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View Full Version : Pinging Forrest: Harbor Freight Tool Grinder Question



lazlo
08-19-2007, 06:28 PM
I've been using my Harbor Freight 46727 (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=46727) tool grinder (the Baldor 500 clone) with plate-mounted aluminum oxide wheels (the 46 grit J&L special), but I'd like to mount a diamond wheel on it.

http://www.harborfreight.com/cpi/photos/46700-46799/46727.gif

The problem I'm running into is that the wheel plates have 8mm x 1.25mm screws (roughly 5/16" in size), but Western diamond wheels have countersunk holes for 1/4" screws.

What is everyone doing to mount a diamond wheel on the HF grinder? I don't want to modify the diamond wheel, but I can't re-tap the 8mm holes for 1/4" flat head socket screws with (82 countersink).

The only two options I seem to have is to re-tap the smaller holes on the mounting plate for 1/4" cap screws, or make a new mounting plate?

Forrest, I know you use the HF grinder to mount your diamond laps -- how do you do this?

Thanks!

Robert

charlie coghill
08-19-2007, 09:23 PM
I am not Forrest, but I have one of the HF grinders that you are speaking of. On mine I remade the backing plates as they had large voids from the casting.

If your backing plates are fine just figure out what the bolt PC is on the grinding wheel. Find center of the backing plate and drill four new holes for the PC of the wheel you are using. Split the distance between the present metric holes.

platypus2020
08-19-2007, 10:13 PM
Charlie,

Where are the voids in the castings, the backing plates on mine are solid, and the replacement backing plates, I bought fron HF parts were also solid. Maybe HF is using different vendors for the parts, they are not great quality, I've had to redrill them numerous times as the 8mm x 1.25mm threads keep stripping out. The replacement backing plates were far better quality than the originals.

Jack

Forrest Addy
08-19-2007, 11:36 PM
I scounged up socket flathead screws that worked for the back plate and ran them in. Problem ignored; expedient used by reflex. The aluminum is soft and the engagement is short so don't over torque the screws or you'll pull the threads right out.

Carld
08-20-2007, 01:02 AM
drill four new holes for the size you need.

lazlo
08-20-2007, 01:10 AM
Where are the voids in the castings

The mounting plates are cast, and the back sides are unmachined, and several people have found large casting voids on the backside.
I actually have what was probably a casting void on the front side -- there's an aluminum plug press-fit into a hole that's not on the bolt hole circle.


the backing plates on mine are solid, and the replacement backing plates, I bought fron HF parts were also solid.
...
The replacement backing plates were far better quality than the originals.

How much were the replacement plates?


I've had to redrill them numerous times as the 8mm x 1.25mm threads keep stripping out.

My aluminum shoulder bolts were way undersize for an 8mm thread, I'm assuming to make tolerance, so it doesn't surprise me that you had problems with them stripping out.

lazlo
08-20-2007, 01:16 AM
I scounged up socket flathead screws that worked for the back plate and ran them in.

There are two sets of threaded holes in the mounting plates: 8mm x 1.25mm thread, and what look like M6 holes.
I'm guessing you drove 1/4 x 20 socket flatheads into the smaller, M6 holes?

Thanks Forrest!

deltaenterprizes
08-20-2007, 10:16 AM
I have one of those grinders I have not used yet and was planning on replacing the wheels and this will help me avoid some problems I hope!

lazlo
08-20-2007, 12:48 PM
There are two sets of threaded holes in the mounting plates: 8mm x 1.25mm thread, and what look like M6 holes.
I'm guessing you drove 1/4 x 20 socket flatheads into the smaller, M6 holes?

As an update on this, you're supposed to use the smaller set of holes for the diamond wheels:

M6 x 20mm (length) flat-head socket screws fit the smaller set of holes perfectly.
I just spun-up a 3M diamond wheel with the new screws and it works perfectly, with no unusual runout.

Just as a reminder, flat-head screws are measured from the top, so the shoulder screws for the big holes are M8 x 16mm (length).

pgmrdan
08-20-2007, 01:01 PM
I assume you're talking about this grinder -

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=46727

and this aluminum oxide wheel -

http://www.jlindustrial.com/catalog/product.jsp?id=CPW-14210H

and perhaps this diamond wheel -

http://www.use-enco.com/CGI/INSRIT?PARTPG=INSRAR2&PMAKA=307-3449&PMPXNO=8204881

or this diamond wheel -

http://www.use-enco.com/CGI/INSRIT?PARTPG=INSRAR2&PMAKA=391-5640&PMPXNO=952556

This diamond wheel is much too expensive for my wallet -

http://www.jlindustrial.com/NOD-91665C/SEARCH:KEYWORD/product.html

I already have the tool grinder but just wanted to see if these wheels are the closest fitting wheels available before I purchase them?

I didn't see a 3M diamond wheel on enco's site. Can you provide a link to the one you're talking about?

Thanks,
Dan

lazlo
08-20-2007, 01:27 PM
I assume you're talking about this grinder -
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=46727

Yep, that's the one. I'll add that to the thread title...


and this aluminum oxide wheel -
http://www.jlindustrial.com/catalog/product.jsp?id=CPW-14210H

Right, although the particular wheel doesn't matter. The aluminum oxide or silicon carbide (green) plate-mounted wheels take a 3/8" socket shoulder screw, which the HF 46727 translates to 8mm x 1.25mm thread x 16mm length. These are the hand-made aluminum shoulder bolts that come with the grinder. Those bolts work fine with the J&L, KBC Tools, or Norton plate-mounted (Type 35) aluminum oxide wheels.

The problem that I ran into is that all the diamond wheels (at least, all the western ones) come with 82 countersunk, 1/4" holes. So if you want to mount a diamond wheel on the HF grinder, you need to use the smaller set of holes on the aluminum wheel plate, with 6mm x 16mm (length) screws.

I've tried 3 different diamond wheels that I've gotten off Ebay, and they all have the same hole pattern.

lazlo
08-20-2007, 01:39 PM
I already have the tool grinder but just wanted to see if these wheels are the closest fitting wheels available before I purchase them?

Any 6" plate-mounted Type 35 wheel will fit the HF grinder. I like the one from J&L Industrial, because it's a Norton wheel.


This diamond wheel is much too expensive for my wallet -
http://www.jlindustrial.com/NOD-91665C/SEARCH:KEYWORD/product.html

I've gotten all my diamond wheels from Ebay. The standard wheel designation is D6A2. I usually pay around $75 for a new Norton/Elgin/3M diamond wheel.

By the way, the "Mesh" ratings on diamond wheels are somewhat higher than the "Grit" rating on an aluminum oxide wheel. I sharpen my scraper
blades with a 220 Mesh diamond wheel, which is about equivalent to 180 grit.

platypus2020
08-20-2007, 01:44 PM
Lazlo,

IIRC, I paid about $25.00 with shipping for the replacement backing plates, shipping was the same or slightly more than the parts.

Jack

Mike W
08-20-2007, 03:18 PM
Why not make a new plate from 6160 or steel? When I bought a US made oxide wheel I had to grind a small amount of clearance in the cast iron guard that the wheel didn't quite clear.

pgmrdan
08-20-2007, 03:24 PM
Now I'm confused.

Some old posts on this forum said this grinder takes 6A2C wheels but you're saying it takes D6A2. I'm not sure what these signify.

Are they both correct?

I also went to the J&L website and found some D6A2C wheels. Are D6A2 and 6A2C both part of D6A2C so they really are both right?

Where does (6" plate-mounted) type 35 fit into this?

Thanks.

lazlo
08-20-2007, 04:13 PM
Some old posts on this forum said this grinder takes 6A2C wheels but you're saying it takes D6A2. I'm not sure what these signify.

Same thing. The 'D' stands for diamond. D6A2 is the standard industry designation. 6A2 is just short-hand.



I also went to the J&L website and found some D6A2C wheels. Are D6A2 and 6A2C both part of D6A2C so they really are both right?

I'm not sure what the 'C' suffix means, but I'm looking at the J&L catalog right now, and the D6A2 and the D6A2C diamond wheels look identical.


Where does (6" plate-mounted) type 35 fit into this?

The aluminum oxide and silicon carbide (green) wheels have a different designation than the diamond wheels. The 6" plate-mounted wheel that the Baldor 500/HF 46727 grinders take is a "Type 35" wheel:

http://images.grainger.com/images/products/1H972.JPG

pgmrdan
08-20-2007, 04:22 PM
So will all Type 35 wheels have the bolt pattern and center hole for the HF 46727? And as long as they're 6" they'll fit?

Mike W
08-20-2007, 05:16 PM
Be aware that the threads on the left end of the spindle are right handed.

lazlo
08-20-2007, 06:34 PM
So will all Type 35 wheels have the bolt pattern and center hole for the HF 46727? And as long as they're 6" they'll fit?

It should. I can tell you for sure that the J&L Industrial Type 35 wheel, and the Norton Type 35 wheel, both fit on my HF 46727.

jimmstruk
08-20-2007, 09:04 PM
Hey guys, check out the newest HSM magazine page 5 for CDCO adv. They have a more economical diamond to think about. The ad dosent tell how deep the diamonds are but the price is good. JIM

charlie coghill
08-20-2007, 09:46 PM
Platypus the voids that I mentioned were casting vioids or flaws in the casting. The voids were located in the bore of the backing plate. The voids may not have been a problem but by machining new ones I knew that they would not be a problem.

pgmrdan
08-20-2007, 10:04 PM
Machinery's Handbook, 21st Edition, page 2004 gives an example of the D6 A 2 C wheel.

D6 is the core shape.
A is the shape of the diamond section.
2 is the location of the diamond section.
C is modification (drilled and countersunk) hole

Table 4 on page 2008 gives the hole modification codes. H is for a straight sided hole.

So a D6 A 2 H and a D6 A 2 C would be the same except for the modified holes. The book gives 10 core shapes.

So lazlo, if you got a D6 A 2 H wheel that would give you what you need because it wouldn't have the countersunk holes. But you said earlier that you've been buying D6 A 2 wheels. They must be D6 A 2 C.

As far as type 35, it isn't listed in my edition. It only goes up to type 28 on page 1990.

Interesting stuff!

Thanks for the information.

Dan

Too_Many_Tools
08-21-2007, 12:53 AM
Excellent discussion guys.

TMT

pgmrdan
08-21-2007, 10:10 AM
lazlo,

Are the D6 A 2 wheels you've been buying really D6 A 2 wheels or are they D6 A 2 C wheels?

lazlo
08-21-2007, 10:59 AM
Machinery's Handbook, 21st Edition, page 2004 gives an example of the D6 A 2 C wheel.

Well that's good to know -- thanks Dan!


Are the D6 A 2 wheels you've been buying really D6 A 2 wheels or are they D6 A 2 C wheels?

The 3M diamond wheel I now have mounted on the HF grinder is marked "D6A2", but like I said earlier, all Western D6A2 diamond wheels are countersunk --
that's why I started the thread: the aluminum shoulder screws that come with the grinder don't fit.

pgmrdan
08-21-2007, 11:04 AM
Maybe you could call J&L or MSC and talk to their technical folks. According to the way it reads in Machinery's Handbook there should be other hole modification codes other than C. And without the hole modification code it sounds like it shouldn't have countersunk holes.

Forrest, can you clear this up?

lazlo
08-21-2007, 11:17 AM
Maybe you could call J&L or MSC and talk to their technical folks. According to the way it reads in Machinery's Handbook there should be other hole modification codes other than C.

You're making this too hard Dan. All 6" plate-mounted diamond wheels have 1/4", 82 countersunk holes.

Just get some M6 flat-head socket screws, and use the little holes on the plate mount.

lazlo
08-21-2007, 11:21 AM
Here's CDCO's diamond wheel, that Jim mentioned. There's no wheel designation, but you can clearly see the 82 countersinks. I guarantee that wheel will fit :)

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330156585678

http://i20.ebayimg.com/07/i/000/aa/11/a9b7_12.JPG

pgmrdan
08-21-2007, 12:02 PM
You're making this too hard Dan. All 6" plate-mounted diamond wheels have 1/4", 82 countersunk holes.

Just get some M6 flat-head socket screws, and use the little holes on the plate mount.

Hey, where's the fun in that? :)

I called J&L. They have 5" D6 A 2 H wheels. We speculated that the H is for 'hole'. He said they have just a plain hole on them.

I found a drawing of a D6 A 2 H here but it's a 5" wheel. It shows non-countersunk holes. http://accuratediamondtool.com/htmlcat/diamondcbn_wheels.html#D6A2H

I called the company that has that website and he said they can provide D6 A 2 H diamond grinding wheels in the 6" size and that the 'H' means a straight sided hole (i.e., no countersink). So, if someone wants them they're available.

And here is another drawing -
http://www.ice-va.com/PDF/ICE%20Catalog%20Diamond%20Wheels%20v.CUST%2038757-14.pdf

Well, I learned something so I'll stop now. :) (I love my Machinery's Handbook!)

Later,
Dan