Carbide insert and holder help needed.

[sundown57]

i do have a manual mill. so thats my plan for this week end is to make a holder or 2. I did have some triangle inserts with no hole so i brazed them onto some stock and that worked well. But rotating them is a problem lol.

 

[Huub Buis]

I mainly use inserts than are hold by a screw (CCMT, DCMT, TCMT) because their profile is lower. I put the thread hole 0.1 mm (0.004") off center so the bolt tension presses the insert against the holder. I do not mill the edges at the appropriate angle (mostly 7°) but mill them straight.

 

[B2]

See fellow HM, @davidpbest ($60) book on carbide inserts etc.

David P. Best - Selected Resources for Machinists

Sharing technical resources, opinions, and anecdotes about machining and equipment.

www.hobby-machinist.com

The book click:

Amazon.com

 

[sundown57]

offsetting the screw is a good idea. thanks. I plan to make a left and right to fit the inserts i have that have holes

 

[mksj]

Most likely they are older style inserts that may have been used in a face mill, some of the older ones were clamped in. Holders typically do have a nomenclature on them that tells you what inserts fit it. Usually on the lathes you have indicated, one would have CXA holders and 3/4" shank insert holders. BXA is typically 5/8" holders and smaller/lighter lathes like 11-14" swing. Due to the size of the holder they are only made to take certain size insert and they are made for either negative, neutral or positive rake holders. Due to the angle and sizing of the insert pocket the insert type needs to match the holder. If you are new to insert terminology David Best has a nice book which outlines all this information.

Thread 'About my book "Introduction to Indexable Tooling for the Metal Lathe"'

Feb 24, 2023

Some of the members here on Hobby-Machinist ask questions about my book “Introduction to Indexable Tooling for the Metal Lathe”. So, I thought I would post some sample pages from the book, to give an overall flavor of the writing style, and include the complete Table of Contents as an attachment here. Have a look at the attached if you’re interested.

When I first got my metal lathe (a Precision Matthews 1340GT), I made the early decision to avoid making and sharpening my own HSS tools if possible. This decision was driven largely by the fact that I have been a...

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[sundown57]

guess i have a lot of learning to do. lol

 

[durableoreo]

I think the machinist means a SNMG insert. That has 8 identical cutting edges. Because these inserts are targeting larger lathe's you have to take heavy cuts to get the chip breaker working. Not an insert for making small stuff. Also when you chip an edge, the bottom edge could also be ruined. To safe money, you have to calculate the price per cutting edge.
Because of the 90° cutting edge (no clearance), this insert is nut suitable to cut up to a shoulder. A WNMG insert has 6 identical cutting edges and a °5 degrees clearance.

Last I looked, square inserts were much less available in small sizes. I have a 9x20 and 3/8 size seems about right. I could not easily find inserts or tool holders in smaller sizes.

Unfortunately, choosing the insert shape isn't the right way to deal with these tools. You'll have to rely on tradition. It's a little frustrating because it's opaque when you're a n00b (like me).

 

[Huub Buis]

Last I looked, square inserts were much less available in small sizes

The way these inserts are used on the lathe, top cutting edge leaning a bit forward, spreads the heat over a larger cutting edge so faster feeds, faster speeds and higher material removal rates are possible. That requires a big and strong lathe lathe, large work piece diameters and so large tooling diameter.