Shank with flat in a shrink holder to get out of a stick - will it work?

gregormarwick · Jul 25, 2019

I have a job in with some hydraulic port cavities that are difficult to access, being at the base of a fairly deep vertical wall.

I have tools on hand, but they have a flat ground on the shank where they were held in a sidelock. New tools minus the flat are on a long lead time.

One 20mm shank, and one 32mm. If I buy standard shrink holders I will have to turn them down a few mm to clear the wall in both cases. The tools are HSS, and I don't have a fancy shrink machine, so they will be in there for good.

So, turned down shrink holders, and tools with a flat on the shank. How bad might I expect the runout to be?

kenton · Jul 25, 2019

I believe tools for shrink fit holders have a tighter shank tolerance than standard tooling. Your HSS will probably not be in the tolerance band.

DMF_TomB · Jul 25, 2019

gregormarwick said:
I have a job in with some hydraulic port cavities that are difficult to access, being at the base of a fairly deep vertical wall.

I have tools on hand, but they have a flat ground on the shank where they were held in a sidelock. New tools minus the flat are on a long lead time.

One 20mm shank, and one 32mm. If I buy standard shrink holders I will have to turn them down a few mm to clear the wall in both cases. The tools are HSS, and I don't have a fancy shrink machine, so they will be in there for good.

So, turned down shrink holders, and tools with a flat on the shank. How bad might I expect the runout to be?

.
full length flat sometimes puts stress on holder and it cracks especially if thin walled. set screw holder often easier to use. sure runout can be higher and it can vary with torque used.
.
measure all tool runout with optical tool presetter and after 10,000 measurements with no noticeable or barely noticeable effect you might be surprised at what runout amounts you actually need to worry about. not what some salesman says you need to worry about.

gregormarwick · Jul 25, 2019

kenton said:
I believe tools for shrink fit holders have a tighter shank tolerance than standard tooling. Your HSS will probably not be in the tolerance band.

Shanks are excellent for size, both of them measure within 3μm of nominal. At least that shouldn't be a concern.

DMF_TomB said:
.
full length flat sometimes puts stress on holder and it cracks especially if thin walled. set screw holder often easier to use. sure runout can be higher and it can vary with torque used.
.
measure all tool runout with optical tool presetter and after 10,000 measurements with no noticeable or barely noticeable effect you might be surprised at what runout amounts you actually need to worry about. not what some salesman says you need to worry about.

Wall thickness on the 32mm shank will be 8.5mm, 20mm will be 8mm. Cracks are a concern for sure.

Runout needs to be just as little as possible. These are form reamers that generate features with fairly tight dimensional tolerances, and tight surface roughness tolerances. Surface finish is usually the first casualty of excessive runout.

DMF_TomB · Jul 25, 2019

gregormarwick said:
Shanks are excellent for size, both of them measure within 3μm of nominal. At least that shouldn't be a concern.

Wall thickness on the 32mm shank will be 8.5mm, 20mm will be 8mm. Cracks are a concern for sure.

Runout needs to be just as little as possible. These are form reamers that generate features with fairly tight dimensional tolerances, and tight surface roughness tolerances. Surface finish is usually the first casualty of excessive runout.

.
when i use bigger cutter like 3"dia multi flute full length assembled mill. it gets sent out tool in tool holder and ground or sharpened as a assembled unit. runout is much lower than way. often 10x lower

kenton · Jul 25, 2019

Tom, have you even read the original post?

DMF_TomB · Jul 25, 2019

kenton said:
Tom, have you even read the original post?

i already replied a end mill with full length flat ended up cracking many tool holders which gave varying runout and tool comp would need changing depending on high high the cutting forces were cause it was cracking the tool holders
.
hair line cracks often go undetected for years giving intermittent problems. it was determined it was coming from the full length flat on shank mills
.
this is dynamic runout changes which runout changes cause crack opening up under load. it gets taught to apprentices to watch out for it from the old timers

kenton · Jul 25, 2019

OP said he needs to turn down a shrink fit to gain access to a feature, you say use a set screw holder. Op says getting tools remade without the flat is not an option, you say assemble the tool holder and get the whole thing ground. Every suggestion you make has already been covered as to why it is not an option.

DMF_TomB · Jul 25, 2019

kenton said:
OP said he needs to turn down a shrink fit to gain access to a feature, you say use a set screw holder. Op says getting tools remade without the flat is not an option, you say assemble the tool holder and get the whole thing ground. Every suggestion you make has already been covered as to why it is not an option.

.
the discussion is will it work and whats discussed is possible problems. if nothing else runout with a shrink fit on completely round shank might be different that the shank with flat cause of uneven pressures with press fit on shank with flat
.
and of course a tool has sharpening error runout. you can take a dowel pin in tool holder and get completely different runout that the actual cutting edges cause it was resharpened with runout and it was discussed how to minimize this
.
and i discussed take 10,000 actual tool in tool holder runout measurements and you usually find runout not causing problems, is much higher that thought before the 10,000 measurements. i measure actual tool in tool holder runout including sharpening runout every day. very few tools have zero sharpening runout
.
i use set screw holders where tool is sharpened tool in tool holder assembled for lowest actual runout. as i said it usually works 10x better

kenton · Jul 25, 2019

DMF_TomB said:
.
the discussion is will it work and whats discussed is possible problems. if nothing else runout with a shrink fit on completely round shank might be different that the shank with flat cause of uneven pressures with press fit on shank with flat
.
and of course a tool has sharpening error runout. you can take a dowel pin in tool holder and get completely different runout that the actual cutting edges cause it was resharpened with runout and it was discussed how to minimize this
.
and i discussed take 10,000 actual tool in tool holder runout measurements and you usually find runout not causing problems, is much higher that thought before the 10,000 measurements. i measure actual tool in tool holder runout including sharpening runout every day. very few tools have zero sharpening runout
.
i use set screw holders where tool is sharpened tool in tool holder assembled for lowest actual runout. as i said it usually works 10x better

That is all fantastic data, but none of it is relevant other than "tools with flats don't work well in shrink fit holders".

Vancbiker · Jul 25, 2019

kenton said:
OP said he needs to turn down a shrink fit to gain access to a feature, you say use a set screw holder. Op says getting tools remade without the flat is not an option, you say assemble the tool holder and get the whole thing ground. Every suggestion you make has already been covered as to why it is not an option.

DMF always gives responses that are about 99% irrelevant to the OP`s question. I think most here realize that and just pass over his rambling.

dandrummerman21 · Jul 25, 2019

DMF_TomB said:
.
the discussion is BLAH BLAH BLAH

Do you have any constructive information to copy paste, or are you still going on about 10000 tools and their runout values?

I do not have any shrink holders, but gut reaction would say it should be fine.

However, as for an actual idea that may or may not help at all...

What if you were to cut the part of the shank with the weldon on it completely off (or grind it down a bit).

I don't know how long the shanks are, and how much would be left, but if you did that, wouldn't that stop any "uneven shrink" you would otherwise face?

Edit: a possibly better idea than above: Grind a groove into the shank where the weldon flat is, so that -none- of the shank around where the weldon flat is against the shrink fit holder. Above and below it would be full diameter, just grooved down where the weldon flat is. This would make the shrink even radially while leaving the shank length the same.

I would think that turning some off the OD of the tool would possibly cause a bigger issue than the weldon flat would, post shrink. But I still don't think it should be "too much" ??

How far down does this tool have to reach?

kenton said:
OP said he needs to turn down a shrink fit to gain access to a feature, you say use a set screw holder. Op says getting tools remade without the flat is not an option, you say assemble the tool holder and get the whole thing ground. Every suggestion you make has already been covered as to why it is not an option.

Doesn't he make you want to bang your head on a wall?

Milland · Jul 25, 2019

Hi Gregor,
I've dealt with similar issues in the past by making small segments from steel of the missing geometry, in your case much like a wide Woodruff key. You can profile a few to fit the measured gap, plus ~25U on the OD, then "superglue" them in place with the thinnest amount of adhesive that still secures the segments.

Before insertion you take the insert and, with a clean, new flat file of sufficient width and fine cut, "round over" the excess insert radius to match the HSS shank material on either side. This can also be done with a strip of medium grit silicon carbide paper on a hard backing, but is more likely to take the stray micron or two from the shank itself.

You do want to make sure your insert is well adhered and will not fall out during insertion, and to correct size. Ideally, check it with a matching diameter hydraulic chuck, something you can progressively tighten and observe wear marks from twisting on the soft insert. A second choice would be a good colleted chuck used similarly.

Otherwise, you'll be very cross...

Milland · Jul 25, 2019

dandrummerman21 said:
Doesn't he make you want to bang your head on a wall?

Are you implying that there's times you DON'T want to head bang?

You've been going to the wrong clubs...

dandrummerman21 · Jul 25, 2019

Milland said:
Are you implying that there's times you DON'T want to head bang?

You've been going to the wrong clubs...

Well, I do still have the long hair to do it. But I haven't been to a metal concert in the last few years. Last show was, uh, Exodus maybe? In 2015.

Getting married and having kids will do that I guess. Oh where has the time gone.

cameraman · Jul 25, 2019

I'm kinda interested in this more from a "learning perspective" .

@Gregormarwick If you have time can you make little sketch (crappy as you like) of this including the rough lengths of everything + obstructive wall (and maybe a link to the intended tool holders ) ?

For worries about runout, the lengths of everything + the height of the interfering wall + form tolerances of the feature you are trying to machine seem pretty important all together … (captain obvious); as you of course know.

Wondering what the actual cutting tool geometries/ edges are ? What tools are you actually using for this ?

Probably you'll have all sorted before you can find time to make a crappy or good sketch of the problem ;-)

Cheers / Ta.

isaac338 · Jul 25, 2019

dandrummerman21 said:
Do you have any constructive information to copy paste, or are you still going on about 10000 tools and their runout values?

I do not have any shrink holders

These two lines are great. "Do you have anything of value to add? Also I don't have any experience with the subject at hand, here's some information I came up with!"

Mike1974 · Jul 25, 2019

Are the flats ground the length of the shank? I thought I saw that, but not in the OP. If it is just a small flat like a weldon (?) it won't matter*. I would be more concerned with the HSS, but you said you measured them and they are good so I guess no problems?

*At another job we were getting into shrink fit and the Haimer guy that came to set it up and show us how to use the machine said flats on endmills were not deal breakers, but he advised in the future to get plain round shanks. Now if it is going to stick out of the shrink fit and leave a gap, I dunno what that might do. I can't imagine it would be much (imagining just a small flat here, just enough for a set screw), if anything at all...

G00 Proto · Jul 25, 2019

Sorry I can't solve your problem on the shrink fit tool... but I can solve a problem that everyone else is having on this thread:

Click on the persons "User Name";
Click "View Profile";
Click "Add to Ignore List";
Click "Yes";

I have been much happier with my user experience since doing this, I no longer have to wade through mumbled up bullshit to read a thread. As a courtesy to those of us that chose to "Ignore" fucktards; please refrain from quoting their asinine keyboard diarrhea. If you find this objectionable, please feel free to use the above forum functions on me. I will be happy to help you sound out the big words if you get confused.

gregormarwick · Jul 25, 2019

Thanks for the replies so far.

Clear a few things up: The flats on these cutters are full length, not weldon. There is a very short cylindrical area near the bottom of the shank, but most of that would fall in the lead in area of a shrink holder I'd imagine.

The flats are pretty shallow, such that Millands suggestion of making inserts would be pretty tough to do. I'll take some measurements tomorrow and post them.

The features in this case are simple SAE (J1926-1) cavities, so nothing demanding in terms of dimensional tolerances, but I do need a good finish. Workpiece is aluminium, 6061/6082 T6. The cutters are full form cavity (everything from thread minor to spot face)

The depth I need to reach from the top of the wall is only 120mm or so, but these are very short cutters, normally used on the surface of the part.

A 32mm shrink holder is 53mm outer diameter, I'd need to turn it down to 49mm.

A 20mm shrink holder is 42mm outer diameter, I'd need to turn it down to 36mm.

The cutters all have a ground face at the base of the shank, so an alternative would be to get some silver steel blanks, bore them to a light interference fit on the shanks, cut some threads in the tops of the shanks of the tools, and pull them in with a drawbar. Of course the cutters are good quality solid HSS, so threadmilling the shanks would be tough, although doable.

Shank with flat in a shrink holder to get out of a stick - will it work?

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