Need Someone With Machinist Knowledge Too Look At This Thread

[Diesel911]

Problem = 17mmH8 Hand Reamer (17mm = 0.6693”) is cutting a larger than 17mm hole Reamed ID = 0.6716” (one end of item was mounted in a Lathe Chuck and the other end of the Hand Reamer was supported by the Lathe Tail Stock Center on the Reamers center drilled hole).

Question what size Hole would a 17mmH7 Reamer make; would it make a smaller hole? And, what would that smaller Hole ID be? Or is there another Reamer that would actually make a real 17mm Hole 17mm = 0.6693”)?

Details:
Reaming the Bushings on a Bosch VE Fuel Injection Pump
Apparently there is very little information on the Subject. There is a Post that has that the Clearance between the Shaft and the Bushing is 0.001” and there is Vanagon Blog that said that Person used a 17mm Reamer when He reamed the Bushings.

I have 2 Fuel Injection Pumps so I am only going to speak about one of them.

Pump 1 Shaft measured over the un-worn area = 0.6682”

17mm = 0.66929 (ENCO Reamer size 17mm Reamer Size 0.6693)

In theory if I use a Reamer I should get a 17mm = 0.6693” Hole.

17mm = 0.6693” Hole
Minus 0.6682” Shaft OD
0.0011 Clearance
Mathematically that sounds great.

I bought a 17mmH8 Hand Reamer. I measured the diameter of the Reamer Blades which is difficult to do accurately and it seemed like more than 17mm?

So I figured that before I do any reaming of bearings I needed to try it out on something else and see exactly what the Reamer really reams to.

I have a small Aluminum Cylinder about 1” thick and 1-¾” in diameter and I mounted that in a Lathe Chuck and drilled a 5/8 Hole through it.

The 5/8” hole is enough to get the Reamers tapered end to start in. One end of the Reamer was in the Aluminum Hole and the other end of the Reamer was supported on the Center of the Tail Stock.

As I reamed the Tail Stock was advanced so that the Reamer did not wonder.

After Removing the Aluminum Cylinder and letting it cool I measured the ID and got; Reamed Aluminum Cylinder ID = 0.6716”. That clearly is not a 17mm = 0.66929 hole.

Reamed Aluminum Cylinder ID = 0.6716”
Minus 17mm = 0.6693”
The reamed Hole is 0.0023” larger than 17mm and the Shaft is actually smaller than 17mm at 0.6682”

Reamed Aluminum Cylinder ID = 0.6716”
Minus 0.6682” Shaft OD
That means a Shaft to Bushing Clarence 0.0034” not the target 0.001”.

And that was reaming the Hole on My Lathe where the Reamer was Well Guided. Without a good guide reaming the Hole by hand is going to result in an even larger Hole.

So that raised a question as to why the 17mmH8 (this is the commonly sold Hand Reamer Size) does not ream closer to a 17mm Hole?

What I found out is that the H8 represents a code as to what level of precision and as near as I can understand it an H7 Reamer would be a more precise Reamer. I guess meaning that it would ream closer to an actual 17mm Hole but I don't know how much smaller the ID would be.

[Dan Stokes]

I have no real input but I'll watch to see what the answer is. Very curious.....

Dan

[Diesel911]

Originally Posted by Dan Stokes

I have no real input but I'll watch to see what the answer is. Very curious.....

Dan

The Wron Bushings in the Bosch VE Pump had about 0.008" Clearance where they were worn the most.

I actually don't believe that the Factory Shaft to Busing Clearance is supposed to be a total Clearence of 0.001" but I am going by info From another Forum.
It is more likely that the total Clearance is 0.002". that would give 0.001" clearance on each side of the Shaft. The VE Pump is entirly lubed by Diesel Fuel.

[barry12345]

Getting the aluminium hot may have upset something. I am not a machinist. Adaquate coolant should have prevented that. Although I would have suspected an undersize hole once the piece cooled to room temperature if any meaningful variation.

On the other hand I was thinking as the aluminium was well chucked the heat of expansion may have drove the internal diameter material larger or less dense than normal. In simple terms a reverse effect of of contained expansion. It has to go somewhere. The chuck would have almost eliminated the external expansion of the material with heat.

So when you cooled the part off and out of the chuck it was oversize. Again not a machinist but have a metal cutting lathe. A little unilathe 13.

No I did not sleep at any particular motel last night or the wife would have left me in no condition to post this today. I too am interested in the right answer by a real machinest.

I doubt the toolmakers spec on his reamer is off but there is always a chance. Really though I am sure of nothing in this case. I wonder as well what the internal diameter would have been if left chucked and still hot. You might be able to rechuck it and heat it up with a propane torch a little and measure the bore. It would not surprise me if it measures much better.

[Diesel911]

Originally Posted by barry12345

Getting the aluminium hot may have upset something. I am not a machinist. Adaquate coolant should have prevented that. Although I would have suspected an undersize hole once the piece cooled to room temperature if any meaningful variation.



On the other hand I was thinking as the aluminium was well chucked the heat of expansion may have drove the internal diameter material smaller or denser than normal. The chuck would have limited the external expansion of the material with heat.

So when you cooled the part off and out of the chuck it was oversize. Again not a machinist but have a metal cutting lathe. A little unilathe 13.

No I did not sleep at any particular motel last night or the wife would have left me in no condition to post this today. I too am interested in the right answer by a real machinest.

I doubt the toolmakers spec on his reamer is off but there is always a chance. Really though I am sure of nothing in this case. I wonder as well what the internal diameter would have been if left chucked and still hot.

I know. It did not actually get hot hot as I was lubing it and the Reamer was being turned by hand. Letting it cool off was just a precuation.
However, Aluminum transfers heat fast and if you hold a piece of it in your hand long enough it can absorb some of your Body Heat.

The original Bushings are Steel Backed with a Bronze inside Diameter and are close to the finished size but not so close as to allow the shaft to go in.

Also when the Bushings are replaced in a Fuel Injection Shop I seriously doubt if they have a reaming setup that has Coolant circulation while they cut the Bushings. It is more likely they simply have the correct Hand Reamer and a nice guide so the Reamer stays centered.

Unfortynatly no one seems to know exactly what size the ID of The Bushings is supposed to end up at.

When I worked at the Naval Shipyard way back I frequently did quite a bit of reaming Oil Pump Shaft Bushings and Valve Guides and other things on the Engines that needed reaming. But, we always had the Factory Reamers for the Job.
I never had to pick which Reamer to use so My knowlege of Stock Reamers and what they can do is limited.

The way I see the Chart Below is that if I have a 17mmH7 Reamer it produces a tighter Fit than the 17mmH8 Reamer that I have and used.

The actual clearance I got with the 17mmH8 was Shaft to Bushing Clarence 0.0034”.
I am thinking that if the H7 Reamer is more precision I could may be get a Clearence of 0.002" something and that would be closer to the spec that people think is correct.

[Frank Reiner]

Diesel911:

In the ISO system of shaft and bore fits, the combination of letters and numbers denote the tolerance range. Capital letters are for bore tolerances, and lower case letters are for shaft tolerances. An H7 and an H8 bore tolerance have the same nominal I.D., but the H8 has a larger tolerance range than the H7.

Note that in the chart that you posted, both a bore tolerance (capital letter), and a shaft tolerance (lower case) are required to define the fit between the shaft and the bore.

An H7 reamer will not necessarily produce a smaller hole that an H8; it will just be in a smaller range (oversize in this case) than an H8.

[97 SL320]

Originally Posted by Diesel911

17mm = 0.66929 (ENCO Reamer size 17mm Reamer Size 0.6693)

ENCO has mostly low end tooling so don't consider any specs to be accurate. ( MSC bought them a few years ago, I doubt quality has gotten much better. )

What you really need to do is grind the flutes off of the first 0.5" to 0.75" to form a slip fit pilot. ( use a collet spinner on a surface grinder or a drill bit sharpener if you can get enough swing. )

An adjustable reamer would be better, just don't bother with the low end ENCO ones as they are going to be difficult to adjust. You would shrink the reamer, insert fully into the bushing, adjust outwards, ream a bit then check bore for shaft fit.

An even better way is to hone the bushing to size as this gives total control. ( See honing connecting rod pin bushings.)

If your part setup on the chuck side is off center at all, you will wind up with a larger hole.


Have a look at practicalmachinist.com for more info.

[wolf1941]

disregarding the quoted size of the reamer -

reamers will hold the dimensions given with in tens -
providing the hole to be reamed is within to be reamed specification -

.625 drilled hole , chances are hole was out of round to start of with and
out of center - we could argue about that one -

we do know removing 0.034 " [0.017 per side] with a hand reamer - feed by hand -
center support good idea , but it takes only one revolution and
the reamer is free floating until the next feed motion comes in -
so the reamer did not see a continues feed motion -
more ore less 10-20 start motion which is bad news for chip control -

chucking the reamer in the tail stock then either push the tail stock
by hand - which gives some kind of free cutting ore galling up indications ,

ore use the hand wheel for continues feed - - no feel what so ever

chips have to be cleared out to prevent- galling - worst case
scenario chip to tool welding - bad news -

small front cutting edged chamfer
is where al the action is - flutes only for guides -

over load the chamfer cutting edge , poor chip clearance ,
no lube to much metal removel the reamer will buckle -
drift of center and the so called no cutting guide flutes will gouge material -

LOL maybe not by inches but enough to ruin your day -

stock removal for reamers depending on size of reamer
in my shop - not more then 0.002 -0.004 per side -
low rpm - high feed -

Wolfgang

[Diesel911]

It is actually much worse then you think. The Guys over on this other Forum are useing adjustable Reamers (not the the ones that expand) but the ones that the Blades Side on. And, on one person came up with any sort of Guide.
I think with no guide it is tough to do accurate job unless the Bushings a already round inside.
Then the other problem is that no one knows what the Clearence Spce really is.

I posted at the tail end of this thread. I go by 300Dman there and at Benzworld
VWDieselParts.com • View topic - injection pump shaft bushings

This one mentions the .001 shaft Clearence but does not say if that is the total Clearance the Clearence on each side of the Shaft
VWDieselParts.com • View topic - I'm rebuilding my Injection Pump!

In this one the guy mounts said fabricated a one piece bushing and replace the 2 piece ones with that and has pic showing the Pump Housing mounted in a Lathe and a Reamer in the Tail Stock. He just said He used a 17mm Reamer no other details.

The Volvo IP housing has a port between the Drive Shaft Bushings. If that Guy made a one piece Bushing He made no mention of the need for that hole?
Vanagon Syncro Project: Search results for Fuel Injection Pump

Since the present total Clearance on My old Bushings is 0.0084" If I get the 0.0034 Clearance that I got on the Aluminum If not to spec I would at least be better off than before.

I am thinking that My Bushing Wear allowed too much pressure to reach the Shaft Seal causing it to grip hard on the Shaft. The Shaft is grooved and you can see the Seal in the Pic. I have never seen a Seal Failure like that on anything.
Also the Seal is 5 Years Old and made of Viton.

[Simpler=Better]

Since you have acess to a lathe, I would drill the initial hole at .5", and then bore it out to size, taking 0.020" cuts, with .005" and .001" finishing passes. Just my $.02

Boring is the "dead nuts" accurate way to do it.

Of course use a rigid tool setup, slow feed rates, and a healthy amount of coolant.

EDIT: Heat can mess with your dimensions. You want everything at room temp when you're cutting it.

[ken1]

Wolfgang pretty much hit it on the head. Reamers are not accurate removing more than .002 -.003 per side. Also an adjustable boring bar in a lath would be the most accurate method to get your desired fit.
Ken

[Diesel911]

Originally Posted by ken1

Wolfgang pretty much hit it on the head. Reamers are not accurate removing more than .002 -.003 per side. Also an adjustable boring bar in a lath would be the most accurate method to get your desired fit.
Ken

I think maybe the point I was trying to get at has been missed. I think that the reamer cutting diameter is larger than 17mm to begin with.
I am going to try to verify that tomorrow. I am going to put the Reamer between the Centers and get the Dial Indicator on the smooth part of the Shaft which has an know OD measurement. I am then going to go over to the Blades and see exactly how much the stick out.

I have 2 Fuel Injection Pump Drive Shafts I also need to Check in a similar manner for run out.

This is something that happened where I used to work. Caterpillar makes a Fuel Injection Pump that resembles a mini V8 Engine. At the Back is an about 2.5 ID Babbitt Bushing but up front is a like 1.5 Brass or Bronze Bushing. The whole Pump is lubed by the Diesel Fuel.

The first couple of Pumps we got in had bad front Bushings and we replaced the Front bushing and it has to be reamed (for some reason you don't need to fool with the rear Bushing).

Sent to a Machine Shop x2 (we gave them the specs) and x2 in a month the Bushings failed again.

My Boss finally Paid for the special reaming setup. After that we never had any trouble with the Front Bushing Failing after we replace one.

So the moral of the story for Me is that a Reamer Will do the correct Job if the Reamer is matched to the Job and you have the proper setup/tools to keep it alighned.

Why did the Machine Shop Fail? I think the reason is easy to under stand. We brought them a job they were not setup to do and it was a small paying job that they were not going to spend a lot of time on.

The bored the Bushing to the desired Spec but likely messed up the alignment.
You see this same issue with the VE Fuel Injection Pumps in the VW Threads. Sent to a Machine Shop and came back extremely Sloppy.

The other issue is the lack of a verfied Spec on the Shaft Clearance.

[Diesel911]

[QUOTE=97 SL320;3349016]ENCO has mostly low end tooling so don't consider any specs to be accurate. ( MSC bought them a few years ago, I doubt quality has gotten much better. )

What you really need to do is grind the flutes off of the first 0.5" to 0.75" to form a slip fit pilot. ( use a collet spinner on a surface grinder or a drill bit sharpener if you can get enough swing. )

An adjustable reamer would be better, just don't bother with the low end ENCO ones as they are going to be difficult to adjust. You would shrink the reamer, insert fully into the bushing, adjust outwards, ream a bit then check bore for shaft fit.

An even better way is to hone the bushing to size as this gives total control. ( See honing connecting rod pin bushings.)

If your part setup on the chuck side is off center at all, you will wind up with a larger hole.


Have a look at practicalmachinist.com for more info.[/QUOTE]

http://www.practicalmachinist.com/vb/general/metric-inch-reamers-270625/
This did not easily clerify things. Apparenlty Reamers are made to be re-sharpend X amount of time so they are made at the upper end of the tolerence limit. For me that means it is oversized to start with.

Then they go on about how different feeds, materials and lubricant all change ths size of the reamed hole.

Essentially what I got from the thread was is that a Professional has a good chance of getting the results He wanted but even the Professional is not going to know for sure untill they start using the Reamer.

How to chose reamers
http://www.magafor.com/article.php?grp=815&famille=680&arbo=3&langue=uk
This is the one that was the most understandable.
http://www.magafor.com/811.php?grp=811

Another site was also helpful but I can't find it to post.

[Diesel911]

Originally Posted by Simpler=Better

Since you have acess to a lathe, I would drill the initial hole at .5", and then bore it out to size, taking 0.020" cuts, with .005" and .001" finishing passes. Just my $.02

Boring is the "dead nuts" accurate way to do it.

Of course use a rigid tool setup, slow feed rates, and a healthy amount of coolant.

EDIT: Heat can mess with your dimensions. You want everything at room temp when you're cutting it.

OK. I am not a Machinist. I have a Lathe but I don't have all the Tooling. There is no Coolant/Lub system (also I hate the smell of that White milky Soulable Oil especially when it gets old).

And I presenly lack the skill.

I do have enough skill that I can make a Reamer Guide to bolt onto the Fuel Injection pump.

[Simpler=Better]

Originally Posted by Diesel911

OK. I am not a Machinist. I have a Lathe but I don't have all the Tooling. There is no Coolant/Lub system (also I hate the smell of that White milky Soulable Oil especially when it gets old).

And I presenly lack the skill.

I do have enough skill that I can make a Reamer Guide to bolt onto the Fuel Injection pump.

If you can turn, you can bore. A sharp 2 flute endmill makes a fine boring bar. Feel free to PM me if you want to chitchat about it later.

I tihnk you're going to have more trouble making a reamer process for a small batch of parts.

Boring setup isn't too bad once you do it once:
-Mount part in chuck
-Confirm that it's centered with dial indicator
-Get your boring bar in the tool post (eyeballing placement is fine)
-Set the autofeed
-make a shallow cut, keeping things lubricated. WD40 is A-ok for this.
-After making the cut, and confirming that the part is smooth, take a measurement.
-take another cut, targeting a specific measurement.
-measure. if it's dead nuts on, they're you're calibrated & setup. if not, play with your setup until you can hit your target on the first try.

I would expect to spend maybe an hour boring a preexisting bushing, most of that setup and finding tools.