[stustev]

I would sell inserts. There is no magic to this. Any machinist could bore the spindle, install the insert, and bore the insert.
Again, demand (qty mainly) determines the insert price.

[stustev]

In all honesty - any machinist could build the insert and then install it. heh
I build mine from S7. Saw to length, face to length and drill a through hole, heat treat, wire edm the taper, grind the OD with a bushing style lead in and face the back side a little.
I am sure most any tool steel will work.
You will see a prussian blue pattern increase a little from the start but quickly the pattern settles in and no further interface development is noticed.

[mactec54]

stustev

After you have bored the spindle out, how do you press the bushing/sleeve into the bored out spindle, you would need just over 12ton with that fit to push it in

[keebler303]

stustev

After you have bored the spindle out, how do you press the bushing/sleeve into the bored out spindle, you would need just over 12ton with that fit to push it in

He said he used liquid nitrogen, I assume it would slide in at that point. No telling what that press fit does to the spindle body and how that effects the spindle bearing preloads though.

[stustev]

He said he used liquid nitrogen, I assume it would slide in at that point. No telling what that press fit does to the spindle body and how that effects the spindle bearing preloads though.

Spindle body deformation is the reason for less the .002 press fit.
I always use liquid nitrogen and always drive the insert in with the Z axis. At first I would push it in by hand (with gloves). One time the humidity was high. Water froze on the insert and it stuck half way in. I had to bore the insert out to remove it. Now I put the insert on a small riser and use the Z axis. This is strong enough to push past the ice.

[mactec54]

Keebler

The liquid nitrogen won't move it that far, stustev said the liquid nitrogen moves it .006 , you only have to do the math to know that number is not possible

[stustev]

He said he used liquid nitrogen, I assume it would slide in at that point. No telling what that press fit does to the spindle body and how that effects the spindle bearing preloads though.

Spindle body deformation is the reason for less the .002 press fit.
I always use liquid nitrogen and always drive the insert in with the Z axis. At first I would push it in by hand (with gloves). One time the humidity was high. Water froze on the insert and it stuck half way in. I had to bore the insert out to remove it. Now I put the insert on a small riser and use the Z axis. This is strong enough to push past the ice.

[stustev]

sorry about the double post
I have not done the math but I have measured a lot of the inserts. .006 shrink is what I measure

[stustev]

math

given the thermal expansion of steel is .000013 inches per inch per degree
then a 2 inch diameter would shrink/expand .000026 inches per degree

given the temperature of liquid nitrogen is -321 degree F
given a standard temperature of 68 degrees F
results in 389 degrees temperature drop

.000026 times 389 = ?

possibly .010114 inches shrink/expansion

looks as if it may be possible to measure a .006 diameter drop

[stustev]

Sorry about the almost double post here - I picked the incorrect column to choose my coefficient - I was/am wrong
I chose the metric at .000013 and should have had the 'not' metric at .0000073

here is the correct math

given the thermal expansion of steel is .0000073 inches per inch per degree
then a 2 inch diameter would shrink/expand .0000146 inches per degree

given the temperature of liquid nitrogen is -321 degree F
given a standard temperature of 68 degrees F
results in 389 degrees temperature drop

.0000146 times 389 = ?

possibly .0056794 inches shrink/expansion?

still close to the observed .006 and if you realize the temperature in a shop is usually higher than 68 you would get a little more than the calculated number above

thank you to the engineer from Louisiana for the call correcting me

looks as if it may be possible to measure a .006 diameter drop

[stustev]

To answer the question about changing spindle bearing preloads. I wondered about that at first. That is one of the reasons why I let the first machine run for a year before doing the second machine. We have seen no noticable reduction in spindle bearing life after the insert installation.
The second machine to get the insert was the VF10. I did it on a Sunday afternoon. I was walking through the shop the next day and the operator asked what had happened to his machine. I asked what he noticed. He said the tools are not sticking in the spindle during a tool change. The machining NOISE was reduced a tremendous amount and the machined finishes were much better. I told the operator I had put an insert in the spindle just like the VF6 sitting next to the VF10.
We also found the machining accuracy was better and the tools last longer.

[mactec54]

stustev
possibly .010114 inches shrink/expansion,

No that is not possible

Different steels shrink by different amounts, here is a chart that will give you a good guide as to how far your 2" bushing can shrink, on this size that you have it is just under .004 that it can shrink, which is plenty for you to fit it in, if the bore is the correct size, & the surface finish is good in the bored out spindle

[stustev]

stustev

possibly .010114 inches shrink/expansion, No that is not possible

Different steels shrink by different amounts, here is a chart that will give you a good guide as to how far your 2" bushing can shrink, on this size that you have it is just under .0004 which is plenty for you to fit it in, if the bore is the correct size, & the surface finish is good in the bored out spindle

I must agree .010114 is too much.
I must disagree .0004 is the correct amount.
The correct calculation is in a post above.
The correct calculation is approximately equal to my observe measurement.

[handlewanker]

Hi, just my 2 cents worth as I've never even seen a Haas.......what is your opinion on having the inserts secured with Loctite?.....this makes for easy removal should the occasion arise.

Some years ago, I bored out a drill press spindle to fit in a 3 Morse taper adaptor that is commonly used in the turret of a capstan lathe.

The Morse taper adaptor is hardened and ground all over, and has a 3 Morse taper bore with a parallel OD......it is used in the turret of a capstan lathe when Morse taper shank tools are used.

The spindle end was bored out to give a .02mm clearance for the Morse taper adaptor and the adaptor was secured with Loctite.
Ian.

[mactec54]

stustev

I have to agree with you as well I had one to many Zeros in there, it should of been .004,(Read the chart)I corrected the post the chart is from a company that does this every day & the numbers are correct

The correct calculation is in a post above.

No that is a theoretical calculation, it is not what will happen, there are to many variables in play, when doing this, but you can dream all you like, you can not measure something like this with a micrometer when it is that cold, you could measure it with a none contact micrometer, like with a laser micrometer, but not everyone has one of those

I think if everyone fitted there tool holders to the spindle taper, then you would not have any of these problems, over a time period, (Many years) you can expect to get some wear, with the taper

Using S7 for your bushing material, heat treated to it's max hardness (61RC) is softer than what the Haas spindle is

For choosing the right material to do this with, you need to have 10/12 RC of hardness difference between the 2 materials being used, the tool holder should be softer than the spindle which are in most cases, so the tool holder wears before the spindle does

The only thing you are doing that makes it better is the curve you are machining into the spindle taper, again, this should be done to the tool holders & not the spindle taper

Doing this to the tool holders has the same effect

Tool holders that stick, you will find that the taper at the top 1.5" of the holder is the problem, they swell when the pull stud is torqued to the 80ft/lbs. that is recommended for them, these same tools that stick will damage the spindle, because the tool holder is tight at the top of the taper
& loose at the bottom, this lets the tool holder move around at the bottom when cutting, causing the damage that you are seeing in the bottom of these spindle taper's, fix the tool holder problem & your spindles will have a normal life

[handlewanker]

Hi without any doubt one of the best tool retention tapers is the Morse taper........once it is driven into contact it is to all and intents a solid fixture with the spindle, having no tendency this side of tomorrow to go slack under any load known to man.

The biggest problem is that with a taper as slow as this the retaining force practically makes it impossible, without a similar dismounting force, to release it.

You find this problem in large lathes where heavy shafting, supported on a revolving centre, tends to drive the centre tightly into the tailstock barrel, so tight that it often require a strip down of the tails stock to remove the centre.

In the factory I worked in many years ago we solved the problem by fitting a spacer collar behind the centre body to reduce the tendency to drive further into the tails stock bore......the collar was custom made to suit the centre and the lathe it was used on.

The same principle would make the Morse taper suitable for a spindle location where the draw bar pull pressure would normally make it impossible to remove the tool, but as a retainer method it is far superior to the ISO30 et al tapers for retention accuracy and retention grip, I have to wonder why it has not been used more often.

BTW, back in the 70's we had a Bridgeport mill that had 3 Morse taper in the spindle, and the draw bar was tightened by a knob on the end with hand pressure only......the previous spanner hex on the draw bar end was removed, due to the grip of the taper making it impossible to remove the tools when someone with a death grip over tightened the draw bar with a spanner.
Ian.

[tjamscad]

Some pictures of the taper.

https://plus.google.com/u/0/photos/1...5/albums/posts

[tjamscad]

I think if everyone fitted there tool holders to the spindle taper, then you would not have any of these problems, over a time period, (Many years) you can expect to get some wear, with the taper

mactec54,

That was a great explanation but I am confused by this statement. There are multiple brand machines in this shop. Would you be suggesting taper the 100+ tool holders for the Haas or Fadals? Maybe your saying that I should only have Haas tool holders used in the Haas machines? Our Fadals, and Cincinnati's dont have sticks and pops on tool changes. The Haas spindle with the insert (VF6) was replaced with a new Haas spindle. After a couple of months the operators started complaining about tools sticking during tool changes. I wanted to call B.S. on the taper thing but I have been at this shop for about 20 months now and I dont get complaints from the VF10 and VR11 operators about tool sticking. I am clearly not as educated as you but from what I can tell the taper thing works.

[mactec54]

tjamsacd

I found that the Haas tapers, have been ground with a very tight tolerance, This could be there biggest problem, the Fadal, Cincinnati & others are loose on the taper spec, they are all within the 7/24 spec, so in most cases you don't get the tools sticking, the tool holders only stick at the top 1" to 1.5" in the Haas spindles, & this only happens when the tool holder has expanded by the pull stud, next time, you see a tool sticking take it & look at the top 1.5" & you will see the marks on the tool holder, when this is fixed that tool will not stick anymore, this is also what damages the bottom of the spindles, because the tool holder is sticking like this (at the top of the spindle taper) the bottom of the tool holder is not seating in the taper correctly, so when cutting it's moving around damaging the bottom of the taper

If a spindle is not able to be rebuilt because of a damaged spindle front, I'm all for doing what has been done by machining it out & fitting a sleeve/bushing, this gives the spindle another life without the big cost that goes with getting a new one

Why the inserted spindles work, is not because of the insert, (the insert is the repair) it is how he has machined the spindle bore, so the tool holder is only touching at the bottom & the top of the spindle taper, this gives the tool holder less surface contact, & will be easy for the tool to be changed, without any sticking of the tools, you will also get better cut quality as well, because the front of the tool holder can seat better in it's taper

[victorofga]

just some thinking..

if you cant reduce the 2.5 ""sticking out"" then you could try reducing stepdown

how much would more the roughing time if stepdown were only 0.875 or 1.00 inch?
you wrote the present setup 1.27 stepdown..


time would be more, but swapping each 2-3 month regularly a spindle ... I think would worth a try..

making one month series, 40 pieces with reduced stepdown in roughing..
even numbers saying its ok, yet, your spindle worn out each 2-3 month..for the extra time on machining you might skip 2-3 or more spindle replacing..

I didn't calculate forces I tried to follow a simple logic..


edit: as others mentioned, a manual drawbar I also think more rigid ... a double length nut tied with wrench extended with a pipe can be very stiff.. if that move, only way if it breaks.. no flexing..

we used endmill with morsetaper, mounted into iso50 taper.. but they were hss mills..
so there were no collet, only directly in the isotaper a morsetaper.. a lot shorter and stronger..
yet, excessed force could snap even a 45 mm endmill..