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J Tiers
08-29-2016, 12:32 AM
needed to sharpen some machine reamers, and have not made the planned pieces to complete the grinder tooling yet. So made up a bit of a kludge, but it works.

may as well say I am aware that drill chucks are not generally very accurate.... I checked this one.... only a couple thou out at the end of the reamer, no matter how I put the reamer in, so it is good enough. Nice, because it already had a shank, so I didn't need to make one.

It's on the old Greenfield base, still using the Dumore TPG as a head.

Shank turns freely, except for a light wave washer spring holding it back against the front "bearing" on the block. Finger hits under the flute to set the position to get the relief on the grind. In this position, it is actually grinding "onto" the edge, as opposed to "off" the edge, so no stoning needed after to remove burrs.

What looks like rust on the reamer is a reflection of a light that is above and to the right of the camera. I turned it on as a side light, and it had not warmed up to good color temp when I took the pics. Pics are after I finished the last one, and had popped the belt off to relieve tension.

http://img.photobucket.com/albums/0803/jstanley/machines/Grinder/IMG_3845_zpsbnocrjrq.jpg (http://smg.photobucket.com/user/jstanley/media/machines/Grinder/IMG_3845_zpsbnocrjrq.jpg.html)

http://img.photobucket.com/albums/0803/jstanley/machines/Grinder/IMG_3847_zpsdoxrqvfd.jpg (http://smg.photobucket.com/user/jstanley/media/machines/Grinder/IMG_3847_zpsdoxrqvfd.jpg.html)

The Greenfield base with extemporized head.....

http://img.photobucket.com/albums/0803/jstanley/machines/Grinder/greenfield%20grinder2_zps4z8rlkki.jpg (http://smg.photobucket.com/user/jstanley/media/machines/Grinder/greenfield%20grinder2_zps4z8rlkki.jpg.html)

10KPete
08-29-2016, 12:40 AM
I'm not a grinder guy so.... it looks like you're touching up the end bevels?

Pete

J Tiers
08-29-2016, 01:15 AM
Yes, that is the part that cuts on a machine reamer. The rest of it is not very important other than as a guide. A 45 degree bevel with an edge and a back relief to allow cutting.

On a hand reamer, that bevel is extended back over several cm.

DR
08-29-2016, 01:38 AM
Could the reamer also be held between centers with the grind head rotated to 45 degrees?

10KPete
08-29-2016, 02:01 AM
Could the reamer also be held between centers with the grind head rotated to 45 degrees?


That wouldn't provide the back relief on the 45* that allows it to cut, unless the center mounting is dogged some way to prevent the reamer rotating between index steps. You wouldn't just rotate the reamer while grinding the 45*!!

But yes, it doesn't really matter how the 45* is achieved; angle the tool, or angle the wheel. What ever works.

Jerry's rig is a bit different so that's why I asked. He does come up with some interesting set-ups sometimes.......

Pete

DR
08-29-2016, 10:46 AM
That wouldn't provide the back relief on the 45* that allows it to cut, unless the center mounting is dogged some way to prevent the reamer rotating between index steps. You wouldn't just rotate the reamer while grinding the 45*!!

But yes, it doesn't really matter how the 45* is achieved; angle the tool, or angle the wheel. What ever works.

Jerry's rig is a bit different so that's why I asked. He does come up with some interesting set-ups sometimes.......

Pete

As you said you're not a grinder guy.

The finger determines the rotational position of the flute tip being ground and supports it so it won't rotate. The relief and final grind are done separately by resetting finger height or wheel height.

My concern with the setup shown is the reliance on the chuck's accuracy for equal grind on each tip. Reamers have centers in the cutting end making accurate sharpening easy.

When I sharpen reamers between centers the end being ground is at the the left from the operators position (opposite from what's shown here). But, my T&C grinder has a reversing head so I can grind "onto" the tip as J mentions if I choose.

J Tiers
08-29-2016, 11:07 AM
Could the reamer also be held between centers with the grind head rotated to 45 degrees?

Yes, I would prefer to have it on centers. I do cutters that way, but you need a stop on the table to get the cutting edges all in line with a 45 degree angle like the reamers, because the table does not turn that far. I'd have the wheel right there and would need to be really sure of the table stop or I'd crowd the wheel badly. If you move the table too far, you grind deeper, or mess up the wheel. The table would have to stop evenly for every flute, and I don't trust the table stop as much as the tested chuck (which will get replaced with something else when and if I put a reasonable workhead on the thing). With a workhead of some reasonable capacity, I could choke up on the reamer shank, for instance.

This way, you can just move the reamer past the wheel and not need a stop anywhere. I'd have to make a fancy setup to get the reamer on centers, a sub-subtable, or the like. I start the reamer to the right of the wheel, bring it back past for the cut, and then return, so the main cut is "dragging", and shouldn't try to hog in. And this way I can just feed in as needed, instead of having to adjust a stop.

The chuck is surprisingly accurate, a couple thou, and it works out OK.

You can see the flexible "finger" that is set to get the relief by a slight rotation of the reamer. Gets tricky with a small one. I need to make a better way to set the finger. With these, I followed the factory and did one slope only, no fiddling with a second relief. A better system would do a better job, but I wanted some sharp reamers.....

DR
08-29-2016, 02:29 PM
As to finger adjusting.....you might Google to find pictures of factory made ones and duplicate the adjusting mechanism. Not complicated.

I got a nice one in an assorted junk box at auction.

J Tiers
08-29-2016, 03:08 PM
As to finger adjusting.....you might Google to find pictures of factory made ones and duplicate the adjusting mechanism. Not complicated.

I got a nice one in an assorted junk box at auction.

I have a design all modeled up and ready with drawings, just haven't made it yet. And When I look at it I keep thinking of improvements! I better make the silly thing so I stop.

Juergenwt
08-29-2016, 08:45 PM
You can not put the reamer between centers and turn the grinder at 45. You have to mount the reamer at 45 so when you move the table you van use the whole face of the wheel.
You could put the reamer between centers if you could move the wheel at 45 across the front of the reamer.

J Tiers
08-29-2016, 09:27 PM
If the center on the wheel end was made so that there was enough clearance for the wheel, it could work. It would be a very strange shaped center, though, some sort of arm with just the center point at the end, set at 90 deg to the arm.

It would probably work great with reamers in the 20mm diameter class. I think it would be close to impossible with a reamer of 2mm, the arm would need to be quite small. And small reamers may have a male center instead of a female center, somewhat in the manner of small taps.

If the wheel (or reamer) was moved in a vertical direction, then a center of nearly any type would work, plus the ground surface would have no concavity. Likewise, use of a cup wheel with a thin edge would work with centers, as the thin edge could pass over and off the relief to ensure a full grind.

As you say, much easier and better to set the reamer at 45 deg, and move it past the wheel, at least, as in this case, if there is no cup wheel available. I actually think I MAY have cup wheels that will fit the TPG, but I'd need to go through a bunch of boxes in the grinder supply cabinet to find them, they are not labeled. And they would probably need a hub adapter that I would have to make.

The problem with the chuck I used is that it has no through-hole of any size. If it had a decent sized through-hole, then the reamer could be chucked with only a little sticking out. That would be much better, with a smaller runout error in most cases.

strokersix
08-30-2016, 10:19 AM
Did you actually sharpen this reamer with the setup shown? Looks to me the long stickout is a serious invitation to chatter, never mind accuracy. I would find a way to pick up the center on the cutting end of the reamer for support and location.

Maybe the finger provides necessary support. Still seems dodgy.

J Tiers
09-01-2016, 10:22 PM
Did you actually sharpen this reamer with the setup shown? Looks to me the long stickout is a serious invitation to chatter, never mind accuracy. I would find a way to pick up the center on the cutting end of the reamer for support and location.

Maybe the finger provides necessary support. Still seems dodgy.

You bet I did. A half dozen or more of them. And I'll do it again, if I don't set up anything better before I need to. I checked the runout and it was less than 2 thou on the worst reamer.

Remember, grinding is not like turning. A thou depth of cut can be a lot when grinding, especially with a somewhat underpowered head like the Dumore 44, and a 3" wheel. I took about 1 thou cuts doing the reamers, and went around once before adjusting in another thou. I stopped when the grind went up to the edge. The 1 thou was partly because the setup is not the best, and partly because the Dumore does not take heavy cuts, and partly because I was not re-conditioning the reamers, just sharpening, I did not have any reason to grind away very much. As it happened, it only took a few times around, probably 3 to 5.

No issue whatever with chatter. Just not enough force applied to cause a problem.

I did make the better finger system

http://bbs.homeshopmachinist.net/threads/71389-Made-that-improved-grinder-finger-support-I-wanted

strokersix
09-02-2016, 11:09 AM
Cool. This is making me think about what I might be able to set up on my old Sioux valve grinder.

J Tiers
09-02-2016, 12:57 PM
Of course, it would be better to "choke up" on the shank of the reamer, but that option was not available using that chuck, and I have no other system available yet. It's in the plan, either a 5C setup, or both chuck and 5C. ER could be better, but I already have and have to have the 5C for the Rivett.