Index Tip Lathe Tools

Indexable Tip Tools: - Cost $0.50

I was given several indexable carbide tips and this inspired me to make my own tool-holders & boring bars for them. These complement my 3/16" H.S.S. tools ground from blanks & my small brazed carbide tip tools.

Since making my indexable tools, I have found them to be invaluable for machining. They work equally as well as my neighbours $189 set at a fraction of the price - My set cost me 50-cents.

I made a set of 4 tool-holders from scrap steel (salvage yard - I used 1/4 of a $2 piece) & Allen-head screws removed from hard discs. Together with the 'free' tips, total cost 50-cents & a few hours work.

To compliment the basic set of lathe tools I added a couple of small indexable-tip boring bars. These were made from round section steel shafts removed from old scrapped inkjet printers. Together with the 'free' tips, total cost 0-cents & a few hours work.

All tool-holders were milled in the lathe using an old 9/16" end mill once owned by my father (at least 35yr old) & a re-ground broken 1/8" drill, used as an end mill. I also used my home-made angle plate with a drilling vice (2-1/2"), though I could have held the steel in my toolpost for machining if I didn't have the angle plate.

The tip mounting surface was milled at an angle of 5-degree down from the horizontal towards the cutting edge. This down-slope enables the use of both positive & negative rake carbide tips.

The first thing to know in making a lathe tool is the vertical distance between where the tool will sit in the toolpost, and the lathes centre height. My lathe can handle a 19mm high tool, other lathes will be different - mine is exceptionally high for a lathe of this size. When you know this, you will know the maximum height of the tool from base to the top of the indexable tip. I made mine at much less than the maximum height, & use packing to bring up to centre.

The manufacturing process for the index tip toolholders is to:

	Using rough rectangular or square section steel bar, cut off a length equal to the required tool length. About 80 to 100mm is enough.
	I then mill all 6 surfaces on the lathe (end mill in the 3-jaw chuck, new tool piece in a drilling vice mounted on an angle plate, in turn mounted on the cross-slide), until I reached the final dimensions of the tool. Note: this can also be accomplished by holding the bar in the 4-jaw chuck & facing off each side.
	The tool tip was tilted outwards in a drilling vice mounted on the angle plate to give the 5-degree angled cut for the tip holder. Machine until you have a good seating a couple of mm deep. Ideally it should be such that, when the tip is attached it is at or just below centre height of the lathe when held in the toolpost - you can always pack under the tool to bring it to height as required, using old feeler gauges or what-have-you.
	Superglue a tip insert into position & drill a pilot hole for the holding screw using the hole in the insert as a guide.
	Cut the thread into the toolholder. I used #6NC32 Allen head machine screws tapped into a 1/8" pilot hole (near enough for this job). These screws were salvaged from an old hard disc casing.
	Remove the insert by gently applying heat from a blowtorch to destroy the superglue. So long as your not too aggressive no harm will be done. 200C is more than ample.
	Clean up the old glue by scraping & replace the insert using the machine screw this time.
	Machine or grind the end of the tool until almost touching the insert.
	Remove the insert & continue grinding a small amount to provide a little clearance at the edge of the tip. then grind the side &/or front clearance angles, the same as you would for a H.S.S. tool.
	clean up burrs etc, re-attach the tip

There you go, a home made index tip tool. All the tools I made have required a 1/8" drill, #6NC32 tap & been machined with an old end mill & a re-ground, broken 1/8" drill.

Indexable tip, Carbide & H.S.S. Boring Bars: - Cost $0

(The boring bar toolholder & the standard boring bar came with the lathe when purchased).

Pictured Left to right:

	Standard style 10mm boring bar.
	2 Indexable tip boring bars - made using above method.
	Broken H.S.S. drill boring bar.
	2 Reground masonry drills as carbide tip boring bars.
	Standard style 10mm boring bar holder.

The reground masonry drill boring bars are just normal masonry drills, with the tips reground as a cutting tool by using a 'greenstone' grinding wheel.

The indexable tip boring bars started out as shafts out of old inkjet printers.

	They were first turned down in diameter on the lathe with the the central axis of the shaft offset to one side in the 4-jaw chuck. This means the end of the shaft will have a lump to one side.
	The end is ground down to accommodate the indexable tip.
	Using the same superglue trick, the screw hole is drilled & tapped.
	Heated to release the tip then the tip replaced using the screw alone.
	The end is finally ground to provide the appropriate clearance angles for the tip.

The H.S.S. boring bar is simply a reground twist drill that the cutting edge had broken on.

I have found that both the H.S.S. & the masonry drill boring bars are very good for boring out holes for small shafts, especially when I need to bore out a small straight or tapered hole.