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Horizontal overarm and bearing: FP1 part doesn't fit FP2??

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Diamond
Joined
Sep 25, 2011
Location
Garbsen, Germany
I am making a new barrel to fix up a spare tailstock for my cylindrical grinder. I'm almost at the last step, which is to cut a straight module 1 rack of 18 teeth.

I was setting this up on my FP2, with a gear cutter mounted on a 22mm horizontal arbor. Normally I have a long-reach head mounted on my FP2, and use that as the horizontal overarm (it comes with a bearing holder that mounts underneath). But for this particular operation there is not enough clearance under the bearing holder. So I decided to try the regular overarm, since its bearing holder has more clearance. This overarm and bearing have been sitting in my tooling cabinet for the past half-decade since I got the mill, just waiting to be used by me for the first time.

Big surprise: they don't fit! The bronze bearing bushing is several mm too high. Here is what happens if I slide the bearing bushing onto the arbor: you can see that the bearing holder won't slide onto the overarm.

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The arbor is not bent. The overarm is not canted. It's just very very far off. Here's another photo to demonstrate. I have removed the 22mm arbor and put a 16mm ground pin into a 16mm collet:

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It's easy enough to fix, I just need to plug the hole and bore a new hole for the bushing. I pressed out the bushing to get some idea of how far off this is:

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But looking at this, I realised that something must really be wacky here. The bearing and the overarm are both stamped with the same 4 digit number. But are they from an FP1 or some other Deckel machine, and just don't fit the FP2? In that case perhaps I should swap them for the correct parts rather than modifying them to fit.

Cheers,
Bruce
 
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I'm sure someone else will be able to answer but I think I have the support bearings for both of mine - I can measure them on monday.
 
I never verified it but it makes sense the FP2 would accept larger cutters compared to the FP1.
I did get the overarm from an FP2 to use on the FP1s because it is longer, for some reason my factory arbors seem a little to long and the extra length allows for full engagement of the dovetails.
Dan
 
Turns out that the arm and bearing are both for an FP1. I should have looked at the casting numbers underneath the arm, which start with 2100-. If if were for an FP2 they would have started with 2200-. Does anyone out there have an FP2 overarm/bearing that they want to trade for an FP1 overarm/bearing?
 
I did something unconscionable: I milled 3mm off the bottom of the bearing housing (the one for my long-reach vertical head) to get the clearance that I needed. My justification is pretty pathetic: when in horizontal mode I am often fighting for clearance and every mm counts. But I know it wasn't good for my karma.

This gear rack is on a tailstock quill. It's module 1, 18 cuts spaced 3.1415mm (pi mm) apart. The left end of the quill (part not ground) is a sacrificial stub for workholding, which I cut off when the part was finished. The cutter is HSS from China, it cost 11 Euros including shipping.

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PS: I noticed that my 22mm horizontal arbor has quite a bit of run out at the far end (around 0.25mm = 0.010"). I thought it was defective, and swapped it for another one that I collected, but that had a similar run-out at the far end. This end play is well-controlled by the bearing, but I was wondering, is it normal that horizontal arbors have this much run-out? I checked the horizontal spindle with a test bar and at 300mm it's less than 0.01mm = 0.0004". So the run-out is definitely in the arbor.
 
...

This gear rack is on a tailstock quill. It's module 1, 18 cuts spaced 3.1415mm (pi mm) apart. The left end of the quill (part not ground) is a sacrificial stub for workholding, which I cut off when the part was finished. ....


But what if the rack you had to cut was longer than your Y travel Bruce?? Alright...just kidding...:)

It's true that there can be clearance issues with these milling cutters, I guess there might be larger ones, more teeth, with the same specs, but haven't ever seen any.

You chose wisely, your karma will benefit from getting the work done without any actual damage to the machine, consider it an improvement!

I've also found some runout on horizontal arbors, and cutters as well some times. Hasn't caused any real issue though, at least for what I've done so far.

(that's an interesting project, I guess this quill was not a trivial thing to make....)

BR,
Thanos

P.S. Isn't that horizontal quill just amazing? You could easily bore the bearing on the bearing housing if you chose so, be it modification or, a new bearing housing from scratch. Can also be done with the horizontal machines that have sliding overarm, but I prefer the quill !
 
Bruce:
Run out of horizontal arbors can often be attributed to spaces/cutters that are not perfectly parallel, not clean or have burrs....when stacked and the arbor nut tightened it can induce run out (a bow) in the arbor.....

Test by loosening the arbor nut (only while supported by the outboard bearing) , rotate some of the spacers and re tighten the nut.(only while supported via the outboard bearing).I will wager that the point of max deflection on the arbor is now different and will have moved....

Ps. Sort of surprised that that grinder uses a straight cut rack....

Cheers Ross
 
I did something unconscionable: I milled 3mm off the bottom of the bearing housing (the one for my long-reach vertical head) to get the clearance that I needed. My justification is pretty pathetic: when in horizontal mode I am often fighting for clearance and every mm counts. But I know it wasn't good for my karma.

I have seen worse Much worse

Peter
 
How about showing your "worst of the worst" photo album instead of teasing us, Peter ? :D
 
Ross, I thought it might be the arbor spacers. So I removed everything from the arbor and measured the run-out. That's the 0.25mm. But I am sure you are right that I could tune this by clocking the spacers. Do you do this? Not sure if it's worth the trouble, given that the end bearing stabilizes the runout.

Here's the tailstock quill in place. I'm happy with how this turned out. The quill is preloaded between the bore and 398 3mm bearing balls. It has no horizontal or vertical play, but moves smoothly back and forth. The handle rotates the hub which has an integral straight spur gear below it. That engages the rack on the quill.

I tuned the preload by starting the OD of the quill about 10 microns over the nominal size (bore ID - 6.000mm) and then ground off 1 micron at a time until I was happy with the fit/preload. That was at about 4 microns over the nominal size, so there is 4 microns (about 0.00015") of interference.

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Here's what the quill looked like coming off one pass on the grinder:

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Cheers,
Bruce
 
Think we had a discussion about the balls , the pre-load and all....glad it worked out for you.
Did you check the "truth" of the height and plane of the tail spindle to the work head?
What material /heat treatment did you choose?

Arbors get bent....easy to tweak if the user is not vigilant. Should never tighten of loosen that end nut without the arbor being fitted into the outboard bearing.

Cheers Ross
 
Ross, I thought it might be the arbor spacers. So I removed everything from the arbor and measured the run-out. That's the 0.25mm.
Bruce

Did you check the spindle with a master arbor The one from your dividing head perhaps
Only then you can tell if it is the arbor
Many times it is and and Not or or

Peter
 
A 0.010" runout at that amount of overhang seems perfectly reasonable for a milling arbor. I bet you can change the magnitude and direction quite a bit, just by bumping it with your fist. The arbor support should all but eliminate the runout if the bearing clearance is set up correctly, and is running with a dynamic film of oil. Most milling cutters for arbors have some runout anyway.
 
Think we had a discussion about the balls, the pre-load and all....glad it worked out for you.

Yes, that's right. My original plan was to grind the original quill down by 0.35mm ~ 0.010" to clean it up, then install 1/8" = 3.175mm balls in place of the original 3.000mm ones. But then I discovered that the original quill had a crack in the MT2 taper, probably from a crash into the wheel or workhead. So since I needed to make a new one, I made it close to the same diameter as the original.

Did you check the "truth" of the height and plane of the tail spindle to the work head?

I did for the tailstock on my machine, that I scraped in. But not for this tailstock, which is probably going to Switzerland as a replacement a worn out one. The point is that the tailstock needs to be scraped into the machine it is going on. Hopefully it's higher than the workhead, otherwise that also needs to be scraped in.

What material /heat treatment did you choose?

It's made from pre-hardened 1.7131 (16MnCr5+C / EC80 / 5115). In principle that steel can be case-hardened or nitrided, but I did not get it hardened, because it's already quite tough and wear-resistant. If it does wear out then I can make another one and get it hardened before the final grind.

Arbors get bent....easy to tweak if the user is not vigilant. Should never tighten of loosen that end nut without the arbor being fitted into the outboard bearing.

I did not know that, I always prepared my arbors off the machine then mounted them. I will heed your advice in the future.
 
Most milling cutters for arbors have some runout anyway.

Indeed, when I was cutting the rack I could hear the cutter fading in and out with each revolution. So I fed slowly on the final pass to get a level cut. Not sure if the cutter or the arbor are to blame, or both of them.
 
Indeed, when I was cutting the rack I could hear the cutter fading in and out with each revolution. So I fed slowly on the final pass to get a level cut. Not sure if the cutter or the arbor are to blame, or both of them.

That has been the case for me 8/10 times I cut a gear or use a slitting saw....
 








 
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