PDA

View Full Version : toolpost grinding



Tony
06-16-2004, 05:06 PM
greets all.
have been thinking of building a small-ish (medium?) toolpost grinder for the lathe.

there are some good threads in the archives.

a bit bigger than a dremel but smaller than the fullblown grinder.

questions:
how fast should this go?
what type wheels are good to use?
*how* do i use it? ...

that is, do i grind on the leading edge? trailing edge? face-on?

what are typical feed rates? (say a 6" stone, more or less, and a 2" diameter workpiece)

anyone ever try making surface grinding attachments/accessories for a mill? would
table speeds be too slow here? bad idea?

any tips greatly appreciated.
-tony

Evan
06-16-2004, 05:15 PM
I've been using the one I made from a cheap drill press and it has been working ok. Well enough in fact that I think I will turf the drill press spindle and make a really sturdy and accurate one with tapered rollers. Still worth the $35 US I spent if only just for the motor and the experience. I recently made myself a nice set of piloted drill bits with it. Bits cost 50 cents each but if bought as piloted would have cost a LOT more.

As to wheel I have been using a 4" CBN wheel. Sure works nice and holds it's shape really well. A bit expensive to buy though unless your wife gives it to you as a present. http://bbs.homeshopmachinist.net//biggrin.gif

Tony
06-16-2004, 05:26 PM
thanks evan.
another quick question: in the lathe, is it best to grind with or against the direction of workpiece rotation?

and what difference does it make? (finish?)

-tony

Joel
06-16-2004, 06:04 PM
Perhaps this will help.

http://bbs.homeshopmachinist.net//Forum1/HTML/002752.html

Sprocket
06-16-2004, 10:14 PM
HSM published a couple of plans for tool post grinders. One was a Rudy Kouhoupt project, and fairly small/light. Another was by D.E. Johnson in Jan/Feb and Mar/April 1999. It used a laminate trimmer for power, and crowned pulleys to change speeds for internal or external grinding. Seemed well thought out for home use, but probably too light for every day. I've thought I'd build one of these, one of these days.... Maybe Neil could help with back issues.

Ragarsed Raglan
06-17-2004, 10:45 AM
KH,

I've been using a T/P grinder for some time now (well, what I mean to say is, I have used one once every now and again over the last 7 or 8 years!). They are a great tool for the odd job ~ no doubts.

One lesson I learnt early on, was that the grinder can only make light cuts, even a reputable manufacturers T/P grinder can only make light cuts. In fact it's a life lesson of grinding ~ period!

I was trying to 'put on' 'alf a gnats knacker' (1/2 RCH US equiv.) and finding the wheel stalling. The answer to the problem was to set the compound slide over to about 6* and then the compound infeed indicator can be read off in 1/10,000ths for every marked 1/1000th, so that one turn of the screw which would normally be 1/10th inch will be 1/100th inch.

Use a 3/4" O/dia stone for internal grinding (will need something like a 1/4" mush head bolt to secure), run at a design speed of about 12,000 rpm. A 2 3/4" O/dia stone makes a good external grinder on a 10" swing lathe. Run this at about 4,000 rpm. My T/P grinder has stepped pulleys for the speed changes, and it uses flat belts on crowned pulleys. Belts are about 1/2" wide polyester/nylon/polysomethingorother.

You'll need a thin edged cupped wheel for face grinding. Make a diamond dressing arrangement which is easy and handy to use 'mid job'.

I always counter grind.

RR

[This message has been edited by Ragarsed Raglan (edited 06-17-2004).]

Dr. Rob
06-17-2004, 02:13 PM
Yeah, do it sometimes. Have a variety of methods. Have adapters / toolpost holders for a 5" angle grinder, a 5" bench grinder, a Dremel and a purpose-made TP grinder with two speeds.

Like Ragarsed said, be nice. Even the angle grinder can't take too much.

As far as rotation goes, I did notice once during a long grinding session that the lathe chuck had been worked loose from its thread and was unscrewing itself. Vibrations + counterrotation, I guess. So keep that in mind.

And just generally, I like those Dremel reinforced cutoff wheels for detailed work. Not the grinding discs; they just break.

Tony
06-17-2004, 03:53 PM
thanks guys.
i must've completely missed that other thread, sorry for the repost.

i want to put together a decent TPG mostly to cut alot of round HSS stock i have on hand. for making the odd tool here and there.

i put together a small one (using an air die grinder) not too long ago for "truing" my 3jaw. it had bellmouthed a bit. but the small grinder didnt work well on larger work. chattered alot. must be the bearings in the cheap airtool.

otherwise i dont work with hardened steel very often. might want to sharpen the occasional punch, but not much else.

is a TPG any good for unhardened steels?
other than maybe loading a buffing wheel on? http://bbs.homeshopmachinist.net//smile.gif

thanks again,
-tony