Also, two different types of disk are used for the two different procedures....
- thin Pferd disks for cutting (about 1 - 2 per rail)
- thick standard disks for bevel grinding (one is enough for all the work)

I second the slightly off-set adjustment nuts. The other thing I learned was that when the skate gets hard to push on the rail, take a wet rag and clean the vertical edges of the rail.

Update on my progress is not so good. Last night I started grinding the X-rails with a brand new 850 watt Einhell grinder. At first I notice a lot more power than my old 500watt Bosch that I used on my Y-Rails. But after about 40 minutes...poof...smoke...no more grinder. Just shows, some things are tougher in life than others. The Bosch is about 10 years old, did a lot of hard work, but is still going.

It looks like we are going to have to add a "Kill" register at the top of the forum for all the dead grinders...:) There is much to be said for a good brand name.

Good idea Alan. I thought Einhell was German...same as Bosch, but it just show you. I think it has to do with the new stuff. They are made to last just soooo long, then we are forced to buy a new one and the company smile. They did not think that we can kill it in the first day.

Einhell is either Swiss or German, but in name only. There must be a reason why one 500W grinder costs R299 and another one costs R899 - you gets what you pay for. ;)

No wonder, this one was R230.00 from Trade Centre:o

Gentlemen,
I think you are pushing your grinders to the limits. I am using Bosch G-100, 670w, 3.0 A, 11000 rpm, 100 mm with success. I grinded my Rails in staggered manner, few minutes grinding then few minutes rest (for cooling), when its head become quite hot, can't touch with fingers I stop and let it cool for some time.
Another thing to watch that don't take big bite i.e. don't dip grinder too much, which put a lot of strain on grinder. Tilt method works fine with small passes and since contact surface is less, it means less load on grinder. For final passes grinder disc may be run parallel to rails. For smooth movement little greasing on horizontal surface of rails (under verticle bolt) makes significant changes and smoothens the passes (as Gerald has said in some post). Also don't put lot of hand pressure on grinder. A uniform pressure is required for uniform result.
Although it takes more time, but it saves grinder and results are also good.
I learnt this from experience. If I am anywhere wrong, correct me.;)
Thanks.

Exactly, the cheapies die without pushing them...

Yeah, even cheapies work better if used right

I agree with Sharma, it requires more patience to get the good out of a cheapie!

but they do work, but if you are in a hurry - any but a few will burn away.

This one that died on me was not pushed hard at all. I set it up at an angle and took light cuts...just like I did with my old Bosch that is still running. The cut is so light that I grab the skate by the height adjusting bolt and pull it along...do about 2 passes and change it to the other side to do about 2 passes there before I drop it a little bit.

Well , may be bad luck! I once had a Chinese elcheapo run for almost 6 months used regularly for fabrication everyday which cost me 15USD (600INR).

some times you just lucky..... :) now I have a german AEC grinder, has been with me for a year now. No issues what so ever.

Dewalt makes 2 amp ratings in the small grinders, I used the larger one, I think it was about $100 at Lowe's. I burned up about 20 -4" blades on my x-rails, but is made nice cutts.

I found some 5-1/2" blades and used those to cutt my y-rails and thought at the time that larger blades would = less blade changes, that was a disaster. My y-rails were too uneven to use for rails, so I wound up having them cleaned up on a milling machine and used the hardened rails. I had to also have the bottom edge of the rails beveled for the inside radius of the angle. If I ever do any more rail grinding I will stick with the small stiff cutting wheels.

The larger diameter and/or thin blades will flex and make bad cutts even with minimal pressure.

Thought I would let others know that the wheel diameter and thickness will make a difference in the quality of your cutt.

As far as I know, Einhell is Asian in origin. The German sounding name is designed to mislead.

For cutting down the height with the thin disk, it is critical to make some very light cuts without flexing the disk at the beginning. Once the starter groove is established, then you can pile on the pressure.

I did exactly like this with thin disc and then before deep cutting I checked the cutting height with Jewellers lens at every few inches.

I couldn't agree more - I burned through the Ryobi router (a cheap brand here in the US) and then burned though another Milwaukee (a better brand) and finished with a final Milwaukee. Even with the trip to the store to exchange it, it only took me less than 2-2.5 hours to do all the rails. I'm sure had I nursed the Ryobi along I could have made it work but the time would have gone up dramatically.

In both cases IMHO the reason is same, hot machine.

David,

Which Milwaukee did you buy and did it fit the skate perfectly? You posted that somewhere (I thought) but I don't find it.

My wife says I can't find anything, though! :eek:

Here is the post where I detailed the specific grinder:

http://www.mechmate.com/forums/showthread.php?t=741

Purchased at HomeDepot for $99.00 USD.

It didn't fit without opening up the inside hole for the head with a die grinder. The orginal ID of the skate is 1.714" and the Milwaukee and Ryobi are both around ~1.82" OD. There was discussion of the nead for 1/4" spacers between the plate and the head but they shouldn't be neccessary if you put the #8 screws in all four spots. (BTW - the Ryobi screws are metric, the Milwaukee is inch)

I also HIGHLY recommend the handles for the sides - they are from McMaster-Carr and are part number 57455K76, you'll need two of them. Drill and tap the end holes to 1/2". See my other posts for more details.

I also highly recommend the SteelMax saw for cutting the rails down. It was completely accurate and took less than 30 minutes to cut down all the rails.

I also wrapped a web shop towel around the head of the grinder (to each side of the handles) and this seemed to work well. It also helped cut down on the number of sparks hitting my hands.

hi there, some news, . . . . . . . i've started to grind Y rail and i think finished the gantry next week.

Some picture of my last work

Cutting rails to 1.1 with grind head top plate.
 

We ordered 2.5X1.5X.25 angle for the rails instead of the recommended 2.5X2.5X.25. Reason: only 1.725 of working height between bottom of grind head top plate and work surface (grinder is Bosch 1710). By using 2.5X1.5X.25 you get more life out of the cut wheel because the uncut rail will completely slide under the bottom of the grind head top plate. Am I making any sense? We used the pferd cut wheels and only used a few wheels cutting 40' of rail to height.

Justin

This post copied from Drawing Corrections thread as a heads-up on using a lower angle iron to prevent multiple passes.

Smith and Arrow cutoff disks
 

First time poster, long time lurker. :)

Does anyone have experience with these cutting disks?

At $47 (including shipping) for a box of 50, these would appear to be a good value for those in the US. (I didn't see the pferd disks readily available)

FYI - in my complete BOM, I have listed the individual screws and washers required to mount the Milwaukee to the skate. It also has all the other screws, bolts, bearings, handles, etc - the BOM can be found here:

http://www.dmoore.com/mechmate/bom.xls

Jeff,

I've never used them but I agree with you. Don't see how you can beat the price.

Would anyone want the hole in the skate cut slightly bigger for a non-Bosch grinder? We might be able to decide on a standard hole size before the next round of Joe's laser cuttings. A slightly bigger hole will not degrade the use of a Bosch grinder.

Gerald,
Good recommendation and change. As you know, I had to oversize my hole slightly, but I was still able to use the RYOBI and BOSCH grinders selectively with the same (4) BOLT pattern. Great idea to make the skate more "universal".

Any other volunteers?

I have never used the skate so I'm not exactly sure what I should be measuring. Are y'all talking about the round part of the motor housing through which the spindle passes? The part that the guard clamps to? That's what I'm guessing.

I have two grinders. A Dewalt DW402 and a Black and Decker Quantum Pro. Both of them measured 1.502"

For all of you lurkers out there that are planning to build a MM one day, now is the time to chime in with your measurements. Go out in the garage and measure your grinder and post the results.

Thanks Doug.

Well, unless someone has a common grinder at bigger than 1.82", the hole size is now firmed up at 1.85" (as per Sean's first prototype, of which he gave me a dxf file)

That works for me as it's not the hole ID that holds the grinder in place, it's the screws into the head. On a side note - the Milwaukee and Ryobi which are basically the same head sizes, the screws on the Ryobi are 6mm and the Milwaukee are #8 screws.

I presume that all grinders have 4 screws placed in a square. What it the thickest screw (surely not 6mm)?

Got some courage to cut the rails
 

Started cutting the rails down. Look at a carpenters method of building a slide to cut down the rails again some off cut material and bobs your uncle.
Kobus made the gadget with the same tape we are talking about put some screws on top just in case it moves.Took me longer to get the hight right then to make it.

Took +/- 15 min to cut through the first rail with one & half disks.The objective is to cut both rails from one side.Had to go home the boss called they wanted to go and watch whales.

I hope that yellow grinder is not an Einhell from Trade Centre. They are fine for cutting the rail but grinding the bevel they are not very strong. Nice going Hennie

No, it is a De Walt Last much longer! I try to keep the el cheepo`s on display for affirmative shopping purposes,You know what I mean:). I have a Bosch for the bevel grinding on my laser cut gadget.Reason why I made the funny wooden block is that my angle iron is 60 x 60 and you have experiance in using the grinding skate ,hight is a problem and I wasnt prepaired to pay more for other angle iron.
Would like to do some more but I am baby sitting today.

Did some more cutting on the y-rails (second one ).It is not such a bad job,dirty yes!I did manage to cut both rails down from one side. wil post pic`s tomorrow,will try and do the x-rails also.

Rails drilled, cut and grind
 

Thank you for the welcome words.
I made this adaption for my Makita grinder form offcut MDF and a few screws, the grinder fits snug into the MDF supports, I made sure that no high squeezing pressure is exerted onto the housing of the grinder body. It worked well for me, the cutting and grinding is off to a great start and completed, the temperature is not of the cutting disc, it is our 11h00 morning temperature in full shade.

nice grinder attachment though!