Author Topic: Indexable insert holder, machining steps  (Read 506 times)

Offline Mike K

  • Full Member
  • ***
  • Posts: 112
  • Country: us
Indexable insert holder, machining steps
« on: September 16, 2021, 06:05:35 PM »
I saw this in an issue of Machinist's Workshop (Apr/May 2011) and was confused about the steps the author took.  It's a pretty standard indexable insert holder.  The work is a square bar with a pocket machined into a corner and a threaded hole to mount the insert.  The screw hole is 6-32 and is on center with the end mill (3/8") path.

The author's steps:
1. Locate screw hole.
2. Center drill about 0.1" deep.
3. Mill the pocket.
4. Return to the hole; drill through and tap.

I'm not as experienced as most and don't understand why the hole wasn't finished first before milling the pocket.  It seems like the author added an unnecessary step by having to return to finish the hole?


Offline chipenter

  • Hero Member
  • *****
  • Posts: 900
  • Country: gb
Re: Indexable insert holder, machining steps
« Reply #1 on: September 17, 2021, 02:59:52 AM »
I think he set zero at the centre of the pocket , I have made holders and always drilled the hole last with the insert in place just to be certain .
Jeff

Offline Muzzerboy

  • Jr. Member
  • **
  • Posts: 97
  • Country: gb
    • The Mighty Shiz
Re: Indexable insert holder, machining steps
« Reply #2 on: September 17, 2021, 06:52:20 AM »
There are various ways you could do this but I guess it made sense to the operator.

Drilling after milling might reduce stresses on the milling cutter it might otherwise see as it transitioned over the drilled hole. But as the spot drill hole would have been milled away, it's not obvious what purpose it (spot drill operation) served in the first place.

Offline Mike K

  • Full Member
  • ***
  • Posts: 112
  • Country: us
Re: Indexable insert holder, machining steps
« Reply #3 on: September 17, 2021, 07:36:33 AM »
Okay, thanks.  I was just curious.

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 2462
  • Country: fi
Re: Indexable insert holder, machining steps
« Reply #4 on: September 17, 2021, 02:49:20 PM »
There are several methods that I have been reading, these I have considered

1: Mill the pocket and then locate the screw hole using the insert (you need a little offset to draw the insert into pocket or it will not be stable.

I made latest holder using mostly these instructions:


2: Or you could use some CAD/CNC to locake the features, bit like this:


Pekka


Offline Mike K

  • Full Member
  • ***
  • Posts: 112
  • Country: us
Re: Indexable insert holder, machining steps
« Reply #5 on: September 17, 2021, 07:48:49 PM »
Thanks for posting that, Pekka.  Stefan has great ideas.

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 2462
  • Country: fi
Re: Indexable insert holder, machining steps
« Reply #6 on: September 22, 2021, 09:30:46 AM »
He explains reasoning and though process pretty well, doesn't he? He also tells when something is opinion or preference. I find his videos informative and more often than not I actually use something he has shown.

There are some pictures of one toolholder I cooked up. Making it was not difficult, designing how to mill the angles and grind the 35 degree insert to 40 degree insert was a challenge. When I decided to use round stock and ER Collet holder in a square block to implement compound angles all came out easy.

https://www.madmodder.net/index.php/topic,12967.msg155361.html#msg155361

Offline Mike K

  • Full Member
  • ***
  • Posts: 112
  • Country: us
Re: Indexable insert holder, machining steps
« Reply #7 on: September 23, 2021, 03:19:11 PM »
Thanks, Pekka.  You do good work.  I hope someday to have a surface grinder, too.

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 2462
  • Country: fi
Re: Indexable insert holder, machining steps
« Reply #8 on: September 24, 2021, 09:03:25 AM »
I happy if that was any inspiration or help. My work is nowhere near same level of the gentlemen I linked, but they have been really inspirational to my work.

If I can make a toolholder, anybody can. For insert holder most important thing is pocket bottom: It must be flat and uniform and hard enough to support the insert. This is to prevent the relatively britle insert from breaking. Very accurate pocket is needed mostly to index the insert (you chip one, change new without disturbing the setup) and you are good to go - even if this happened just before finishing. Most of the time you could get away with just a fence on one side of the insert to counter the cutting forces. Some cases you could use just a pin to index one side of the insert (just put it to abut the insert to counter screw tightening torque, or tightening the screw might cam the insert out of index.

I made the pocket, because I wanted. I could just as easy to mill the top flat and put there a separate piece (fork kind of thingy) with glue/screw/solder and it would have worked fine, but milled pocket just looks more professional. Most likely does not affect my work at all, but we hobbyist work for the love of the art and not for profit.

That is actually a TCG American model but made in England, sold to Sweden, resold to Finland and I ended up buying it with 500, because it one fried saw advertisement and offered to drive half the distance (about 740 km one way....) I rented the lorry on the morning, set off, buyer had a forklift to load and another friend offered come take it off near here at his storage, returned the lorry back late night. Weighting bit over a metric ton made it proverbial to transport home last 20 km and shove it into garage was another story.

There was a bunch of accessories with it. Some usefull, some worn out, some worn out beyond repair.

I needed to put new bearings into spindle and have new belt made. Crap load of cleaning and making sure that all oil galleries works. Nothing fatal or show stoppers, all basic stuff just a lot of TLC.

Making new shroud for the grinding wheel, balancing arbour and dust removal "system" has been taking some time too. Some fittings and features are still work in progress, I make them as I need them.

Pekka