your tail stock bearing surfaces if it would work. That's usually pretty easy to spot and almost for sure most of it will be on the first 20% on the front. They always wear the most there. Better might be what some add is sort of a tow bar linkage to the bottom leading edge of the tail stock and to a slotted bar attached to the rear vertical face of the carriage. They used a short length of shop made U shaped channel with a simple vertical drilled hole in both, a short length of bar again with a hole at each end, space the carriage away from the tail stock the correct distance, set the bar in place and drop two pins in and it's ready to be used. That way you can use the carriage hand wheel to pull the tail stock with maybe a bit more control. I distinctly remember seeing a few YT videos showing how they did it, but damned if I could find a link for you with the search terms I used. But that was done mostly for larger drills with deeper holes so the lathes power feed could be used.

To be honest, my gut feeling is you'd be much more certain of the results with the tail stock locked down and the reaming done more conventionally. The tail stock weighs quite a bit so any added misalignment with it loose on the lathe way's is going to help steer that reamer even more. That taper almost for sure indicates a misalignment some where, but reamers don't always do the expected. A rough rule of thumb is half the recommended drilling rpm and a fairly high feed rate for reaming. What allowance are you leaving after boring for the reaming? All that's ok? A real shot in the dark, but are you reaming with the tail stock quill lock lightly snugged up? With a taper reamed hole like your seeing I still have real doubts it's related to anything but a slight alignment issue. I use Relton's A9 for aluminum as my drilling & tapping fluid, but haven't done enough reaming with it to be 100% sure of how it performs over anything else. I'd also be a bit leery about changing your cutting fluid if your happy with what your already using. At your 10ths level and the way that A9 works when drilling it might give you a slightly over size hole. There's enough past posts on the PM forums to believe even the cutting fluid used can sometimes show a size change depending on what's being used.

Yeah if that bottom block is anything like both my Asian lathes were I'd build a new steel block that's longer, fits between the ways tighter and thicker for less deflection in it. Even the two machined areas that are meant to pull up against the bottom of the lathe ways looked like a hybrid cross between an angle grinder and a mill were used to "machine" them. The more you can spread what in reality are fairly significant pulling loads on that block, the less the part will deflect where it shouldn't be doing so. Mine showed a fairly large difference after getting rid of the OEM part. With it, the tail stock lock always felt almost a bit uncertain as it tightened.
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Re: Boring a bearing journal vrs reaming

Post by Mr Ron »

RSG wrote: Sun Oct 24, 2021 7:38 am
**Edit** - I just thought of a question! Is it possible to leave the tail stock lock open and push the tail stock by hand when reaming a .625" hole? I'm wondering if it would sort of float the same way a floating reamer would?
That is how I was taught in school to ream on a lathe. The purpose was to "float" the reamer.
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Harold_V
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Re: Boring a bearing journal vrs reaming

Post by Harold_V »

Mr Ron wrote: Sun Oct 24, 2021 2:10 pm
RSG wrote: Sun Oct 24, 2021 7:38 am
**Edit** - I just thought of a question! Is it possible to leave the tail stock lock open and push the tail stock by hand when reaming a .625" hole? I'm wondering if it would sort of float the same way a floating reamer would?
That is how I was taught in school to ream on a lathe. The purpose was to "float" the reamer.
I think I've made mention of this before, but in case I haven't, and it's rather critical for large diameter reamers, which are quite rigid and will readily behave as a boring bar, when you chuck the reamer in the tailstock, grip it by only a very short portion of the shank----no more than ¼", so the end is free to seek center. Couple that with a sliding tailstock instead of hand cranking the quill and you may just achieve acceptable results. A lot depends on the amount of material you leave to ream, which, in this case, would best be very little.

Assuming that all of the cutting edges of the reamer are sharp, and that precious little remains to be removed, the reamer may yield excellent results. Note that one bad edge can be the cause of poor performance, including oversized results. The dull edge causes the reamer to deflect. That can be partially eliminated by removing only a trace of material (a couple thou).

If you wish to do so, you might benefit by trying various conditions. I'd suggest you bore first, leaving only a couple thou for the reamer. Vary the spindle speed, both up and down, at which you ream. You may discover that the reamer behaves better when it is used over recommended speeds. That was my experience with the switch plates I reamed.

Keep in mind that reamers are multi-toothed cutters, so they perform well with elevated feed rates. When you remove very little, as in this case, you often can overfeed with benefits. One of them is you avoid bell-mouth and entry chatter.

Experiment, but not on parts that you intend to use. Use a piece of material that can be discarded once you are satisfied with the results you achieve. Once that happens, make notes so you can duplicate the operation in the future without going through the same experiments time and again.

For reaming, I like to use the same cutting fluid(s) I use for tapping.

H
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